Spatiotemporal Variability in Individual Blue Catfish Growth during Introduction and Expansion in Virginia Tidal Rivers

Blue Catfish were introduced in the James, Rappahannock and York Rivers of the Chesapeake Bay watershed over forty years ago and expanded into all Virginia tributaries of the Chesapeake Bay.  This study investigates how growth parameters changed spatially and temporally as Blue Catfish populations increased in this novel environment. Understanding variability in life history across time and space is paramount to formulation of population dynamics models. We analyzed growth data from 8,393 Blue Catfish collected by Virginia Division of Game and Inland Fisheries from 1995–1996, 2002–2011 and 2014 from the James, Rappahannock and York River Systems. We extended the von Bertalanffy growth function to nonlinear mixed-effect models with random effects of river system, sampling year and year class. Further, we evaluated demographic and environmental influences on growth. Using an information theoretic approach, we recommend the best model describing spatial and temporal variability in von Bertalanffy growth parameters featured cohort and river system as random effects. The results of this study support differences in individual growth across river systems and a decline in growth over time, providing crucial information for formulation of population dynamics models considering spatial and temporal variability in Blue Catfish abundance.