Growth and Mortality of Hatchery-Reared Striped Bass Stocked Into Non-Natal Systems

Due to practical constraints (costs, hatchery proximity) and/or difficulties obtaining local broodstock (for endangered or imperiled populations), stocking programs often utilize fish from non-local sources for the purpose of population enhancement.  This practice of cross-stocking could be counter-productive; fish from different populations may be ill-suited for a given system whose environmental conditions differ from those of the natal habitat to which stocked fish are adapted.  However, few studies have evaluated this possibility, especially in coastal environments.  Here, we used tag-return data (1990-present) to compare the growth and mortality of striped bass fingerlings of Roanoke River (North Carolina, USA) origin stocked into three different systems: 1) the Albemarle Sound estuary (natal system), 2) the Tar-Pamlico River, and 3) the Neuse River.  Growth in non-natal systems (Tar-Pamlico and Neuse) was similar to that in the natal estuary (von Bertalanffy K’s=0.54-0.62).  Total instantaneous mortality was significantly higher in non-natal (Z=0.48-0.51 year^-1) vs. natal (Z=0.33 year^-1) systems, but we suspect this was due to greater anthropogenic stressors (e.g., fishing mortality) rather than the population origin of stocked fish.  Our results illustrate that depleted populations can be enhanced by stocking fish from nearby populations.  Still, there are genetic concerns with this practice that need to be considered in the context of long-term population resiliency.