Final report of the fisheries catch assessment survey in the Ugandan waters of Lake Victoria for the March 2010 survey

This report presents findings of the CAS conducted in the Ugandan waters of Lake Victoria in March 2010. The results of the previous ten CASs conducted under the same programme in July, August, September and November 2005; in March, August and December 2006; in March, and August 2007; in February and December 2008 are included to show the emerging trends. The report also presents total annual catch estimates for the Ugandan part of the lake from 2005 to 2010.

An instance of cyclonic upwelling in the southern offshore waters of Lake Victoria

Evidence is presented that cyclonic upwelling took place in the southern offshore waters of Lake Victoria on the 22nd to the 23rd March, 1969. Before this, the main upper thermocline was tilted downwards in the leeward northern half of the lake in response to the accumulation of epilimnetic water. Cyclonic upwelling might be quite common because of the frequent occurrence of storms on Lake Victoria, and probably on other tropical African lakes. However, to my knowledge, it has never been reported from any lake.

Chemical, microbiological and sensory examinations of dried Lake Tanganyika sardine presently marketed in Zambia

Proximate composition, PH, total aerabic counts, coliform counts, appearance and taste of dried Lake Tanganyika sardine (Limnothrissa miodon and Stolothrissa tanganicae) sampled at Lusaka markets were analysed for the period July 1969 to February 1970. Water content for the dried sardine varied between 7 and l4% and oil content between 8 and 14% according to season. Flavour of the cooked sardine was scored as good to fair, which discredits the common belief that is poor in quality. Cooked fish scores correlated poorly to the oil content and bacterial counts of the dried fish.

The feeding of three commercially important fish species in Lake Chilwa, Malawi

The diets of the three species of fish that predominate in the Lake Chilwa fishery are described in relation to various parameters using a semi-quantitative method of analysis of the digestive tract contents. Barbus paludinosus Peters fed during the day on zooplankton, non-filamentous green algae and some higher plant material; small fish fcd predominately on zooplankton but with increasiug size the diet was more varied. Clarias mossambicus Peters fed throughout the day and night and had a highly varied diet with fish becoming the major food item in large fish, Tilapia shirana chilwae Trewawas fed mainly during the day on higher plant material, filamentous green algae and zooplankton; smaller fish fed predominately on zooplankton. The importance of flexibility in the diet of the three fish species is stressed.

The challenge of Lake Chilwa

Lake Chilwa and its environs present a unique challenge to science for two reasons: 1. The welfare of its people and the fish and crops on which they depend on incomes as well as subsistence are dominated by the vagaries of the periodic rise and fall of the lake. Inyears of high level the lake provides a relatively good living for the people of the plain and the fish is a major source of dietary protein for the densely populated Shire Highlands. Fish catches and fish consumption decline in years of low lake level. Could knowledge of the biology of the lake and the hydrology of the lake basin assist in stabilizing the fishing industry? 2. The area is underdeveloped, with the traditional matrilineal way of life, but it has considerable potential for a fishing industry, for agriculture, for livestock, for bird preservation and tourism and possibly, at some future date, for minerals. How can these interests be reconciled and in what order should developments take place?

Nutritive value of fish of Lake Tanganyika [part] I: Amino acid composition

The amino acid composition was determined of three economic important fish species of Lake Tanganyika, representing 95% of the tolal catch:Stolothrissa tanganicae Regan, Limnothrissa miodon Boulenger and Luciolates stapersii Boulenger. The analysis of the whole sun dried fish indicate that, compared with Tilapia macrochir, beef and the whole hen's egg, the fish is of a very high nutritive value. The free amino acids in the dried fish count for an average of 11 %, indicating the degree of auteolysis.

The potential for clupeid fishery in Lake Kainji, Nigeria

The potential for a clupcid fishery in Lake Kainji has been examined using both experimental fishing samples and the results obtained from those of the commercial fishermen. A total annual production of 1,400 tons has been estimated. In money terms, this amounls to N198.800 (£99,400) per annum. This production has been sustained by the abundant zooplankton food available the year round on the lake. Recommendations for the effective methods of cropping clupeids were made, bearing in mind the need to maintain the fishery on a sustained yield basis. The place of c1upeids in the ecology of the lake was examined and on the basis of the evidence available it was recommended that Pellonula afzeluisi could be exploited on a large commercial scale without any adverse effects on the fishery in the lake.

Past trends, present stocks and possible future state of the fisheries of the Tanzania part of the Lake Victoria

The Tanzania part of Lake Victoria is the most important single fishery resource for the country. Past fishing practice caused disparity between the relative abundance in the catches and in the available stocks by overfishing some species while under-fishing others. Preliminary studies of distribution pattern, biomass estimates, etc, as derived from bollom trawl exploratory data, and the trend of the commercial catch statistics from 1958 to 1970, suggest that many of the commercially preferred species may not have the biotic potential 10 sustain higher yields under present ecological and fishing regimes. Haplochromis and a few other fish might be the only hope. Geographic extension of fishing to deeper waters may not be very promising as species diversificarion and fish density decline with depth. To develop and manage the fisheries, make full use of the resource and ensure economic and biological perpetuation of thc fishery, the appropriate fishing strategy cannot be properly developcd overnight.

Some characteristics of the fish fauna of a dam in the Lake Victoria region of Tanzania including the effects of multispecific stocking with tilapia species

Malya dam had been stocked with several species of Tilapia. However all but the species endemic to the region, T esculentus, made only marginal contributions to the fishery. T. zilli particularly had failed to establish itself, probably because its niche had been previously filled by T. rendalii. Planktivorou Tilapia species predominate in Malya dam but in smaller dams in the region herbivoorous tilapia are relatively more abundant. Six non-cichlid species and one of Haplochromis were found in the dam. Tilapia esculenta the most economically important species, was estimated to grow within 9-10 cm first year and 16-18 cm second year. The largest, specimen caught was 30.5 cm and the smallest mature individual 19 cm. The fish of the dam grew more slowly and matured at a smaller size than those of the same species in Lake Victoria The biological pattern of T. esculenta in Malya dam was similar to that of this species in Lake Victoria.

The ADP/FS frame survey of Lake Kyoga and Lake Kwania

The report provides a summary of the frame survey results carried out in lakes Kyoga and Kwania in 1990. The ADP Fisheries Survey of Lake Kyoga is charged with a stock-assessment programme. The term stock-assessment is generally used to express the need of fisheries managers for knowledge on fish stocks which are allegedly over-exploited already. Stock-assessment can be very comprehensive, costly and time-consuming. Essentially however, investigations into exploited stocks and the fishery should provide viable answers to the questions of management at the shortest possible notice. Surveys should in any case provide indications concerning the rate of exploitation. That requires the execution of a catch assessment survey (CAS).

Evaluations of the pelagic resources in the Burundi waters of Lake Tanganyika and the evolution of the fisheries

The important pelagic fishery resources of northern Lake Tanganyika were identified after a preliminary scientific evaluation, and in Burundi, with governmental assistance they were rapidly developed and exploited more intensively until overfishing was thought to have occurred. At this point, legal measures were introduced in order to protect the resource by restricting fishing effort and maintaining the total yield near the apparent maximum sustained limit. Complementary biological research on the fish stocks did not accompany the rapid fishery development and now an intensive stock assessment programme has been launched by the Government and UNDP in order to define more precisely the available fish stocks and to consider, with the co-operation of the neighbouring lacustrine states, suitable ways of ensuring optimum levels of fish harvest from year to year.

Fishery resource assessment and monitoring in the development and control of fisheries in the Lake Volta

Gill-netting and rotenoning have been used for assessing and monitoring fish stock abundance in Volta Lake. The lake and the main gear types used on it have been described. Before a gill-net sampling plan was set up, a preliminary survey was undertaken which largely determined the final form of the plan. An investigation as to whether or not the lake was being overfished concluded that it was being underfished. Commercial and experimental catch data analyses disclosed that the adults of the small species were being little utilized. Commercial sized species were also not being harvested according to their apparent proportion in the population. Production is presently fluctuating between approximately 37,000 and 40,000 tonnes. A high correlation between commercial and experimental catch was realized. Developments which have followed in the wake of stock assessment and monitoring studies include: introduction of monofilament nylon net, development of a special scoop net to permit mass harvest of clupeids after they have been attracted to light, and the design of a larger canoe which would help to extend the fishery into open water. New regulation and management policies will have to be formulated in the light of new findings before a rational exploitation of all the species can be achieved.

Past trends and recent research on the fisheries of Lake Victoria in relation to possible future developments

EAFFRO and UNPP/LVFRP bottom trawl exploratory data have been used to describe the depth distributional pattern. relative abundance and magnitude of the demersai fishes in Lake Victoria. The results have been compared with the commercial catch estimates, and various interpretations of the trends in the annual catches and experimental biomass estimates in relation to possible future developments of the fishery have been suggested. Though it is highly desirable to develop the fishery such as by supplementary trawling, certain social and biological consequences and considerations needs to proceed in graded steps guided by several research disciplines. The past trends of the fisheries of Lake Victoria are briefly considered. Recent exploratory bottom trawl data, by EAFFRO and UNDP/LVFRP, have been used to define demersal fish stocks of Lake Victoria in terms of their magnitude, relative abundance and distribution pattern by depth. Enstence of disparity between the relative abundance of the various species in their commercial catches and in their present biomass estimates is pointed out and the various aspects associated with the necessary modification of the fishing practices are discussed. Further and continuing research of the bio-socio-economic vectors of the fishery will be necessary in order to generate the rationale of an efficient fishing regime for a rational management strategy and realistic utilization of the fishery resource.

Batho-spatial distribution pattern and biomass estimate of the major demersal fishes in Lake Victoria

A generalized bottom trawl exploratory survey was carried out on Lake Victoria to: (i) define the distributional pattern and magnitude of the lakewide demersal stocks, (ii) determine the commercial potential of Haplochromis spp. and (iii) evaluate trawling as a commercial fishing technique for Lake Victoria fisheries. Preliminary results suggest that: (i) bottom trawl catches are more representative of the stocks, (ii) species diversification and fish density decrease with increasing mean depth and (iii) at least 80%of the catchable demersal ichthyomass is Haplochromis. Though bottom trawling is a much more efficient fishing technique for the Lake Victoria fisheries, bio-socio-economic consideration impose that mechanization of the fishery should better proceed in graded steps. Besides demographic and nutritional considerations indicate the necessity for rational management and increased direct human utilization of the fishery resource.

Retail prices of split, smoked, dried bream and dried Lake Tanganyika sardines at Lusaka markets, 1968-1970

This paper reports the results of a retail price survey at Lusaka markets on split, smoked, dried bream (Tilapia spp.) in 1968-69 and dried Lake Tanganyika sardines (Limnothrissa miodon and Stolothrissa tanangicae) in 1969-70. During the survey periods the average prices of these products maintained a level 70% to 130% higher than those fixed by the Government. Price fluctuations in relation to season, size and quality of the products were discussed. The prices were affected by season and size of the products but not by quality in terms of appearance and smell of the non-cooked products.