The diet of Cape hakeMerluccius capensison the south coast of South Africa

Abstract

In stomach contents of Cape hake Merluccius capensis collected during demersal research surveys (1989–1994) on the south coast of South Africa, fish remains accounted for 92% by mass, crustaceans for 5% and cephalopods for 3%. Fish prey consisted of 51% pelagic, mainly anchovy (33%), round herring (11%) and pilchard, 24% horse mackerel and 17% demersal fish, mainly M. capensis. This dietary composition contrasts with that documented for the same species on the West Coast, where crustaceans and mesopelagic fish are more important in the diet of small and medium-sized (<50 cm) M. capensis, and horse mackerel are of minor importance in the diet of larger hake. Cannibalism was a more prominent feature in M. capensis on the South Coast (accounting for up to 25% of the diet) than it is on the West Coast, where interspecific (hake-on-hake) predation on Merluccius paradoxus is common. On the South Coast, M. capensis adapt their diet not only to exploit larger prey species but also larger prey items within a species, the length and size range of prey increasing significantly with predator length. The maximum ingestible prey size was around 50% of body length. Hake as small as 15 cm were piscivorous and cannibalistic, but the minimum length at which hake preyed on horse mackerel was 30 cm, and generally fish >15 cm were consumed at that length. Horse mackerel was an important food source for large M. capensis (>50 cm) on the South Coast.