Largemouth Bass Predation on Stocked Striped Bass in Smith Mountain Lake, Virginia

Abstract

First-year survival of striped bass Morone saxatilis stocked into lakes and reservoirs is often poor, but causes of mortality have not been determined. We quantified losses of stocked, age-0 striped bass to predation by largemouth bass Micropterus salmoides in Smith Mountain Lake, Virginia, where first-year striped bass survival averages 25% and the largemouth bass is the principal littoral piscivore. To examine their diet composition and abundance, largemouth bass were sampled throughout the month following the stocking of striped bass in two coves in 1994 and one cove in 1995. We used a bioenergetics model to extrapolate total prey consumption over the month and the numerical contribution of striped bass to the largemouth bass diet. Only 14 striped bass were recovered in 1,147 largemouth bass stomachs over the 2 years. Percentage losses of striped bass to largemouth bass predation were 0.1% in each cove in 1994 and 3.0% in the single cove in 1995. Predation may have been constrained by the small size (24–74 mm) of striped bass and by the availability of spawning alewives Alosa pseudoharengus as alternate prey (i.e., adult alewives constituted the bulk of the largemouth bass summer diet). In pool experiments, largemouth bass ate significantly more alewives than striped bass when both prey were available; their consumption of striped bass increased in trials where alewives were absent. Abundance of alternate prey and their use by largemouth bass should be assessed before selecting striped bass stocking sites. Spreading the stocking over multiple sites to reduce predation mortality was unnecessary in Smith Mountain Lake.