Food consumption and absorption efficiency by newly settled summer flounder, Paralichthys dentatus (Linneaus, 1766)

Abstract

As part of a project to determine the energetic basis of growth rate variation, 24-h experiments were conducted to investigate differences in rates of food consumption and absorption efficiency, between and within cohorts (defined here as offspring from a single set of parents) of newly settled laboratory-reared summer flounder, Paralichthys dentatus (Linneaus, 1766). Food consumption, absorption efficiency and growth were measured for fish which had been fast-growing and slow-growing larvae (referred to as grade 1 and grade 3 fish, respectively) from each of five sets of parents (referred to as cohorts 1, 2, 3, 4 and 5) at constant temperature (20±1 °C), salinity (30±2‰) and light regime (16L:8D), at fish sizes of 15, 20, 25 and 30 mm total length (range: 2.9–59.0 mg dry weight).Significant differences in the rates of consumption of brine shrimp (Artemia sp.) nauplii, on both a per-fish basis (447–5105 nauplii (day)−1) and a weight-specific basis (12–49% body weight (day)−1), absorption efficiency (46–96% of the consumed ration), and specific growth rate (1.08–10.79% body weight (day)−1) existed among fish at each size. Significant differences were also found in food consumption between grade 1 and grade 3 fish within a cohort, although not at all fish sizes. There was no overall effect of cohort on food consumption (p=0.083); however, significant differences in absorption efficiency among cohorts existed (p=0.000). As expected, this study suggests that differences in the rates of food consumption directly influence growth rate variation in this species.