Variation in and among early life history traits of laboratory-reared winter flounder Pseudo-pleuronectes americanus

Abstract

We analyzed variation in and among early Life history traits of laboratory-reared winter flounder Pseudopleuronectes americanus. We measured lengths and ages at hatching and metamor- phosis, lengths at 2 wk intervals through the larval period and into the first 3 wk of the juvenile period, and after 23 wk of juvenile life. Variation in traits was quantified and compared by the coefficient of variation (CV = SD/mean). CVs for lengths-at-ages increased from hatching (0.03) to an asymptotic value of = 10 % by 2 to 4 wk after first feeding. There were 2 peaks in variation in lengths-at-age during the early life history; one at Week 4 (the approximate midpoint of the larval period) and another Week 10 (during the latter portion of the metamorphic window and early juvenile life). These may reflect commensurate changes observed in growth rates. Variation In length at hatching and metamorphosis was relatively low (3.0 and 5.3 %, respectively), and less than variation in age. Lengths-at-transitions were also less variable than lengths at fixed ages during the larval and juvenlle periods. These findings imply a target size for life period transitions. Length and age at metamorphosis were positively correlated, as were sequential average lengths calculated from fortnightly measures. Length and age at metamorphosis, and growth and developmental rates through the entire larval period, were positively correlated when calculated from the bivarlate measure of individuals. The pattern of variation in and correlations among early llfe history traits established in the larval period appears to propagate through metamorphosis and into early juvenile life. The population consequences of these associations, and their potential use in analyzing the results of early Life history studies, are discussed.