CANNIBALISM AND INTRAGUILD PREDATION IN CLUPEOIDS

This paper provides empirical data of anchovy egg mortality caused by cannibalism and sardine predation. Rates of anchovy egg mortality during the period 1986 to 1988 averaged ca 0.01 h-1, representing a survival rate of about 55 % over the 60 h incubation period. Some 56 % of 3325 anchovy stomachs and some 88 % of 1225 sardine stomachs in samples collected during the period 1986 to 1988 contained anchovy eggs. Of 750 sardines and anchovies caught in co-habited areas during this period, 67 % of the anchovy and 87 % of the sardine had anchovy eggs in their stomachs. Mean numbers of eggs observed in stomachs per kg of fish mass of the co-occurrent collections were 24 in anchovies and 2117 in sardines. It was estimated that up to 56 % of the total anchovy egg mortality was the result of sardine predation and up to 6 % was the result of anchovy cannibalism. Fluctuations in anchovy recruitment and cycles in the abundance of clupeoid species in the Benguela system are likely to be attributable at least in part to these 2 mechanisms.