Lake Victoria is the most productive freshwater fishery in Africa. Fishery yield from the lake is of the order of magnitude of 800,000 – 1,000,000 t valued at 350 – 400 million $ at the beach, with export earnings estimated at US$ 250 million. The fishery is supported by three main important fish stocks, the Nile perch, Rastrineobola argentea (Dagaa, Omena or Mukene) and Nile Tilapia (Oreochromis niloticus). Over 75% of the Nile perch is directly to the fish processing factories for export while Dagaa and tilapia are serving the regional and local markets.
Background to the fisheries
Lake Victoria had a multi-species fishery of over 500 endemic fish species with tilapiine and haplochromines being the dominant species. Haplochromines comprised 83% of the catches (1970s) and commercial fishery was based on the tilapiine (i.e. the Oreochromis esculentus and Oreochromis variabilis). Other important fisheries included Bagrus spp. (the catfish) Clarias spp., synodontis spp. Chile spp., Protopterus spp., and Labeo spp. In 1950s and 1960s Nile tilapia (Oreochromis niloticus) and Nile perch (Lates niloticus) were introduced to boost fish production and Nile perch to feed on the haplochromines and provide table fish. Following the introductions of the Nile perch and Nile tilapia in the 1950s and 1960s to boost table fish production, the fish production increased 5 folds in the late 1980s. Nile perch contributed about 60% of the total catch while haplochromines which were 80% of the total biomass by 1970s by then reduced to only 1% of biomass. The other endemic species and native tilapia also declines substantially and the introduced Nile tilapia (Oreochromis niloticus) colonised the space previously occupied by the native tilapiine. Eradication or reduction of the haplochromines which constituted different trophic groups resulted in unutilised niches in the system, resulting to increase of detritus material and zooplanktons. These resulted in increase in some detritus feeders such as Caridina niloticus and zooplanktivores such as Rastrineobola argentea. These changes linked with the excessive fishing pressure, predation and competition among the species shifted the multispecies fishery of Lake Victoria to the current three species fishery (Nile perch - Lates niloticus, Dagaa, or Omena or Mukene - Rastrineobola argentea and Nile Tilapia - Oreochromis niloticus). The Nile perch fishery reached its peak production in the 1980s and this was followed by the industrialisation of the Nile perch fishery in the 1990s with currently about 35 fish processing factories lakewide.
Dagaa sun drying
Current Status of the fish stocks
The total fish catch from the lake has been increasing over the years due to increase in fishing effort but with changes in the contribution of different species. While there was a declining trend in the mid 1990s due to reduction in the contribution of Nile perch, with improved catch assessment surveys, the overall total landings have actually been increasing. In 2000 the estimated annual landing was about 620,000 t of which Nile perch contributed 42%, Dagaa 40%, Tilapia 17% and other species 1%. The estimated total catch in 2005 was 804,000 t of which Nile perch contributed 29% dagaa 48%, haplocromines 13%, tilapia 9%, and other species less than 1%. In 2006 the estimated total catch was 1,061,107.6 t Nile perch contributed 24% Dagaa 54%, Tilapia 7%, Haplochromines 13% and other species less than 1%. The Frame survey data indicated that fishing effort has been increasing substantially between 2000 and 2006. The number of fishers increased by 52%, from 129,305 to 196,426; Number of fishing crafts increased by 63% from 42,493 to 69,160; Number of fishing crafts using outboard engines increased from 4,108 to 12, , a 211% overall increase in motorization. This suggests that the fishers go far in search of fish. Over the same period, the total number of gillnets also increased by 88%, from 650,653 in 2000 to 1,222,307 in 2006 and longline hooks by 61% from 3,496,247 to 9,044,550 hooks respectively.
The standing crop of fish in Lake Victoria has remained fairly constant over the years. The mean standing stock for Lake Victoria was estimated at 2.17 m t. during LVFRP II hydro-acoustic surveys (1999 to 2001) and 2.12 m t. during the IFMP hydro-acoustic surveys (2005 to 2006). However, the mean standing stock of Nile perch is observed to have declined from 1.29 million tonnes in 1999/ 2001 to 0.82 million tonnes in 2005/2006 surveys and its contribution from 59% to 39% of the total standing stock. Meanwhile mean standing stock of dagaa is estimated to have increased from 0.48 to 0.83 millions tonnes and that of other species from 0.37 to 0.47 millions tonnes during the same period. Fish densities were generally higher in inshore compared to offshore waters.
Nile perch landed
The historical and current information generated through the different Resource and Socio-economic monitoring studies developed with support from MRAG team to provide management guidance. The conclusions from the analysis suggest that:
The Nile perch stock is probably at about 40% of the unexploited level. This is approximately at the desired management level. It is below the level which will provide maximum sustainable yield, but above a level at which recruitment to the stock is likely to be significantly impaired as the stock size has been declining since 2000. Continued fishing at current effort levels will most likely lead to decline in catches and biomass. Allowing effort to continue to increase is likely to result in over-exploitation of the stock and effort should be halted.
Dagaa is considered underexploited as the current biomass is probably greater than 50% of unexploited biomass. The FMDST cautions against significant increase of fishing effort until a more robust analysis is possible;
Tilapia lack long term series data but appear to be fully exploited. It is proposed to prohibit fishing within 200m of the lake shore to create a buffer within which to monitor Nile tilapia
Efforts are underway to control and manage fishing effort on Lake Victoria. The Partner States completed a Regional Plan of Action for Management of fishing effort (RPOA-Capacity) in November 2006 with FAO Support. Framework for operationalization and implementation of the actions plans identified in the RPOA-Capacity document is soon to be initiated.