Assessing the Contribution of Anadromous Herring to Largemouth Bass Growth

Abstract

Juvenile anadromous river herring (alewife Alosa pseudoharengus and blueback herring A. aestivalis) spend the first 3 to 7 months of life in headwater lakes of coastal systems. Systems that support herring often produce trophy largemouth bass Micropterus salmoides. Even though biologists, managers, and anglers have speculated about the value of anadromous herring as a key prey for resident predators, the contribution that herring make to the diets of these predators has not been assessed. Herein, we quantified largemouth bass diets in two coastal lakes, Santuit and Coonamessett ponds, that contained anadromous herring, and we used bioenergetics modeling to evaluate the importance of herring prey to largemouth bass growth. During May through November 1994, largemouth bass diets consisted of various fish species, crayfish, and other invertebrates. Although not the most important prey overall, herring were the most important fish prey consumed in both lakes based on number of individuals consumed. In both lakes, herring were primarily eaten by largemouth bass that were fewer than 300 mm in total length after mid-August. Coonamessett Pond largemouth bass ate more herring and other fish prey and achieved better growth than did those in Santuit Pond. Bioenergetics modeling simulations revealed that water temperature does not explain the presence of trophy largemouth bass in southeastern Massachusetts. Because largemouth bass grow better on a diet that includes herring, we conclude that juvenile herring are an energetically valuable and a potentially key prey for largemouth bass. However, factors other than energetics mediate the use of herring by these resident predators. Further investigations into spatial dynamics, size structure, and foraging behavior are necessary to understand the mechanisms that drive interactions between largemouth bass and anadromous herring.