Trophic resource overlap between age-0 striped bass and largemouth bass in Smith Mountain Lake, Virginia

摘要

Small body size in fall and low winter survival of fingerling striped bass Morone saxatilis stocked into Smith Mountain Lake, Virginia, have been attributed to slow growth during summer months. Although small size at stocking appears to be the primary factor restricting fish prey consumption and rapid growth, trophic competition may also be a contributing factor. We examined the food habits of sympatric populations of age-0 striped bass and largemouth bass Micropterus salmoides over the 1994 and 1995 growing seasons to assess temporal and length-related patterns and similarities in trophic resource use. With increasing predator length, food habits for both species shifted from zooplankton to insect and then to fish as the principal prey items over both growing seasons. Except for fish smaller than 50 mm during June and July 1994, diet overlap was insufficient (Schoener's index value <0.60) to suggest trophic competition. Striped bass between 50 and 100 mm long primarily ate aquatic insects and cyprinids, whereas largemouth bass in the same length range ate aquatic and terrestrial insects. Cyprinids were the principal fish prey of striped bass less than 100 mm long, with age-0 alewives Alosa pseudoharengus becoming the predominant prey for larger individuals. Darters and age-0 sunfishes constituted the primary fish prey of largemouth bass regardless of body length. Although temporal and length-related segregation by food habitats may be sufficient to minimize trophic overlap, limitations in these resources may cause interspecific competition, especially for smaller individuals. We recommend releasing striped bass at a larger size (>50 mm) and earlier in the growing season to minimize the potential for trophic competition with age-0 largemouth bass immediately after stocking.