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Meeting documents


Report of the Symposium on


held in connection with the


Twentieth Session

Praia do Carvoeiro, Portugal, 23 June - 1 July 1998

Rome, 1998


The present text is the final version of the report adopted on 26 June 1998 by the participants in the Symposium and presented to the Twentieth Session of the European Inland Fisheries Advisory Commission.

A selection of papers presented at the Symposium will be published in the journal "Fisheries Management and Ecology".


EIFAC Member States
European Community
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FAO Fisheries Department
FAO Regional and Sub-Regional Fisheries Officers

European Inland Fisheries Advisory Commission.
Report of the Symposium on Water for Sustainable Inland Fisheries and Aquaculture held in connection with the European Inland Fisheries Advisory Commission, twentieth session, Praia do Carvoeiro, Portugal, 23 June - 1 July 1998.
FAO Fisheries Report. No. 580, Suppl. Rome, FAO. 1998. 56p.


The Symposium on Water for Sustainable Inland Fisheries and Aquaculture was held in Praia do Carvoeiro, Portugal, from 23-26 June 1998, in concomitance with the Twentieth Session of the European Inland Fisheries Advisory Commission (EIFAC). Sixty eight participants from 23 countries attended the symposium; 27 papers and 6 posters were presented. The Symposium concluded that those in charge of fisheries and aquaculture development should seek collaboration with other agencies and sectors of society in order to improve coordination of water resource management and to ensure that the needs of inland fisheries and aquaculture are adequately represented in management plans. An urgent requirement would be an economic and social evaluation of inland fisheries, aquaculture production, fishing communities, fish populations and aquatic environments in general.




Session A:

Assessment of quantitative and qualitative characteristics of water resources


Session B:

Water requirements of inland aquaculture systems


Session C:

Water requirements for inland fisheries


Session D:

Water resources issues and conflicts


Session E:

Strategic planning of water resources


Session F:

Conclusions and recommendations


Annex I:

Participants in the Symposium


Annex II:

Abstracts of contributions submitted to the Symposium



Session A



Session B



Session C



Session D



Session E


Annex III:

Address by Mr H. Ackefors, Chairman of the Symposium



1. A Symposium on Water for Sustainable Inland Fisheries and Aquaculture was convened in conjunction with the Twentieth Session of the European Inland Fisheries Advisory Commission (EIFAC) in Praia do Carvoeiro, Portugal, from 23 to 26 June 1998. The Symposium was convened by Mr R. Müller (Switzerland) and chaired by Mr H. Ackefors (Sweden). The Symposium was attended by 68 participants from 23 countries.

2. The objective of the Symposium was to establish the place of inland fisheries and aquaculture in the context of water management. The Symposium examined the requirements for water as well as technical aspects of water use for inland fisheries and aquaculture.

3. The Symposium was organized in sessions:

Session A: Assessment of quantitative and qualitative characteristics of water resources, Chaired by J. Lundqvist (Sweden)

Session B: Water requirements of inland aquaculture systems, Chaired by L. Varadi (Hungary)

Session C: Water requirements for inland fisheries, Chaired by S. Hughes (UK)

Session D: Water resources issues and conflicts, Chaired by M-J. Collares-Pereira (Portugal)

Session E: Strategic planning of water resources, Chaired by U. Grosch (Germany)

Session F: Conclusions and recommendations, Chaired by H. Ackefors (Sweden)

4. The main documentation consisted of 27 experience papers and 6 poster papers.


(a) Identification of the problem

5. Ground and surface freshwater resources are finite but demand on them from various sectors and interests in society is increasing (Fig.1). Scarcity results mainly from consumptive uses of water within the river or lake drainage basin. In particular huge amounts of water are lost through evapo-transpiration from agricultural crops. This "green" water is not adequately quantified, costed or controlled. Equally important is the impact of intensified use of water in lotic and lentic systems. This "blue" water is available for allocation but is subject to loss of quality by pollution and eutrophication. Growing scarcity is therefore leading to competition between the various users and is becoming a major issue in Europe and elsewhere.

figure 1.

Figure 1 Rate of withdrawal of water as compared to population growth showing that the withdrawal rate is about 2.5x the rate of population growth.
A Population growth 1900 - 2000
B Water withdrawal by category globally and in Europe
(G = global: E = Europe)

(b) Needs and approaches

6. Improvement of, or finding alternative uses for water that has been degraded through excessive eutrophication and pollution requires high levels of management based on scientific knowledge and monitoring programmes. Modern society requires intensified use of water. Such use should be characterized by high efficiency with a high level of socio-economic benefit/unit of water/unit of area. It must also be characterized by low environmental impacts both for continuous, sustainable production within any particular system as well as avoiding any impacts downstream of the exploited system.

7. Development of techniques for intensive, low impact use of water requires considerable research for improved management of individual aquatic and terrestrial systems. Inland fisheries and aquaculture are efficient users of scarce water resources as compared to many alternative claimants. It is important to highlight this quality of inland fisheries and aquaculture so as to improve official and public perceptions and facilitate acceptance of these sectors within the overall allocation process. Awareness of the environmentally friendly nature of fisheries should also be promoted among environmentalists and other non-governmental interest groups which have similar aims in improving the sustainability of the semi-natural and natural ecosystems of Europe.

8. Within the aquaculture sector concerns have been expressed about certain types of systems which are described in more detail in the following sections.

(c) Still-water pond systems

(i) The place of fish ponds in the landscape

9. Still-water ponds are man-made polyfunctional water bodies. They have been associated with various human activities, but their major income has always been generated from fish-farming. It is important that the significance of such ponds be reappraised in the context of the more general changing perceptions as to how the landscape should be used within Europe. Fish pond systems are crucial in determining the hydrological characteristics of the surface waters in many regions in central Europe and particularly in specific regions within Austria, the Czech Republic, Germany and Hungary. In such landscapes ponds provide a rich mosaic of habitats for a wide range of plant and animal species whose communities have been preserved in a relatively natural state.

10. The present state of the ponds has been arrived at through many centuries of fish-farm management as well as the agriculture in their vicinity. The recent trend to higher intensity fish farming, as well as intensification of agricultural practice in the catchment, has resulted in an increase in nutrients in Czech fish ponds. This has produced excessive eutrophication which has led to changes in the biotic structure of the fish pond ecosystems resulting in:

11. The development of the Czech ponds exemplifies this shift from the more or less natural pond ecosystems common until the middle of this century to the hypertrophic situation today.

12. The solution to these problems is an understanding of seasonal patterns and the range of fluctuation of those critical parameters that reflect both ecological stability and production efficiency. However, any actions proposed to improve the production should also be appraised from the environmental and economic viewpoint and related to the needs of other users of the landscape.

13. Future proposals for research and monitoring of the fishery, as well as criteria for management aimed at securing sustainability of production and ecological stability, should take these wider issues into account. Future changes in legislation and local regulations should be based on such proposals.

(ii) The impacts of fish ponds on water quality

14. The impact of carp pond effluents on associated streams and lakes is controversial. Three German fisheries institutes (Institute of Inland Fisheries in Potsdam-Sacrow, Department of Fisheries in Königswartha and Department for Carp Pond Culture in Höchstadt) were commissioned to investigate nutrient inputs and outputs of carp ponds in the three main carp pond regions of Germany: Saxonia, Bavaria and Brandenburg. The studies concluded that:

15. Carp ponds, therefore, should not be considered as detrimental to the environment but rather as mechanisms for improving water quality. On these grounds current attempts to require a reduction of the yield level below 1,500 kg/ha cannot be justified There is similarly no reason to impose a fee for water used in carp ponds.

16. Even though the loads during harvesting are very low compared to the retention capacity of ponds, efforts should be made to reduce further the load from the ponds during harvesting.

(d) Introduced species

17. Past activities of EIFAC concerning species introductions resulted in an appraisal of impacts at regional and national levels as well as the elaboration of a Code of Practice together with ICES (EIFAC/OP 23, Codes of practice and manual of procedures for consideration of introductions and transfers of marine and freshwater organisms). Although this Code has not been widely used per se because of its cumbersome administrative process, it has been incorporated into national legislation and regulations. The case of introduction of species into Greece exemplified the continued relevance of the introduction issue to European inland fisheries management: Twenty-three exotic species have been introduced in Greece and a further 14 transferred from one aquatic system to another within the country. Many of these were intentional and made for different purposes including enhancement of fish production, ornamental fish production and biological pest control. Introductions such as the carp (Cyprinus carpio), the tench (Tinca tinca), common whitefish (Coregonus lavaretus) and some Asiatic carps proved useful. Other introductions or transfers were harmful to local fish fauna. Introduction of perch in Lake Kastoria resulted in environmental damage, transplants of Aristotles catfish into Lake Volvi, resulted in the elimination of the native wels and release of Acheloos wild trout fingerlings into tributaries of river Nestos and Attakmon genetically polluted the local population. It was therefore concluded that the previous EIFAC initiatives to control introductions were still valid and that future proposals for introductions or transfers and public works, such as canals, which can cause mixing of different fish faunas, should apply the EIFAC/ICES guidelines.

(e) Conclusions

18. It was concluded that inland fisheries planners and administrators need to participate pro-actively in fora at all levels concerned with the allocation and consumptive use of water and management of living aquatic resources. Such participation is necessary to:

(i) ensure that water is assigned for the maintenance of aquatic ecosystems and living organisms. Such allocation should include criteria for water use, including quantity, quality and timing which should be established on the basis of scientific evidence;

(ii) ensure that the aquaculture sector is not penalized by unrealistic requirement for effluent quality. It was recognized that for its part the aquaculture sector would need to be responsible in its approach to improving the quality of its discharges;

(iii) limit the potential damage resulting from introductions and transfers of exotic fish, and other animals and plants within the inland waters of Europe; and

(iv) promote awareness and knowledge of the social, economic and environmental significance of inland fisheries and aquaculture among decision-makers and stakeholders at all levels.


(a) Identification of the problem

19. Aquaculture in ponds was established originally in regions where water resources were readily available but supplies are now becoming limiting in some areas due to population increase, industrialisation, environmental concerns and other factors. Several fish farms have had to convert from production to nature conservation or recreational areas. Many intensive fish farms are having problems in the disposal of their effluents. Despite these difficulties, the need for fish as healthy food is increasing, and efforts are being made in many countries to increase the proportion of fish in the diet. However, studies and trend analyses indicate that some conventional aquaculture systems need to evolve and adapt to changing social, economic and environmental conditions in many European countries.

(b) Needs and approaches

20. There is a variety of commercial aquaculture systems in Europe including fish ponds managed at various levels of intensity, intensive flow-through systems and cage culture. The design and operation of most of these are based on conventional principles in which water efficiency does not play a significant role. There are examples of newly built, well designed, intensive systems which include water recyling, and treatment of the recycled water and the effluents. Recently research into ways of improving water efficiency in existing systems has been intensified. There is also a tendency to develop new systems with low water requirements per unit production, and low envronmental impact, especially in countries where water shortage is already a major constraint to aquaculture development. There have also been attempts to improve water efficiency through the shared use of water resources but integration among various water users is not a common practice in Europe although promising experiences are reported from Asia.

(c) Fish pond systems

21. The water efficiency of a conventional fish pond can be improved by accurate estimation of the water budget using hydrological equations that assist in:

22. The serious water shortage in Israel encouraged the development of new types of water efficient pond production systems. Different commercial scale low-discharge intensive pond systems have been developed and successfully applied. These include intensive-extensive systems based on intensive ponds combined with large water treatment ponds, low-exchange intensive ponds that are continuously aerated and mixed ponds where daily water exchange is limited to 3-20 percent.

(d) Intensive fish production in tanks with water recyling and water treatment

23. The operation of these systems is based on frequent recycling of water between the production tanks and a water treatment unit. A typical water treatment unit consists of two major components: a unit for the removal of suspended solids (e.g. sedimentation tank) and a biological treatment unit where organic carbon (BOD) is further removed and ammonia is nitrified. The water use efficiency of such a system can be very high and discharges may be practically eliminated. The use of this type of systems will probably be limited to the production of high value biomass such as fish seed or expensive market-size fish. Most of the intensive fish production systems in use release fairly large amount of nutrients into the surrounding environment and extensive research and development work is being carrying out on effluent treatment of such systems.

(e) Integrated aquaculture systems

24. Integration of aquaculture with irrigated farming systems is an important means for improving overall productivity and was exemplified by case studies from Asia and Australia. Although ecological and socio-economic conditions are different in Europe the possibilities of integrated aquaculture/irrigated farming systems should be explored during resource use planning in the future.

25. The examples from Australia and Bangladesh indicate that integration of aquaculture with existing irrigated farming systems has the potential to enhance productivity, water use efficiency and overall environmental sustainability. Cage culture in irrigation canals and water reservoirs is one technology for such integration. Numerous aquatic habitats are created by irrigation systems which can also be used for various forms of aquaculture. A flexible system of moving cultured fish between habitats should be feasible. For example, stocking material for reservoirs can be obtained from irrigated rice fields, where the short growing season of the crop only permits the harvest of fingerling. If a pragmatic and flexible approach is adopted all habitats can be used for fish production giving a year round supply of fish and minimum wastage of stocks. This type of integration has ecological and social benefits as well as the capacity to generate economic revenue. Fishes in irrigation systems enhance the yield of land crops, alleviate the pressure of terrestrial and aquatic pests, and lower the population of human and animal disease vectors.

(f) Conclusions

26. Aquaculture must be accepted and legally recognized as a legitimate user of water.

27. The availability of freshwater resources for aquaculture production will continue to decrease in the future but new methods and production systems are available for the more efficient use and protection of those water resources that remain. While there is little need to introduce these into many countries at present, medium- and long-term planning of aquaculture development should consider their potential for the future. Research and development of new types of water efficient fish production systems should get priority in formulating R&D programmes.

28. The possibility of integrating aquaculture into irrigation systems should be considered as an option for improved efficiency of water use. However a flexible approach is suggested which uses all type of habitats created by existing agronomic practices, the hydrological cycle and the features of the landscape. The principle of integration may also be applied on a wider scale, and more active collaboration among the various water users, planners and administrators is necessary. Collaboration between countries in which water shortage already exists and where such problems are anticipated in the future should also be promoted in order to exchange information and execute joint projects.


(a) Identification of the problem

29. There is adequate knowledge on the water quantity and quality requirements of fish for their management in many different aquatic ecosystems. Increasing pressures on water resources, coupled with a heightened public demand for sustainable development, means that there is now a need to manage the environment as a whole. Central to this is an improved understanding of the different demands placed on the aquatic system and how these demands relate to one another, and better communication and acceptance of how the requirements of one user will modify and compromise those of another.

(b) River augmentation

30. Recreational coarse fisheries (catch and release), salmon fisheries (removal) and trout fisheries (put and take) are economically and socially important. In the UK for example, they involve people from some 11% of households who spend over UKú 3 thousand million per annum and contribute significantly to local economies.

31. Water resource planning principally targets public water supply, although ecological considerations are gaining a voice through legislation and licensing regimes. Water resource deficits need to be addressed and can often be solved by interbasin transfers. The environmental impacts of river flow augmentation schemes have been identified and are being assessed. Climate change may modify water resource yields in the future. Public concern for the environment and the views of local stakeholders should be co-opted to influence planners and politicians so that they make provisions for the conservation of aquatic ecosystems.

32. It was recognized that ground water augmentation of rivers could benefit water quality and flow regimes in ways that are directly advantageous to fish and wildlife during low summer flows. However, these benefits can be at the cost of increased turbidity, stressful temperature changes and scour, and reduced fish growth and survival rates. It was also evident that minor changes in the temperature regime can have major impact on fish recruitment. If such river augmentation schemes are adopted, flexible operating regimes may mitigate unnecessary detrimental impacts.

33. Applying the precautionary approach may reduce the risk of any management activity. At the same time, failure to make timely decisions may diminish its potential benefits and also poses the risk of more damaging alternatives being implemented. There is scope to be less cautious where the dangers of change are clearly reversible, provided a clear commitment is made to adaptive management.

(c) Anthropogenic impacts on river fisheries

34. River regulation in the highly stressed urban river system around Berlin demonstrated significant management difficulties that are not found in more natural, rural systems. In particular increased nutrient loading, introduction of exotic species and hydraulic engineering caused habitat loss, declining water quality, fish population change and adverse socio-economic consequences.

35. A decline in catches of high value species together with reduced demand for freshwater fish has affected employment levels in the fishery. High levels of organic toxins have also affected fish marketability, but this situation is improving.

36. Economic survival of the fishery whether as a source of food or as a social heritage has become increasingly dependant on the creation of an artificial market for zooplanktivorous fish. Water quality is improving and a change in the fishery has been observed, but continued political intervention is essential to maintain this process.

(d) Donor lake management

37. Management regimes within lakes and reservoirs that serve as water resource donors can impact on resident fish communities and associated fisheries through changes in the composition of the zooplankton and the nutrient status.

38. Large crustacean zooplankton form an import component of the diet of zooplanktivorous fish. Bottom-drained dams can selectively export sufficiently large amounts of these organisms as to change the species composition of the zooplankton towards smaller organisms. The loss of suitable prey can reduce fish growth and affect population viability. Managing water supply reservoirs so that discharge techniques closely resemble natural lake systems allows a more stable plankton flora and fauna that support more valuable fisheries.

39. A case study of coregonid management in commercial fisheries impacted by eutrophication provided a good example that will enable managers to identify options for the future. In particular increased eutrophication within the investigated range resulted in less effective stocking support for vendace (Coregonus albula) fisheries, potentially enhanced production of whitefish (Coregonus lavaretus) and a general shift towards greater catches of low-value small cyprinids.

40. In Lake Sevan, Armenia, there is a conflict between the need to abstract from a country's sole water supply and the needs of an important fishery: in this case it is clear that the wider needs of society have to take precedence.

41. Excessive abstraction has resulted in falling lake levels, eutrophication and changes in the fishery. Endemic species have declined but introduced whitefish has become an increasingly important element in the commercial catch. A further drop in lake level exposed nutrient-rich sediments and, together with population declines following increased poaching of whitefish, resulted in an increase of zooplankton sufficient to restart the eutrophication process. This situation may be reversible given the financial resources and political will.

42. Where a resource is stressed and a natural fishery has degraded, there may be scope to introduce new fish species to provide an alternative. The potential risks can be high and similar considerations apply to those set out in paragraph 17 above.

(e) Conclusions

43. Water resources are generally under pressure at existing levels of demand. There is significant scope for reducing withdrawals and managing impacts in order to comply with new environmental awareness. Given current levels of demand it will not always be possible to protect the environment fully, but the appraisal process must be carried out so as to balance priorities and apply mitigation measures.

44. Case studies showed that the current state of knowledge is probably sufficient to frame technical interventions to mitigate continuing impacts by other users or to rehabilitate impacted systems. The few exceptions are being addressed in the long term by structured programmes of research. Public incapacity to improve the aquatic system lies more in the sphere of policy making and allocation among different user groups. The new need is for political processes that will facilitate compromise by stakeholders and favour integrated resource management. This change in management orientation is being stimulated by the need to protect biodiversity, and to ensure sustainability, social welfare and economic benefit. An important aspect of this political process is better communication that will help reduce conflicts between sectors and encourage cooperation and coordination.

45. Fishery scientists should continue to build understanding of the impacts of hydrological change on fish communities. Robust environmental appraisal processes must be carried out to properly balance resource priorities, and guide decisions on allocation and on any mitigation measures that may be necessary.

46. It is important that concepts of social and economic value and use are developed for inland fisheries and aquaculture so that fisheries interests can be properly represented in the allocation debate. Collaboration with local stakeholders and with other groups expressing public concern for the environment should be sought in order to influence planners and politicians.

47. The precautionary approach to decision making should be applied where potential changes are deemed to be irreversible.

48. Managers of fisheries and the environment should consider different water resource uses as potential mechanisms to reduce eutrophication and to improve lake and river fisheries.

49. Stocking of new species in stressed systems may provide alternative fishery resources but potential risks to the wider environment should be carefully considered and the appropriate guidelines respected.


(a) Identification of the problem

50. Increasing demand for aquatic resources by a diverse array of user groups has resulted in environmental degradation, loss of habitat and conflict between various stakeholder groups. The mechanisms for assessing the impact of various activities are reasonably well established but overcoming the problems is still complex. This is because mechanisms for resolving conflicts among fishermen and between fishermen and other users are only now being developed. The key problem to be addressed is the promotion of sustainable use of water resources at an optimal level of exploitation, acceptable to all users, whilst maintaining the potential to meet the needs and expectations of future generations.

(b) Identification of the issues and conflicts

51. In rivers there is often considerable conflict between user groups. Either one activity is directly incompatible with the other or may lead to a deterioration of the environment or resource that is unacceptable to other users. This was demonstrated in a number of case studies presented:

(c) Resolution of conflicts

52. A number of mechanisms were adopted in an attempt to resolve the conflicts identified in the case studies.

53. Temporal and spatial zoning was used to harmonise the conflicts between nature conservation, recreation, and fishing. For example, in Belgian rivers kayaking is restricted to certain parts of the river during daylight hours and only when flows were above a certain, arbitrarily set, threshold discharge level. Similarly, in Lake Saimaa, gill-netting was prohibited around the seal breeding areas.

54. The problems relating to hydropower schemes and flow regulation were more difficult to solve because the economic value of water presents an overriding argument. However, establishment of minimal acceptable flows for fisheries and habitat modification to enhance the fisheries were the approaches being adopted.

55. The multiple user situation in the Guadiana was more complex to resolve and several parallel actions were proposed, including improved control of water resource development schemes, establishment of nature reserves, rehabilitation of degraded habitats, stock enhancements methods, promotion of the-beneficiary-pays principle, and integrated river basin management.

(d) Conclusions

56. If aquatic resources are to be exploited on a sustainable basis in the future, concerted effort is needed to resolve the conflicts between user groups. Where possible, this must be based on available scientific evidence, close liaison between user groups, full cost-benefit analysis and transparency in the decision-making process. If this is to be successful it must involve cross education of all user groups, recognition of stakeholder participation and needs, and be probably implemented at the local community level. It is recommended that aquatic resource planning and management tools such as the river basin management plans being developed by the European Union member countries be used to facilitate the process of integrated water resource management.

57. If fisheries are to be represented, there is a need for improved long-term trend analysis and economic and social evaluation of fisheries and associated externalities. It is recommended that priority be given to developing and promoting economic evaluation of inland fisheries and marketing of the products. There is also the need for robust methods for prioritising demands for aquatic resources which balance human requirements against the protection of the environment and biodiversity.


(a) Identification of the problem

58. World food production has to be increased over the next three decades to satisfy the additional demands of a world population, which will have grown to about 8 thousand million by 2025. It is not anticipated that substantial increases in supply can be obtained from oceanic fisheries. Therefore, any future growth in fish protein supply will have to come from aquaculture. In view of the problems of water supply caused by growing demand, existing aquaculture production using conventional methods is likely to be endangered. Those responsible for the inland fisheries and aquaculture sectors in Europe and elsewhere must take part in the wider discussions and decisions concerning future water resource allocation and water quality management.

(b) Needs and approaches - river basin management

59. There is a great need for the restoration of lakes and other natural waterbodies as historically increased nutrient loadings have accrued in the sediments and make control of the level of fish production and the quality of the fish difficult. Effluent discharges from sewage plants and agricultural runoff still contain nutrients in high concentrations. Residues from cosmetic and pharmaceutical products are having a harmful influence on fish through contamination of the flesh and alteration of sex ratios.

60. Rehabilitation of inland fisheries can benefit from European Union legislation on water quality, where ordinances specific to water management and food quality set standards that must be adopted by the member states.

61. Integrated management of river basins is considered to be the most effective approach to ensuring sustainable use of water resources and protection of river quality.

62. Management plans for waste disposal and sewage treatment should be at the highest level of available technology in order to eliminate the degradation within river basins caused by existing anthropogenic activities and to ensure sustainable development of economic activities such as aquaculture.

(c) Identification of water sources for aquaculture

63. The aquaculture industry today faces a challenging situation in which it will have to produce more fish with less water so as to meet the expected demand in the future.

64. Use of recycled city water, desalinated brackish or seawater or recycled pond water are possible sources for aquaculture, although public prejudice limits the use of the first, and up to now aquaculturists are not able to cope with the price of the second.

65. Various strategies to intensify aquaculture have already been developed and new ones are under study. These include water harvesting in dual purpose reservoirs, recycling of pond water from one year to the other, development of intensive flow-through systems based on recycled pond water and others based on biofiltration.

(d) Conclusions

66. EIFAC member countries should be aware of a growing demand for fish in the near future that cannot be filled by catches from the sea or from inland waters.

67. Against the background of growing world population future demand for fish will have to be satisfied through aquaculture and fish stock enchancement.

68. Therefore those responsible for decisions on ground and surface water allocation and management at all administrative and technical levels must make adequate water available for aquaculture and for maintenance of quantity and timing of stream flows.

69. Greater efforts in the development of more efficient purification systems are needed to protect ground and surface water from unacceptable pollution deriving from urban and industrial drainage systems.

70. There should be a comparable emphasis on river and lake rehabilitation and improvement as a means to maintain and enhance valuable recreational, commercial and subsistence fisheries.


71. The participants of the Symposium on Water for Sustainable Inland Fisheries and Aquaculture proposed the following recommendations which were subsequently adopted by the Twentieth Session of EIFAC:

(a) Authorities and those in charge of fisheries and aquaculture development must seek collaboration with other agencies and other sectors of society in order to improve coordination of resource management.

(b) It is vital that governments empower fisheries and aquaculture authorities to promote actively the interests of inland fisheries and aquaculture, as well as adequately participate in resource management decision-making.

(c) Authorities in charge of fisheries and aquaculture need enhanced capacity to implement policies and regulations related to management of living and physical aquatic resources. Greater resources must be made available to these authorities. It is realized that in many cases these authorities lack manpower and financial and information resources to be able to participate actively in intersectoral negotiations and policy-making. There is a need for research and development to fill key information gaps.

(d) There is a need for management strategies for water resources in general that incorporate the needs of inland fisheries and aquaculture. Those responsible for water allocation should consult with fisheries and aquaculture authorities. Authorities responsible for fisheries, aquaculture and water resource planning should collaborate to formulate appropriate strategies, identify options for their implementation and identify key stakeholders who should participate in this process. These strategies must encompass a range of aspects including social, economic and recreational considerations, biodiversity and the wider aquatic environment.

(e) In view of river basin management plans which have to be prepared for a deadline of December 1999 in the EU member states, authorities representing inland fisheries and aquaculture management must identify groups responsible for the production of these plans and ensure that the needs of inland fisheries and aquaculture are adequately represented in the plans.

(f) Key government departments must recognize that inland fisheries have economic, social, biological and other values. For inland fisheries and aquaculture to be properly represented in the allocation of resources there is a need for improved economic and social evaluation of fisheries, aquaculture and associated aspects. It is recommended that priority is given to developing and promoting economic and social evaluation of inland fisheries, aquaculture production, fishing communities, fish populations and aquatic environments in general.

Annex I

Participants in the Symposium

Department of Zoology
Stockholm University
S-10691 Stockholm
Fax: (+46-8) 167715
E-mail: [email protected]

Interdepartmental Ichthyological Commission
27, Tverskaya St.
Moscow 103050
Fax: (+7-095) 2992221 

National Board of Fisheries
Box 423
S-40126 Göteborg
Fax: (+46-31) 7430444
E-mail: [email protected]

Finnish Game and Fisheries Research Institute
Saimaa Fisheries Research
FIN-58175 Enonkoski
Fax: (+358-205) 751 609
E-mail: heikki [email protected]  

Department of Agricultural Engineering
Technion, Israel Institute of Technology
Technion City
Haifa, 2000
Fax: (+972-4) 8221529
E-mail: [email protected]

Inland Fisheries and Aquaculture Service
Fishery Resources Division
Food and Agriculture Organization of the United Nations
Via delle Terme di Caracalla
I-00100 Roma
Fax: (+39) 0657053020
E-mail: [email protected]

Inland Fisheries Institute
Ul. Oczapowskiego 10
10-719 Olsztyn 5
Fax: (+48-89) 5272505
E-mail: [email protected]

Direcção-Geral das Florestas
Av.a João Crisóstomo No. 26-28
P-1050 Lisboa
Fax: (+351-1) 3156188
E-mail: [email protected]

Jørgen BOHN
Danish Directorate of Fisheries
Stormgade 2
DK-1470 Copenhagen K.
Fax: (+45) 33963903

Ministry of Food, Agriculture and Fisheries
Holbergsgade 2
DK-1057 Copenhagen K.
Fax: (+45) 33145042

Direcção-Geral das Florestas
Av.a João Crisóstomo No. 26-28
P-1050 Lisboa
Fax: (+351-1) 3156188
E-mail: [email protected]

Dep. Zoologia e Antropologia
Centro de Biologia Ambiental
Faculdade de Ciências, Univ. Lisboa
Fax: (+351-1) 7500028
E-mail: [email protected] 

Christian COURCOL
Ministère de l'Agriculture et de la pêche
19 Avenue du Maine
F-75732 Paris Cedex 15
Fax: (+33-1) 49555984 

University of Hull
International Fisheries Institute
Hull HU6 7RX
United Kingdom
Fax: (+44-1482) 470129
E-mail: [email protected]  

Teresa CRAVO
Direcção-Geral das Florestas
Av.a João Crisóstomo No. 26-28
P-1050 Lisboa
Fax: (+351-1) 3156188
E-mail: [email protected]  

Ministry of Agriculture and Forestry
Department of Fisheries and Game
P.O.Box 232
FIN-00171 Helsinki
Fax: (+358-9) 1604285

Valentina G. DUBININA
Interdepartmental Ichthyological Commission
27, Tverskaya St.
Moscow 103050
Fax: (+7-095) 2992221

Aristotle University of Thessaloniki
Department of Zoology
Laboratory of Ichthyology
Box 134
GR-54006 Thessaloniki
Fax: (+30-31) 998279
E-mail: [email protected] 

Service de la Pêche
DGRNE - Région Wallonne
av. Gouverneur Bovesse, 100
B-5100 Jambes
Fax: (+32-81) 327470 

Institute of Hydroecology and Ichthyology
24d Bagramian st. 902
Yerevan 375019
Fax: (+374-2) 151048
E-mail: [email protected]

Station de Recherches Forestières
Ministère de la Region Wallonne
Avenue Maréchal Juin, 23
B-5030 Gembloux
Fax: (+32-81) 615727
E-mail: [email protected]  

Fischereiamt Berlin
Havelchaussee 149
D-14055 Berlin
Fax: (+49-30) 3041805
E-mail: [email protected]

Direcção-Geral das Florestas
Av.a João Crisóstomo No. 26-28
P-1050 Lisboa
Fax: (+351-1) 3124996
E-mail: [email protected]

Matthias HALWART
Inland Fisheries and Aquaculture Service
Fishery Resources Division
Food and Agriculture Organization of the United Nations
Via delle Terme di Caracalla
I-00100 Roma
Fax: (+39) 0657053020
E-mail: [email protected] 

Peter-Diedrich HANSEN
Berlin University of Technology
FB 7 - Institute for Ecological Research and Technology
Department of Ecotoxicology
Keplerstraße 4-6
D-10589 Berlin
Fax: (+49-30) 8318113
E-mail: [email protected]


Comenius University
Faculty of Natural Sciences
Department of Zoology
Mlynská Dolina B-1
842 15 Bratislava
Fax: (+42-7) 65424138
E-mail: [email protected]

National Coarse Fisheries Centre
Environment Agency
Arthur Drive, Hoo Farm Industrial Estate
Worcester Road
Kidderminster, DY11 7RA
United Kingdom
Fax: (+44-1562) 69477
E-mail: [email protected] 

Vejle County
Damhaven 12
DK-7100 Vejle
Fax: (+45) 75835571
E-mail: [email protected]

National Coarse Fisheries Centre
Environment Agency
Arthur Drive, Hoo Farm Industrial Estate
Worcester Road
Kidderminster, DY11 7RA
United Kingdom
Fax: (+44-1562) 69477
E-mail: [email protected] 

Marine and Freshwater Resources Institute
Snobs Creek Fish Hatchery
Private Bag 20
Alexandra. VIC. 3714
Fax: (+61-3) 57742659
Email: [email protected]

Fisheries Department
Ministry of Agriculture
Gedimino pr., 19
2600 Vilnius
Fax: (+370-2) 391176

Iphigenia KAGALOU
Technological Educational Institute
Department of Ichthyology and Fisheries
P.O.Box 152
GR-461 00 Igoumenitsa
Fax: (+30-6) 6528131 

Federal Agency for Water Management
Institute for Water Ecology, Fisheries and Lake Research
Scharfling 18
A-5310 Mondsee
Fax: (+43-6232) 384733
E-mail: [email protected] 

Institut für Binnenfischerei
Jägerhof an Sacrower See
D-14476 Groß-Glienicke
Fax: (+49-33201) 40640
E-mail: [email protected]

Administration des Eaux et Forêts
Service de la Chasse et de la Pêche
Boîte Postal 411
L-2014 Luxembourg
Fax: (+352) 485985
E-mail: [email protected]

Vejle County
Damhaven 12
DK-7100 Vejle
Fax: (+45) 75835571
E-mail: [email protected] 

Department of Limnology
P.O.Box 27
FIN-00014 Helsinki
Fax: (+358-9) 7085257
E-mail: [email protected]

Antonin LELEK
Research Institute Seckenberg
Dept. of Ichthyology II and Fish Ecology
Senckenberganlage 25
D-60325 Frankfurt/M
Fax: (+49-69) 746238
E-mail: [email protected] 

Tema Vatten
Linköpings Universitet
S-581 83 Linköping
Fax : (+46-13) 133630
E-mail: [email protected]

Adelaide MARQUES
Direcção-Geral das Florestas
Direcção de Serviços de Caça e Pesca nas
Águas Interiores
Av.¬ João Crisóstomo, 26-28
P-1050 Lisboa
Fax: (+351-1) 3124981
E-mail: [email protected] 

Centre "Mariculture VNIRO"
17 Krasnoselskaya Str.
Moscow 107140
Fax: (+7-095) 264 9154, 264 9187

Department of Fisheries and Aquaculture
Ministry of Agriculture and Rural Development
Hakyria P.O.Box 7011
Tel-Aviv, 61070
Fax: (+972-3) 6971451
E-mail: [email protected] 

Christopher MORIARTY
Marine Institute
Fisheries Research Centre
Dublin 15
Fax: (+353-1) 8205078
E-mail: [email protected]

EAWAG, Fisheries Section
CH-6047 Kastanienbaum
Fax: (+41-41) 3492168
E-mail: [email protected]

Pentti MUNNE
Ministry of Agriculture and Forestry
Department of Fisheries and Game
P.O.Box 232
FIN-00171 Helsinki
Fax: (+358-9) 1604285

Heiner NAEVE
Secretary EIFAC
Food and Agriculture Organization of the United Nations
Via delle Terme di Caracalla
I-00100 Roma
Fax: (+39) 0657053020
E-mail: [email protected]

The University of South Bohemia
Faculty of Agriculture
Applied Ecology Laboratory
37005 Ceské Budejovice
Czech Republic
Fax: (+420-38) 45146
E-mail: [email protected] 

Institute of Zoology
Bulgarian Academy of Sciences
1 Tzar Osvoboditel blvd.
1000 Sofia
Fax: (+3592) 882897
E-mail: [email protected]

Manuel Rodrigues PEREIRA
Direcção-Geral das Florestas
Av.a João Crisóstomo No. 26-28
P-1050 Lisboa
Fax: (+351-1) 3124996
E-mail: [email protected]

Jean-Pierre PROTEAU
Unité de Recherche et d'expertise "Ressources Ichtyologiques"
361 rue J.F. Breton
F-34033 Montpellier Cedex 1
Fax: (+33-4) 67635795
E-mail: [email protected] 

Finnish Game and Fisheries Research Institute
Saimaa Fisheries Research and Aquaculture
FIN-58175 Enonkoski
Fax: (+358-20) 5751609
E-mail: [email protected]

Danish Institute for Fisheries Research
Dept. of Inland Fisheries
Vejlsoevej 39
DK-8600 Silkeborg
Fax: (+45) 89213150
E-mail: [email protected]

Direcção-Geral das Florestas
Av.a João Crisóstomo No. 26-28
P-1050 Lisboa
Fax: (+351-1) 3124996
E-mail: [email protected]

Finnish Game and Fisheries Research Institute
Saimaa Fisheries Research
FIN-58175 Enonkoski
Fax: (+358-205) 751 609
E-mail: [email protected]

Department of Marine and Natural Resources
Leeson Lane
Dublin 2
Fax: (+353-1) 6616798

Employment and Economic Development Centre for Central Finland
P.O.Box 44
FIN-40101 Jyväskylä
Fax: (+358-14) 4437335 

German Anglers Alliance
Eitelsdorfer Straße 32
D-12555 Berlin
Fax: (+49-30) 6561390

The University of South Bohemia
Research Institute of Fish Culture and Hydrobiology
Laboratory Pohorelice
Vídenska 717
69123 Pohorelice
Czech Republic
Fax: (+420-626) 424243
E-mail: [email protected] 

Vattenfall Utveckling AB
S-16287 Vällingby
Fax: (+46-8) 7396802
E-mail: [email protected]


Danmarks Sportsfiskerforbund
Worsåesgade 1
DK-7100 Vejle
Fax: (+45-75) 820209

Finnish Game and Fisheries Research Institute
Pukinmäenaukio 4
P.O.Box 6
FIN-00721 Helsinki
Fax: (+358-205) 751201
E-mail: [email protected]  

Frantisek VACHA
The University of South Bohemia
Research Institute of Fish Culture and Hydrobiology
37005 Ceské Budejovice
Czech Republic
Fax: (+420-38) 45146
E-mail: [email protected]

Ministerie van de Vlaamse Gemeenschap
Afdeling Bos en Groen
De Ferraris-gebouw, 4de verd.
Emiel Jacqmainlaan 156, bus 8
B-1000 Brussel
Fax: (+32-2) 5538105
E-mail: [email protected]

Fisheries Research Institute (HAKI)
P.O.Box 47
H-5541 Szarvas
Fax: (+36-66) 312142
E-mail: [email protected]

Álvaro Branco VASCO
Direcção-Geral das Florestas
Av.a João Crisóstomo No. 26-28
P-1050 Lisboa
Fax: (+351-1) 3124986
E-mail: [email protected]

Imperial College
8 Princes Gardens
London SW7 1NA
United Kingdom
Fax: (+44-171) 5895319
E-mail: [email protected]


Christian WOLTER
Institut für Gewässerökologie und Binnenfischerei
Abt. Biologie und Ökologie der Fische
Müggelseedamm 310
D-12561 Berlin
Fax: (+49-30) 64181750
E-mail: [email protected]

Zdzislaw ZAKES
Inland Fisheries Institute
Ul. Oczapowskiego 10
10-719 Olsztyn 5
Fax: (+48-89) 5272505
E-mail: [email protected]

Annex II

Abstracts of Contributions Submitted to the Symposium

( E - Experience Papers P - Posters )

Selected papers will be published in "Fisheries Management and Ecology"
EIFAC/XX/98/Symp. E 01

Drainage basin morphology:

Starting point for balancing water needs, land use and fishery protection


Malin Falkenmark1 and Jan Lundquist2

1 Stockholm International Water Institute, Stockholm, Sweden

2 Department of Water and Envonmental Studies, Linköping University, Sweden

The drainage basin including the coastal zone may be seen as a large-scale system of interlinked natural resources and ecosystem services that support human activities on land and in the sea. Social and economic activities in the drainage basin have to be consistent with the hydrological and ecological needs for human wellbeing. They also have to pay proper attention to their impacts on ecosystems downstream. A macro-scale ecosystem approach to a basin has to consider: i) direct uses of water both instream and after extraction when pollutants may be added to the return flow, and ii) indirect uses of water for agriculture where the river may be depleted and the water returned to the air through evaporation. Both uses have repercussions on the quantitative flow and quality of water which may damage water-based instream ecosystem services.

This paper addresses relations between different types of intervention and their consequences. Two analytic models are introduced: i) a conceptual model which distinguishes between urban and rural water uses and their respective tools, and ii) a conceptual model for handling spatially ordered land/water use segments subject to different types of interference. Finally the paper comments on the need for sustainable development to develop methodologies for cross-disciplinary dialogue and for balancing water needs, land use and fishery protection.

Keywords: Drainage basins; Water needs; Basin planning

EIFAC/XX/98/Symp. E 03

Balances of phosphorus and nitrogen in carp ponds


R. Knösche1, K. Schreckenbach1, M. Pfeifer2 and H. Weissenbach3

1Institute of Inland Fisheries, Potsdam-Sacrow, Germany

2Saxonian States Institute for Agriculture, Department of Fisheries, Königswartha, Germany

3Bavarian States Institute for Fisheries, Department for Carp Pond Culture, Höchstadt, Germany

The impact of pond effluents on natural waters is controversial. For this reason the federal states of Brandenburg, Saxony and Bavaria, investigated the impact of carp ponds on surface water using a standardised methodology. Hungary has collaborated with the study since 1997.

Data from 23 ponds (0.25 - 122 ha) are available for the calculation of inlet-outlet differences. An average difference of 0.68 kg P ha-1yr-1 was obtained. This means that every hectare of pond surface releases 680g P less than it receives with the incoming water. This result was independent of the amount of fish harvested (up to 1500 ha-1yr-1).

The average retention of phosphorus (P balance) was 5.1 kg P ha-1yr-1. Phosphorus retention increased with increasing production intensity. Nitrogen retention increases with production intensity form ranging from 42 kg ha-1yr-1 in German standard ponds to >290 kg N ha-1yr-1in pig-cum-fish ponds in Hungary.

A predominantly mineralised sludge suspension is released during harvesting at loads significantly below 1% of the retention capacity of the pond. Under usual pond management regimes the sludge load during harvesting ranges from 50 to 200 l ha-1. The corresponding load ranges from 2 to 10 g ha-1.

This study indicates that ponds are not a burden on the environment. By contrast they actually improve the water quality. Pressures to reduce the intensity of pond production can not, therefor, be justified on the basis of supposed impacts on water quality. However, even if loads during harvesting are low compared to the retention capacity of the pond more should be done to reduce the pollution of streams by pond outlets downstream. This can be done by limiting pond drainage to periods when the suspensoids have settled or by short-term sedimentation of the sludge in a special settling pond downstream of the rearing facility.

Keywords: Pond effluent; Aquaculture; Nitrogen retention; Phosphorus retention

EIFAC/XX/98/Symp. E 04


Impacts of long-term changes in fishery management

on the trophic level and water quality in Czech fish ponds


Libor Pechar

Applied Ecology Laboratory, University of South Bohemia, Ceské Budejovice, Czech Republic


Institute of Botany, Academy of Sciences, Trebon, Czech Republic

Management of Czech fish ponds changed little from the Middle Ages until the end of the 19th century. Fishpond ecosystems developed more or less naturally with little human interference. Modern breeding mechanisms were introduced during the first half of the century. During the 1930s liming and manuring of the ponds became common. A greater density of stocking led to applications of artificial foods in the form of pellets and grains. These changes in pond management led to an increase in fish production form about 50 kg ha- 1 yr-1 to more than 500 kg ha-1yr-1 over the last 5 decades. The trend towards higher stock densities and nutrient loads has resulted in shifts in species composition and productivity throughout the pond systems.

At the same time the quality of the water and the sediments is deteriorating and the functioning of the pond ecosystem is disturbed. There are now massive blooms of phytoplankton and particularly cyanobacteria accompanied by great fluctuations in oxygen concentration and pH. Excesses of some breakdown products such as ammonia have become more common and pose serious risks to the fish stock. These changes in management can be considered as a long-term experiment on pond ecosystems as there have been similar trends in stocking and fertilisation in most of the Czech fish pond regions. Data collected since 1925, when systematic research on the ponds was started, allows the mechanisms responsible for the observed changes to be traced.

Keywords: Aquaculture; Eutrophication; Czech Republic; Management


EIFAC/XX/98/Symp. E 05

An annotated checklist of introduced fish species in inland waters of Greece


P.S. Economidis1, E. Dimitriou2, R. Pagoni2, E. Michaloudi1 and L. Natsis2

1Aristotle University, Zoology Department, GR-54006 Thessaloniki, Greece

2Greek Ministry of Agriculture, Fishery Service, GR-11143 Athens, Greece

3Lake Pamvotis Municipal Foundation (DELI), GR-45500 Anatoli Jannina, Greece

Over the last 7 decades more than 10 exotic fish species have been introduced into the inland waters of Greece. Some introductions were deliberately planned to take advantage of particular ecological or economic qualities of the species concerned. These include rainbow trout, some Alaskan salmon, vendace, grass carp and silver carp. Other introductions such as that of the pumpkinseed and the false rasbora were unintentional. Further transfers were made of species between various basins within the country including carp, tench, crucian carp, bitterling and Aristotles catfish. Some species have become fully acclimatised and have built up important populations. In some cases the transfers and introductions have had considerable negative impacts particularly where introduced species have outcompeted native forms as in the case of the mosquito fish versus Greek toothcarp in the Western Grecian marshes and Aristotles catfish versus the wels in Lake Volvi.

Keywords: Introductions; Greece; Inland waters

EIFAC/XX/98/Symp. E 07

Aquaculture/agriculture systems integration - an Australian prospective


B.A. Ingram1, G.J. Gooley1, L.J. McKinnon1 and S.S. de Silva2

1Marine and Freshwater Resources Institute, Alexandra, VIC 3714, Australia

2 School of Aquatic Science & Natural Resources Management, Deakin University, Warrnambool, VIC 3280, Australia

With the global emphasis on ecologically sustainable development of natural resources within the primary production sector, it is logical to integrate irrigated agriculture practices in order to enhance productivity and efficiency of water use. Water is currently under-utilised in irrigated farming systems in Australia because it is routinely used only for a single purpose. Long term sustainability factors and water management costs to the community indicate that farmers will need to diversify and increase total farm productivity and profitability as well as to conserve water and other resources.

The possibilities of integrating aquaculture with irrigated farming systems is being evaluated in three projects in the Goulburn Murray Irrigation District (GMID), which covers 490,000 ha of irrigated farmland in south-eastern Australia.

Semi-intensive cage culture trials using silver perch are being undertaken in a range of irrigated farming systems including irrigation supply channels, groundwater supplies and on-farm storage dams. Diets, feeding rates, stocking densities, and initial size at stocking were examined during preliminary trials. Results indicate that both survival and growth of fish under these conditions are comparable, or superior in some cases, to fish reared in conventional aquaculture ponds. Water quality at some sites has contributed significantly to survival and growth.

A study is being undertaken to assess the feasibility of the cage culture of silver perch and rainbow trout in three public irrigation water storage reservoirs as part of a larger project investigating methods for enhanced fisheries production in Australian lakes and reservoirs. This study has shown that conditions within each storage, particularly water quality, wind and wave action, and cage fouling, have varied considerably and have had a major influence on the growth and survival of both species of fish.

In the GMID approximately 221,000 m3 yr-1 of mostly saline groundwater is pumped for irrigation purposes and to mitigate the effect of rising water tables and increasing salinity levels. Over the past three years, mariculture trials using a range of marine, estuarine and freshwater species have been undertaken in two saline groundwater evaporation basins, which are part of an integrated agriforestry and salt reclamation system. Species tested to date included 2 oyster, 2 prawn and 7 fish species. Some species have exhibited exceptional survival and growth rates under trial conditions.

These projects indicate that the integration of aquaculture with existing irrigated farming systems has the potential to enhance productivity, water use efficiency and overall environmental sustainability in the GMID. Future studies aim to address the potential impact of cage culture on water quality as well as overall cost-benefits of such operations.

Keywords: Aquaculture; Irrigation; Australia; Enhancement
EIFAC/XX/98/Symp. E 08

Improvements to pond management techniques

to enhance production of juvenile Australian native fish


B.A. Ingram and A.S.H. Gason

Marine and Freshwater Resources Institute, Snobs Creek, and Deakin University, Warrnambool,

Alexandra, VIC 3714, Australia

Production of juvenile fish in earthen ponds fertilised to provide blooms of plankton is relatively common and an integral part of most aquaculture operations. The fry of three species of Australian freshwater percichthyid fish (Murray cod, trout cod and Macquarie perch) are reared in fertilised earthen ponds at the Marine and Freshwater Resources Institute Snobs Creek Hatchery, Victoria for production of juveniles (35-55 mm in length). These juveniles are subsequently released into the wild to re-establish populations of endangered and threatened species and to enhance recreational fisheries.

Changes in, and relationships between, a range of ecological parameters (e.g. plankton bloom succession patterns) and certain water quality parameters (e.g. Nitrogen and Phosphorus concentrations, temperature, dissolved oxygen, pH, etc.) occurring within these ponds are complex and play a key role in the successful rearing of juvenile fish. A better understanding of how these parameters change and interact with each other, and how these could be managed to provide and sustain beneficial conditions, can improve pond productivity and, in turn, fish production.

Over the past seven years five ponds at the Snobs Creek Hatchery (and ponds at two other locations) have been studied to identify, describe and manipulate processes that may influence juvenile fish production. Data collected from over 100 pond fillings have included eight water quality parameters, phytoplankton, zooplankton and zoobenthos composition and abundance, and fish survival and growth rates for the three species of fish.

As a result of this study, changes to pond management procedures dictated by more stringent monitoring and management of water quality and zooplankton communities in the ponds have resulted in substantial improvements in pond productivity (water quality and plankton production) and associated fish production. Controlled fertilizer application, pond aeration and pond flushing, have reduced problems associated with undesirable or degraded water quality (e.g. high pH, high unionized ammonia and low dissolved oxygen). Consequently, production of juvenile fish has become more reliable and consistent as survival rates for all species have increased and become less variable since the study began. For example, survival rates for Macquarie perch have increased from an average of 48% prior to the study to 69%. This study has also identified fish stocking densities, fish size at stocking and timing of stocking, which will optimize growth and survival.

Keywords: Aquaculture; Ponds; Australia
EIFAC/XX/98/Symp. E 09

Fish farming in irrigation systems: an integrated and flexible approach


C.H. Fernando1 and Matthias Halwart2

1 University of Waterloo, Faculty of Science, Department of Biology, Waterloo, Ontario, Canada, N2L 3G1

2 Food and Agriculture Organization of the United Nations, Fishery Resources Division, 00100 Rome, Italy

Harvesting fish in irrigation systems, sometimes involving some form of husbandry or even culture, is a practice that dates back at least two millennia. Though seldom recorded it seems to have been widespread in the tropics and subtropics, especially in rice fields. In this century, improved management for land-based crops and the demands for the successful raising of aquatic organisms were not generally compatible, but with the advent of integrated crop protection this situation has changed drastically. Moreover, irrigation systems using stored or diverted water have increased exponentially during the past half-century but fish farming within these irrigated systems has not expanded equally so that today there is a huge potential for this integrated enterprise. We propose a systematic approach to fish farming development at irrigation system level that will make this integration a viable enterprise.

The whole range of aquatic habitats created by irrigation systems can be integrated with fish farming. Small and large irrigation reservoirs, the extensive network of irrigation canals, the irrigated fields themselves as well as adjacent ponds or aquatic refuges of various sorts are all potential sites for nursing or grow-out of fishes. In many countries there is now relatively easy access to fish seed even in inland areas. Permanent water bodies should be combined with a central pool of culture species harvested from short-lived habitats that serve as nurseries. A flexible system of moving culture fishes within the system of habitats should be feasible. For example, stocking material for reservoirs can be obtained from irrigated rice fields where the short maturation period of the crop only permits the harvest of fingerlings. If a pragmatic and flexible approach is made to use all habitats for fish production there could be a year round supply of fish and a minimum wastage of stocks of cultured fish.

The use of high yielding fishes of good quality is essential for economic viability. In areas where a high diversity of fishes with a requisite biomass of desirable species already exists, these indigenous fishes can be harvested but their yields may only be adequate for low income rural areas. Common carp has traditionally been a preferred cultured species. We propose tilapias as an alternative since they are cheap to raise, give high yields, and are also palatable.

Aside from economic revenues, this type of integration also involves ecological and social benefits. High densities of fishes in irrigation systems enhance the yield of land crops, alleviate the pressure of terrestrial and aquatic pests, and lower the populations of vectors of diseases of man and domestic animals.

The chequered history of fish farming in irrigation systems has been due to many factors. However, major constraints have been removed and there is new scope for a more efficient use of irrigation water combined with a better integration of terrestrial and aquatic food crops. Raising and harvesting fish from the whole range of irrigation facilities and created habitats is a feasible proposition that holds great prospects for a sustainable development.

Keywords: Aquaculture; Enhancement; Irrigation; Rice-fish farming
EIFAC/XX/98/Symp. E 10

Water use and conservation for inland aquaculture ponds


Claude E. Boyd and Amit Gross

Department of Fisheries and Allied Aquacultures, Auburn University, Alabama 36849, USA

The general hydrologic equation, inflow = outflow ▒ change in storage, can be used to make accurate estimates of water use by ponds for inland aquaculture projects. The primary inflows are precipitation, runoff, and regulated water additions. The main outflows are evaporation, seepage, overflow after storms, and intentional discharge. Direct estimates of rainfall are available in most regions. Watersheds for embankment ponds (levee ponds) are limited to insides and tops of embankments and runoff into ponds is negligible. Runoff into watershed ponds may be estimated using climatic data and the water accounting method or predicted by the curve number technique that takes into account both climatic conditions and runoff producing characteristics of watersheds. Evaporation predictions may be obtained from evaporation pan data normally available in a region. The pan coefficient for estimating evaporation from small ponds is 0.8 rather than the value of 0.7 typically used for lake evaporation estimates Seepage estimates can be made by measuring seepage in existing ponds in the area or predicted from soil characteristics. Storm overflow may be estimated from direct rainfall, runoff potential, and capacity of ponds to store runoff. The amount of intentional discharge is determined from management plans. An equation can be made that will permit estimations of regulated water addition from wells, streams, or other water bodies necessary to maintain the proper depth of water in all types of ponds. Water conservation measures such as maintaining storage capacity in ponds equal to the normal, maximum daily precipitation, reduction in seepage beneath dams and through pond bottoms, fish harvest without draining ponds and water reuse will be discussed. Even with implementation of water conservation measures, pond aquaculture is a water intensive endeavour that consumes more water per unit area than irrigated agriculture. Reduction in effluent volume not only reduces water consumption, but it reduces the pollution potential of pond aquaculture.

Keywords: Aquaculture; Water conservation; Inflow/outflow relationships
EIFAC/XX/98/Symp. E 11

Low water discharge ponds


Yoram Avnimelech

Dept. of Agricultural Engineering, Technion, Israel Institute of Technology, Israel

The use of intensive fish farming systems, which aim to save water and land, and to increase production and profits, is expanding. A common methodology to maintain water quality in such ponds is to change the water a few times a day, thereby removing unwanted metabolites from the system. For this large amounts of water are needed. In addition, this approach places a burden on the environment and its use is limited since the disposal of pond effluents is not allowed, or restricted, by the environmental authorities in most countries. This limitation will probably hold everywhere in the near future. Different alternatives for low or zero discharge systems are presented and analysed here. This review is based in part upon aquaculture experience in Israel, where limitations in water availability encouraged the development and operation of zero discharge systems.

The main features, advantages, limitations and suitability to different sets of conditions of the following technologies are discussed:

1. Intensive - extensive systems based upon the recycling of water between intensive ponds and a reservoir used as a water treatment component.

2. Biofiltration systems where the water is cycled through a device to filter out suspended particles and to biodegrade organic components, ammonium and nitrites.

3. Low exchange, intensive ponds with a daily water exchange rate of up to 20%. Biological water treatment is taking place within the aerated, mixed water, similar to many industrial bioreactors. Nitrogen control and protein recycling is possible through feed composition adjustment.

Keywords: Aquaculture; Recycling systems; Zero discharge; Pollution
EIFAC/XX/98/Symp. E 12

Efficiency of existing oxbow lake management systems in Bangladesh

to introduce cage culture for resource poor fishers


M.A.K. Chowdhury and A. Yakupitiyage

Agricultural and Aquatic Systems Program, AIT, Pathumthani 2120, Thailand

A total of 5488 ha of oxbow lakes in the delta of the River Ganges have recently gained importance as a potential fishery resource. There is a growing need to utilize this resource sustainably to its full potential. Cage aquaculture by resource poor or fisherfolk is being considered as a complementary activity to existing stock enhancement programs. Existing management systems of eight different lakes are reviewed in this study. Water quality issues are analysed on the basis of the largest lake- Baluhar, to assess suitable and problem areas for cage culture. Transparency of Lake Balahur was above 100 cm during the study period that indicates its suitability for low volume high-density cage culture. Other water quality parameters, specially dissolved oxygen, pH, ammonia and nitrite records were also suitable. Non fisheries activities, such as the use of agricultural pesticides in the lake catchment and jute retting in its basin, are identified by the majority of fisherfolk as the most harmful to fish. It is recommended that an Integrated Pest Management (IPM) programme, using rice-fish based nursery systems in the lake catchment, be promoted to encourage the reduction of the use of pesticides. It is further recommended that a unified management system replace the existing dispersed systems under different management bodies.

Keywords : Oxbow lake; Cage culture; Bangladesh; Lake management
EIFAC/XX/98/Symp. E 31

Water quality management in semi-intensive fishpond of Bangladesh


M Anwar Hossain

Department of Fisheries, Mohammadpur, Dist. Dhaka Country, Bangladesh

Bangladesh is rich in pond fisheries. The range of temperature, rich soil, abundant water and the fast growing carp species make it possible to grow fish all year round. There are about 292,744 ha of ponds in the country. Most of the ponds are borrow pits, constructed for raising the foundation of the homesteads above flood level. Village ponds are using for bathing, washing, drinking, cooking, small-scale agriculture and animal husbandry. Because of poor water quality management the production level is low (about 4000 kg ha-1 yr-1) when compared with other South East Asian countries. The success of aquaculture depends to a considerable level upon sound water quality management. Pond water can be consider excellent at pH 6.5-9.0, Transparency 20-40 cm, Oxygen 5.0-8.0 mg l-1, Carbon dioxide 0.5-1.0 mg l-1, Alkalinity 100-300 mg l-1, Phosphorous 0.5-1.0 mg l-1, Phytoplankton 40,000-45,000 l-1 and Zooplankton 2000-3000 l-1. At these values survival, reproduction and growth of fish are sustainable. Semi-intensive culture calls for higher stocking rates with larger size fingerlings, regular use of fertilizer and supplementary feed, partial harvesting and immediate restocking. Pollution takes place as the rainwater carries silt, vegetable matter, manure, faeces, garbage and agricultural insecticides into the pond water. This increases pH, decreases DO concentration, lowering plankton productivity and generally adversely effects the pond ecosystem. Toxicity of many substances such as NH3 and H2S are greatly influenced by the pH of the water. There is now a trend among pond owners to use lime to increase pH, prevent disease and reduce the capacity of sediment to bind plant nutrients. Higher sediment pH values also create more favourable condition for microbial growth. Summer kills of fish are a major problem in the semi-intensive fishponds in Bangladesh. These occur because of oxygen depletion in the fishpond due to excessive use of fertiliser and accumulation of decaying organic matter on the bottom. A productive pond will typically have super saturated DO at the late afternoon and undersaturated DO at dawn. Maximum fish production rates are possible under these conditions provided that the nighttime level does not fall below 1 to 2 mg l-1. Workers and researchers should conduct awareness, training and extension programs at the village level to disseminate the water quality management package to pond owners.

Keywords: Bangladesh; Aquaculture; Water management
EIFAC/XX/98/Symp. P 01

Effect of body weight on oxygen consumption and ammonia excretion by juvenile pikeperch, Stizostedion lucioperca (L.) (Percidae) reared in recirculating water system


Zdzislaw Zakes

Inland Fisheries Institute, 10-719 Olsztyn, Poland

The effects of body weight on oxygen consumption and ammonia excretion by juvenile pikeperch was estimated by using fish obtained by artificial reproduction reared in a recirculating water system at the experimental hatchery of the Inland Fisheries Institute in Olsztyn. The fish were kept in circular tanks with a volume of 0.2 m3. Oxygen consumption [(OC) mg O2 kg-1 h-1] and ammonia excretion [(AE) mg TAN kg-1 h-1] were calculated from the difference in dissolved oxygen (DO) and total ammonia nitrogen (TAN = NH4-N + NH3-N) concentrations between the influent and effluent waters. Samples were taken at 60-minute intervals, taking into consideration the flow rate, tank volume and fish biomass present in the rearing tanks. The experiments took place in June, July, August and September for groups of fish of 1.6, 7.1, 17.3 and 38.1 g [body weight (BW)], respectively.

For pikeperch reared at 22 C with continuous (18 h per day) feeding with trout dry feed, mean AE and OC rates decreased from 38.67 mg TAN kg-1 h-1 and 701.4 mg O2 kg-1 h-1 for fish weighing 1.6 g to 11.94 TAN kg-1 h-1 and 243.36 mg O2 kg-1 h-1 for fish weighing 38.1 g. Significant differences in AE and OC (ANOVA and Scheff's test, P < 0.001) were found among the groups. AE was directly proportional to OC - the regression equations were very highly significant. The mean oxygen/feed ratio (OFR, kg O2 consumption kg-1 of feed fed day-1) and ammonia/feed ratio (AFR, kg TAN kg-1 feed fed day-1) were calculated. Juvenile pikeperch (1.6 g BW) produced an estimated 0.572 kg O2 kg-1 feed day-1 and 0.0315 kg TAN kg-1 feed day-1. Fingerlings (38.1 g BW) produced 0.154 kg O2 kg-1 feed day-1 and 0.0076 kg TAN kg-1 feed day-1, respectively. The mean rates of ammonia excretion and oxygen consumption (mg TAN or O2 kg-1 h-1) were related to body weight (BW in g) using relations:

AE = 46.41 BW-0.3682 (R2 = 0.9734)

OC = 831.97 BW-0.3512 (R2 = 0.9842)

Keywords: Aquaculture; Recirculating systems; Oxygen consumption; Ammonia excretion
EIFAC/XX/98/Symp. P 04

Efficiency and economic performance of microstrainers for waste water treatment

in rainbow trout production


H. Wedekind and R. Knösche

Institute of Inland Fisheries Potsdam-Sacrow, Jägerhof am Sacrower See, D-14476 Groß Glienicke, Germany

Commercially available microstrainers were tested under conditions of simulated use with rainbow trout. The removal efficiency was calculated for suspended solids, sludge dry matter residuals, and for several chemical water quality criteria (COD, N- and P-compounds). Different mesh sizes and varying waste loads were investigated in a series of experiments. The cost of investment, the operational costs and the economic performance were also analysed.

The results indicate that the microstrainers led to a significant removal of suspended solids and to a reduction in phosphorous in the wastewater. The amount of rinsing water and the removal efficiency for particles were directly related to the waste load at the filter inlet. The volume of sludge collected varied considerably under different experimental conditions.

The economic performance of wastewater treatment by microstrainers was calculated for different filters and production levels. Their impact on the production costs for rainbow trout will be presented and discussed.

Keywords: Microstrainers; Trout culture
EIFAC/XX/98/Symp. P 08

Effluent loadings from post-harvest flow-through storage facilities

for unfed marketable carp


I. Stibranyiová and Z. Adámek

Research Institute of Fish Culture and Hydrobiology, University of South Bohemia,

Laboratory Pohoø elice, 691 23 Pohoø elice, Czech Republic

Effluent loadings in two flow-through winter storage facilities for post-harvest unfed marketable carp (1.7 0.3 kg) were investigated over 173 days. Holding basins ranged between 144 to 600 m3 with flow rates of 0.2 - 8.3 l t-1 fish biomass s-1, water temperatures of 0 - 10 ░C and fish biomasses of 1 - 60 t. The quality of the outflow water appeared to be little affected by culture conditions. Dissolved oxygen (DO) decreased by 3.29 mg l-1 and 410 g t-1day-1 at average flow rates of 1.7 l t-1s-1 and was correlated with flow rate (p<0.05) of water and storage time (p<0.01) of carp. The average pH was lower by 0.15 in the outflow than in the inflow water and there were effects of temperature (p<0.001), storage time (p<0.01) and DO uptake (p<0.001). Organic loadings were 0.6 mg l-1 and 37 g expressed as biochemical oxygen demand and production decreased with decreases in water temperature and increases in storage time (p<0.01). The chemical oxygen demand increment was 0.6 mg l-1 and 69 g t-1day-1. The concentration of total ammonia nitrogen rose by 0.08 mg l-1 and 18 g t-1day-1. Orthophosphate and total phosphorus discharge reached 0.01 mg l-1 and 1 g t-1day-1 and 0.05 mg l-1 and 9 g t-1day-1, respectively.

Keywords: Aquaculture; Carp; Effluents; Water quality

EIFAC/XX/98/Symp. E 13

Aspects of Fisheries and Water Resource Management in England and Wales


Simon Hughes1 and Steve Morley2

1 National Coarse Fisheries Centre, Environment Agency, Kidderminster, DY11 7RA, UK

2 Environment Agency Midlands Region, Solihull, West Midlands, B91 1QT, UK

The Environment Agency in England and Wales has wide ranging duties and powers relating to environmental regulation and management, including freshwater fisheries and water resources.

Freshwater and migratory fish populations in England and Wales form a significant resource, and are exploited by commercial and recreational fisheries. Results of recent research suggest that up to 2.9 million anglers are involved in the recreational fishery. The resource consists principally of indigenous and naturalised cyprinids, but also includes strongholds of species endangered elsewhere in Europe such as bullhead (Cottus gobio L.); species of high ecological value such as Atlantic Salmon (Salmo salar L.) and commercially important species such as eels (Anguilla anguilla L.). Each component of this resource is under pressure from a range of sources including water abstraction, habitat modification, land use change, chronic and sporadic water pollution and climate change.

Water resources perform a key role in sustaining the European economy. They are under significant pressure and the past 32 months of drought has exposed the relative fragility of water supply systems. Climate change is a major concern and is driving a re-assessment of water supply yields. The Agency needs accurate assessments of environmental requirements to strike the right balance between the needs of aquatic ecosystems and of economic efficiency.

There are no objective methods available to predict changes in fish communities likely to arise from different water resource management options, other than for relatively simple systems. A case study describes the Agency's response to proposals for strategic water resource development options centred on a highly regulated lowland river.

The paper concludes that Fishery managers have a poor understanding of the factors that influence most types of fish community due to the complex nature of aquatic ecosystems and the fact that they comprise variable and harsh sampling environments. Consequently it is extremely difficult to manage water resources using anything other than a precautionary approach. Some steps that may mitigate this position are outlined.

Keywords: Inland fisheries; Water management
EIFAC/XX/98/Symp. E 14

Potential impact of groundwater augmentation of river flows on fisheries:

A case study from the River Ouse, Yorkshire


I.G. Cowx

University of Hull, International Fisheries Institute, Hull HU6 7RX, UK

Many lowland rivers in the UK are under increasing pressure from abstraction of water for potable supply or irrigation. Many schemes, existing and proposed, attempt to mitigate the loss of flow by augmentation from upstream reservoirs or pumping of groundwater into adjacent rivers. The impact of flow regulation by reservoirs is well documented but little attention has focussed on the effect of groundwater augmentation on the biota, particularly fisheries, in the receiving river. This paper examines the potential effects of pumping groundwater into minor tributaries of the Yorkshire Ouse in England on the cyprinid fisheries downstream of the discharge points and in the main river channel. Concerns were raised with respect to poor water quality and reduced water temperature. In particular it was predicted that small reductions in river water temperature brought about by discharge of cold (10░C and less) groundwater would have serious detrimental effects on cyprinid recruitment and juvenile growth in the receiving river leading to a decline in the stocks.


Keywords: Inland fisheries; Groundwater; Temperature

EIFAC/XX/98/Symp. E 15

Long-term effects of river regulation and anthropogenic degradation

on fish community structure and fisheries in urban watersystems


C. Wolter1, J. Minow2, U.A. Grosch3 and A. Vilcinskas2

1 Institute of Freshwater Ecology and Inland Fisheries, D-12561 Berlin, Germany

2 Institute of Zoology, Free University of Berlin, D-14195 Berlin, Germany

3 Berlin Fishery Board, Havelchaussee 149/151, D-14 055 Berlin, Germany

Statistics of commercial catches of the last two decades were analyzed and compared with hydrological and water morphological conditions to identify the cause of changes in fishery production in Berlin waters. Additional data were provided by a fish monitoring programme, which covers 160 representative waters in the whole Berlin territory, the first large-scale survey of fish assemblages in lowland waterways, and unpublished surveys between 1994 and 1997.

The urban parts of Berlin are densely populated and the waters are under high anthropogenic pressure including shipping, hydraulic engineering, pollution, leisure-time and recreation use.

Most Berlin waters are polytrophic or hypertrophic with an annual nutrient input of 595 t total phosphorous and 8640 t total nitrogen.

A total of 34 fish species have been recorded, 8 of them allochthonous. According to historical records 7 autochthonous fish species, including all the anadromous species, are now extinct or missing. Today the fish community is dominated by very few eurytopic species, roach, common bream, white bream and perch, which contribute more than 85 % of all individuals caught.

Two "faunal breaks" could be characterized in the changing fish community structure over time. The first was the changing of river characters from barbel to bream zone caused by damming and river regulation. This started in the 13th century and ended at the beginning of our century with the extinction of the anadromous fishes. The second break was during the 1960s and 1970s, with the eutrophication of Berlin waters and the near total loss of submerged macrophytes. All phytophilic fish species declined dramatically and a mass development of eurytopic species started. The catch of pike, common carp and tench became negligible and today eel and pikeperch are the main commercial fish species. Parallel to the changes in the fish community structure the profitability of fisheries production decreased. This caused a decline in the number of persons employed in fisheries of more than 75 % since 1950.

Keywords: Inland fisheries; River regulation; Fish community structure; Urban waters
EIFAC/XX/98/Symp. E 16

Commercial fisheries versus water quality in lakes, with special reference

to coregonid management


Maria Bninska

Inland Fisheries Institute, 10-719 Olsztyn 5, Poland

Environmental agencies in Poland have adopted a new system, based on a ranking procedure, for classifying the quality of lake ecosystems. The new system is used alongside the old one. It divides the lakes into four categories of water quality: i) first category (high quality, pure water) < 1.50 points; ii) second category (moderately polluted) < 2.50 points; iii) third category (low quality, polluted) < 3.25 points, and iv) fourth category over 3.25 points - degraded. This new system has been used to analyse commercial fisheries, and especially coregonid management, on the basis of water quality.

Data were collected from 38 lakes that had been subject to environmental quality controls in the period 1985-1994. Data on commercial fisheries in these lakes were collected for the 27-year period between 1968 and 1994. They comprised detailed statistics of fish catches by species and size-categories, and numbers stocked in the lakes.

The lakes were divided into two groups, high and low quality, based on the mean point score for the whole sample (2.273 points). The group of good-quality lakes (< 2.273 points) included 22 lakes of total area 15 520 ha, that of low quality (> 2.273 points) included 16 lakes of total area 10 967 ha.

Statistical analyses were performed on the two sets, as well as on the whole sample.

The two groups differed significantly (one- and two-way t statistics) not only with respect to water quality parameters, but also the effectiveness of fisheries management. In low-quality lakes more stocking material (in terms of numbers) was needed to obtain 1 kg of coregonid catch. Commercial yield of coregonids (whitefish and vendace) amounted to 7.07 kg ha-1yr-1 in good-quality lakes, and made up 28.4% of total fish landings, while in the low-quality group the respective values were 5.86 kg ha-1yr-1 and 19.0%. The effectiveness of vendace stockings depended significantly on only one environmental parameter, the chlorophyll content of the water: at higher chlorophyll levels (and thus also primary production levels) more larvae were needed to produce 1 kg of commercial catch.

Keywords: Inland fisheries; Stocking rates; Commercial fisheries
EIFAC/XX/98/Symp. E 17

Some preliminary results of stocking with Mugil cephalus in several Greek lakes


D.C. Bobori1, I. Rogdakis2 and P.S. Economidis1

1 Aristotle University, Zoology Department, GR-540 06 Thessaloniki, Greece

2 Aquaculture Center of Acheloos, GR-30001 Neochori Mesologiou, Greece

This study examines the possibility of using some Greek lakes as extensive mullet farms. The growth of Mugil cephalus Linnaeus, 1758 was studied in three lakes (Volvi, Pamvotis and Amvrakia), as well as in fish cages in the Mesolongi lagoon. Stocking material originating from both a hatchery and from fishing in the river Acheloos estuary was released in lakes in early summer. Measurements were taken during the period June 1995-April 1996 in lake Volvi and June 1996-April 1997 in the other two lakes. Different patterns of growth were observed. Increase in weight was substantial in all samples from the lakes, especially during the first months. Increase in weight diminished notably during the cold period. The length-weight relationships, the condition factor K, the gonadosomatic index and the hepatosomatic index, were also estimated from samples from Lake Volvi. The preliminary results revealed that Mugil cephalus adapted easily to freshwater environments, where it grows well. It is concluded therefore that stocking of lakes with fry of this species is effective for the enhancement of fishery production. There also appear to be no harmful ecological side effects.

Keywords: Stocking; Mugil cephalus; Fisheries enhancement; Lakes; Greece
EIFAC/XX/98/Symp. E 19

Water outflow as a cause for changes of trophic conditions

for zooplanktivorous fishes in reservoirs


Luchezar Pehlivanov

Institute of Zoology, Bulgarian Academy of Sciences, 1000 Sofia, Bulgaria

The seasonal changes and vertical distribution of zooplankton, the export of zooplankters by outflow through water management installations and the feeding of zooplanktivorous fishes were studied in two Bulgarian reservoirs.

In a bottom drained reservoir planktonic crustaceans larger than 1.0 mm were found to be selectively exported as a result of their diurnal vertical migrations. Increases in water outflow for irrigation resulted in a decrease in total zooplankton abundance, as well as in changes in zooplankton size and species composition in June. In the same time drastic changes occurred in the feeding patterns of bleak and juvenile pikeperch - the principal zooplanktivores in this reservoir. It is easy for bleak to switch toward feeding on phytoplankton and aerial insects but a deficiency in available large prey organisms is suggested as the main cause of down-stream movement in pikeperch juveniles. This migration through the drain contributed to mortality in this species.

In the other reservoirs studied water is discharged from the surface and changes in abundance and composition of zooplankton corresponded to those occurred in natural lakes. Changes in the trophic responses of zooplanktivores (mainly the juvenile cyprinids and percids) were equally not found. Outflowing water carries with it mainly small-sized zooplankters from the groups (rotifers, small cladocerans, juvenile copepods) most numerous in the superficial water level of the reservoir. Furthermore, outflow exports a relatively small part of total zooplankton number and thus does not disturb the natural zooplankton succession.

Keywords: Artificial lakes; Zooplankton; Discharge
EIFAC/XX/98/Symp. E 30

Dynamics of population parameters of Coregonus lavaretus related with eutrophication

of Lake Sevan (Armenia)


Bardukh Gabrielian

Institute of Hydroecology and Ichthyology, Yerevan 375019, Armenia

Data on stocks and catches of the main commercial fish species of Lake Sevan are analysed for the period from 1976 to 1995. It is shown that the state of the Coregonus lavaretus population depends mainly on the conditions for survival of juveniles at the early stages of development. These conditions, in turn, are closely related to the changes in the physical and chemical composition of the lake's water associated with the eutrophication of the reservoir. Negative changes have occurred in the reservoir's ecosystem as a result of unprecedented increases in fish catch and the continuous extraction of water for energy generation and irrigation in the 90s. The have affected the equilibrium among the various trophic levels which has increased the process of eutrophication of the lake.

Keywords: Eutrophication; Lakes; Coregonus lavaretus

EIFAC/XX/98/Symp. E 20

Finnish lake fisheries and conservation of biodiversity - co-existence or conflict?


Pekka Salmi1, Heikki Auvinen1, Matti Sipponen2 and Juha Jurvelius1

1 Finnish Game and Fisheries Research Institute, Saimaa Fisheries Research, FIN-58175 Enonkoski, Finland

2 Employment and Economic Development Centre for Central Finland, FIN-40101 Jyväskylä, Finland

The conservation of aquatic biodiversity and the protection of endangered species have become increasingly important challenges in the management of water resources. There is constant tension between the users and conservationists of the aquatic resources. This paper focuses on the interaction and conflicts between the fishery and the protection of endangered species in the lakes of Eastern Finland drawn from three case histories.

The endangered Saimaa seal (Foca hispida saimensis), numbering about 200 individuals, inhabits the central parts of the Saimaa lake system. Conservational measures have been adopted in Lake Pihlajavesi, with a population of 50 seals, because young seals are caught as by-catch in the mostly recreational gill net fishery. The endangered population of Lake Saimaa Arctic char (Salvelinus alpinus) has a small self-reproducing population left in Lake Kuolimo and attempts have been made to re-establish this species in other parts of the Saimaa lake system. Natural reproduction of the land-locked salmon (Salmo salar saimensis) has been prevented by the construction of a hydroelectric dam during the 1960's. The population has been kept alive by maintaining brood stock in hatcheries and by collecting spawners from the river mouth. However, the number of adult fish trying to enter the spawning river is low and the sub-species can be regarded as endangered because of high fishing mortality during the feeding migration, which covers wide areas of the Saimaa Lake system.

Finnish lakes are exploited by multi-species fisheries involving a range of fishing methods and user groups. The problems in each case described in this study arise especially from the use and regulation of gill net fisheries. The gill net is a popular means of fishing among the recreational, subsistence and commercial fishermen. The lake fisheries in Finland are managed primarily by a large number of local and regional institutions. Our study deals with the attitudes towards and awareness of the need for protection among the users and other interested parties, the possibilities for the management regime to support biodiversity and sustainable use of resources and the opportunities for co-operative arrangements among the interest groups. We also analyze the proposed system of zoning the activities between different lake areas.

Keywords: Inland fisheries; Lake management; Conservation policy
EIFAC/XX/98/Symp. E 21

Restriction of the circulation of small pleasure-boats on the rivers of Wallonia (Belgium)


B. De Bast and P. Gérard

General Directorate for Natural Resources and Environment, Ministry of the Walloon Region,

B-5100 Jambes, Belgium

The Regional Authorities of the Walloon Region (South of Belgium) regulated the circulation of pleasure-boats, particularly kayaks so as limit the conflicts between different users of rivers (nature conservation, recreational fishery and canoeing). The regulation was promulgated in 1994 using the federal law of 1973 on nature conservation as its basis. It was made necessary by the recent and important development of river based recreational activities and by the need to protect the aquatic environment, the river and the associated fauna and flora.

Limitations are determined according to season, flow and time of the day. Authorized types of boat are described, and the conditions for access to the embarkation and disembarkation sites along the river are set out. The general limitations to canoeing on the rivers are fixed as follows:

Minimal flow rates have been determined for rivers of intermediate importance, where the necessity of the protection is the highest because of the very high activity of rented kayaks and risk of overcrowding the river. When the flow is reduced to the minimal rate, navigation is automatically prohibited. The minimal flow rates were assessed by direct observations at reference sites under different hydrological conditions. Moreover, the Ministry of the Environment may impose the local closure of navigation for nature conservation. An information system allows the kayak operators and the sportsmen to be informed daily on the possibilities for navigation.

Keywords: Boats; Rivers; Resource use conflicts
EIFAC/XX/98/Symp. E 22

Instream flow requirements in Sweden


Björn S. Svensson

Vattenfall Utveckling AB, S-162 87 Vällingby, Sweden

Standardised methods for determining instream flow needs in connection with hydropower development are still not established in Sweden. However, claims related to conflicting uses of running waters have long engaged the Water Right Courts. Historically, the floating of timber has constituted a strong reason for regulating rivers. Later, the creation of large reservoirs and the subsequent alteration of the natural river flow have mainly been related to the generation of hydroelectricity. During the last decades the expectations of stakeholders have also been directed to recreational fishery and maintenance of biodiversity. Dry channels below diversion points are no longer considered acceptable. Swedish legislation allows for regular review and reissue of permits to regulate rivers and operate hydroelectric power plants. However, it is only possible to enforce changes that are economically reasonable. The maximum loss of electricity that must be endured by a producer without reciprocal demands for compensation amounts to 5%.

Fisheries may nowadays be regarded as the second most important use of riverine resources. The accumulated knowledge of fish ecology makes it possible to use models for the management of populations. However, decisions regarding minimum releases of water are usually still based on the natural hydrography rather than on documented relationships between fish yield and the characteristics of the watercourse.

During the past seven years Vattenfall, the largest producer of hydroelectricity in Sweden, has been carrying out R&D activities to test, improve and introduce instream flow methods for the management of regulated rivers. Experiences regarding biotope adjustments as an alternative to increased releases of water are presented and economic and biodiversity aspects are discussed.

Keywords: Instream flow methodologies; River rehabilitation; Legislation; Economics; Biodiversity
EIFAC/XX/98/Symp. E 23

Effects of irrigation and agriculture run-offs on the Evinos River delta in central-western Greece: A case study of conflicts between agriculture, fisheries and aquaculture


Alexis J. Conides1, Kostantinos Bogdanos1, Ierotheos Zaharias1,

Effrosini Diapouli2 and Aristidis Diapoulis1

1 National Centre for Marine Research, Agios Kosmas, Hellinikon, 166 04 Athens, Greece

2 Ministry of Agriculture, Karaoli & Dimitriou 15, 18531 Piraeus, Greece

Aquaculture and small-scale artisanal fisheries have always been affected by other coastal human activities, such as industry, urban development and agriculture, through the excessive run-off that is discharged into receiving water bodies. It is well established that river deltas are key fishery ecosystems that play a very important role as pathways for migrating anadromous and catadromous fish. They are also the areas that receive the fry of most marine and freshwater species during their early life stages. Excessive run-off from intensive agriculture on the adjacent land area can cause tremendous alterations in water quality affecting significantly the biodiversity of all parts of the river. This study describes the situation in the delta of the Evinos river related to the current land use profile and irrigation scheme. The main problems arising from the discharge of wastewater both in the upper river area as well as into the sea without pre-treatment, are identified through a flux model. The final effects on the water quality of the river delta and upper river area are modelled and possible impacts on aquatic organisms are estimated. Finally, a proposal is made for sustainable agriculture practices in the area, which aim to eliminate adverse effects on river-based aquaculture and fisheries.

Keywords: Resource use conflicts; Agriculture; Aquaculture; Inland fisheries
EIFAC/XX/98/Symp. E 24

On the problems of water resources management of the Russian southern rivers from the standpoint of fisheries


V.G. Dubinina1 and S.V. Kozlitina2

1 Interdepartmental Ichthyological Commission, Moscow, 103050, Russia

2 Azov Research Institute of Fisheries, Rostov-on-Don, 344007, Russia

Depleted fish stocks in freshwater bodies and inland seas of Russia are primarily a consequence of intensive river-flow regulation by hydropower dams and irrational utilisation of river water resources. This paper summarises the results of mathematical simulations of the hydrological and ecological impacts of the construction of hydropower stations and the irreversible withdrawal of river-flow on the state of spawning grounds and water ecosystems of the Caspian and Azov Seas basin. The degree to which unfavourable conditions have arisen in the aquatic ecosystems is emphasised. The paper is based upon the authors' data on the Don River and on joint studies on the Kuban River and the rivers of the Caspian basin.

This analysis makes it possible to draw the following conclusions:

1. Most of the adverse effects of water management in the river basins were shown not to be inevitable. They might have been avoided, as the considerable regulatory capacity of the many water bodies is sufficient to permit management of the water regime to protect spawning grounds downstream.

2. Natural fish reproduction is an index of proper aquatic ecosystem function and may be used as the main criterion for river water management. In particular it can be used to determine permissible quantities for river-flow withdrawal. Under these conditions the fundamental requirement is for the conservation of an ecologically secure state and for sustainable aquatic ecosystems. In this context the standard for irreversible river-flow withdrawal must be a constant value in years of variable flow probability. It should not exceed natural long-term fluctuations. Then the conditions that enable fish reproduction reach their critical level only in particularly dry years (close to 90-95% river-flow probability).

3. A series of hydrological, physico-chemical and biological characteristics have been taken as secure and critical ecological indicators for aquatic ecosystems. These include: river discharge and flow in years of 25, 50, 75, 90 and 95% river-flow probability; quantity and duration of floods; areas of floodplain and delta inundated; water regime parameters such as, current velocity, depth, temperature, turbidity, oxygen regime, etc., various biological characteristics including population dynamics, stock size, catches and commercial return to the fishery of selected year-classes.

The requirements for an outlet of water bodies (bay, sea, lake etc.) for river-flow must also be considered and secure and critical ecological ratings depend on such indicators as level regime, salinity, the availability of fattening and feeding areas of juvenile and adult fish and fish productivity.

4. Analysis of optimal, normal and critical changes in the river water regime enables the quantity and timing of water needed for the reproduction and conservation of fish species of commercial value. It was shown that:

5. Data for 1981-1990, showed that the volume of irreversible withdrawal of river-flow in the Kuban River basin exceeded the predetermined standard by 2.5 times (ecological disaster). In the Lower Don River by 2 times (ecological crisis), in the Ural River by 1.5 times (ecological risk) and in the Lower Volga basin it approached the critical level.

Standards developed for irreversible withdrawal of riverflow and for flush volumes formed the basis for a revision of "The regulations for water consumption from water bodies". A programme has been set up for a stepwise returning of water to the damaged river systems in an effort to increase the effectiveness of natural reproduction of anadromous and semi-anadromous fish in the Caspian and Azov Seas.

Keywords: Flow criteria; Inland fisheries; Indicators; Volga River; Kuban River; Don River; River-flow withdrawel
EIFAC/XX/98/Symp. E 25

Threats imposed by water resources development schemes on the conservation of endangered fish species in the Guadiana River Basin in Portugal


M.J. Collares-Pereira1, I.G. Cowx2, F.Ribeiro1, J.A. Rodrigues1 and L. Rogado3

1 Centro de Biologia Ambiental, Faculdade de Ciências, 1700 Lisboa, Portugal

2 University of Hull, International Fisheries Institute, Hull HU6 7RX, UK

3 Instituto de Conservação da Natureza, Lisboa, Portugal

The fish fauna of the Guadiana river in southern Portugal is characterised by 30 species, of which 22 are native (5 amphibiotic, 11 primary and 6 secondary fish taxa) and the remaining exotic. However, 14 of the indigenous species are considered endangered or critically endangered. Despite this bleak scenario there is increasing pressure to further exploit the water resources of the catchment for domestic supply, agriculture and recreation. To meet this demand nine impoundments have already been constructed in the region and a further thirteen are planned, including the big Alqueva reservoir, mainly to supply water resources for agriculture, and for the tourist industry, especially in all the southern region. Thus, for meeting increasing demands of water, two water transfer systems were projected from Alqueva system to Sado and Mira basins respectively, and are presently under study. In addition, during summer months due to severe droughts there is an intense abstraction of water for agriculture in the isolated pools, which are important refuges for fish, which developed such survival strategy.

This paper examines the status of the fish populations in the Guadiana in Portugal, assesses the impact water resource development schemes are having on the fish stocks and biodiversity and suggests management options for conserving and enhancing the already degraded stocks.

Keywords: Water abstractions; Portugal; River fish
EIFAC/XX/98/Symp. E 26

Vitellogenin - a Biomarker for endocrine disruptors in fish populations


P-D. Hansen1, H. Dizer1, B. Hock2, A. Marx2, J. Sherry3, M. McMaster3, Ch. Blaise4

and U.A. Grosch5

1 Berlin University of Technology, Dept. of Ecotoxicology, Berlin, Germany

2 Munich University of Technology, Department of Botany, Munich, Germany

3 National Water Research Institute, Burlington, Ontario, USA

4 Centre Saint-Laurent, Montréal, Québec, Canada

5 Berlin Fishery Board, Havelchausse 149/151, D-14 055 Berlin, Germany

The increasing bias in fish population sex ratios to females has become a matter of concern both to scientists and environmental authorities. For example, in the extensive waterways in Berlin, Germany, 70% of the fish population is female. Two questions arise form this shift; firstly are endocrine pollutants influencing the sex differentiation in fish? And, secondly, is the biomarker vitellogenin an appropriate tool for determining endocrine effects of pollutants such as estradiols, phthalates, alkyl-phenols, and alky-ethoxylates,

The presence of vitellogenin in male fish was chosen as an indicator of exposure to estrogenic compounds as it is easily detected in blood serum by means of a competitive enzymatic immunoassay (EIA) using monoclonal antibodies. In this way male fish exposed to effluents can be used to monitor endocrine disruptions through multiple measurements of vitellogenin production.

Fish were kept in tanks within a flow through system and exposed to mixtures containing known amounts of effluent and surface. The dilution steps (10%, 20% 30% and 40% effluent) adopted are representative of the effluent loading in Berlin waterways throughout the year.

A significant increase of vitellogenin was detected in the serum of fish exposed to > 20% effluent. The kinetics of the production of vitellogenin in male fish was demonstrated by induction experiments using 17b -Estradiol. The endocrine impacts of selected single contaminants of the effluents were also investigated.

There is a safety factor of more than 100 between the concentrations of non-phenols in the effluents and their endocrine impacts. The safety factor for bisphenol A is approximately 3,000. There is, however, no safety factor for the concentrations of the hormones in the effluents and waterways.

Results from on-site exposure experiments with fish placed in effluent from the Berlin-Ruhleben sewage plant and cause effect studies with selected contaminants of the effluent pose a further questions as to whether increased vitellogenin synthesis in male fish is the correct answer to the sex ratio problem in European waterways.

Keywords: Hormones; Sex reversal in fish; Pollution; German rivers
EIFAC/XX/98/Symp. P 05

Water supply for aquaculture in Denmark


Paul Landsfeldt and Annette Holm Sørensen

Vejle County, Damhaven 12, 7100 Vejle, Denmark

The first fresh water fish farms appeared in Denmark at the end of the 1800s. Today there are about 450 fish farms, which produced 34.000 t mainly of rainbow trout in 1995. Most fish farms have land ponds and draw water from weirs in the streams. A number of fish farms also use groundwater from drillings or springs. The operation of fish farms in Denmark is regulated by the water supply act, which sets out the amounts of water that must be restored to the river. This was changed in 1995 to make it possible to eliminate dead reaches of river and to create passage for fish and invertebrates.

In Vejle County the possibility of voluntary agreements were first explored and have resulted in the restoration of riffles that function well as passages. Some water flow has also been restored in the dead reaches although this is often less than half of the median minimum flow.

Where possible, compensation can be given in the form of additional water catchment approvals for ground water from upstream reservoirs. This has been the case especially where the whole water flow is restored to the stream. Recovering of ground water will not be allowed along vulnerable streams within 400 m.

In Denmark aquaculture and agriculture are not taxed for the use of surface- or groundwater.

Keywords: Aquaculture; Denmark; Permissible flows; River restoration
EIFAC/XX/98/Symp. P 06

Impact of trout farms on fish growth, species composition and water quality in a small lowland brook


B. Rennert1, K. Kohlmann1 and U. Grosch2

1Institute of Freshwater Ecology and Inland Fisheries, D-12561 Berlin, Germany

2 Berlin Fishery Board, Havelchaussee 149/151, D-14 055 Berlin, Germany

Investigations were carried out on a small lowland brook approximately 50 km Southwest of Berlin, Germany where 4 commercial trout farms are operating. They mainly produce rainbow trout (Oncorhynchus mykiss) and in some cases brook trout (Salvelinus fontinalis). The distance between the 1st and 4th farm is about 10 km. Individual growth of brown trout (Salmo trutta f. fario) upstream and downstream from the trout farms was estimated as follows. Brown trout originating from the brook were reproduced artificially. One summer old progeny were PIT tagged and stocked in an area 1 km upstream from the first trout farm and a second area 3 km downstream from the last trout farm. The individual growth of these fish was measured over a period of two years by recapture with electric fishing gear twice a year and the fish species composition in both areas was examined. Additionally, water was analysed for NH4-N, NO3-N, total-N and total-P bi-weekly over the two years.

PIT tagged brown trout stocked downstream of the trout farms showed significantly better growth than their siblings stocked upstream of the farms even after the first winter. This difference increased steadily and became highly significant. At the end of the study the mean body weight of tagged brown trout downstream of the farms was 273.5▒43.67 g compared to 80.0▒14.26 g upstream of the farms. The fish species community upstream of the trout farms was strongly dominated by brown trout (98.7 % of the total number of captured fish). The other species found there were brook trout (0.9 %), rainbow trout (0.3 %) and stickleback (Gasterosteus aculeatus) (0.1 %). Downstream of the trout farms 7 species were present. Brown trout were again dominant (65.2 %). Other species present were rainbow trout (15.2 %), stone loach (Noemacheilus barbatulus) (6.3 %), stickleback (5.7 %), brook trout (4.0 %), gudgeon (Gobio gobio) (2,4 %) and eel (Anguilla anguilla) (1.2 %). In all cases the nitrogen and phosphorus values were significantly higher downstream of the trout farms.

It is concluded that the growth of brown trout and the number of species downstream are higher due to the nutrient output of the farms but the farms obstruct fish migration to the upstream area.

Keywords: Trout farms; Growth rates
EIFAC/XX/98/Symp. P 07

Relations between the users of water in Bütgenbach and Robertville reservoirs (Belgium)


V.G. Frank1, P. Mergen2 and J.C. Philippart3

1 Service de la Pêche, Ministère de la Région Wallonne, 5100 Jambes, Belgium

2 Facultés Notre Dame de la Paix, 5000 Namur, Belgium

3 Laboratoire de Démographie des Poissons et d'Aquaculture, Station d'Aquaculture, 4500 Tihange, Belgium

The "Warche" stream and its two reservoirs, Bütgenbach and Robertville, is exploited intensively for several different uses including:

The Walloon Region has established the following water quality objectives for the different uses:

The constraints on water quality upstream of Robertville are thus very diverse and this part of the Warche basin is a very sensitive zone.

Recent observations show a water quality to be relatively good in the upper part of the basin but reveal two major problems:

Some problems for the flora and fauna have been caused by the modification of the environment caused by the two waterbodies:

Management of the different uses of water in the Warche basin, and especially in the reservoirs, is complex and needs a multidisciplinary approach, which takes into account the experience of similar situations elsewhere.

Keywords: Belgium; Reservoirs; Multi-purpose management; Eutrophication; Coregonids
EIFAC/XX/98/Symp. E 27

Development and use of surface waters and the related fate of the fisheries

in the Berlin area, Germany


Ulrich Grosch1, Bernhard Rennert2 and Volker Hilge2

1 Berlin Fishery Board, Havelchaussee 149/151, D-14 055 Berlin, Germany

2 Institute of Freshwater Ecology and Inland Fisheries, D-12561 Berlin, Germany

Berlin has a population of some 3.5 million inhabitants and covers an area of 889 km2, of which 57 km2 (6.4 %) consist of rivers and lakes of different sizes. The landscape is characterised by glacial deposits, slow flowing lowland rivers and shallow lakes with a maximum depth of 16 m. There are some 60 lakes (> 1 ha) and more than 500 natural pond-like waters. Primary fishing waters are the Rivers Spree, Dahme and Havel, the latter being lacustrine in form. Today there are 13 full-time and 17 part-time fishery enterprises and about 40,000 - 50,000 recreational fishermen. The main fish species of commercial interest are the European eel (Anguilla anguilla L.), pike perch (Stizostedion lucioperca L.), perch (Perca fluviatilis L.), rudd (Rutilus rutilus L.), pike (Esox lucius L.), common carp (Cyprinus carpio L.), tench (Tinca tinca L.) and the European catfish (Silurus glanis L.). In recent years the total catch from the commercial fishery has been about 100 t of high valued fish with another 400 t of lesser-valued species like bream, rudd and bleak.

Human activities over decades including the use of water for industrial purpose, navigation on the waterways and recreation has changed the waters and their fish stocks and reduced the economic basis of the fishery. Discharges by the chemical industry located in the city caused grave problems in the 1980s when the contamination of fish by DDT, HCH, Lindane, and PCBs led to an interdiction of marketing of the catch until 1993. Heavy eutrophication originating from upstream agriculture and effluents from sewage plants presents another problem. Measures taken are described which should lead to better water quality and ultimately help sustain the fishery enterprises.

Keywords: Pollution; Rivers; Lakes; Germany; Commercial fisheries; Recreational fisheries
EIFAC/XX/98/Symp. E 28

The development of inland aquaculture in arid climates:

Water utilization strategies applied in Israel


Dan Mires

Ministry of Agriculture and Rural Development, Hakyria, Tel-Aviv, 61070, Israel

Israel has a temperate climate with marked differences between the northern and southern regions. In the North, rainfall ranges between 250-600 mm y-1 and in the South between only 25-200 mm. During the last thirty years, water consumption has increased dramatically in all sectors. Although in most cases water allocation for inland aquaculture has been given the lowest priority, aquaculturists have learned to cope and thrive on brackish water sources not fit for human consumption or agricultural crops. Since most water sources are already fully exploited, further development of all sectors will depend on their capacity to use recycled city water, desalinated brackish or seawater or recycled pond water. In this respect, inland aquaculture is handicapped by the public prejudice, which will not allow the use of the first, and farms are still not able to cope with the price of the second. Further development of inland aquaculture will depend therefore on farmers' capacity to use seawater and to repeatedly recycle pond water.

In spite of some severe fluctuations, which occurred mainly after climatic catastrophes or outbursts of new diseases, a general positive production trend has existed throughout the years. The total national production of pond-raised fish in 1996 was approximately 16,800 t compared to 12,118 t in 1986, 13,291 t in 1976 and 8,513 t in 1966. Based on very conservative estimations of population growth and per capita consumption, the demand for fish is expected to double within the next twenty years.

The aquaculture industry today faces a challenging situation in which it will have to produce more fish with less (inland) water in order to meet the expected demand. Various strategies have already been developed in Israel and new ones are actually under study. These include water harvesting in dual purpose reservoirs, recycling of pond water from one year to the next, development of intensive flow-through systems based on recycled pond water and others based on biofiltration. Some of the more sophisticated systems are still facing information gaps as well as economic problems that will need to be solved through R&D before they can be adopted by the industry.

Keywords: Recycling of water; Aquaculture
EIFAC/XX/98/Symp. E 29

Environmental protection and management of Louros River basin (Epirus - Greece)


Y. Paschos1, I. Kagalou1 and L. Natsis2

1 Technological, Educational Institute, Department of Ichthyology and Fisheries, "XENIA" Igoumenitsa, Greece

2 Municipal Company of the Lake of Ioannina, Mavili St., Anatoli Ioannina, Greece

A study was performed which aimed at the protection and management of the Louros River basin. The Louros River is located in the northwestern part of Greece (region of Epirus) and is a typical river ecosystem with a varied fauna and flora including a number of bird species. The main economic activity in the area is trout Salmo trutta aquaculture, which has been practised since 1963 using the river water. There are also some agricultural activities along the river and in the last years the whole region has become a developing tourist "site" because of its natural beauty.

The quality of the river water was monitored and the organic load from the aquaculture sites estimated. Five sampling points were established along the river where parameters including temperature, pH, conductivity, DO, NO2, NO3, P and BOD5 were measured. The organic load was estimated from the BOD5. Climatological and hydrogeological data for the study area were also collected.

The surface water quality model (QUAL 2E) was applied appropriately modified to estimate the impact of aquaculture effluents on river water quality and to project their future activity.

An integrated management plan was developed using the data from the field studies and the model's predictions, in order to:

(a) control point and non-point pollution sources;

(b) support the operation of the fish-farming units, providing them with guidelines for development relative to the protection of the Louros River. The self-purification ability of the river seems to be quite large. Nevertheless, the fish-farming units have to improve their operations through the construction of new ponds and primary-settling tanks so as to minimise organic and suspended solid loads, make more efficient use of water, improve fish nutrition, etc.,

(c) provide the basis for sustainable development of economic activities including aquaculture while ensuring the conservation and protection of the natural environment.

Keywords: Aquaculture; Greece; Pollution

Annex III

Address by Mr H. Ackefors, Chairman of the Symposium

Dear participants at the symposium,

It is a great pleasure for me as a chairman of this symposium to welcome you all. The European water situation is a serious matter. We are dependent on water for our interior environment as well as our external ones. The circulation of blood is essential for our bodies if we want to live and so is the hydrological cycle. Without water no primary production is possible.

Most of the water on earth is salt water and only a little fraction is freshwater. A source which unfortunately is still wasted in many countries and areas and in some countries availability of water is a question of life or death. I do not have to remind you of the terrible pictures we have seen on our television screens. But even in certain parts of Europe there is a water shortage; in some countries only 2,000 to 4,000 cubic metres of waters are available per year and capita while in most parts of Europe 5,000 to 20,000 cubic metres are available. Iceland has the most abundant water resource, with close to 700,000 cubic metres per capita and year.

The amount of available water is closely linked to population growth. Between 1940 and 1990, world population more than doubled from 2,300 million to 5,300 million human beings. Simultaneously, per capita use of water doubled, from about 400 to 800 cubic metres per person and year (Engelman and LeRoy, 1993). The population growth is now exponential. By the year 2000 we are expected to be 6,000 million, in the year of 2025 8,500 million and by the year 2050 10,000 million people.

The movement of people from the central parts of the continents towards the coastal zone will make the water shortage worse. In the so called Dobris Report on Europe's Environment, it is stated that the European coastline is 143,000 km long including islands and that 200 million European people (out of 680 million) live within 50 km of coastal waters (Stanners and Bourdeau, 1995). On a global basis it is estimated that 37% of the population live within 100 km of a coastline, 49% within 200 km and 66% within 400 km (Cohen et al., 1997). This means that the freshwater resources will be utilised very unevenly. Already today water is transported from one part of the countries to another, even in countries where resources are considered abundant.

A sustainable water policy means among other things that we must provide a secure supply of drinking water. The drinking water must be safe and it must be provided in sufficient quantity and with sufficient reliability. This is stated by the Commission of the European Communities. This is necessary to stress with regard to industry, agriculture, forestry, fisheries, aquaculture, transport and power generation. In this symposium this will be approached from different angles although fisheries and aquaculture will be the focus.

Pollution is unfortunately a threat to freshwater resources in many parts of Europe. As an example it might be mentioned that 85% of the ground water lying beneath agricultural land exceeds the EU guidelines for nitrate concentration levels in drinking water (Stanners and Bourdeau, 1995).

Let us first define what we mean with pollution. One definition might be "the direct or indirect introduction as a result of human activity, of substances, vibrations, heat or noise into the air, water or land which might be harmful to human health or the quality of the environment, result in damage to material property, or impair or interfere with amenities and other legitimate uses of the environment". Pollution is normally characterised as "point source" or "diffuse source". The latter is of course much more difficult to detect and to measure.

Eventually, increasing pollution loads will outstrip the self-purifying capacity of water systems. If no counter-measures are taken, anthropogenic assault will gradually lead to a situation where water is not only the source of life and human and ecosystem well being, but also a source of disease, ecosystem disruption and social disorder. Such a scenario may aptly be termed hydrocide (Lundqvist, 1998).

Aerial fallout is a threat to many countries, especially from the emission of pollutants such as SO2, NOx and ammonia into the air. Acidification of sulphate from burning of coal and oil or other substances and the emission of nitrogen oxides from the traffic is a threat to many areas of Europe. In Sweden 25% of the lakes (more than 20,000) are acidified by acid pollution (Henriksson and Brodin, 1995). Industrial emissions from Western Europe, especially England, are the main reason. This is another reason why we have to include all countries in Europe in our discussions. Pollution is not stopped at the borders of the various countries.

In Sweden 18% of the drainage areas of the lakes and 50% of the forest areas are influenced by too high acid (mainly sulphur) precipitation (SNV, 1991). To counteract the acidification, 7,500 lakes are limed. At present Sweden spent 140 million SEK every year for this purpose. Due to international agreements the sulphur precipitation has decreased by 50% since 1989. But it is estimated that the aerial fallout must decrease by 70% to prevent further acidification. Unfortunately, the Fennoscandian Shield consists of slow-weathering rocks such as granite and gneiss, which offer far less protection against acidification (low buffer capacity) than readily weatherable sedimentary rocks that dominates on the continent of Europe (Chadwick and Kuylenstierna, 1990; SNV, 1991).

The survival threshold for different plants and animals in acid waters varies. Acid waters heavily influence the reproduction, and sometimes important elements in the diet are eliminated. pH 6.5- 6.0 is the critical limit for crayfish and roach while other species as perch and pike might be hardier. Eel is supposed to be able to live in pH 4-5 and sometimes down to 3.5 (SNV, 1991). One of the reasons for the susceptibility for low pH in the environment is aluminium. At pH around 6 aluminium hydroxide may precipitate on the gills of the fish. At pH around 5 aluminium ion is toxic to fish.
Another pollution problem is eutrophication. High level of nutrients in a lake can lead to excessive growth of micro- or macro-algae at the expense of the natural plant and animal community. The oxygen demand by the algal biomass or resulting from its decomposition can disrupt the natural balance of the ecosystem.

Pollution implies also that fish and shellfish will become a health hazard for human populations (Ackefors et al., 1990). In freshwater, the concentration of heavy metals in fish may be high as well as halogenated hydrocarbons as DDT and PCB. The accumulation of radionuclides has increased, especially in freshwater fishes, after the Chernobyl accident in 1986. Caesium-137 has long been a threat to fish consumers living close to inland waters.

Let me finish this introduction with the prime objective of this Symposium, viz., to establish the place of inland fisheries and aquaculture in the context of water management. The Symposium should focus on institutional, administrative and legal instruments for a fair allocation of water to these sectors. The Symposium aims at examining the requirement for water for inland fisheries and aquaculture, the social, economic and policy dimension of water use with particular reference to inland fisheries and aquaculture.

In the various sessions we will look at the water resources from the quantitative and qualitative aspects, the requirements of inland aquaculture systems and fisheries. We will look at resources issues and conflicts, and strategic planning of water resources.

Once more very welcome to a Symposium with very important issues to be discussed.


Ackefors, H., V. Hilge and O. Lindén, 1990. Contaminants in fish and shellfish products. In Aquaculture Europe ┤89 - Business Joins Science, edited by N. De Pauw and R. Billard. Europ.Aquacult.Soc.Spec.Publ., (12): 305-44

Chadwick, M.J., and J.C.I. Kuylenstierna, 1990. The relative sensitivity of ecosystems in Europe to acidic depositions. Stockholm, Stockholm Environment Institute.

Cohen, J.E., J. Gallup, A.A. Mellinger, J. Sachs and Ch. Small, 1977. Estimate of coastal populations. Science, 278:1211-2

Engelman, R., and P. LeRoy, 1993. Sustaining water: population and the future of renewable water supplies. Washington, Population and Environment Program, Population Action International, 56 p.

Henriksson, L., and Y.W. Brodin (eds.), 1995. Liming of acidified surface waters. A Swedish synthesis. Berlin, Springer, 458 p.

Lundqvist, J., 1998. Avert looming hydroxide. Manuscript. Linköping, Department of Water and Environmental Studies, Linköping University

SNV (Swedish Environmental Protection Agency), 1991. Acidification and liming of Swedish freshwater. SNV Monitor 12. Stockholm, Swedish Environmental Protection Agency, 144 p.

Stanners, D., and P. Bourdeau (Eds.), 1995. Europe's environment. The Dobris Assessment. Copenhagen, European Environment Agency