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

摘要

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/m~2 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/m~2 and, thus, reducing the food available per fry increased mortality by 28.3 per cent.