NEAFWA 2017

AUTHORS: Daniel M. Wilson, Virginia Department of Game & Inland Fisheries

ABSTRACT: Abstract. ?" Striped bass Morone saxatilis has been introduced primarily into southwest and western United States reservoirs to take advantage of underutilized pelagic forage and provide additional game fish opportunities. Difficulties in assessing pelagic forage and their relationships with striped bass in reservoirs have made it challenging for managers to measure supply-demand relationships that would indicate striped bass populations remain within acceptable levels for both optimum striped bass growth and competing piscivores. Gizzard shad Dorosoma cepedianum were monitored with fall nighttime electrofishing gear to determine catch per unit effort (CPUE) and percent of the population that were adults (?- 150mm) with striped bass growth at Smith Mountain Lake, Virginia. Additional clupeid species occupy Smith Mountain Lake; threadfin shad Dorosoma petenense, alewife Alosa pseudoharengus, and blueback herring Alosa aestivalis. These additional species were not included in the analysis due to vulnerability of fall electrofishing but impacts from predation were expected to be similar. Comparisons showed little correlation for overall gizzard shad abundance and striped bass growth but showed strong correlation with adult gizzard shad abundance (> 140 fish/hr) and percent of the gizzard shad population that were adults (> 50%) when compared to striped bass growth of ages 3 and 4. Years when striped bass growth was slowest, gizzard shad recruitment was highest but very few young-of-year (YOY) persisted to adults. Each reservoir has its own unique hydrological parameters, physical characteristics, and biotic factors dictating forage production but this study demonstrated a simplistic approach to a density dependent relationship for pelagic predator and prey species. Annual monitoring of multiple forage species can require more resources than most managers have available. However, this approach of monitoring gizzard shad populations by comparing adults and YOY, may provide a tool to determine if striped bass populations are balanced with a reservoirs existing forage base.