Relative Importance of Various Predators in Clarias gariepinus Fry Mortality in Cameroon

Sulem S.Y.; Brummett, R.E.

Relative Importance of Various Predators in Clarias gariepinus Fry Mortality in Cameroon

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Sulem S.Y.

Brummett, R.E.

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Aquaculture

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To estimate the relative importance of the most common predators of Clarias gariepinus fry, increasing levels of protection were afforded to exclude amphibians, aquatic arthropods and birds. At a stocking density of 10 larvae/m² in nursing ponds, fencing off amphibians resulted in a 28 per cent decrease in mortality. Holding fry in hapas to protect them from both amphibians and aquatic arthropods decreased mortality by an insignificant 5.7 per cent. Installation of bird-netting over the hapas reduced mortality by 21.7 per cent. The remaining 4.9 per cent of total mortality, which could not be explained, was attributed to opportunistic cannibalism, disease and/or handling stress. Increasing stocking density to 40/m² and, thus, reducing the food available per fry increased mortality by 28.3 per cent.