Effects of Stocking Hybrid Striped Bass in Spring Lake, Illinois

Abstract

Spring Lake, a 101-hectare impoundment that supplies potable water to Macomb, Illinois, was stocked with hybrid striped bass (striped bass Morone saxatilis ♀ x white bass M. chrysops ♂) from 1980 through 1985 at rates of 20-30 fish/hectare. Fish from the 1982 stocking reached the 432-mm minimum legal length in 28 months. Fish stocked when they were 20 mm long in June grew better and had higher survival rates than those stocked at larger sizes or later in the summer. Hybrid striped bass ate primarily gizzard shad Dorosoma cepedianum. Adult largemouth bass Micropterus salmoides, white crappies Pomoxis annularis, and channel catfish Ictalurus punctatus also relied heavily on gizzard shad, whereas juveniles fed mainly on invertebrates. Only white crappies showed any major seasonal change in food habits. By the end of 1985, white crappies were attaining a length of 200 mm 1 year earlier than in 1980. Numbers of white crappies and average sizes increased while fishing pressure and catches of other target species remained relatively unchanged. Some spillway loss of hybrids occurred.