by S. Chimbuya
Chief Ecologist (Aquatic)
Department of National Parks and Wildlife Management
The Department of National Parks and Wildlife Management has the responsibility for national fisheries and aquaculture development. It is charged with generating a research agenda. That agenda should be reviewed periodically to determine how it meets the demands of the clientele. The department is primarily responsible for fisheries and aquaculture research and is also concerned with farm research and demonstration. The department however is not sufficiently staffed and funded in order to carry out all the research that it would like to undertake. It is in this context that the Department would like to share its vision of appropriate research areas in both fisheries and aquaculture.
Fisheries Research and Development (Capture fisheries)
The resource base can be divided into two categories:
The fish resource is the target organism for capture fisheries development. The primary objective in fisheries is the rate of exploitation of the fish at a level that will leave behind a viable breeding population that can sustain the fisheries. It means that we are aiming at a sustainable catchable biomass of the fish resources for our aquatic resources.
Most of our fisheries are based on a number of species (multiple species fisheries). Most literature on fisheries biology and management is based on single species. In Zimbabwe we have only one such mono species fisheries i.e. the Kapenta fisheries. In a single species fishery it is relatively easy to carry out research and obtain tangible results on mean exploitable biomass, recruitment strength, natural and fishing mortality growth rates, and general ecology.
It is therefore relatively easier to design the fishing gear knowing these biological parameters. In a multiple species fisheries the research that will guide management is rather difficult. For most of the time we are working on single species, and designing gear to exploit these resources despite this shortcoming. Research in capture fisheries arises out of the following questions.
of the fish resource itself we ask:
From the results of this research we can design the fishing gear determine the rate of removal by the gear, and assign the fishing pressure for any water body.
Thus with regard to fish resources we are concerned with the bio-geography of fish resources, the specific biology and ecology of individual fish species and the allowable exploitable biomass.
In a water body with multiple expoitable fish species design of fishing gear is very difficult. Most gear is selective for size and species. The main objective in the research on fishing gear is to determine the exploitation rate of the various gear. A combination of gear has to be found to enable the exploitation of the full range of exploitable fish species. The species assemblages are not always the same; a combination designed for one water body may not apply to another water body.
Fish resources exist within different aquatic environments whose varying characteristics affect the biology of resident fish species. Research should be aimed at determining those critical aspects of the environment that affect the viability of resident fish species. This belongs to the realm of limnology. Both abiotic and biotic components of the habitats should be characterised. The questions we ask with regard to the aquatic environment are:
What is the spatial distribution of the aquatic environments?
What is the water status of these environments: are they annual or perennial?
What is the magnitude of level of fluctuation?
What are the basic physical and chemical limnological parameters that we need to monitor, do these fluctuate seasonally?
What is the level of primary products? What is the rate of nutrient loading? What are the sources of the nutrients?
How does the quality and status of the water affect the biology of the fish?
by S . E . Mutsekwa
Ecologist (Aquatic)
Department of National Parks and Wild Life Management.
Introduction
In 1989 Zimbabwe's fisheries produced an estimated total of 20000 tonnes of fish. About 89% of this came from Kariba. There are varying estimates of the projected production from the existing resources by the year 2000, but reasonable estimates seem to be in the region of 29 000 tonnes per annum (Van den Bossche et. al. 1990).
Ken Muir (1982), suggests that to relieve malnutrition in Zimbabwe's national diet, 5% of the daily protein requirement should come from fish. This would amount to a caput consumption rate of 10 kg/yr. With a projected population of 16 million, Ballarin (1984), predicts that Zimbabwe will require between 48 000 and 160 000 tonnes of fish by the year 2000. The lower estimate represents the amount required to sustain the 1981 consumption levels, while the upper estimate is that which is required to sustain adequate nutrition.
How then will the shortfall be made up? There are several options.
Increase output from capture fisheries: If the predictions of Vanden Bossche (et. al. 1990) are correct, then by the turn of the century the total production would fall short of the likely requirements by an estimated 19000 – 131000 tonnes. However, if the number of impoundments increases, according to Grizic (1977 as cited in Balarin 1986), then the yields realized would satisfy an improved consumption rate of between 4 – 6,5 kg/ind/yr. The present rate of consumption in this estimate is such that as the water storage capacity increases fish production will increase correspondingly.
Import: The Zimbabwean market can easily attract fish and fishery products from our neighbours. But inflow is severely limited by foreign exchange. Government policy is that we should be self-sufficent in fish and fish products.
Supplement fisheries production by aquaculture: If we define aquaculture as “fish rearing in man-made impoundments” (Ballarin 1986), all the present fisheries in Zimbabwe are a form of semi-aquaculture practice, because all water bodies in this country are man-made and have been stocked.
However, for the purposes of this document the term aquaculture will be limited to the activities outlined below:
Classical use of ponds, cages or tanks for fish rearing.
Land-based units to produce seed for river or lake stocking for angling or other purposes.
Production of aquarium fish for sale.
Stocking and managing small farm dams by controlled fishing with some use of manure.
In 1987 aquaculture contributed about 0.89% of the total fish production in the country. Balarin (1982), puts the potential maximum production of aquaculture at 2000 – 2500 tonnes per year, although there is no explanation on how this figure was obtained. I strongly question the credibility of this estimate. It does not take into account the increased opportunities that will arise as a result of increased market demand for fish, the changing economic environment, changing technology and the effect the increase in the number of impoundments will have on the opportunities for aquaculture development. The potential aquaculture production in Zimbabwe cannot be predicted with any degree of accuracy because it is dependent on unpredictable variables. What should be done, however, is to strive to meet the projected shortfall in fisheries production by technically intensifying production systems, diversifying the species to optimally utilize the available climatic variations and improve the fish stocks.
The aquaculture option needs to be thoroughly examined in the light of its present status, the problems that it is facing and is likely to face, going by the experience of other African countries. After examining these questions, a course of action should be charted.
The Present State of Aquaculture In Zimbabwe
Production
Total aquaculture production in 1989 was cited at 800 tonnes, (Vanden Bossch et. al. 1990). A large proportion of this production is likely to have come from the few privately owned commercial production units.
These commercial operations are most of the time self-contained with their own seed production systems. Quite a large proportion of them deal in exotics like Oreochromis niloticus and Oreochromis aureus with Machrobrachium rosenbergii being produced at the Kariba Prawn Farm.
These are adopted mainly because they exhibit better growth and lower feed conversion ratio than the indigenous species (this applies to the first two species) and because of high market value (the third species). Cray fish farming is being undertaken by one individual but the attempt to produce marron have failed.
A number of communal dams and ponds have been stocked through Agritex. The total number of these ponds is yet to be ascertained. Again, total production from these is not known but it is not very significant, considering the combined production figure and also the fact that these dams and ponds are mainly stocked with wild fry which perform very poorly.
A lot of interest has been expressed in catfish farming but this is hampered by the shortage of seed. Seed production in ponds has not been a very attractive option because of the cannibalistic nature of the catfish. Further development awaits the demonstration of a more efficient technique.
Research
The Government has six fisheries research stations which are charged with carrying out aquaculture research. Up to the present moment very little aquaculture research has taken place at these institutions, most of which propagate fish for fry sale to small-scale commercial farmers and for stocking communal dams. With the exception of Nyanga Research Station, all the other stations have been propagating what in actual fact are wild fish. As a result the fry produced were of a very inferior quality. There has been very little selection for better attributes such as better growth, better feed conversion ratio, improved temperature tolerance or disease resistance.
The private sector has again taken the lead in feeds research. This has been fairly easy for the private sector to undertake because Zimbabwe has a fairly well established animal feeds industry. The major limitation the feeds industry faces is lack of extensive field trials, hence the feeds have not been of an optimum quality. Government has not taken an active part in feeds research; there is no fish pathologist in government service.
Constraints Facing Aquaculture Development
Whatever achievements Zimbabwe has attained in aquaculture, these have been with very little support from the government. Indeed at times researchers have been fascinated spectators watching the private sector doing it alone.
Government has failed to provide the strong research back-up service that is required to fuel this initiative. This failure has been due to the following factors:-
Inappropriate and ill-defined research goals: As already stated, Government research stations have been engaged primarily in fry production, an activity which I think should be left to the private sector. Furthermore, in most cases the decision on species of fishes to be propagated was left to the Research Officer on site. With the limited resources and infrastructure it was not possible to carry out any other work.
This has left the private sector with nowhere to go for the latest in technical developments or for technical advice.
Lack of manpower: Both in numbers and specialised skills the aquaculture research group is very weak.
Lack of resources: Departmental budgets have been diminishing for the past few years. Most of the time the Division has been receiving allocations which cannot meet its requirements even for recurring expenditure.
How Can Aquaculture Meet The Challenge?
With the foregoing in mind, the need to redefine our research goals is urgent.
Production of good quality seed for fish farming.
Good quality seed in sufficient and predictable quantities is vital for the development of sustainable aquaculture. With the exception of exotics like O. niloticus and O. aureus, all the other fish being propagated are essentially wild. The wild indigenous stocks need to be improved by selection and controlled propagation. The selected stocks are developed, and can then be used as gene banks by the farmers to produce fry for stocking. Encouraging people to dig ponds or stock their dams alone is not good enough. Failure to provide enough seed to stock these structures or providing substandard seed will have the effect of quickly disillusioning the people who undertake such projects and thereby also discourage would-be participants. This has been the major cause of failure of the various drives to promote aquaculture in most African countries.
Diversification of species
The next issue to address is “seed of which species and why”. Currently aquaculture is dominated by a few tilapia species. Balarin (1986) indicates that there are nine indigenous species suitable for aquaculture in Zimbabwe but he only lists five, namely O mossambicus, O macrochir, O andersonii, T rendali and Clarias gariepinus.
Tilapias were the first group of fish to be farmed in Zimbabwe and they still remain the dominant group. This, however does not mean that they are the only species suitable for aquaculture.
Physically Zimbabwe can be divided into two major regions. These are the High and Middle Velds (which I will group together as the Highveld) and the Low Veld. In the Low Veld the temperatures are suitable for year-round culture of warm water fish, but in the High Veld about 5 out of 12 months in the year are too cold for the culture of warm water fish. The High Veld forms the greater part of Zimbabwe's total surface area. Balarin (1986) calculates that only 2.2% and 22.1% of Zimbabwe are suitable for year-round culture of cold water and warm water fish respectively. This means that at the moment, about 75% of Zimbabwe is being utilized for fish production for about only half the year. Cyprinids and silurids are among the species that can tolerate lower temperatures.
There is the almost untouched but very important question of the aquarium fish industry. This country has a lot of indigenous fish which can hold their own in the local as well as the international aquarium fish trade.
The aquarium fish industry at the moment is just catching these fish in the wild and exporting them. This is not quite satisfactory, and breeding of such fish in captivity should be looked at as a matter of urgency. Diversification of the species for culture is necessary.
Target-specific regions for aquaculture:
The last question to be asked in connection with aquaculture development is “where?”. Aquaculture is a relatively new form of land use in Zimbabwe. As a result it will have to conform with other forms of land use that are already in practice. As already mentioned, some places will not be suitable for culture of certain species for geographical reasons.
Therefore there is a need to build up a proper Geographical Information System data base. This will show locations of various activities, resources, soil types, rainfall patterns etc. This information will help us in streamlining our development plans and distribute resources among relevant activities in proper regions.
Conclusion
The problem of limited resources is going to be with us for a long time BUT we cannot afford to keep on waiting for generous allocations. Time is not on our side. We have to be aggressive and seek out solutions to meet our objectives and funds to fulfil these objectives. Fulfilling the objectives is not an easy task. We will need a lot of energy and some positive thinking.
REFERENCES
| Balarin J.D. (1982) : | Fish Farming Possibility In Zimbabwe. Prefeasibility Evaluation For a Case Study Of The Potential For Fish Culture Development. Mombasa Research and Development Section, Baobarb Farm Ltd. 37p (Mimeo). |
| Balarin J.D. (1984a) : | National Reviews For Aquaculture Development in Africa. FAO Fish Circ. 1: 71p. |
| Balarin J.D. (1986) : | The Status of Fish Farming in Zimbabwe and Future Prospects : Proceedings of the Fish Forum. 21 March 1986. |
| Ken Muir D.H.S. (1982) : | Fish Production Prospects in Zimbabwe. Zimbabwe Agric. J. 79 (1) : 11–7. |
| Venden Bossche J.P., Bernacksec G.M. (1990) : | Source Book For the Inland Fishery Resources of Africa: 1. CIFA Technical Paper. No 18.1. Rome, FAO. 1990 240p. |
by Dr. Cecil Machena
Senior Ecologist (Aquatic)
Lake Kariba Fisheries Research Institute
I Name of Institution
Lake Kariba Fisheries Research Institute
P.O. Box 75
Kariba
II Research Staff
There are five research posts held by the individuals listed below:
| i) | Dr C. Machena: | Senior Ecologist and Officer-in-charge |
| ii) | Mr M.Z. Mtsambiwa: | Ecologist |
| iii) | Mr H. Nyaruwa: | Ecologist |
| iv) | Miss R.A. Sanyanga: | Ecologist |
| v) | Miss P.C. Chifamba: | Ecologist |
III Role of the Institute
The Institute is funded by the public and carries out its roles in the following three broad categories of functions:
These are briefly described below.
Research
Research is both basic and applied. Basic research is carried out to understand the biological basis of fisheries production.
Current research programmes emphasize understanding of the biological and ecological factors of the environment to facilitate improved management regulations. These factors relate to evaluation of conditions which affect life cycles and behaviour and mechanisms that govern the size of commercial stocks. It is also important to learn more about the critical hydrolittoral zone.
Fish stock assessment studies evaluate the fisheries potential of the lake.
Environmental factors relate to the limnological and hydrobiological aspects of the lake. Basic physical-chemical properties of the lake as well as the abundance, distribution and dynamics of other aquatic fauna and flora are important.
Understanding the aquatic environment and the behaviour of fish populations and how the environment influences the behaviour is important to formulate management measures for the fishery.
Research is also carried out to assess the aquaculture potential of the Lake Kariba environment.
Applied research in our context is research that is responsive to the needs of fishing communities. Fishing communities during their day-to-day operations encounter problems, and because they are practically involved in the fishery, they make important observations on fish behaviour. Changes in fishermen's behaviour may be related to changes in fish behaviour.
Problems fishermen face often relate to gear suitability, craft, fishing methods, fish product development and marketing. Fishermen also experience poor catches; they then move to other areas or fish in prohibited areas.
Fisheries management
The overall aim of fisheries management is to exploit the potential that exists in the fishery and do so sustainably. Fisheries management is both exploitation and conservation.
As regards exploitation it is important to know the biomass, the rate of production or rate of renewal of fish populations. This is very complex for multi-species tropical fisheries because these populations comprise many fish species with very different production rates and behaviour. Hence different management measures may need to be introduced for each fish type.
Conservation is conducted by enforcing a number of management regulations. These pertain in Kariba to mesh size, restrictions, prohibition of fishing in breeding and reserve areas and curbs on the number of fishing vessels.
Extension activities
Extension work pertains to creation of dialogue and communication systems between fishing communities and fisheries managers and researchers in the development of fishing activities.
Extension work aims at raising the productivity and welfare of fishing communities, setting up demonstration and training programmes both for fishing-gear development or processing techniques, for example - and related activities.
From extension activities, problems within the fishery and those experienced by fishing communities are identified.
IV Current research programmes
There are a number of programmes taking place. These are described briefly below.
Inshore fish studies
This programme aims:
to evaluate inshore fish species biomass and species distribution.
to evaluate environmental and biological factors that cause variations in the distribution and abundance of fish.
to determine the effect of fishing intensity on fish populations through comparisons between fished and non-fished areas.
to study strategies adopted by commercial fish species in response to heavy fishing pressure.
to study the biological aspects of Synodontis zambezensis in relation to fecundity, growth rates, mortality rates, feeding habits etc.
Development of gear and other techniques for the commercial exploitation of Synodontis zambezensis and other small species.
S zambezensis which is now the most abundant fish is not exploited commercially because it is not caught in the commercial gill-nets with a minimum restriction of 4 inches.
Evaluating the pre-recruitment biology of kapenta Lymnothrissa miodon.
Kapenta is the most socio-economically yielding fish on the lake. But it is short lived, with a maximum life span of two years. Hence the coventional Virtual Population Analysis techniques (VPA) of assessing stocks and exploitation rates through cohort development cannot be applied.
The population levels of this fish are greatly influenced by recent fluctuations in the environment.
This study therefore seeks to identify breeding areas, growth and mortality rates of the juveniles and to understand how the environment affects these.
Post-recruitment biology of Limnothrissa miodon.
This project looks at fishing mortality, densities, migratorial patterns of kapenta and environmental factors that influence these parameters.
Sustainable development of aquaculture in Kariba. The programmes aims:-
to study growth, feed conversion ratios, and production potential in cages.
to assess the environmental impact of aquaculture, resulting from present and planned activites, such as fish pond farming, fish cage culture and prawn farming and
to assess suitable aquaculture sites and ways of minimising environmental impact.
to study the potential of aquaculture in the lake.
V Collaboration
There is collaboration in research activities with the Department of Fisheries in Zambia. This is funded by NORAD and DANIDA, who will also fund possible collaboration with institutions outside Zimbabwe e.g. Danish Institute of Marine Research, Humberside International Fisheries Institute, University of Bergen.
Collaboration with the University of Stockholm is funded by SAREC.
by F. Tambara
Fisheries Extension Specialist, Agritex
Introduction
Small-scale fisheries (fish farming/aquaculture and small scale dam fisheries) in Zimbabwe are still in an early stage of development. Considering also the present focus on the communal/small-scale agricultural sectors, the extension service has a major role to play in the future expansion of fish production. Agritex is in the process of improving its institutional capacity in this domain, and intends to mobilise its field service to provide farmers with the information and support that is required. This improved delivery should make existing knowledge of aquaculture and fisheries available to a much wider section of the population.
Nevertheless, it is recognised that aquaculture and small-scale fisheries still require much attention from researchers, on a wide spectrum of subjects ranging from basic fish biology to agricultural economics.
There is a need to continue with applied/adaptive research intended to prepare suitable extension packages for farmers. This requires a broad perspective which projects aquaculture (or dam fishing) as a part-time activity for farmers, and a useful addition to the overall farming system. On-station trials, interdisciplinary collaboration, on-farm trials, catch monitoring, economic data collection/monitoring etc.… are all part of this approach. This would involve DRSS (Department of Research and Specialized Services) and DNPWM (Department of National Parks and Wildlife Management) stations -- and even Agritex is involved in various aspects of these activities.
There are also in Zimbabwe significant opportunities for basic science research and the importance of this kind of research should not be underestimated. Such a capacity exists within the Aquatic Ecology Branch of the Department of National Parks and Wildlife Management (including Lake Kariba Fishteries Resedarch Institute) and at the University of Zimbabwe (Department of Biological Sciences and Lake Kariba Research Station). A good example of the key issues that must be enlightened at this level is - “If the indigenous Oreochromis mossambicus is to be the cornerstone of tilapia production, what are the ecological/ environment parameters that influence its reproduction, and how can these be manipulated to limit its precociousness/stunting?” Without some scientific answers to such basic questions, applied research is just “shooting in the dark”.
Answers to questions of basic science will also be most useful to the commercial sector. Methods used by this sector are generally more intensive, and major operators are carrying out important applied research, which nevertheless still requires sound scientific support.
Direct Support To Research
One of the objectives of Agritex, through the Project “Support for Rural Aquaculture Extension” is to promote the linkage between research and extension. Apart from the established exchange of information, it will be possible over the coming 18 months to provide limited material support to specific research projects of direct relevance to extension. This support is intended to provide established national researchers (or supervised university students) with the means to carry out appropriate projects that might not otherwise be possible for lack of means.
Researchers should submit project ideas directly to Agritex or through their departments. Most particularly submissions are solicited from the Department of National Parks and Wildlife Management and from the University of Zimbabwe, as well as from DRSS and Agritex (COFRE or Committee for On-Farm Research and Extension).
The following is a non-exclusive list of some of the technical “question marks” that have been raised in the context of developing aquaculture and small-scale fisheries in Zimbabwe. It is likely but not obligatory that suitable research topics for assistance will correspond to priorities expressed in this list.
Topics For Research Attention:
Aquaculture And Small Dam Fisheries
Species selection for ponds
Indigenous breams - species biology, physiology, requirements
Oreochromis mossambicus
Tilapia rendalli
Oreochromis macrochis
in monoculture or polyculture
Egypt strain (best growth in optimum conditions)
Species selection for dams
Stocking requirements for small dams
Ecological niches of currently stocked species
Ecological niches of newly identified useful species
Stocking procedures (size, quantities, frequency etc)
Pond ecology
Limnological characteristics of ponds in regions of Zimbabwe
Before and after aquaculture management
Stunting in tilapias
Clarification of causes and influences
Management of pond environment to reduce
reproductive effort
Control of predators
Otters/Birds in ponds
Crocodiles in dams
Pathology
Natural/husbandry pathogens
Fry production
Production inputs
plankton development
Cattle manure as primary input
Field/Kraal/Feedlot manure
Ageing/Composting and efficiency
Links with intensive husbandry
Chickens/Pigs/Goats
Management for production
Hormone manipulation of sex
Use of predator fish
Stock assessment in small dams
Methods of rapid stock assessment in small water
bodies
Establishing recommendations for sustainable fishing
effort
artificial stock enhancement - fertilisation etc…
Aquaculture and farming systems
Integration of pond aquaculture into the communal farming system
Water management (irrigation, vlei garden)
Links with horticulture
Links with intensive animal husbandry
Role in soil conservation strategy
Economics of the fish pond within the communal farming system
Variations to suit different local conditions
Insertion into farm calendars and cash flow cycles
Sociological impact of fish farming in communal areas
Who needs fish farming?
Participation of women
Nutritional impact of fish farming
Cooperative dam management.
by J. Minshall
Senior Curator of Ichthyology
Natural History Museum of Zimbabwe, Bulawayo
The Natural History Museum of Zimbabwe has the responsibility for collection of “ALPHA” data on the fauna of this country and its neighbours. In other words, to find out what animals occur in Zimbabwe, what they are and where they are found. Expeditions take place to all parts of the country, collections are made; the animals are preserved and stored in the museum.
The taxonomic status of each animal is determined to the species level by the curator, with the collaboration of experts around the world. The data is made available to scientists in the form of published papers in Arnoldia Zimbabwe and Syntarsus, in A5 and A4 format respectively. The layman gets to know about this data through lectures, articles in popular publications such as Zimbabwe Science News and The Zimbabwe Fisherman and books such as “The Fishes of Zimbabwe”, “The Snakes of Zimbabwe” and “The Birds of Zimbabwe”.
The museum informs the Department of National Parks and Wildlife Management about the species found in the areas under their control. The vast collection of specimens preserved over the past 95 years makes this possible. The collections of species are accessioned like a libraary of books and are available on loan to bona fide scientists the world over.
Curators are also concerned with “BETA” research, which is the study of the ecology of species in relation to their environment, and this occurs particularly in collections where the taxonomic problems are almost solved - such as in the higher vertebrates like Birds and Mammals. To sum up -the museum adheres to four principles:- Collection, Preservation, Investigation and Education.
The Department of Ichthyology consists of one curator and one technician in charge of approximately 70 000 specimens accessioned in 5 500 lots. Over 300 species of fish are within this collection from all over southern Africa. It is an important research tool, under-utilized at present.
Here are some ideas on a viable fisheries industry in Zimbabwe.
It would be useful for fisheries research officers to compile their own card indexes on fisheries literature in Zimbabwe, which is at present housed in three libraries -- belonging to the University, the Department of National Parks and Wildlife Management and the Natural History Museum.
Departmental Administrators must insist that Research Officers publish their findings. The Zimbabwe Science News is an excellent medium for much of the scientific research being done today. “The Transactions of the Zimbabwe Scientific Association” is an excellent outlet for more serious papers.
All activities concerning production of fish for food should come under one ministry. At present, research and extension work in fisheries is divided between several ministries and five departments.
The catfish Clarias gariepinus is Africa's future farm fish and research should concentrate on this species. South Africa has now about 45 catfish farms; a Catfish Farming Association produces data on culture methods and brings out a regular newsletter.
Lake Kariba is our most important fish farming area. Steep shorelines must be chosen for pumping water, to ponds set back from the lake -- otherwise the cost of lengthening pipelines becomes prohibitive (note the existing prawn farm at Chalala). Cage culture in sheltered coves sould have a bright future in Kariba, using Oreochromis, Clarias and perhaps some Cyprinids.
Areas of good water supply should be identified all over Zimbabwe and owners of such land encouraged by Government to set up fish farms, with capital aid if necessary.
A large hatchery-cum research station should be set up in a suitable area to produce fingerlings which can be bought by Government and commercial growers specializing in Clarias and Oreochromis. Experimental work on hybrids of our indigenous species can take place here. Small family fish farms can be supplied with seed fish, subsidized by Government.
Lastly, Government should back Agritex with money, equipment and personnel in order to fight the erosion which is destroying many of the rivers, streams and dams in Zimbabwe. This is the only way to preserve the precious gene pool of indigenous fish.
by J. M. English
Fisheries Manager
Claremont Orchards
Trout farming in Zimbabwe is restricted to the cooler, upland areas of the eastern highlands. This is the only part of Zimbabwe with the necessary abundance of relatively cold, clear and unpolluted water necessary for rearing trout. Suitable water sources and sites for commercial trout farms are the biggest limiting factors in the expansion of the trout farming industry. The combination of summer water temperatures reaching as high as 25 C and altitudes of up to 2000m, adversely affecting oxygen saturation levels, make Zimbabwe a marginal area for trout.
Claremont Orchards is one of the few large commercial trout farms in the country. The farm is not engaged in any pure research. The farm does however have a stock improvement program. Comprehensive records are maintained on water temperature, feed, growth and food conversion ratios. Records are also maintained on outbreak of disease, treatment and daily mortality and probable cause. This information is used as the basis for daily farm management decisions.
The Nyanga Trout Research Centre (NTRC), operated by the Department of National Parks and Wildlife Management, is ostensibly in charge of trout research. The Centre, constrained by inadequate design, lack of adequate funding and pressure to supply stock trout for stocking the National Parks dams has, however, contributed little to commercial trout production.
Claremont Orchards is a member of the Trout Producers Association (TPA). The TPA, aware of the constraints facing the NTCR, sought and obtained permission to construct a small research facility on the Maroro river within the National Parks. This facility provides the NTRC with a place where research into matters of interest to commercial trout producers can be carried out. The TPA has a research committee and operates the research facility in conjunction with the NTRC. The research is conducted by the NTRC staff. The TPA research committee includes members of the TPA, the Ecologist (Aquatic), NTRC, a member from the Department of Veterinary Services and a member of the University of Zimbabwe who act as advisers on the research program. Research at this facility has for the past two years concentrated on comparison of the commercial trout diets in Zimbabwe after it was found that deficiencies in local diets were responsible for many of the problems being experienced by local trout farms. (Jauncy 1989). Assistance in the research prgram has come from Dr Southgate and Dr Jauncy of Stirling University under assistance from the British Overseas Development Agency.
The high summer water temperatures and altitude combine to reduce available oxygen in the water in summer to a level that subjects the trout to stress for a large part of the day. Result: the trout gets more susceptible to stress-related disease. The most economically important of these is a myxobacterial infection that affects a large proportion of the trout farms in the country. The disease was first recorded at the NTRC in the early 1970's and currently affects trout on farms on the Nyangombe and Tsanga river catchments in Nyanga and is known to occur in the Vumba. The disease usually manifests itself late September/early October as water temperatures rise above 18°C.
Heavy losses occur in trout that are under stress, fingerlings up to about 100g being the most susceptible. The level of infection in large trout appears to depend on the level of stress in the pond and the general health of the fish.
The level of infection has been controlled to some extent by improving the trout diets in line with Dr Jauncey's recommendations and by addition of Vitamin C to the diet on the day of feeding. Outbreaks of the disease are effectively controlled by feeding Oxytetracycline at the rate of 75mg/kg of trout for 10–14 days. However, unless the trout grow beyond the susceptible size or stress is drastically reduced by heavy destocking or reduced temperature, the disease will recur in 4–5 days requiring regular repeat treatments. To reduce stress by destocking is often uneconomic as is artificially reducing the water temperature. Alternative treatments such as Oxalinic acid, Trimethoprim, Sulphadiazine and combinations of these are short-lived or not effective. Dipping all the fish in a copper sulphate dip is effective but is extremely time consuming and can result in unacceptably high treatment losses. Formalin baths are effective but again time consuming and prohibitively expensive on a large scale. Baths of Quarternary Ammonium compounds have not proved effective.
Urgent research is required to find suitable cost effective methods of treating this myxobacterial disease. The disease organism needs to be definitively studied. A possible line of investigation is towards an immersion or oral vaccine to be used on newly hatched trout fry. Alternative treatments to the use of tetracycline must also be investigated, bearing in mind delay times between last treatment and the slaughter and marketing of the product. An alternative or parallel line of research is towards breeding a strain of trout resistant to this pathogen. To be successful this research will need to combine the skills of farm researchers, pathologists and chemists.
Other lines of research requiring attention include improving the strains of trout in Zimbabwe with emphasis on tolerance to marginal conditions, improved growth and food conversion ratios in these conditions and the development of local techniques for breeding trout out of season to improve the year-round supply of trout to the market.
Zimbabwe is entering a period of structural adjustment aimed at opening the economy to market forces. In addition sanctions on trade with South Africa may be lifted, resulting in new competition in the market. If the trout farming industry in Zimbabwe is to survive and thrive, the problems and constraints currently facing the industry will have to be aggressively tackled and resolved. To achieve this, current levels of research in the trout industry will need to be increased considerably. It is questionable whether the Department of National Parks and Wildlife Management will be granted adequate funding for research in commercial aquaculture. Serious consideration must be given to returning the onus for such commercial research to the Department of Research and Specialist Services in the Ministry of Agriculture, as aquaculture is usually a part of wider agricultural enterprises.
by Ron Evans
Fisheries Manager
Rothmans
I am running an intensive land-based project on the Western Bank of “Mazvikadei Dam” near Banket, breeding, rearing and fattening bream for the internal market with a production target of 300 tonnes per year of gutted frozen fish.
Until 1986 I was a Principal Research Technician at Henderson Research Station. I am aware of the constraints on funding and staffing research programmes, no matter how small or basic their requirements. However, it is pertinent here to quote the then Minister of Agriculture, Cde Mahachi, who said when opening the Fish Forum in 1987, “I am confident that as a source of inexpensive and acceptable protein, aquaculture can be a feasible solution, leading to an increase in the supply of protein, employment, utilization of resources and possibly foreign currency earnings”.
In order to justify the Minister's confidence and to realise the full potential for aquaculture in Zimbabwe, the entrepreneur, investor, farmer, co-operative or non-governmental organization must have access to locally pertinent information, guidelines from National Parks and Wildlife Management (the responsible authority since 1971), data and research papers.
I would suggest as a major priority that a research fellow should collate and publish all of the data relating to Zimbabwe aquaculture since the first fisheries conference held at Henderson in 1960, including a fully comprehensive list of papers and references. This may appear to be a daunting task, but could probably be accomplished within a year and would be invaluable in identifying areas of necessary research. It could perhaps be part of a master's thesis.
An urgent need at this time is for a research programme to quantify the nutritional requirement of those indigenous species that could be cultured as a food protein source.
Allied to this is the need for a programme to evaluate the fish feeds that are available in Zimbabwe from animal wastes, crop residues and commercially produced feeds.
There is in Zimbabwe no commercial supply (apart from a single trout hatchery), of seed stock, broodstock or fingerlings of any species, and the market is wide open for National Parks and Widlife Management, an N.G.O., or an entrepreneur to set up such a facility.
I would propose that National Parks and Wildlife Management takes a very serious look at the possibility of importing broodstocks of our indigenous species, to improve the genetic potential of our stock, particularly in regard to O. machrochir, T. rendalli, and O. mossambicus.
I would suggest that National Parks and Wildlife Management looks very seriously at the potential of exotic species that could be introduced to complement our indigenous species.
In this respect the introduction of locally produced grass carp fry to Lake Manyame could delay the eutrophication of this very major water reservoir. Similarly a selection of the filter-feeding carps would be invaluable in the biological reclamation of Lake Chivero. It must be kept in mind that the three most commercially successful cultured species in Zimbabwe are exotic kapenta, trout and bass.
Finally, may I appeal to National Parks and Wildlife Management, other research organizations, the University and the F.A.O., to please publish your findings. We the producers are eager, even desperate for knowledge, to know who is doing what, with which species and where. Information itself is of no use at all until someone who needs that information has access to it.
by B.E. Marshall
Lecturer
Department of Biological Sciences, University of Zimbabwe
The Department of Biological Sciences is the only teaching department at the university that presently offers any courses in aquatic ecology. A variety of expertise, which could be applied to aquaculture, is available in other departments but I propose to restrict my comments to my own department. The comments that I make in this paper represent my own views.
Historical background
The University of Zimbabwe has been involved with aquatic ecology since its inception 30 years ago. Some of the early work in the departments of zoology and botany was concerned with aquatic invertebrates, the ecology of bilharzia snails, fisheries and the Kariba weed Salvinia molesta. This led to the formation of the Nuffield Kariba Research Station which was established at Sinamwenda in the early 1960's.
In its early days the research station was administered by the Division (now Department) of Biological Sciences and a number of people were awarded higher degrees for their work on various aspects of the ecology of Lake Kariba. The station was moved to Kariba town in the mid-1970s and relatively little work was done there at this time. It has since been reconstituted as the University's Academic Common Services. This means that it provides facilities for research which can be used by research workers either within or outside the university. The Centre for Applied Social Studies has used it as a base for extensive work on the fisheries around the lake while the Department of Biological Science has had four postgraduate students (two of whom have now been awarded doctorates) working there. In addition to these students, a Research Fellow is presently investigating the parasites of fish in the lake. The research station now operates as an independent unit and will not be discussed further in this paper.
A considerable amount of work was done on Lake Chivero (formerly Lake McIlwaine) through the Hydrobiological Research Unit which had been established in response to the increased problems of water pollution in the lake. This work was largely concerned with limnological aspects such as benthic fauna, blue-green algae and nutrient cycling but some work was done on fish, notably Tilapia rendalli. Funding for the Hydrobiology Research Unit ceased in the late 1970s and very little work has been done on the lake since then.
The University's involvement in fisheries research has been relatively limited, perhaps because the Department of National Parks and Wildlife Management has been primarily responsible for this. The department is especially concerned with aquaculture and the University has not been involved with this field to date.
There have never been any specialised courses in fisheries or aquatic ecology but about 10 master's degrees and 10 doctorates have been awarded in this field.
The present situation
Teaching
At present the department teaches only one course in aquatic ecology; this is called “Applied Ecology”, is taught to final-year B.Sc (Honours) students and lasts for four weeks. However, changes to the structure of the degree course, which came into effect in 1991, may make it possible to increase instruction in this subject by offering it as an optional course with a longer duration than the present one.
The department hopes to offer a Master's level degree in “Tropical Hydrobiology and Fisheries” in the future but the introduction of this programme has been slow because there is presently only one staff member capable of teaching this course. It is intended that this course should cover both “Limnology” and “Fisheries”, despite the view sometimes expressed that these are different subjects! I believe that we are required to produce graduates with a thorough knowledge of basic aspects of aquatic ecology and capable of finding employment in resource management (fisheries or water) as well as in aquaculture. A degree of specialisation is possible, however, because each student would be required to carry out a research project lasting 9–12 months and some at least would work in fisheries or aquaculture.
The department also offers opportunities for degrees through research work (M Phil. or D. Phil) and these can be done on either a full-time or a part-time basis. Almost any topic can be investigated and aquaculture students would be welcome. The only proviso is that a project must conform to the normal academic standards demanded by the university. This means that the work must be an original contribution to the subject; repeating work done elsewhere, on the ground that it has not been done in Zimbabwe, does not constitute an original contribution.
The major limitation on the teaching that can be carried out is a lack of staff. At present there is only one person with experience in this field in the department and there is clearly a need to find others capable of doing so. The teaching of aquaculture, in particular, is limited by a lack of facilities and it is unrealistic, and probably undesirable, to attempt to find the funds needed to establish them on campus. However, there are facilities near Harare at Henderson and on Lake Chivero and, further away, at Nyanga and Lake Mutirikwe which could be used for teaching and research. If these facilities were to be used in this way their operations would have to be reconsidered and might have to be changed. This would require close co-operation between the university, the Department of National Parks and Agritex.
Research
Much the same limitations apply to research on aquaculture and fisheries. The staff member working in this field is primarily interested in fisheries and limnology which means that nothing has been done in aquaculture. One other member of staff is interested in fish genetics but this work is not yet at a stage where it can have any impact on local aquaculture.
At present, we have no students registered for higher degrees in this field. This is unfortunate because this is one way in which we could without a major investment, make a contribution to the development of aquaculture in Zimbabwe.
Conclusions
It is clear from the foregoing that the Department of Biological Sciences has a relatively limited involvement in aquatic ecology because it has so few staff working in this field. This could be increased relatively easily by taking on members of the Department of National Parks or Agritex as part-time postgraduate students but it is more difficult to get full-time students. This is because student stipends are so poor that few are willing to take them up and it has been difficult to find funds for students. Many donor agencies, for example, seem to be willing to provide equipment or material help but will not provide a salary for students. This would be an immediate and relatively inexpensive way of increasing research output in aquaculture.
