The Effect of Aquatic Vegetation on Survival and Foraging Return of Juvenile Largemouth Bass

Agencies typically introduce aquatic vegetation to increase recruitment of sport fishes (provides predation refuge), but this can also reduce the foraging return of juvenile fishes. Objectives of this study were to determine if aquatic macrophytes 1) reduce predation mortality and 2) reduce the foraging ability of juvenile largemouth bass.  Interactions between 10 juvenile and one adult largemouth bass were observed in tanks with and without vegetation. Vegetation significantly reduced the capture efficiency, search time and number of captures of adult largemouth bass, resulting in higher juvenile survival in vegetated trials. For objective 2 juvenile largemouth bass were tested in aquaria while feeding on chironomids or juvenile fathead minnows with different levels of structural complexity (five simple vegetation densities [0, 125, 250 , 500, and  1000 stems/m²] and three complex vegetation densities [using branched stems; 125, 250, and 500 stems/m²] when feeding on 30 chironomids or five juvenile fathead minnows.  Foraging return was similar among all stem treatments when chironomids were used as prey. Piscivorous trials are ongoing.  Preliminary results suggest vegetation provides a predation refuge that increases juvenile largemouth bass survival without reducing foraging return.  As such, vegetation enhancement may improve largemouth bass year-class strength.