Estimates of annual consumption of food by anchovy and other pelagic fish species off south africa during the period 1984–1988

Abstract

Information on the abundance, rate of intake of food and species composition of the diet of pelagic and mesopelagic fish off the west and south coasts of South Africa is presented, and estimates of the average quantity of phytoplankton and different size components of zooplankton consumed annually by these fish are given. Data, for anchovy Engraulis capensis were considered to be more accurate than those available for other species and are examined in some detail. The average monthly biomass of this species during the years 1984–1988 was estimated to be 352 000 tons off the West Coast and 754 000 tons off the South Coast. The biomass of anchovy peaked in May off the West Coast and in December off the South Coast. The rate of intake of food by the anchovy population was estimated to be 1, 88 per cent of dry body mass per day, and some 90 per cent of the diet consisted of meso- and macrozooplankton. The average monthly biomass of the total fish assemblage (anchovy, pilchard Sardinops ocellatus, round herring Etrumeus whiteheadi, lanternfish Lampanyctodes hectoris and lightfish Maurolicus muelleri) was estimated to be of the order of two million tons off each coast. The total annual consumption of carbon by these fish in the two regions was 2, 0 and 1, 6 million tons respectively, some 95 percent of this meso- and macrozooplankton. Sources and magnitudes of error in these estimates are critically examined. © 1991 Taylor & Francis Group, LLC.