EUROPEAN INLAND FISHERIES ADVISORY COMMISSION
Budapest, Hungary, 1-7 June 2000
PROGRESS REPORT, SUB-COMMISSION I
Ad hoc Working Party on Fishing Gear Selectivity
Convenor: R. Müller
Good progress has been made. The manuscript on gill-netting for roach has been finalized and submitted to the publisher.
Ad hoc Working Party on Eels
Convenor: W. Dekker
In September 1999 the Joint EIFAC/ICES Working Party on Eels met in Silkeborg, Denmark to:
assess trends in recruitment and their causes, in fisheries and the effects on stock and yield of the species;
investigate the impact of fisheries in selected systems, especially with regard to the consequences for spawner escapement;
investigate the options for developing escapement targets for selected systems;
define relevant units where these targets would apply;
suggest type of management actions that may lead to the required escapement;
advise on international coordination of research on this species in the future.
The general picture throughout Europe is showing declining yields in eel fisheries. Recruitment of glass eel from the ocean remains at very low levels. Development of escapement targets has been explored; several options are available, but shortage of data limits their application at the current time. The potential effects of re-stocking glass eel were discussed.
The report of the Silkeborg meeting has been published by ICES (ICES CM 2000/ACFM:6 "Report of the EIFAC/ICES Working Group on Eels) and it should be discussed in Budapest whether it is worthwhile that this report is also published as an EIFAC Occasional Paper under these conditions. In the report, suggestions have been made for future work of the Working Party, with a view to future scientific advice on eel fisheries. The report of the Working Party was used by ICES/ACFM in giving advice to the European Commission in Brussels on management of the European eel fisheries. The central theme in the advice is to work towards an international management plan for the eel, meanwhile reducing the fishing mortality to the lowest possible level until such a plan is agreed upon and implemented. As far as known, no action has been yet undertaken in Brussels.
ICES/ACFM has set Terms of Reference for the 2000 meeting of the working group, paralleling the 1999 ones, but focusing on the American eel. This meeting will be chaired by Dr L. Marshall (Canada).
Recruitment of glass eel in 2000 is even less than in previous years in many places in Europe and yield of fisheries is still in decline. The recommendation to develop a management plan so far has not led to open and explicit steps in Brussels. The ToR for the 2000 meeting change the focus of the working group towards the American eel, while halting the lines of thought on the development of scientific tools as proposed by the working group in its 1999 report. The conjunction of these observations is a matter of great concern.
Ad hoc Working Party on Electric Fishing
Convenor: I. Cowx
The Ad hoc Working Party on Electric Fishing has been active during the last intersessional period. The group contributed to the European Committee for Standardization workshop on fish monitoring organised by CEN/TC230/WG2/TG4 in Älvkarleby, Sweden from 16-18 September 1998.
The aim of the meeting was to formulate guidelines for the standardization of use of electric fishing for monitoring fish population in freshwaters in EU countries. The meeting examined all aspects of electric fishing from gear types to be used in various sized water bodies, sampling strategies, data to be recorded, and safety aspects. Members of the EIFAC working group made invaluable contributions to the formulation of the guidelines and ensured that the proposals were both practical and achievable. A draft of the guidelines is attached in Annex 1 (reference CEN/TC230WGZ/TG4 N11).
These guidelines form a component of the development of standards in the area of fish monitoring which is fundament to the requirements of the EU Water Framework Directive. Further standards are being developed on:
i) Scope and selection of fish sampling and methods;
ii) Sampling of fish with gill nets.
It is felt important that EIFAC experts should also contribute to these working groups.
It is recommended the scope of the EIFAC working group on electric fishing is widened to take on board these developments and thus renamed Working group on fish monitoring in fresh waters.
Ad hoc Working Party on Stocking and Introductions
Convenor: I. Cowx
Members of the Ad hoc Working Party on Stocking and Introductions contributed towards the EU review on Analysis of the Environmental And Economic Impact of Operations to Reinforce the Aquatic Fauna of Fresh Waters for Fishery Purposes
The aims of the project were:
To audit the state of knowledge of the results of operations concerning restocking of fish for fishery purposes (including leisure fishing) in fresh water, in particular concerning the impact on the environment and genetic interactions with wild populations.
To analyse the economic importance of restocking, in particular for Community aquaculture companies, and provide hypotheses of likely developments in the medium-term.
Data were received from collaborators in the majority of EU member states of EIFAC, plus FAO, FEAP and other international agencies, although some limitations and gaps still exist.
In addition, similar data were collected from non-EU member states of EIFAC and the report on this region is being collated at present. Again, data from a number of countries are lacking and this may undermine the value of the final report. Unfortunately it has proven difficult to find alternative sources of data for Eastern European countries as databases in central agencies which collate such information are lacking.
A summary of the report of the EU member states is attached for information (Annex 2).
Synopsis on Alosa alosa and Alosa fallax
Mr. Aprahamian informs that he has prepared a draft of the Alosa synopsis but checking of some references and part of the text has still to be done and permission from a number of authors and publishers to reproduce some of the figures has still to be obtained. The draft synopsis will be made available for the meeting in Budapest.
Ad hoc Working Party on Mapping of Fish Distribution and Aquatic Habitat Quality
Convenor: A. Lelek
Unfortunately, due to of lack of money and institutional backing no progress could be achieved.
WATER ANALYSIS - SAMPLING OF FISH WITH ELECTRICITY
This document provides procedures to be used by trained persons in evaluating fish populations in streams, rivers and littoral areas of lakes for the purpose of classification of ecological status. These procedures allow standardization of sampling methods for descriptions of fish populations.
The document describes a sampling approach using electricity, which can be used in characterizing species composition, abundance and age structure of fish fauna in running water. Sampling-related issues include obtaining permissions, concerns about endangered species, protective measures of importance for the user of the sampling apparatus and co-ordination of activities with other sampling programmes.
The processing of samples covers taxonomic identification, counting, measurement of size (length) and examination of fish for external anomalies. Following the possible collection and preservation of samples for further examination or analysis of preserved specimens according to other standards of procedures, the live fish are released at the site of sampling.
2. Normative references
EN 25667-1: 1993 Water quality -Sampling - Part 1: Guidance on the design of sampling programmes (ISO 5667-1: 1980)
IEC 60335-2-86 Safety of household and similar electrical appliances - Part 2-86: Particular requirements for electric fishing machines
It should be recognized that the sampling strategy to be adopted should provide information on the current status of the population and effects of various anthropogenic activities thereon. Catch data are directly related to population density. The strategy should be to sample a defined area of river with the best available fishing equipment and qualified personnel to provide estimates of:
- Fish abundance;
- Species composition;
- Population structures (age or size).
Abundance in this context is a relative or an absolute measure of assessment based on a single electric fishing run of a known area of water. Where practical or appropriate multiple fishing of the known area should be carried out to assess the efficiency of the sampling effort to obtain absolute estimates of population density.
To ensure repeatability, fishing effort, fishing equipment and fishing protocols should be the same on all occasions. When changing equipment, comparative experiments with old and new equipment should be conducted, to make it possible to compare new and older data.
When reporting all information should be included about:
- Fishing personnel;
- Gear used including voltage, current pulse-frequency, current configuration;
- Area of site;
- Water temperature
- River discharge
3.1 Number and size of study sites
To ensure that conclusions on abundance and age structure are valid for the target population(s), a sufficient number of sites (n) must be included. This number depends on the spatial variation among sites and whether assessing temporal trends or comparisons between populations is the main aim. The spatial variation is expressed as the coefficient of variation CV = (standards deviation among sites)/ (population mean). For comparisons among populations, the minimum number of sites (n) for different CVs required is the following:
The CV can be determined from a pilot study or from data from similar populations. For determination of temporal trends fewer sites may be required.
The selection of sites should be representative of habitats/biomes within the watershed. Due consideration should also be given to ease of access and safety of operational personnel.
The timing of sampling should be linked to an understanding of the life history strategies of the target species. In most circumstances sampling should be carried out towards the end of the growing season when juveniles are of a sufficiently large size to be caught by electric fishing. Subsequent sampling of a particular site should be carried out at the same time of year.
All sampling should be done in daylight hours. The area of the river to be sampled is dependent upon width and habitat variation. This can be categorized as:
Minimum of length to be sampled
small stream < 5 m
small rivers 5-15 m
large rivers and canals > 15 m
>50 m of river margin either on one side or on both sides
>50 m of littoral zone
Clothing: Any part of the operators likely to come into contact with the electric field should be protected by the use of appropriate waterproof (electricity insulating) clothing. Adequate protection from climatic conditions, like warm clothes in cold weather, should be worn.
Lifejackets should be worn when wading in deep and when sampling from boats.
Nets: net handles must be made from electricity insulating material,
Mesh used on nets must be knotless.
Containers: containers must be of an adequate size for the welfare of the number of fish placed in them. Oxygenation can be used if appropriate. Containers likely to come into contact with electric fields should be made from non-conducting material.
Communication: suitable methods of communication should be available for emergency use.
First Aid: appropriate first aid equipment must be available and one member of the survey team should be trained in CPR.
Fire Extinguisher: if petrol
generators are used in boats a suitable fire extinguisher must be carried.
Anestethics: anaesthetics should be used where appropriate for the handling of some species.
Principle components of the electric fishing apparatus are the power source, the control box, and the electrodes.
All equipment must comply with current IEC and other relevant legislation.
Backpack equipment should be:
- light enough to be carried for extended periods;
- have a method of quick release from the wearer;
- batteries must be non-spill.
Generator equipment must be designed or modified to make it suitable for electric fishing use.
Calibration: Where possible, any new electric fishing equipment or technique should be calibrated against the old equipment or techniques. Appendix to contain example of method of electrically comparing equipment. (Frank Rummler please complete the Appendix)
6. Fishing procedures
6.1. Safety aspects
Staff must be protected against the hazards of electric shock, drowning, tripping and falling, inhalation of exhaust gases and manual handling.
An experienced team leader must be appointed to every team of operators and should have on-site responsibility for safety, first aid, and for the equipment and protective clothing. However, every member of the team has a responsibility to work in a safe manner and to inform the leader of any deficiencies.
No person should carry out electric fishing alone.
In the depot, storage of electric fishing equipment must be under secure, safe, dry and clean conditions. After use, all equipment should be returned to storage in such a manner that it is suitable for use on the next occasion.
On site, a clear system of working signals should be laid down before operations begin and followed by all members of the team. Before the start of each day's work the team leader must brief the team on the work to be done and specify the tasks each person has to perform.
Equipment should be checked on site when fully assembled and while electrically dead, paying particular attention to plugs and sockets to ensure that they are correctly fitted and seals fully tightened. A system for checking equipment should be established and followed. This must include checks on the mechanical operation of safety switches before the equipment is energized.
Generators should be started and control units energized only when the electrodes are in the water and each team member has verbally acknowledged that they are ready for operation.
Do not put hands anywhere in the water when electric fishing equipment is operating. Do not touch any metallic part of an electrode unless it is physically disconnected from the electricity supply. Nothing should be taken from on or around the electrode by hand; fish and debris should be transferred to a non-conductive container before being handled.
When working from the bank ensure that the generator and control gears are secure to prevent them from falling into the water. Unless specifically designed for the purpose ('back-pack equipment') a control box must not be carried while energized. The generator must not be moved when it is running.
When working from a boat all members of the electric fishing boat crew must be familiar with the principles and practice of safe boat handling. On electric fishing boats, all metal surfaces including gas tanks, toolboxes, generator frame, etc., should be electrically connected together, regardless of whether the boat hull is metal or non-conductive. In non-metal boats, the whole power unit must be guaranteed against indirect contact by suitable shielding. The generator and control gear must be securely fastened to prevent movement. Care must also be taken to avoid tipping or rocking the boat that may cause operators to lose their balance. Lifejackets must be worn at all times.
Electric fishing equipment must be properly maintained and be checked regularly for mechanical and electrical faults.
6.2 Fishing procedures
6.2.1 Wadable rivers
Small brooks should be electric fished from the bank or by wading. DC or PDC should be used. Where the size of stream allows, it is preferable to use two anodes. The operators should fish upstream so that water discoloured by wading does not affect efficiency. They should move slowly, covering the habitat with a sweeping movement of the anodes and attempt to draw fish out of hiding. To aid effective fish capture in fast flowing water any catching net should be held in the wake of the anode. Switching the electrode on and off should be appropriate to the waveform being used, e.g. with smooth DC it is necessary to recreate the electric field in order to initially stimulate the fish whereas with pulsed DC the waveform achieves this automatically. For absolute estimation stop nets could be used to delimit survey zones but for relative estimation it is adequate to use partial barriers such as shallow riffles or weirs when non-territorial and mobile species are expected to be present. Equipment (power source and control box) is best sited on the bank with access to the stream section achieved by fitting long cables (e.g. 50-m length) to the anodes. An alternative is to use backpack-mounted machines. If the brook is of uniform depth then it is possible to float the power source in a small boat to be towed behind the fish catching team.
6.2.2 Non-wadable rivers
Whenever water deeper than 0.5 m is to be sampled a boat should always be used, as wading beyond this depth can be hazardous. Operators holding electrodes and dip nets obviously need to place themselves in positions to optimize use of the electric field. It is often advantageous if staff can adapt to using an electrode in one hand and a dip net in the other. The waveform should be DC, either smooth or pulsed. The boat should move downstream in such a manner as to facilitate good coverage of the habitat, especially where weed beds are present or hiding places of any kind are likely to conceal fish. In slow moving water it is not necessary to match boat movement to water flow and the boat can be controlled by ropes from the bankside if required. In more rapid water it is important to allow the boat to travel at the same speed as the water flow, only using outboard motors or paddles for manoeuvring, such that the boat remains close to immobilized fish. The larger the river, the more difficult and hazardous it becomes to set stop nets, and they can be dispensed with. Whereas good efficiency of capture can more or less be achieved with any waveform in small streams, for larger rivers best practice with regard to manipulation of pulse shape and frequency should be adopted to improve capture rates for specific target species.
Electric fishing for absolute estimates of fish populations in large rivers is difficult. Qualitative and, to a lesser extent, abundance information can be obtained by using conventional electric fishing with hand held electrodes in the river margins and delimited areas of habitat. Alternatively, where resources exist capture efficiency can be improved by increasing the size of the effective electric field relative to the area being fished by increasing the number of catching electrodes. Arrays comprising many pendant electrodes can be mounted on booms attached to the bowsprit of the fishing boat. The principal array should be entirely anodic with separate provision being made for cathodes. Electric current demands of multiple electrodes become high so large generators and powerful control boxes are needed. Often, however, it is still only possible to sample the margins with any reasonable degree of efficiency and fish in the deeper water evade capture.
7. Identification and measurements of fish, release of catch
For the purpose of minimum requirements according to the Council Directive, establishing framework for Community action in the field of water policy, the following should be standardized: data pertaining to fish population ecology (species and age composition). Fish should be handled in ways that minimize damage due to handling and holding. Oxygenation of water may be critical.
7.1 Identification of catch
All fish should be identified to species by external morphological characters. In cases of specimens with unclear external characters (hybrids, and closely related species, or juveniles), preserved sub-samples should be brought to the laboratory for further examination.
7.2 Measurements of the fish
In principle, all fish shall be measured (length - preferably fork-length - recorded to the nearest mm). In cases of expected significant length overlap between year-classes, structures to identify age could be sampled (scales, otoliths). Whenever the number of a certain species at a site exceeds 30 specimens, then the use of representative samples for age determination is sufficient.
7.3 Release of catch
Except for fish needed for further examination, all fish shall be released at the capture site following the conclusion of the survey. Excessive mortality (> X%) shall be recorded.
8. Performance data
The results should be presented as species composition, abundance, age structure, and area of the sampling site.
8.1 Species composition
Species composition is a list of proportional representation of all species caught.
Abundance of each species per catch is reported as recorded (counted) numbers and as numbers/100 m2. This means that the abundance reported is the crude field data, not estimated abundances using different methods.
8.3 Age structure
Age can be estimated from length-frequency data, scales or other body parts. Scales should be taken at the appropriate place for the species.
Age structure is to be reported for each species as mean length and standard deviation and number of fish in the sample. For abundant species the number in each young age class (e.g. 0+, 1+, >1+) based on length-frequency data are reported in order to document possible recruitment failures.
8.4 Optional additional measurements
Weighing individual fish and total catch per species is optional.
When the catch is large (more than 200 individuals of a species) it is appropriate to weigh the whole catch and then take a sub-sample to count all individuals, thereby calculating the actual number of fish.
All fish can be checked for external anomalies. This should be reported as anomalies per species.
9. Test report
9.1 Performance data
Quality of data is influenced by the design of the sampling programme, accuracy and precision of measurements and the reliability of the system used to manage (record, store, maintain and retrieve) the information.
Quality assurance and quality control can be achieved by:
- good education and training of field team;
- consistency of the protocol (this standard method);
- control of completeness of the data reported;
- well defined and described definitions?
- quantified objectives ?
10. Test report
10.1 Equipment and performance
Fishing method (wading upstream, boat, beam boat)
Time of the day
Manufacturer of equipment
Model of equipment
Voltage Current (ampere)
Conductivity of water
Temperature of water
Anode type (beam, ring)
Were block-nets used?
For boat-fishing also:
depth of fishing
wind direction & strength
Locality co-ordinates (GPS)
Average width (of wetted area)
Fished area (m2)
Water current class (slow, intermediate, rapids)
Water level (low, intermediate, high)
Substrate (dominating, subdominant)
Habitat type (pool, flat, run, riffle)
Helophytes (missing, sparse, intermediate, rich)
Bottom vegetation (missing, sparse, intermediate, and rich)
Dominating type of bottom vegetation (algae, mosses, phanerogams)
Surrounding (riparian zone) classified
Large woody debris
ANALYSIS OF THE ENVIRONMENTAL AND ECONOMIC IMPACT OF
OPERATIONS TO REINFORCE THE AQUATIC FAUNA OF FRESH WATERS
FOR FISHERY PURPOSES
by I.G. Cowx and P.A. Godkin
University of Hull International Fisheries Institute, UK, for the European Union
The stocking, transfer or introduction of fish species is a practice frequently used in the belief they will improve the quantity or quality of catches and have long-term beneficial effects on fish stocks. This study examined: the state of knowledge of the results of restocking operations of fish for fishery purposes (including leisure fishing) in fresh water, in particular concerning the impact on the environment and genetic interactions with wild populations; assessed the economic importance of restocking; and provided likely developments in the medium-term. Information was collected from EIFAC member countries, available literature and other international agencies, for the period 1985-1997.
Capture fisheries production in EU countries has been relatively stable since 1985, fluctuating between about 970 000 t and 122 000 t, with an estimated value of 350 million ECU in 1997. Sport and subsistence recreational fishing are extremely important activities in all countries, but in recent years they have undergone major, often adverse, changes. Aquaculture production from inland waters in EU countries has increased by 17% per year from 180 000 t in 1985 to 400 000 t in 1997. By contrast the increase in production for stocking was about 7% per year from around 4000 t in 1985 to 7500 t in 1997.
The estimated total value of inland production from the EU member states in 1997 was about US$ 1160 million of which over US$ 819 million was generated from aquaculture. Of the total aquaculture production, approximately US$ 87 million was for stocking purposes.
The socio-economic importance of inland fisheries does not lie at a national level - numbers employed (<5000) and the value of the sub-sector are low in relation to the fisheries sector as a whole. Its importance lies in the contribution made to local social and economic welfare. However, recreational fisheries have great potential to generate employment (and additional income generation) externally. Investment in this sector is marginal and mainly targeted at aquaculture.
All countries report stocking to some degree as more conventional approaches to management have failed to control decline in the fish stocks. Information on quantities of fish stocked was difficult to access. Salmon probably represents the species that has received the greatest attention, with an estimated 20 billion individuals, of various juvenile life stages, mainly eggs and fry, were stocked in 1998. High levels of stocking were also recorded for rainbow trout, coregonids, whitefish, eel, common carp and various cyprinids to support recreational and commercial inland fisheries.
The frequency of fish introductions into individual countries varies considerably: Italy (50 new species) contributes most to introductions followed by the UK (38 new species) and France (36 new species). Information on the reasons for introductions are incomplete but the principal reasons were aquaculture (19.8%) and improvement in wild stocks (46.6%).
Licensing is the most widely used technique to exercise legal and administrative control over stock enhancement activities. There appears to be no banning of fish transfers per se or introduction of exotic species.
Most stock enhancement activities, either deliberate or accidental, have had negative effects on indigenous fish communities and other fauna through predation, competition, loss of genetic integrity, reduction of biodiversity, introduction of pathogens and change in ecosystem dynamics. The general opinion about introductions is that they are detrimental, and the effects are usually irreversible. There is paucity of information about the efficacy of stock enhancement activities both from the production and economic perspectives and thus a need for comprehensive cost:benefit analyses of stocking operations, as well as other enhancement activities, to be undertaken on a national and European basis.
It appears that little or no consideration is given to the fish and fisheries in development proposals. Natural fisheries are all too often being replaced by fisheries that are sustained through stock enhancement strategies. If this situation is not to deteriorate further, the reasons behind the general demise of the stocks need to be identified, and mechanisms to ameliorate problems and enhance the fisheries are required. Concerns over the introduction of a new species are similar to those for stocking. Introductions are generally irreversible and proposals for new introductions call for extreme caution.
Recreational and commercial inland fisheries represent an extremely important commodity which is under threat from many sources. These fisheries need sound development proposals that will maintain and enhance their role to society including:
maintaining the fisheries in the face of other aquatic resource developments;
identifying mechanisms by which the dependence on operations to reinforce the aquatic fauna do not conflict with environmental issues;
identifying alternative mechanisms to enhance the fisheries other than stocking; and
investment in the sector to promote inland fisheries, especially recreational fisheries.
There are a number of strategies that should be adopted to minimize the potential impact of stocking operations.
Develop mechanisms or protocols to improve the efficacy of stocking operations.
Develop strategies which will minimize the genetic effects of cultured fish and introduction of different strains on the wild stocks of the recipient water body.
Improve control over fish movements to stem the continuing dispersion of pathogens and the accidental introduction of fish in consignments of a target species.
Investment in inland fisheries should be forthcoming in any future development programmes.
There are two potential areas for development:
improved management of inland fisheries, including rehabilitation of degraded fisheries; and
development of fish farms specifically set up to support stocking for inland fisheries.