A 119-day experiment was conducted to investigate the effects of feeding rate and reproductive performance of stunted (S) and
non-stunted or normal (N) Nile tilapia (Oreochromis niloticus). Both the groups were reared in tanks re-circulated with bio-filtered
water and fed with floating pellets (30% crude protein) twice daily. Seed were harvested weekly from the mouths of incubating
females. The study showed that early stunting with subsequent high feeding rate can improve both growth and reproductive output
in female Nile tilapia. Broodfish type and feeding rate showed significant (Pb0.05) effects on both the frequency of spawning and
the seed output. In general, seed output from normal broodfish increased linearly over the experimental period at all the feeding
rates. However, seed output from stunted broodfish showed a linear increment for 3% feeding rate, exponential increment for 2%
but quadratic for 1% showing decline after 10th week of the trial period. Results also showed that trends of seed output from
stunted broodfish increased linearly with the increase in feeding rate showing that optimum rate could be higher than 3%. While
from normal group the relationship was quadratic; increasing from 1%, peaked at 2% and declined at 3% feeding rate. Final GSI of
the stunted females was significantly (Pb0.05) higher than that of normal females. The GSI of stunted fish showed a decreasing
trend with the increased feeding rate. Both the broodstock groups fed at 1% biomass grew linearly whereas at 2 and 3%, they grew
exponentially. As compared to the normal, stunted broodfish had significantly (Pb0.05) higher fat content in viscera although
similar levels were in carcass and ovary. Carcass fat content was significantly (Pb0.05) lower in fish fed at 1% biomass but
significantly (Pb0.05) higher in the ovary and viscera of fish fed at 3% biomass. This study shows that tilapia hatchery operators
could manipulate the seed production according to the seasonal demand by using appropriate broodstock stunting and feeding
strategies.
A 119-day experiment was conducted to investigate the effects of feeding rate and reproductive performance of stunted (S) andnon-stunted or normal (N) Nile tilapia (Oreochromis niloticus). Both the groups were reared in tanks re-circulated with bio-filteredwater and fed with floating pellets (30% crude protein) twice daily. Seed were harvested weekly from the mouths of incubatingfemales. The study showed that early stunting with subsequent high feeding rate can improve both growth and reproductive outputin female Nile tilapia. Broodfish type and feeding rate showed significant (Pb0.05) effects on both the frequency of spawning andthe seed output. In general, seed output from normal broodfish increased linearly over the experimental period at all the feedingrates. However, seed output from stunted broodfish showed a linear increment for 3% feeding rate, exponential increment for 2%but quadratic for 1% showing decline after 10th week of the trial period. Results also showed that trends of seed output fromstunted broodfish increased linearly with the increase in feeding rate showing that optimum rate could be higher than 3%. Whilefrom normal group the relationship was quadratic; increasing from 1%, peaked at 2% and declined at 3% feeding rate. Final GSI ofthe stunted females was significantly (Pb0.05) higher than that of normal females. The GSI of stunted fish showed a decreasingtrend with the increased feeding rate. Both the broodstock groups fed at 1% biomass grew linearly whereas at 2 and 3%, they grewexponentially. As compared to the normal, stunted broodfish had significantly (Pb0.05) higher fat content in viscera althoughsimilar levels were in carcass and ovary. Carcass fat content was significantly (Pb0.05) lower in fish fed at 1% biomass butsignificantly (Pb0.05) higher in the ovary and viscera of fish fed at 3% biomass. This study shows that tilapia hatchery operatorscould manipulate the seed production according to the seasonal demand by using appropriate broodstock stunting and feedingstrategies.
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