VARIATION IN LARVAL GROWTH-RATE AMONG STRIPED BASS STOCKS FROM DIFFERENT LATITUDES

Field observations of a variety of fish species at different latitudes suggest that there is an inverse (countergradient) relationship betwe en growth rate within the first growing season and the length of the g rowing season. In this study, larvae of striped bass Morone saxatilis from four different latitudes-Hudson River, New York (NY) (41 degrees N); Nanticoke and Patuxent rivers, Maryland (MD) (38 degrees N); Sante e-Cooper river system, South Carolina (SC) (33 degrees N); Apalachicol a River, Florida (FL) (30 degrees N)-were raised in captivity under id entical conditions to determine if differences in growth could be dete cted among the populations. Larvae from two mothers per latitude were reared at two temperatures (17 degrees C and 21 degrees C) with replic ation. The general result was that MD and NY larvae exhibited the high est growth rates and SC larvae grew the slowest. At 17 degrees C, a si gnificant difference in standard length growth rate was detected betwe en MD larvae, the fastest growing population, and SC larvae, the slowe st growing population. At 21 degrees C, the rank order for growth in s tandard length was MD = NY > FL = SC. No significant differences in dr y weight growth were found at 17 degrees C. At 21 degrees C, a signifi cant difference in dry weight growth rate was detected between NY larv ae-the fastest growing population-and SC larvae-the slowest growing po pulation. Significant differences among the populations also were foun d in egg weight and egg oil volume. However, these maternal effects di d not exert a statistically significant influence on growth rate. Resu lts indicate the existence of a countergradient relationship between l arval growth rate and the length of the growing season among striped b ass from different latitudes.