Variation in Larval Growth Rate among Striped Bass Stocks from Different Latitudes

Abstract

Field observations of a variety of fish species at different latitudes suggest that there is an inverse (countergradient) relationship between growth rate within the first growing season and the length of the growing season. In this study, larvae of striped bass Morone saxatilis from four different latitudes—Hudson River, New York (NY) (41°N); Nanticoke and Patuxent rivers, Maryland (MD) (38°N); Santee–Cooper river system, South Carolina (SC) (33°N); Apalachicola River, Florida (FL) (30°N)—were raised in captivity under identical conditions to determine if differences in growth could be detected among the populations. Larvae from two mothers per latitude were reared at two temperatures (17°C and 21°C) with replication. The general result was that MD and NY larvae exhibited the highest growth rates and SC larvae grew the slowest. At 17°C, a significant difference in standard length growth rate was detected between MD larvae, the fastest growing population, and SC larvae, the slowest growing population. At 21°C, the rank order for growth in standard length was MD = NY > FL = SC. No significant differences in dry weight growth were found at 17°C. At 21°C, a significant difference in dry weight growth rate was detected between NY larvae—the fastest growing population—and SC larvae—the slowest growing population. Significant differences among the populations also were found in egg weight and egg oil volume. However, these maternal effects did not exert a statistically significant influence on growth rate. Results indicate the existence of a countergradient relationship between larval growth rate and the length of the growing season among striped bass from different latitudes.