Browsing by Author "Shoko, Amon Paul"

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    Aquaculture of nile tilapia (oreochromis niloticus linnaeus, 1758) with an assessment of its economic benefits in the lake Victoria basin, Tanzania
    (University of Dar es Salaam, 2013) Shoko, Amon Paul
    Fish stocks in Lake Victoria have drastically declined while the demand for fish has exponentially increased, leading into inadequacy of fish. Aquaculture has the potential of bridging the widening gap created by the increasing demand. Despite the enormous potential for aquaculture development in the Basin, this sub-sector is still underdeveloped. This thesis examined the aquaculture of Nile tilapia (Oreochromis niloticus) and assessed its economic benefits in the Basin. Assessment on fish pond performance suggests that, despite low fish yield due to poor pond management, aquaculture offers an opportunity for increased productivity. Investigations on diurnal dynamics of water quality parameters showed that dissolved oxygen and un-ionized ammonia were beyond the acceptable limits for fish growth suggesting a need for frequent water quality monitoring in ponds. The effects of integrating fish farming with vegetables on fish growth, yields and economic benefits revealed higher performance from integrated than from non-integrated system, pointing to the importance of integrating fish farming with other on-farm activities. The effects of stocking density on production and economic benefits in polyculture and monoculture systems were assessed. It is suggested that the choice of an optimum stocking density is an important aspect in attaining higher performance in any culture system. Investigation on the reproductive biology of Nile tilapia showed that its early breeding behaviour in captivity is not affected by culture system and thus, its production can be improved through proper pond management. The practical application of the results is discussed in detail in each chapter and a synthesis is presented at the end of the thesis.
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    The effects of different diets and stocking density on the growth performance of abeochromis variabilis (Boulenger, 1906) under aquaculture conditions.
    (University of Dar es Salaam, 2002) Shoko, Amon Paul
    The effects of different diets and stocking density on the growth performance of Oreochromis variabilis (L.) (Osteichthyes: Cichlidae) fry were investigated in a hatchery. The diets and stocking density experiments were conducted in a modified 1000-litre circular polytex tanks and 20-litre plastic buckets respectively. O. variabilis fry in the diets experiment were fed on different experimental diets while those reared on stocking density experiment were fed on 'dagaa' fishmeal ad-libitum for 84 and 56 days respectively. The diet that contained cotton seed cake as the main ingredient showed better growth performance than the soyabean meal and composite diet. Fishmeal control diet showed no significant difference (p>0.05) in growth rate over cotton seed cake. Overall mean survival rate for all experiments was 89 ± 1.74% and was not influenced by diets. The conclusion generally reached was that diets containing cotton seed cake could be used to replace fishmeal in feeding O. variabilis. In both small and large size grades of O. variabilis fry cumulative weights increased with increasing stocking density. Lower stocking densities (1 fish fry per litre] showed higher specific growth rate (SGR), Apparent protein efficiency ratio (APER), Apparent food conversion efficiency (AFCE) and better Apparent food conversion ratio (AFCR) than medium (2 fish fry per litre) and high stocking densities (3 fish fry per litre). Overall mean mortality in the size graded stocking experiment was 10 ± 1.47% and 11 ± 1.57% for large and small grades respectively. High and low stocking densities gave highest yield per unit fry tank and better individual fish growth respectively. It is recommended that the choice of stocking density is essentially a trade-off between maximum growth, optimal biomass gain and economic considerations, which may dictate densities that result into a net reduction in overall production costs.