REVIEWS OF STOCK ENHANCEMENTS OF LARGEMOUTH BASS AND CRAPPIES WITH CONSIDERATION OF FACTORS AFFECTING STOCK ENHANCEMENT SUCCESS

Stock enhancement of centrarchid populations is a common practice among state natural resource agencies across the U.S.  Success of centrarchid stock enhancements varies, and the factors that influence success are unclear.  We reviewed published literature on largemouth bass and black and white crappie stock enhancements.  We examined system size, stocking size, stocking density, and subsequent hatchery contributions.  For largemouth bass, system size ranged from 1-8,484 ha.  Stocking size ranged from 23-315 mm TL.  Stocking density ranged from 1-645 fish/ha.  Contribution of hatchery fish to a year-class ranged from 0-100% and from 0-90% in the fall and spring after stocking, respectively.  Median stocking contributions were 15% and 14% for the fall and spring, respectively.  For crappies, system size ranged from 58 to 12,270 ha.  Stocking size stocked ranged from 39 to 117 mm.  Contribution of hatchery fish to a year-class ranged from zero shortly after stocking, to 92% in the fall for age-2 fish.  However, median stocking contribution for crappies was 0%.  We summarized other factors that potentially influence success of centrarchid stock enhancements.  For example, logistic regression indicated that stocking largemouth bass raised on minnows (rather than pellets) and stocking larger largemouth bass were practices more likely to result in high fall contributions to the year-class.  For crappies, handling and hauling mortalities appeared to influence success of stock enhancements.  Mortality at the end of the hauling process ranged from 3.5% to 94.0%.  Ninety-six hour handling mortality ranged from 7.0% to 56.0%.  Careful consideration of hatchery rearing methods and stocking procedures are likely to improve centrarchid stock enhancements and increase the likelihood that stocking programs achieve their goals.