Alewives | Something fishy going on... Part 1

In early July 2022 we drove to Northern Michigan to drop our older daughter off at summer camp for two weeks. For the weekend we stayed at a house about 25 miles east of Ludington. My husband and I drove up into Ludington State Park on the shores of Lake Michigan. As we drove in, gorgeous white sand dunes lined the road. It was early evening, so a transition time with beachgoers emerging from trails through the dunes, colorful umbrellas, chairs and towels in hand, headed back to their cars.

Ludington State Park (MI), Lake Michigan, July 2022

We parked and got out of the car to walk out on the beach. We were immediately greeted by what I can only describe as, frankly, a strong, unpleasant odor. Putrid is too strong a word, but it was fishy, and rotten. We walked over a dune path and emerged on the beach. The view was incredibly picturesque – gorgeous wide white sand beach and cottonball clouds. But a quick stroll closer to the water revealed the source of the smell – there was a band of dead, washed up small, silver fish stretching down the beach in both directions.

These fish are alewives, and wash-up like this is, somewhat unfortunately, not an uncommon occurrence on the shores of some Great Lakes. The history of the issue is well-explained in Dan Egan’s book The Death and Life of the Great Lakes that I refer to time and time again. It’s a story of ecological imbalance.

River herring are a species well known to east coast North Americans for centuries. They hatch in the rivers flowing into the Atlantic and then head into saltwater for much of their life before heading back to the freshwater to spawn.

River herring were first found in Lake Ontario in the late 1800s. It’s unknown how they got there – whether they made their way on their own through the St. Lawrence River or accessed it through the canals dug at the end of that century. For several decades they lived in some ecological balance as the Atlantic salmon and lake trout were natural predators. But once the evolving commercial fishing industry ramped up and overfishing of salmon and trout became an issue, the river herring became massively overpopulated. By 1931 they had been found in Lake Erie and by 1954 in the waters of all Great Lakes.

The Great Lakes river herring quickly evolved to be a smaller, toothless version of the East Coast river herring. They lacked natural predators, and quickly came to dominate the fish mass of the lakes, especially Lake Michigan, where by 1965 they were likely 90 percent of the lake’s fish mass. By this point they had also come to take on another name – alewives.

My dad was living in Chicago in the summer of 1967 when the city experienced the most infamous alewife happening of all time. There was essentially a massive die-off of alewives that dumped billions of fish carcasses on the shores of Lake Michigan around Chicago. 30 miles of shoreline were “smothered”, as Egan writes, by piles of decaying fish sometimes shin deep. The cost of management and clean-up in Chicago was pegged at $50 million – $350 million in 2017 dollars. The price tag across the entire summer and all the shores impacted: close to $1 billion in 2017 dollars.

To most people, the die off was seen, and smelled, along the shore. However, in the water, there were reports of piles of carcasses at the bottom of the lake over 6 feet high and live schools of the fish were so thick that boaters described running into one being like running into a snowbank.

What happened?

The reason turns out to be to be biological maladaptation. The fact that the alewives, originally saltwater fish, were able to live in the freshwaters of the Great Lakes didn’t mean that they were able to thrive. Their bodies simply didn’t work well due to the lack of salt. They experienced kidney stress, stunted thyroid activity, and an inability to handle the dramatic water temperature changes the Great Lakes can experience. But their mere survival had thrown Lake Michigan completely off-balance with no real predators to keep the population in check.

So what did they do about it? Stay tuned for Part 2 of the story in my next post.