Countergradient variation in growth of young striped bass (Morone saxatilis) from different latitudes

Common garden experiments were undertaken to test the hypothesis that the genetic capacity for growth of striped bass (Morone saxatilis) varies inversely with length of the growing season across a latitudinal gradient (i.e., countergradient variation (CnGV) in growth). Newly hatched larvae were obtained from six native anadromous stocks spanning most of the natural range of striped bass (Florida to Nova Scotia). Growth experiments were conducted under conditions of unlimited food at three temperatures (17, 21, 28 degrees C) and commenced after larvae had exhausted maternal energy resources (i.e., yolk and oil) and had begun to metamorphose. Mixed-model nested ANOVA demonstrated that length and dry weight growth differed significantly among latitudes in most comparisons. South Carolina fish ranked consistently as the slowest growing group in virtually all comparisons, but the rank order of the other latitudes differed among trials. North Carolina and Gulf of Mexico fish generally had intermediate rates of growth whereas New York, Maryland, and Nova Scotia fish generally had the highest growth. Overall, the average growth rate of progeny from the 28 mothers tested in this study had a strong positive correlation with latitude of origin, strongly indicating CnGV in growth.