The status of the artisanal fishery of Lake Victoria, Kenya

Annual catches of fish in Lake Victoria, Kenya from 1976-1998 are assessed, catches from 5-15 boats selected randomly from targeted landing sites were recorded. Twenty three of the 256 Kenyan landing sites were covered by the survey. Selection of landing sites was not random but rather influenced by the presence of infrastructure and accomodation. Parameters recorded for each sampled fishing boat were: number of crew, gear type, size, time and duration of fishing. Catches were sorted into species and weighed

Stock assessment of Lates niloticus (L.), Oreochromis niloticus (L.) and Rastrineobola argentea (Pellegrin) using fishery dependent data from the Tanzanian waters of Lake Victoria

Catch data were collected from three beaches in the Mwanza area of lake Victoria, Tanzania for Oreochromis niloticus (L.), Rastrineobola argentea (Pellegrin) and Lates niloticus (L.). Sampling took place in October 1997 and February, June and September 1998. The CPUE for O. niloticus was 3.9 to 6kg boat super(-1) and for R. argentea from 98 to 282 kg boat super(-1). There was no obvious trend in catch rates for L. niloticus. The modal length for O. niloticus recorded at Chole beach was 34cm TL. In February, fish were larger (41-45 cm) than in the other surveys. Rastrineobola argentea caught in October 1997 had modal length at 65 mm TL with some smaller fish. In February and June prominent length modes occurred at 45 and 58 mm respectively, which may represent the same cohort as the small fish caught in October 1997. In September 1998, there were two length modes at 46 and 60 mm. The 60 mm fish may represent the same cohort seen in previous surveys, suggesting growth from approximately 30 mm to 60 mm in an eleven-month period. Lates niloticus landed at Kayenze beach over the four surveys had a modal length of 46 cm TL. Fish species encountered on the three beaches during the surveys were O. niloticus, R. argentea, Bagrus docmak Forsskall, Clarias gariepinus (Burchell), Protopterus aethiopicus Heckel, Labeo victorians Boulenger, Synodontis afrofischeri Hilgendorf, Synodontis victoriae Boulanger, Schilbe intermedius (L.), Brycinus jacksonii (Boulanger), Mormyrus kannume Forsskall and Haplochromine cichlids

Results of the first hydroacoustic survey of the Ugandan waters of Lake Victoria

A lakewide hydroacoustic research programme was designed in the Ugandan waters of Lake Victoria in order to ascertain the status of fish stocks. Data obtained from the hydroacoustic surveys were complemented with by catch data from multi mesh gillnets and frame trawls to validate acoustic estimates. Fish were distributed over the whole survey area, though the densities and species composition varied from place to place. Echo traces showed the fish formed schools during daytime and became more dispersed towards evening. Approximately equivalent indices of abundance were estimated for Rastrineobola argentea and Haplocromines. The distribution of the freshwater prawn, Caridina nilotica and the lakefly Chaoborus sp. was patchy. Dense swarms of Chaoborus larvae were observed to disperse from the lake bottom as the night approached thus assuring echo-traces formed by fish on the echogram and making their interpretation difficult. Caridina nilotica were observed to form dense echo-traces at the thermocline

Forage strategy of juvenile Lates niloticus (L.) in Lake Victoria, Kenya

Six KMFRI stations located in Nyanza Gulf of Lake Victoria (Kenya) were sampled in order to investigate the forage strategy of juvenile Lates niloticus. Thirty speciemens were collected using a bottom trawl at each station and sorted into three size classes 1-2 cm and 3-20 cm total length. Stomach contents were analysed and taxonomic keys used to identify zoplankton and other insects. Caridina nilotica was the dominant food item in both frequency of occurrence and numerical abundance. In fish examined from 1-2 cm T.L., cladocerans were prominent food items, while at 2-3 and 3-20 cm, C. nilotica was dominant

Zooplankton-fish interactions in the littoral zone of Nyanza Gulf, Lake Victoria

Samples of zooplankton and fish were collected from six sampling points in Nyanza Gulf, Lake Victoria in Kenya from June to December 1998, using 76 mu m memo-filament mesh size strainer and an 80 mu m mesh size plankton net. Identification and enumeration were done in the laboratory. Occurrence, numerical and points methods were used in stomach anlaysis of fish. Copepoda, Rotifera and Cladocera were the major zooplankton groups identified, zooplankton such as Moina, Daphnia and Caridina nilotica were important prey items for Lates niloticus, Oreochromis niloticus and Rastrineobola argentea

Reproductive biology of Orechromis niloticus (L.) (Pisces: Cichlidae) in the Nyanza Gulf of Lake Victoria

Fish samples were collected using seine and trawl nets in Nyanza Gulf, Lake Victoria (Kenya) in order to study the reproductive and gonadal patterns of Oreochromis niloticus; samples were collected from June 1998 to February 1999. The variation in relative condition factor and monthly variation in gonad weight showed spawning took place between June and July. Most ripe fish were recovered between November and February, while a slight drop in GSI for males was noted between November and January. External factors triggering reproductive strategy are now being addressed

Feeding ecology and population characteristics of Oreochromis niloticus (L.) and trophic interactions in the fish community of Nyanza Gulf, Lake Victoria, Kenya

Oreochromis niloticus (L.) were caught by beach seining, hook and line and trawling from Nyanza Gulf, lake Victoria (Kenya) in order to study their feeding ecology and population characteristics. Collected fish were weighed and TL measured immediately after capture. Fish were dissected and sexed. Stomach contents were removed and preserved in 4% buffered formalin for laboratory analysis. In the laboratory items were sorted into categories such as three quarters, half and quarter and awarded 20, 15 and 5 points respectively. Main food items for O. niloticus from November 1998 to March 1999 were insects, algae, fish and plant material. Increase in insects in the diet of O. niloticus might be attributed to the lake infestation by water hyacinth which harbours different species of insects

Recent trends in the distribution patterns and catch rates from trawl surveys in Lake Victoria, Tanzania

Trawl surveys to assess the stocks of Lake Victoria (Tanzania) for estimates of biomass and yield, together with the establishment of exploitation patterns, are being undertaken under the Lake Victoria Fisheries Research Project. Preliminary surveys to establish the sampling stations and strategy were carried out between October 1997 and February 1998. Three cruises to cover the whole of Tanzanian waters were undertaken with 133 sampling stations. Data on each rates, species composition, and distribution were collected. Three sampling areas were designated: area A, B and C. In each area, almost the same distribution pattern over depth was found. Lates niloticus (L) formed over 90% of the total catch. Most L. niloticus were from 5-40 cm TL. Abundance decreased with depth, few fish were found deeper than 40m and most fish were caught at <20 m deep. Catch rates varied considerably between stations and areas. Area A had the highest catch rates with little variation over the stations. There is an indication of recovery of species diversity compared with the surveys of RV Kiboko(1985 and 1989)

The fish stocks of Lake Victoria, Uganda

An experimental bottom trawl survey was carried out in the Uganda sector of Lake Victoria from November 1997 to December 1998 to estimate the composition, distribution, and abundance of the major fish species. In 12 cruises, 295, thirty-minute hauls were taken in waters from 4-60 m deep. Nile perch, Lates niloticus (L) made up 95% of the catch by weight. Haplochromine cichlids and L. niloticus occurred in all areas sampled while Nile tilapia, Oreochromis niloticus (L.) and other tilapiines were restricted to waters less than 30 m deep. In waters deeper than 40 m, catches were generally near zero. Species diversity and abundance decreased with increasing water depth. In waters less than 30 m deep, the area where the artisanal fishermen operate, the mean catch was 126kg hr super(1)

Feed conversion, protein efficiency, digestibility and growth performance of Oreochromis niloticus fed Delonix regia seed meal

Oreochromis niloticus fingerlings (mean weight 5.27~c0.29g) were fed raw and boiled Delonix regia seed meals following standard procedures. The weight gain, specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), net protein utilization (NPU) were determined as growth indices. Diet formulated with seed boiled for 80 minutes showed significantly (P<0.05) high values for the growth indices. Carcass nutrients composition were significantly (P<0.05) higher than in the control (raw) diet. Delonix regia seed meal when boiled has high potential of being utilized efficiently by O.niloticus. The implications of the respective index in fish metabolism are discussed

Rents drain in fishery: the case of Lake Victoria Nile Perch fishery

Many fisheries are potentially very valuable. According to a recent report by the World Bank and the FAO (2008), global fisheries rents could be as high as US$ 40-60 billion annually on a sustainable basis. However, according to the report, due to the “common property problem”, most fisheries of the world are severely overexploited and generate no economic rents. The Lake Victoria Nile perch fishery could be among the most valuable fisheries in the world. Unfortunately, also this fishery has fallen prey to the common property problem with excessive fishing effort, dwindling stocks and declining profitability. As a result, there is a large and growing rents loss in this fishery (compared to the optimal) reducing economic welfare and economic growth opportunities in the countries sharing this fishery. As in other fisheries, the biological and economic recovery of this fishery can only come though improved fisheries management

Fish species identification guide for Lake Victoria: enumerator's field guide

This document can be considered as the first step in the direction of a complete fish species catalogue for fisheries purposes of the Lake Victoria. (PDF contains 55 pages)

The changing ecosystem of Lake Victoria, East Africa

Dramatic changes are occurring in the Lake Victoria ecosystem. Two-thirds of the endemic haplochromine cichlid species, of international interest for studies of evolution, have disappeared, an event associated with the sudden population explosion of piscivorous Nile perch (Lates: order Perciformes, family Centropomidae) introduced to the lake some thirty years ago. The total fish yield has, however, increased 5-fold from 1970 to 1990, but this yield is now dominated by just three fish species: the introduced Nile perch (Lates niloticus), Nile tilapia (Oreochromis niloticus), and a small endemic pelagic cyprinid (Rastrineobola argentea); these three have replaced a multispecies fishery. Contemporaneously the lake is becoming increasingly eutrophic with associated deoxygenation of the bottom waters, thereby reducing fish habitats. Conditions appear to be unstable.

The design of multimesh, multidepth gillnet fleets for use in the Lake Victoria Fisheries Research Project

Multimesh, multidepth gillnet fleets are useful in assessing fish stock abundance, size distribution and depth distribution. Using data collected on net mesh selectivity for Nile perch, Lates niloticus (L.), in the Kenyan waters of Lake Victoria, suitable mesh sizes for gillnet fleets for use in the Lake Victoria Fisheries Research Project were determined. The modal selection length for Nile perch in the mesh sized used in the earlier experiment were determined, as was the size range vulnerable to capture. Initial trials suggest 60% of the Nile perch swim within 5 m of the bottom. Setting and hauling of the nets is simple and quick, allowing the nets to be used at the same time as other sampling programmes.

Methodology of the Lake Victoria Fisheries Research Project's Co-management survey

In this book section, the theoretical background to the methodology is outlined, questionnaire development described, sample selection outlined and biases and shortcomings to the survey noted.