Alewife

Fascinating facts about the Alewife

• Alewives reach a typical standard length of about 30 cm (12 in) and are one of the smaller shad species in North America. They have a deep, laterally-compressed body, a bronze-colored head and a grey-blue to greyish-green back.
• Alewives entered the Great Lakes via the Welland Canal, bypassing Niagara Falls, and by the 1950s were abundant in Lake Huron and Lake Michigan, with their peak abundance lasting until the 1980s while lake trout were essentially wiped out.
• When alewives exploded in the Lakes, they experienced massive seasonal die-offs that left many fish washed ashore in windrows on the shorelines.
• To curb the alewife surge, fisheries introduced Pacific salmon, first coho, then Chinook, into the Great Lakes, hoping the predators would eat the invaders. The salmon did catch some alewives and even sparked a new sport-fishing industry, but the control was only partial. This illustrates the limits of biological control: adding a predator can create a new fishery without fully solving the original problem.
• Dams and other barriers have blocked alewives from reaching historic spawning streams, contributing to population declines that led several states to ban their capture. In Boston’s Mystic River, a fish ladder with monitoring cameras is helping alewives return to their birthplace each spring.

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