Effects of the Introduction of Mississippi Silverside (Menidia audens) and Florida Largemouth Bass (Micropterus salmoides floridanus) on the Feeding Habits of Young-of-year Largemouth Bass in Clear Lake, California

Abstract

Young-of-year largemouth bass in Clear Lake, California, switched from feeding largely on blue-gill (Lepomis macrochirus) to feeding largely on Mississippi silverside or on a mixture of prey species following the establishment of the silverside in the lake in 1967. Choice of prey, however, was influenced by relative abundance of the prey, the habitat occupied by the bass, time of day, and size of the bass. The bass usually switched to a predominantly fish diet at a smaller size when silversides were the main prey than when bluegill or Sacramento blackfish (Orthodon microlepidotus) were the main prey. The success of the introduction of small numbers of Florida largemouth bass into the lake in 1969-1971 was demonstrated by the presence of significant numbers of bass that could be classified as intergrades between Florida and northern largemouth bass (M.s. salmoides), the subspecies originally introduced into Clear Lake. No meaningful differences in the feeding habits or average lengths of the intergrades and “pure” northern bass were found.