Spatio-Temporal Variability in Size of Age-0 Blue Catfish in Chesapeake Bay Subestuaries

In the Chesapeake Bay region, the abundance of introduced Blue Catfish Ictalurus furcatus has increased dramatically, but environmental effects on critical life-history processes such as growth of this species are largely unexplored. Here, we evaluate the effect of temperature on monthly time series of sizes of young-of-year (YOY) Blue Catfish in the James, York and Rappahannock rivers from 1996 to 2014. Specifically, we describe spatial and temporal variability in growth of YOY Blue Catfish by developing a linear model that relates fish size to the total number of growing degree-days (GDDs, °C day) experienced by each fish during its first year of life. This model explained 53% of the variability in size of YOY Blue Catfish. Warmer years accumulated more GDDs, and thus, mean lengths of Blue Catfish were higher during those years. Although the James River accumulated the most GDDs, changes in mean length of YOY Blue Catfish were lowest in this river. This discrepancy is likely related to differences in population size, invasion history, and productivity of these subestuaries. In some subestuaries, increases in the mean size of YOY Blue Catfish due to increasing water temperatures may be offset by local conditions that may serve to limit growth.