Size-Dependent Alewife Predation on Larval Walleyes in Laboratory Experiments

Abstract

Abstract Alewives Alosa pseudoharengus can be significant predators on larval fish, and fishery managers must consider potential predation when developing stocking strategies. We conducted laboratory experiments to determine sizes of larval walleyes Stizostedion vitreum that alewives can capture. Adult alewives (122 ± 1.52 mm total length, TL) preyed intensely on larval walleyes from the time the larvae hatched until they reached about 16 mm TL. All larval walleyes smaller than this size were captured on the first strike by an alewife. Avoidance behavior by larval walleyes was first observed when they reached 16–19 mm TL, and although some survived the first strike, all were consumed by the end of 1 h. When larvae averaged about 25 and 30 mm TL, few were captured on the first strike, and 75% and 33%, respectively, were consumed within 1 h. When larvae were about 34 mm TL, only 5% were eaten by the end of 1 h. Alewife gape height and width were both about twice as large as the largest larval walleye body h...