Feeding biology of the hottentot, Pachymetopon blochii (Val.), with an estimate of daily ration

Abstract

Gut content analysis shows the hottentot to be an omnivore, consuming a wide variety of algae and invertebrate prey. Amphipod crustaceans and rhodophytes are the dominant food items, although hydroids, echinoderms and molluscs are also eaten in smaller quantities. Geographic variation in the diet was negligible, although seasonal trends were marked. A progressive change in diet occurs with fish size, larger individuals consuming progressively more algae. The hottentot diet differs from those of a number of co-occuring sparids in being far more generalized. Hottentot feed throughout the diet cycle, although feeding activity is markedly higher during the rising tide. The feeding cycle is further modified by a tendency to select particular food items at night. Available mathematical feeding rate simulation models for continuously feeding fish were improved to incorporate an asymptotic consumption rate. The resultant model was used to calculate daily consumption rates for hottentot, giving a value of 2, 5% body weight per day. This is compared with values calculated using earlier models, and with published feeding rate values for other species.