International Journal of Marine Science2016, Vol.6, No.31, 1-7
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produces the optimum number of eggs. Wild strain
Oreochromis shiranus
brooders that are above 138g show a
rapid decrease in the number of eggs produced. On the other hand, improved strain brooders did not register a
remarkable decrease in number of eggs spawned hence any brooder above 100g is suitable for selection.
Recommendations
The study recommends that 100g (17cm SL) and above brooders of wild and improved strains of
Oreochromis
shiranus
are the best brooders to select for breeding purposes. Brooders from 60g (15cm SL) and above can be
used for breeding when the hatchery operator has inadequate number of the first choice of brooders. Wild strain
brooders below 60g (15cm) and above 132g (18cm SL) are not the ideal candidates to use for a breeding program
because it is costly to manage them due to insufficient number of eggs that are spawned.
There is no cut-off point for improved strain brooders of
Oreochromis shiranus
above 100g. However, small
brooders (below 100g) are not cost-effective to be used at the hatchery. Finally, it is advisable to use standard
length as a selection criterion for brooders because of its accurate measure on number of eggs spawned.
Acknowledgement
Authors sincerely thank staff in the department of Fisheries Science at Mzuzu University for their valuable input and support towards
this work as well as National Aquaculture Center for housing the experiment.
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