Lipid Content and Condition in an Estuarine Teleost

Abstract

The value of lipid content as a measure of the feeding level of fish compared with condition factor was assessed using two populations of juvenile Rhabdosargus holubi, one from the closed West Kleinemond estuary and the other from the open Kowie estuary. Results from feeding experiments conducted in the laboratory showed that total lipid level could be related to feeding level, and was not affected by temperature although food intake at 15°C was half that at 2°C. Condition factor was affected by temperature. R. holubi from the West Kleinemond estuary showed a seasonal variation in lipid content (6,4% in summer, 0,75 % in winter) but those from the Kowie estuary showed little or no variation (1-2 %). It is suggested that the difference in the fat content of the fish between the two estuaries in summer was related to the lipid content of the food, which was much less in the Kowie estuary. The condition factor of West Kleinemond fish declined in winter while that of Kowie fish remained stable. It is considered that condition factor is a more sensitive index of the actual feeding level of fish than the lipid content since the latter may be affected by the lipid content of the food.