Comparative Ecology of Juvenile Striped Bass and Juvenile Hybrid Striped Bass in Claytor Lake, Virginia

Since the introduction of hybrid striped bass M. chrysops x M. saxatilis to Claytor Lake, Virginia in 1993, relative abundance of striped bass Morone saxatilis has dropped disproportionately to stocking density. Potentially deleterious interactions between the two fishes that may limit recruitment to age 1 were considered in terms of trophic relationships, physiological indices of health, overwinter survival, and post-stocking predation.

Both fishes preferred habitat types characterized by structure-free sand or gravel substrates, but striped bass and hybrid striped bass did not exhibit significant diet overlap during the growing season. At a total length of approximately 120 mm, the juvenile moronids shifted from a mixed diet of zooplankton and invertebrates to a diet comprised primarily of age-0 fishes. However, after becoming piscivorous striped bass preyed primarily upon age-0 alewife Alosa pseudoharengus, while hybrid striped bass consumed age-0 sunfishes.

Striped bass achieved mean total lengths of 229 and 173 mm by the end of the growing season in 2001 and 2002, respectively. Stocked into the reservoir three months later than striped bass, mean hybrid striped bass total lengths reached 133 mm at the end of the 2002 growing season. Condition factor, relative weight, and lipid index values were low, but nearly equivalent for both striped bass and hybrid striped bass throughout this study. Overwinter starvation of smaller (< 150 mm total length) striped bass was observed for the 2001-2002 sampling season. Predation upon stocked fingerlings was not considered significant in limiting juvenile survival; only three fingerling moronids were found in the examination of stomach contents of 200 potential predators captured near stocking sites.

It does not appear that resource competition with hybrid striped bass during the growing season resulted in increased overwinter mortality of juvenile striped bass. Delayed stocking of hybrid striped bass lessens the potential for trophic competition between striped bass and hybrid striped bass at this early life-stage.