Further observations of the feeding ecology of postlarval pinfish, Lagodon rhomboides, and spot, Leiostomus xanthurus

Abstract

The effect of current on feeding, temporal variation in food consumption, and the effect of predator and prey size on food preferences were evaluated for postlarval stages of pinfish, Lagodon rhomboides, and spot, Leiostomus xanthurus. Field and laboratory observations indicated that pinfish feeding rates decreased as water current velocity increased. Similar behavior was noted in spot from field observations, but spot feeding rates in the laboratory were highest when a slight current was present. Mean gut contents of postlarvae collected at midday over a 2-mo period ranged from 0.4 to 38 copepods/fish. The mean coefficient of variation for the number of copepods per fish in a single midday sample (n = 20 fish) was 20 percent. Maximum daily feeding rates were estimated at 17 and 26 copepods/h for spot and pinfish, respectively. Field and laboratory data confirmed that as postlarval size increases the size of their prey also increases. Refined estimates of postlarval evacuation rates and daily rations also are presented. Daily ration estimates as a percent of the fish's wet body weight were 9 percent for both species. The ration estimates for both species were greater than metabolic needs estimated from oxygen consumption measurements.