Great Lakes: In America’s Great Lakes, invasive mussels made the water look cleaner but broke the food chain; native whitefish could now vanish from some areas within five years
For centuries, lake whitefish has beem more than just a fish in the Great Lakes region of North America. It was a source of food, income and tradition for Indigenous communities. Towns along the lakes built their economies around the demand for this fish with some places becoming major fishing hubs.One such place was Sandusky, Ohio. A book published in 1888, Sandusky of To-Day, also described the town as the largest fresh water fish market in the world and called lake whitefish Sandusky’s pride.But more than a century later, the fish that once filled the waters of the Great Lakes has sharply declined. Scientists now warn that it could disappear from some parts of the region within the next five years.According to The Gaurdian, researchers say the main reason behind the decline is the spread of invasive zebra and quagga mussels. These small freshwater creatures have changed the Great Lakes ecosystem by disturbing the food chain that young whitefish depend on.
Mussels changed food chain
The decline of lake whitefish began to become noticeable in the 1990s when fishers and researchers started finding fewer young and juvenile whitefish in Lake Erie.Scientists later linked the fall in whitefish numbers to the arrival of invasive mussels. Zebra and quagga mussels reached the Great Lakes after travelling in the ballast water of ships from overseas.The mussels themselves did not directly attack whitefish. But, they did affect the tiny organisms that support the fish population.Before the mussels spread widely, young whitefish relied heavily on diporeia, a small shrimp-like crustacean found in cold, deep waters. These creatures are rich in oil and provide an important food source for whitefish fingerlings, or newly hatched young fish.However, zebra and quagga mussels consume phytoplankton which includes tiny algae and bacteria that diporeia feed on. As mussels removed large amounts of phytoplankton from the water, diporeia populations declined.This created a chain reaction. With fewer diporeia available, young whitefish struggled to find enough food during a critical stage of their growth.
Zebra mussels are an invasive species that can drastically change freshwater ecosystems.
Hidden cost of clean water
The spread of invasive mussels has created a complicated situation in the Great Lakes. While the mussels have damaged parts of the natural food chain, they have also removed phosphates and other pollutants from the water.Today, quagga and zebra mussels cover large areas of lakebeds across hundreds of miles of the Great Lakes. A major survey of fish populations in western Lake Erie, released last year, warned that lake whitefish could disappear from some parts of the Great Lakes within five years if the decline continues.For Indigenous fishers, the loss has had a serious impact. William Ortiz of the Little Traverse Bay Bands of Odawa Indians says whitefish remains an important source of income for his community. “It’s the biggest source of income for the tribe’s fishers. We rely on whitefish probably more than anything,” he said.Ortiz began commercial fishing for whitefish in Lake Michigan in 2015. He said he noticed a steady decline during his years on the water. “From 2015 to 2020, there was a noticeable decline. I did it full-time for nine years, but it’s hard to make a living when there’s not a lot of fish out there,” he said.
Scientists search for solution
The decline of whitefish has pushed researchers and conservation officials to look for solutions to control invasive mussels. Some studies have explored whether native fish that eat mussels could help reduce their numbers. Recent research suggested that freshwater drum, also known as sheephead, may be able to control mussel populations in certain areas. A study published in June found that freshwater drum in western Lake Erie and areas around Sandusky consumed large amounts of quagga and zebra mussels between 2013 and 2023.Government agencies are also testing methods to remove mussels directly. In Ohio, the department of wildlife has used large tarps placed on the lake bottom, with carbon dioxide injected underneath to kill mussels. Officials have also used high-pressure water jets to destroy mussel colonies.Travis Hartman of the Lake Erie Fisheries Program at Ohio’s department of wildlife said these methods worked effectively, but using them across the Great Lakes would be difficult. “Both methods were very effective, but as you might imagine the scale and cost of effectively treating extremely large areas is a significant challenge,” he said.“It’s fair to say that we are finding ways to be successful, but we have not found cost-effective large-scale ways to meet the needs at a Great Lakes scale,” he added.Last year, two Michigan congressional representatives introduced a bill proposing $50 million every year for 10 years to support research into controlling invasive mussels in the Great Lakes. The proposal is currently before Congress.
