PhD Theses

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Browsing PhD Theses by Author "Kapinga, Imani"

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    Assessment of the effects of aspilia mossambicensis and azadirachta indica in controlling prolific breeding in farmed Nile Tilapia (oreochromis niloticus linnaeus, 1758)
    (University of Dar es Salaam, 2019) Kapinga, Imani
    There is growing demand of fish for food as the world population is expected to reach more than nine billion people by 2050 yet fish production from capture fishery has stagnated at 90 million tonnes since the late 1980s (UN 2017,FAO 2018). Therefore, further increase in global fish production is expected from aquaculture which is currently the fastest growing animal protein production system. Nile Tilapia, Oreochromis niliticusis the second (next to carp) most important finfish species cultured worldwide in terms of production. This is due to its hardiness, tolerance to varying degrees of environmental factors, high resistance to diseases and wide consumer acceptability. Despite these attributes, smallholder tilapia farming in Tanzania is constrained by pond over-crowding due to early maturation and prolific breeding often leading to poor water quality, increased competition for food, oxygen and space, as well as diversion of energy from somatic growth. Use of synthetic hormones to produce all-monosex is the most widely used technique to control the prolific breeding. Nevertheless, hormonal sex reversal in Tanzania is limited by its high costs, lack of skills and hormone unavailability. Therefore, this study assessed suitability of two medicinal plants Aspilia mossambicensis and Azadirachta indica in controlling breeding of Nile tilapia. Phtytochemical screening of Aspilia mossambicensis and Azadirachta indica leaf powders showed presence of two phytocompunds namely alkaloids and flavonoids which are known for their antifertility properties. The phytocompunds are are structurally or functionally similar to sex hormones capable of interfering reproduction in fish. Dietary inclusion of leaf powder from the two plants reduced prolific breeding by inducing histological alterations fish gonads. There was also a shift of sex ratio in favour of males. The reduction was higher content of antifertility phytocompounds in the former. Furthermore, growth and feed utilization was reduced at high doses whereas survival and haematogical parameters were improved. Therefore, dietary inclusion of 2.0g kg-1 and 4.0 g kg-1 of Azadirachta indica and Aspilia mossambicensis leaf powders. Respectively can be used by smallholder farmers to reduce prolific breeding of Nile Tilapia.