By Alan Marble

229t6stor Dead AlewivesAt least, that is what my dog Goose tells me, as he surreptitiously crunches down on yet another dried dead fish off the Lake Michigan beach.  Goose is one of our two Labrador retrievers.  He is going on 11, and, while his hearing is just fine, he has reached that stage of life where he gets to choose which commands to obey.  The first command we teach our pups is, “Leave it!”  Translated, that means whatever the pup is doing, or eating or even thinking, stop it right now.   With Goose, not so much.

The aforementioned dead fish are alewives, singularly alewife. Like potato chips, of which it is said that you can’t eat just one, you don’t have just one dead alewife on the beach.  You have a bunch.  More on that in a minute.

Talk about unintended consequences; the human race sure knows how to leap-before-it-looks.

An important industrial milestone was achieved in the early 20th century when the Welland Canal was completed, linking the Atlantic Ocean and the upper Great Lakes. Shipping bolstered the economy of cities from Duluth to New York, and many points in between. 

Along with the ore freighters, however, came a couple of marine invaders which began establishing themselves in Lakes Huron and Michigan.  Relatively small in stature, these fish made up for their size with their amazing ability to reproduce themselves.  Enter the alewife and the lamprey eel.

Anadromous in their native Atlantic Ocean, lampreys and alewives evolved to live in saltwater and breed in freshwater.  The lack of a saltwater source was of no importance, however, as they adapted to living and spawning in freshwater.  Unseen as they moved into the upper Great Lakes, they found themselves in vast inland seas, a sterile and largely lifeless aquatic environment.  Commercial fishing for lake trout in the 1940’s was lucrative, and in 1945 a record haul of 6.5 million pounds of lakers went from Lake Michigan to fish markets throughout the eastern half of the country.  Ten years later, they were all but gone.  The Department of Conservation (now the Department of Natural Resources), utilized 1,400 miles of gill nets to sample the lake trout population.  Those miles yielded a measly 8 lake trout.  For all intents and purposes, lake trout had been extirpated from Lake Michigan. 

Unregulated commercial fishing rang the bell, and the lamprey eels delivered the knock-out blow.  As unlovely as any creature in our lakes, the lamprey eel is not a true eel, but a jawless fish that has a circle of rasping teeth which burrow through the soft skin of lake trout and related species of fish.  The suction action keeps them attached to their hosts as they secrete an enzyme into the wound to prevent coagulation.  Over the course of 18 months of adult life, the average lamprey kills 40 to 50 trout and salmon.  They spawn in the spring, in rivers such as the Platte, and die, as do all Pacific salmon.

With the top-line predators all but eliminated, the alewives took over.  Spawning in huge numbers, with few fish around to dine on them, their population took on staggering proportions.  The Department of Conservation estimated that, in 1965, alewives comprised 90% of the biomass of Lake Michigan, at the incredible weight of 5 to 6 billion pounds.  Let’s use a checklist here:

A.         Huge numbers of alewives.  Check

B.         No one home to eat alewives.  Check

C.        Alewives are a small relative of ocean herring, are bony, skinny, oily and taste awful (unless you are a salmonid).  Check

D.        DDT, widespread throughout the state for insect control, all but eliminated our common fish-eating coastal birds (tern species, gull species, mergansers) by interfering with calcium formation in their eggs, leading to totally failed nests.  Check

So, what to do?  Mother Nature, who is highly effective when she is taking care of population balance issues, is unfortunately ruthless and messy.  Die-offs of millions upon millions of alewives began in the 1960’s and stretched into the 70’s.  Piles 8 feet high of dead fish stank up the place, and coastal communities turned to bulldozing and burning huge numbers of dead fish.  The peak die-off occurred in 1967.  With an alewife population estimated at 5 billion fish, given an alewife’s 5-year life-cycle, you have a billion fish dying each year.  Given the fact that Lake Michigan’s prevailing winds are southwesterly and northwesterly…well, you get the point.  Add to that huge numbers of young alewives still coming through the canal, and others hatching in natural reproduction.  It began an incredible cycle generating millions of fish with massive die-offs, without an end in sight.

The truly amazing story of what happened next is for another day. In a nutshell, the Department of Conservation introduced coho salmon from Oregon into tributary streams.  Dow Chemical of Midland, MI, donated thousands of hours of testing and developed what came to be the gold standard of pesticides, which killed the larvae of lampreys without affecting the surrounding aquatic flora and fauna.  The 660,000 smolt coho salmon (5 inches in length), planted in the Platte River and Bear Creek in the spring of 1967 ventured forth into a target-rich environment.  Biologists (and everybody else) held their breath and waited.  Eighteen months later, in September of 1967, those little salmon did just what they were supposed to do; return to the streams in which they were planted.  In that time those salmon grew from perhaps 2 ounces to 20 pounds, gorging on alewives.  They all spawned in the rivers, and died, as do all Pacific salmon species.

Alewives, nearly a hundred years later, are now part of our Great Lakes.  They are the primary forage fish for the even larger Chinook salmon, which have largely replaced coho salmon (live longer, get bigger, easier to raise in hatcheries, more successful in natural reproduction).  The current die-off, which is two months in duration and still going on, is “normal” but also alarming to DNR fisheries personnel.  The dying fish are smaller (younger) on average compared to die-offs of 10 years ago.  The die-off is also larger than recent die-offs.  Sport fishermen are seeing huge schools of what are believed to be alewives on their onboard sonar screens. 

What’s next?  Hard to say.  It’s sort of like what they say about Michigan’s weather…stick around, it is bound to change.