The Alewife, the Sea Lamprey, and How the Salmon Fishery Was Invented

Every charter boat working out of Ludington, Oswego, Sheboygan, and Frankfort is fishing for a species that does not belong here, stocked on purpose, to fix a problem caused by two other species that also did not belong here. The Great Lakes salmon fishery is not a natural resource. It is an engineered one, built in about ten years by people who took a large gamble.

Here is how it happened.

The lakes before

Into the early 20th century, the Great Lakes ran on a native system. Lake trout were the apex predator, a long-lived, deep-water, slow-growing fish that supported one of the largest commercial fisheries in North America. Below them, native lake herring (cisco), bloater chubs, whitefish, and sculpin filled the forage roles. The commercial catch out of the lakes in a good year ran into the tens of millions of pounds.

That system was already under strain from a century of intense commercial netting and from habitat damage — logging that silted spawning reefs, dams on the tributaries, and untreated discharge in the harbors. Then two things arrived that it had no defense against.

The sea lamprey

Sea lamprey are Atlantic natives: eel-shaped, jawless, with a rasping disc of a mouth. They attach to a fish, rasp through the skin, and feed on blood and body fluid. A single lamprey kills roughly 40 pounds of fish in its parasitic phase, and most fish attacked do not survive.

Niagara Falls kept them out of the upper lakes for as long as there was a falls in the way. Canal work — the Welland Canal, improved repeatedly through the 19th and early 20th centuries — removed that barrier. Lamprey were confirmed in Lake Erie in 1921, Lake Michigan in 1936, and all five lakes by 1938.

What followed was among the most complete predator collapses on record. Lake trout catch in Lake Huron fell from millions of pounds a year to essentially nothing by the late 1940s. Lake Michigan followed. Superior’s deeper, colder refuge held longest and still crashed. By 1960 the native apex predator was functionally gone from three Great Lakes.

The response was the Great Lakes Fishery Commission, created by treaty between the United States and Canada in 1955 specifically to deal with lamprey. Its control program — barriers on tributaries, traps, sterile-male release, and a selective lampricide, TFM, applied to larval nursery streams — has held lamprey to a fraction of peak abundance ever since. It is one of the longest-running invasive species control programs anywhere, and it has to be run every year forever. Stop, and the lamprey come back.

The alewife

The alewife is a small Atlantic herring that also found its way in through the canals, reaching Lake Michigan by 1949. With lake trout gone, nothing ate them.

The population exploded to a degree that is hard to overstate. By the mid-1960s alewife made up the overwhelming majority of the fish biomass in Lake Michigan. They are poorly adapted to fresh water and to Great Lakes winters, and they die in massive synchronized events. In 1967, alewife die-offs put an estimated tens of thousands of tons of rotting fish on Lake Michigan beaches. Chicago ran bulldozers on the lakefront. Beaches closed. It was a public health and tourism crisis on a lake serving millions of people.

Tanner’s gamble

Howard Tanner became Michigan’s chief of fisheries in 1964 and, by his own later account, was told to do something spectacular.

The logic was clean. There was an enormous, unexploited forage base of alewife. There was no predator to eat it. Pacific salmon were available from Oregon hatcheries, they eat exactly this kind of forage fish, they grow fast, and they draw anglers.

Michigan stocked coho salmon in 1966 into the Platte River and Bear Creek. In 1967 the returning fish were enormous and the response was instantaneous — a full-blown gold rush of boats on Lake Michigan, and a tragedy in September 1967 when a sudden storm caught a fleet of small boats that had no business being out and killed several anglers.

Chinook followed in 1967. They grew even faster and bigger, and the modern king salmon fishery was born. New York, Wisconsin, Ohio, Indiana, Illinois, and Ontario all followed with their own programs. Within a decade the Great Lakes had a recreational fishery worth billions of dollars annually, built on a stocked, largely non-reproducing predator eating a non-native forage fish.

It also worked ecologically, in the narrow sense. Alewife abundance dropped. The beach die-offs stopped.

The bill comes due

Engineered systems require constant management, and the Great Lakes have been proving that for fifty years.

The forage base shrank. Salmon are efficient. Combined with the arrival of zebra and quagga mussels in the late 1980s and 1990s — which filter plankton out of the water column and cut productivity at the base of the food web — alewife numbers fell hard. Lake Huron’s alewife population effectively collapsed in the early 2000s, and its chinook fishery collapsed with it, almost overnight.

Stocking became a balancing act. Agencies around the lakes now cut chinook stocking repeatedly to keep predator demand from outstripping the forage that remains. This is not a failure; it is the management the system requires. The Great Lakes Fishery Commission coordinates the science across eight states, two nations, and multiple tribal authorities.

The natives came partway back. Lamprey control plus stocking plus harvest limits have restored natural lake trout reproduction in Lake Superior, which is now largely self-sustaining, and produced meaningful natural reproduction in Lake Huron. Cisco restoration work is ongoing. Lake sturgeon, a species that predates all of this by millions of years, is slowly rebuilding under intense protection.

And chinook started reproducing on their own. Substantial fractions of the kings caught in Lake Huron and Lake Michigan are now wild fish from Michigan and Ontario tributaries, not hatchery fish — a stocked exotic that naturalized.

Why the history is useful on the water

Because it explains what you are looking at. When Lake Huron’s king fishing fell apart and its walleye fishing exploded, that was the alewife collapse changing which predator the lake could support. When Lake Michigan stocking numbers drop, that is a forage calculation. When you catch a wild-clipped chinook in the Manistee, that is a fifty-year-old decision still playing out.

Harvest limits, stocking allocations, and seasons across these lakes shift year to year in response to exactly this science. Check the current regulations with the state agency before you fish — the numbers change because the lake does.