The lake trout used to be the fish to catch in the Great Lakes. But by the 1950s, severe overfishing and an infestation of an eel-like, blood-sucking parasite called the sea lamprey had drastically reduced the number of lake trout and other fish.
Then, a fish called the alewife invaded the Great Lakes through man-made canals.
Without enough lake trout to keep them in check, alewife populations exploded, and have since varied wildly year to year. Dead alewives have been spotted washed up on beaches in piles stretching miles along Great Lakes coasts.
In 1964, the Department of Natural Resources hired a fish biologist named Howard Tanner. They asked him to figure out how to deal with the alewife problem, and left him with an order: “Make it spectacular.”