PERFORMANCE OF LOCALLY FORMULATED FEEDS FOR REARING OF AFRICAN CATFISH IN TANZANIA

Fisheries is an important food production sub-sector, providing almost 20% of the world\u2019s protein supply; however, the trend in fish production from capture fisheries has reached its limits due to overfishing. A study was conducted to evaluate the performance of two locally formulated feeds as possible replacements for an imported costly commercial feed (CMF) commonly used in rearing of African catfish ( Clarias gariepinus Burchell) in Tanzania. Two feed types, namely TAF 1 and TAF 2, denoting TAFIRI feed type 1 and 2 were formulated from fish meal ( Rastrineobola argentea ) and soybean ( Glycine max L.), respectively. Nine concrete tanks of 12 m3 each were stocked with 320 catfish fry each, and fed with formulated feeds at 5% of their mean body weight for four months. Water in the tanks was wholly flushed out on a weekly basis and fish sorted for the fast growers to reduce cannibalism. On a monthly basis, fish were randomly sampled for body length and weight. The mean values for temperature, dissolved oxygen and pH ranged from 21.62\ub10.04 to 25.16\ub10.05 \ub0C, 5.43\ub10.05 to 5.7\ub10.07 mg O2 L-1, and 6.5\ub10.05 to 6.61\ub10.03, respectively. Feed TAF 1 was the best performer with weight gain of 33.72\ub10.89, average daily gain of 0.28\ub10.01, FCR of 1.35\ub10.05 and specific growth rate of 4.61\ub10.04. Fish fed on the commercial feed performed the poorest, with weight gain of 6.17\ub14.8, average daily gain of 0.05\ub10.004, FCR of 1.56\ub10.11 and specific growth rate of 2.98\ub10.05. Results from this study suggest that locally formulated feeds can cost effectively be used for the rearing of African catfish in Tanzania.La p\ueache et l\u2019aquaculture constituent un sous secteur important de production alimentaire, fournissant environ 20% des besoins en prot\ue9ines mondiales\ua0; par ailleurs, la tendance de la production des poissons \ue0 partir de la p\ueache dans les lacs et les oc\ue9ans a atteint ses limites par suite d\u2019une trop forte pression sur les resources halieutiques. Une \ue9tude \ue9tait men\ue9e pour \ue9valuer la performance de deux aliments locaux formul\ue9s afin de remplacer les aliments commerciaux ch\ue8rement import\ue9s couramment utilis\ue9s dans la nutrition des poissons ( Clarias gariepinus Burchell) en Tanzanie. Deux types d\u2019aliments TAF 1 et TAF 2, aussi appel\ue9s aliments TAFIRI type 1 et 2 \ue9taient formul\ue9s \ue0 partir des aliments de poissons ( Rastrineobola argentea ) et du soja ( Glycine max L.), respectivement. Neuf r\ue9servoirs de 12 m3 chacun \ue9taient approvisionn\ue9s chacun avec 320 clarias, et nourris avec des aliments formul\ue9s sur base de 5% de leur poids corporel moyen pendant quatre mois. L\u2019eau dans les r\ue9servoirs \ue9tait renouvel\ue9e une fois la semaine et ainsi le triage des grands poissons pour r\ue9duire le cannibalisme. Chaque mois, les poissons \ue9taient al\ue9atoirement \ue9chantillonn\ue9s pour les mesures de la longueur du corps et du poids corporel. Les valeurs moyennes de la temp\ue9rature, de l\u2019oxyg\ue8ne dissous et du pH variaient de 21.62\ub10.04 \ue0 25.16\ub10.05 \ub0C, 5.43\ub10.05 \ue0 5.7\ub10.07mg O2 L-1, et 6.5\ub10.05 \ue0 6.61\ub10.03, respectivement. L\u2019aliment TAF 1 \ue9tait le meilleur et a induit un gain de poids de 33.72\ub10.89, un gain quotidien moyen de 0.28\ub10.01, un FCR de 1.35\ub10.05 et un taux de croissance sp\ue9cifique de 4.61\ub10.04. Les aliments de poissons import\ue9s ont induit une performance inf\ue9rieure \ue0 celle des aliments locaux avec un gain de poids de 6.17\ub14.8, un gain de poids quotidien moyen de 0.05\ub10.004, un FCR de 1.56\ub10.11 et un taux de croissance sp\ue9cifique de 2.98\ub10.05. Les r\ue9sultats de cette \ue9tude montrent que les aliments localement formul\ue9s peuvent remplacer efficac\ue9ment et de mani\ue8re \ue9conomiquement comp\ue9titive les aliments import\ue9s pour l\u2019\ue9levage du poisson-chat en Tanzanie

Response of fish stocks in Lake Victoria to enforcement of the ban on illegal fishing:are there lessons for management?

Most small-scale inland fisheries in the Global South prohibit fishing gear with smaller meshes than is legally permitted. Nonetheless, in most instances, this is not strictly enforced. But starting in 2017, Uganda and Tanzania ramped up enforcement on Lake Victoria. We used time series hydro-acoustic data to determine whether the strict enforcement achieved the management goal of increased biomass (t) of commercial species and an increase in the biomass of big Nile perch (>50 cm). The biomass for 2018–2021 (under strict enforcement) was expected to be greater than in 2007–2017 (prior to strict enforcement). The biomass of key species fluctuated annually, but no spatial or temporal differences in biomass associated with strict enforcement were evident. Similarly, the biomass of big Nile perch did not increase. Our findings suggest that mesh sizes may have limited influence on fish biomass dynamics in Lake Victoria, and that high primary productivity of the lake, high turnover rates of fish species, and limited compliance by fishers likely counteract the effects of high fishing effort on biomass and size structure of fish. Therefore, the high cost of strict top-down enforcement and the societal cost of lost lives, jobs, and livelihoods may not be justified