Growth and Mortality of Hatchery-Reared Striped Bass Stocked into Nonnatal Systems

Cross-stocking involves the use of fish from nonnatal sources to augment populations. This practice may not be effective, especially if fish from different populations are not well adapted to the environmental conditions of the areas intended for enhancement. Yet, the ecological consequences of cross-stocking have received little attention, particularly in coastal environments. We used tag return data (1990-2010) from an ongoing stock enhancement program to compare the growth and mortality of hatchery-reared Striped Bass Morone saxatilis of Roanoke River origin between their natal (Albemarle Sound estuary) and two nonnatal systems (Tar-Pamlico and Neuse rivers) in North Carolina. Despite their Roanoke River origin, stocked juveniles exhibited high fidelity (>90%) to nonnatal systems and similarly high growth as in their natal habitat (von Bertalanffy K values were statistically similar among systems and ranged from 0.54 to 0.61). However, time-at-liberty estimators of total mortality (Z) indicated stocked Striped Bass experienced significantly higher mortality in nonnatal (Z values, 0.48-0.51) versus natal (Z = 0.33) systems. Therefore, while cross-stocking may not contribute to stock rebuilding, it appeared to be an effective management tool for supporting local put-and-take fisheries for this recreationally and commercially important species.