Virginia Institute of Marine Science
Transactions of the American Fisheries Society
The combined effects of conspeciﬁc density and climate warming on the vital rates of invasive ﬁsh species have not been well studied, but may be important in predicting how successful they will be in the future. We evaluated the effects of temperature and population density on monthly time series of sizes of age-0 Blue Catﬁsh Ictalurus furcatus in the James, York, and Rappahannock River subestuaries (deﬁned here as tidally inﬂuenced bodies of water that feed into the Chesapeake Bay) from 1996 to 2017, using growing degree-days (GDDs, °C day) as a measure of thermal time. Our pre- dictive linear mixed-effects model explained 86% of the variation in the length of age-0 Blue Catﬁsh. In addition, it indi- cated a strong positive effect of temperature on the growth rate of age-0 Blue Catﬁsh, with individual ﬁsh biomass during warm years up to 63% higher than during cool years. Growth rate was inﬂuenced negatively by the abundance of age-0 and older ﬁsh, resulting in at least fourfold differences in the predicted biomass of Blue Catﬁsh by the end of the ﬁrst year of life depending on conspeciﬁc density. We also observed regional differences in the growth rates of Blue Catﬁsh in the three subestuaries we examined; although growth occurred in all subestuaries, growth was highest for the Rappahannock River population even though this river accumulated the fewest GDDs. Rising water temperatures due to global climate change will likely increase the growth rate of age-0 Blue Catﬁsh in the Chesapeake Bay region, potentially intensifying the negative impacts of this invasive species on the ecology of Chesapeake Bay. However, individual populations respond differently to warming temperatures, and thus, potential increases in the growth rate of age-0 Blue Catﬁsh may be par- tially offset by local conditions that may serve to limit growth.
Nepal, Vaskar and Fabrizio, Mary C., Density-Dependence Mediates the Effects of Temperature on Growth of Juvenile Blue Catﬁsh in Nonnative Habitats (2020). Transactions of the American Fisheries Society, 149(1), 108-120.