INDIVIDUAL VARIATION IN GROWTH AND DEVELOPMENT DURING THE EARLY-LIFE STAGES OF WINTER FLOUNDER, PLEURONECTES-AMERICANUS

We studied phenotypic variation in larval and juvenile growth and deve lopment, using laboratory-reared winter flounder, Pleuronectes america nus. Larvae were reared individually to metamorphosis and beyond and w ere measured at weekly intervals. Growth in length was rapid until 30 d but slowed thereafter until metamorphosis. Standard length peaked an d often declined as metamorphosis approached, and notochord length dec reased during flexion. Length at 30 d (an index of larval growth rate) was inversely related to age at metamorphosis, confirming previous as sertions that larvae that grow rapidly also develop most rapidly. The relation between growth rate and larval-period duration, however, was not straightforward. The time from the day of peak larval length until metamorphosis (7-35 d) appeared to be inversely related to larval gro wth rate. Juvenile growth rates during the first 3 weeks following met amorphosis were unrelated to length at 30 d. Additional juveniles, rea red in groups as larvae and tracked as individuals following metamorph osis, showed no change in growth rates during the first 4 weeks of the juvenile period in relation to increasing age at metamorphosis or lar val growth rates. These results are consistent with earlier findings t hat size at age does not diverge continually throughout the larval and juvenile periods. Compensatory juvenile growth among fish that grew s lowly as larvae was observed but not to the same extent as previously reported. We emphasize the utility of the individual-based approach fo r identifying patterns of phenotypic variability in growth and develop ment during the early life stages in fishes.