Adverse Effects of Alewives on Laurentian Great Lakes Fish Communities

Abstract

The alewife Alosa pseudoharengus, an invader to the Laurentian Great Lakes from the Atlantic Ocean, has been blamed for causing major disruptions of Great Lakes fish communities during the past 50 years. We reviewed the literature and examined long-term data on fish abundances in the Great Lakes to develop a new synthesis on the negative effects of alewives on Great Lakes fish communities. The results indicated that certain fish populations are substantially more vulnerable to the effects of alewives than others. More specifically, the effects of alewives on other fish populations appeared to follow a continuum—from such fishes as slimy sculpin Cottus cognatus, lake whitefish Coregonus clupeaformis, and bloater Coregonus hoyi, which were relatively unsusceptible—to Atlantic salmon Salmo salar, lake trout Salvelinus namaycush, and emerald shiner Notropis atherinoides, which were highly susceptible. Intermediate species in this continuum included yellow perch Perca flavescens, deepwater sculpin Myoxocephalus thompsonii, and burbot Lota lota. The predominant mechanism by which alewives exerted their negative effect appeared to be predation on the larvae of other fishes. The key factor in the extirpation of Atlantic salmon from Lake Ontario, however, was probably early mortality syndrome induced by a diet rich in alewives. We conclude that the degree of restoration of the native Great Lakes fish community depends in part on the degree of control of the alewife population.