ABSTRACT. East Africa's Lake Victoria provides resources and services to millions of people on the lake's shores and abroad. In particular, the lake's fisheries are an important source of protein, employment, and international economic connections for the whole region. Nonetheless, stock dynamics are poorly understood and currently unpredictable. Furthermore, fishery dynamics are intricately connected to other supporting services of the lake as well as to lakeshore societies and economies. Much research has been carried out piecemeal on different aspects of Lake Victoria's system; e.g., societies, biodiversity, fisheries, and eutrophication. However, to disentangle drivers and dynamics of change in this complex system, we need to put these pieces together and analyze the system as a whole. We did so by first building a qualitative model of the lake's social-ecological system. We then investigated the model system through a qualitative loop analysis, and finally examined effects of changes on the system state and structure. The model and its contextual analysis allowed us to investigate system-wide chain reactions resulting from disturbances. Importantly, we built a tool that can be used to analyze the cascading effects of management options and establish the requirements for their success. We found that high connectedness of the system at the exploitation level, through fisheries having multiple target stocks, can increase the stocks' vulnerability to exploitation but reduce society's vulnerability to variability in individual stocks. We describe how there are multiple pathways to any change in the system, which makes it difficult to identify the root cause of changes but also broadens the management toolkit. Also, we illustrate how nutrient enrichment is not a self-regulating process, and that explicit management is necessary to halt or reverse eutrophication. This model is simple and usable to assess system-wide effects of management policies, and can serve as a paving stone for future quantitative analyses of system dynamics at local scales.

Proximate compositions of five economically-important fish species from Lake Victoria and Lake Tanganyika, Tanzania were determined using standard methods and procedures of the Association of the Analytical Chemists. Samples of Lates niloticus, Oreochromis niloticus, Rastrineobola argentea, Limnothrissa miodon and Stolothrissa tanganicae were collected during the dry and rainy seasons (December 2012 to March 2013) and (June to September, 2013). Protein contents (17.35-21.44 g/100 g) were significantly (p<0.05) higher in wet seasons and lower (16.13 -19.77 g/100 g) during the dry season in all the species. Similarly, lipids contents were significantly (p<0.05) higher during the wet seasons (1.01 -3.19 g/100 g) and lower (0.79 -1.79 g/100 g) during the dry season in all the species, while carbohydrate (1.89 -4.46 g/100 g) was significantly (p<0.05) higher during the dry season in all the species. The present study showed that these species are good sources of protein in desirable quantities for normal growth, development and as a remedy to nutritional and health related problems. High contents of protein and lipid during wet season make the fish species desirable for consumption during this period. These fish species are therefore recommended to diabetic consumers due to their low carbohydrate contents.

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Comparative study was conducted to observe the growth performance, length and condition factor of Oreochromis niloticus fed with two different diets using standard methods and procedures. The fish were fed with two different formulated Kunduchi Locally processed Feed (KLF) for a period of six weeks. Maximum weight gain of (10.74 to 12.48 g) was recorded with Kunduchi locally feed (KLF) with specific growth rate of (5.56 to 6.37 % per day), while minimum w Feed (AAF) with specific growth rate of (5.14 to 5.73 % per day). observed during the whole experimental period. in the 'b' values among all the experimental ponds and the value of the exponent 'b' ranged from (2.38 to 4.03) indicating both negative and positive allometric growths. The condition factor 'K' of all the experimental fish was above 1.0 (1.53 fishes from all the experimental ponds. The use of locally processed formulated diet such as KLF is therefore recommended as a step in boosting the aquaculture sector.