Are the exploitation pressures on the Nile perch fisheries resources of Lake Victoria a cause for concern?

Abstract

Lake Victoria is one of the African Great Lakes, and an important source of affordable protein food in the form of fish. It provides employment, income, and export earnings to the riparian communities. Despite this importance there are major concerns about the status and exploitation of the fisheries. This study assesses if current extraction rates/yield of Nile perch, Lates niloticus (L.), from Lake Victoria are sustainable for the foreseeable future. The paper reviews trends in catch and effort in the Nile perch fishery and models the expected scenarios using ECOPATH. The fishery exhibits, classic indicators of intensive fishing, erring towards overexploitation, including: (i) decline in total estimated catch of Nile perch in recent years from the peaks in the 1990s. This is coupled with a shift in contribution of catches from higher trophic level species (Nile perch) to lower trophic level (dagaa) species. (ii) Three major trends in the fishing effort are evident: (a) almost doubling of the number of fishers and fishing boats between 1990 and 2000, and the even greater expansion between 2000 and 2002; (b) a large scale increase in the number of gears operational in the lake; and (c) the propensity for use of ÔillegalÕ gears. (iii) Catchper-unit-effort has declined from about 80 to 45 kg per boat day. (iv) Predictive modelling (ECOSIM) of the future of the Nile perch fisheries under a scenario of increased fishing effort suggests that the fisheries are unsustainable and will decline in the long term. It appears that the Nile perch stocks in the three riparian countries are under intense fishing pressure, and unless concerted action is taken, the potential for degradation of the resources is prevalent. In view of the importance of these fisheries, it is recommended that a precautionary approach to further intens-ification of the fisheries is adopted until such time empirical evidence shows that the fisheries are capable of further expansion and intensification. The main options for management are devolvement of responsibilities for the fisheries to the communities, enforcement of existing regulations, improved monitoring and data collection processes, reducing post-harvest losses and increasing the value of the products to the export market.

Nile perch distribution in south-east Lake Victoria is more strongly driven by abiotic factors, than by prey densities

“…Since the start of the fisheries concerns have been voiced that Nile perch stocks are declining and may collapse if fishing pressure will continue to increase (Mkumbo, 2002;Balirwa et al, 2003;Getabu et al, 2003;Ogutu-Ohwayo, 2004;Matsuishi et al, 2006;Mkumbo et al, 2007). However, stock assessments based on Nile perch catches and population size structure showed no signs of overfishing or long-term decline of the Nile perch stock, although, since the 1990s the stock shows short-term decadal fluctuations (Kolding et al, 2008).…”

Le lac Victoria (Afrique de l'Est) malade de la perche du Nil : réalité, mythe ou mystification ?

“…Ainsi, entre 1990 et 2000, le nombre de pêcheurs a plus que doublé en Tanzanie et en Ouganda. Cette tendance semble s'être encore accélérée entre 2000 et 2002 (Matsuishi et al, 2006). Cet essor se traduit bien évidemment par des chiffres : la production annuelle de poisson était inférieure à 100 000 tonnes jusqu'au début des années 1980.…”

Ecological, environmental and socioeconomic aspects of the Lake Victoria's introduced Nile perch fishery in relation to the native fisheries and the species culture potential: lessons to learn

“…The research record suggests otherwise. For the Lake Victoria fisheries the best available information includes at least 2000 references ranging from probably unused historical records found in Graham (1929), EAFFRO (1953EAFFRO ( -1967, associated records of the Lake Victoria Fisheries Service (LVFS), Annual Reports of Fisheries Departments to information summarized by Balirwa et al (2003Balirwa et al ( , 2004, LVFO (2005) and most recently, Pringle (2005) and Matsuishi et al (2006). As a follow-up to lack of information since the last century, Pringle (2005) recalls evidence of reported overfishing with imported nets.…”

“…The increase in boat power (outboard engine-propelled) of 47% further indicates expansion and intensification of the fishery. By analysing catch and effort data and modelling expected scenarios, Matsuishi et al (2006) concluded that Nile perch exhibits classic indicators of overexploitation such as decline in total catch over time.…”

“…The new fishing regimes now simulate fishing patterns earlier observed in the native fisheries that collapsed. While Nile perch catches have started to decrease (LVFO, 2005;Matsuishi et al, 2006), management interest lies in more information on the abundant but small (<60 mm) indigenous cyprinid, Rastrineobola argentea.…”