INFLUENCE OF PREVIOUS EXPERIENCE ON THE FEEDING-HABITS OF LARVAL WEAKFISH CYNOSCION-REGALIS

Larval weakfish Cynoscion regalis (Bloch & Schneider) were examined to determine the influence of dietary conditioning on prey selection. Ex periments were conducted with larvae in each of 4 age classes (8, 11, 14 and 17 d posthatching). Larvae were given a monospecific diet of ei ther large rotifers, small rotifers, or brine shrimp nauplii for 5 d p rior to an experiment. Larvae were then given a choice between the fam iliar prey and one of the other prey types. In separate experimental t rials, the conditioned prey was administered in 3 different proportion s (10, 25 or 40 %) of the total ration. Larvae consumed both prey type s in all trials, but analysis of gut contents often showed a significa nt deviation from expected ratios of the 2 prey. In experiments with t he 2 size classes of rotifer, all ages of larvae chose the familiar pr ey. In the large rotifer/brine shrimp experiments, larvae 11 and 14 d posthatching could be conditioned to large rotifers; however, larvae 1 7 d posthatching always chose brine shrimp, even when initially condit ioned to rotifers. In comparisons of small rotifers and brine shrimp, larvae never showed a preference for rotifers. These results indicate that effects of dietary conditioning on prey selection vary with larva l age and relative prey size.