Effect of particle size and concentration on feeding behaviour, selectivity and rates of food ingestion by the Cape anchovy Engraulis capensis

Abstract

Engraulis capensis (Gilchrist) is capable of both filter and particulate feeding, the latter being the dominant mode. Food concentrations required to initiate filter feeding were inversely related to particle size. Turning rate, swimming speed and feeding mode also depended on prey size. The anchovy switched from filtering to biting at a threshold prey size of 0.710 to 0.720 mm; the feeding mode employed by the fish on prey approximating this size depended upon prey concentration. Biting clearance rates were greater than those for filtering, and the fish fed at maximum rate over most of their prey size spectrum. These results indicate that E. capensis had adapted its feeding behaviour to maximise food intake and to minimise energy expenditure. The selective grazing of E. capensis may have a significant effect on the structure of its prey communities.