The Great Lakes region is known for its abundance of seafood, from walleye to yellow perch. But what about oysters?
You may be surprised to learn that there are indeed oysters in the Great Lakes, but not the kind you’re thinking of. These freshwater “oysters” are just as delicious and desirable as their ocean-dwelling counterparts, and they’re virtually free of charge.
In this article, we’ll explore the world of freshwater mussels and their important role in the Great Lakes ecosystem. We’ll also take a closer look at the challenges facing these endangered and threatened species, and what we can do to help protect them.
So grab a seat and get ready to dive into the fascinating world of Great Lakes “oysters”.
Are There Oysters In The Great Lakes?
As mentioned earlier, there are indeed “oysters” in the Great Lakes, but they’re not the same as the ones found in the ocean. These freshwater “oysters” are actually mussels, and they play a crucial role in the ecosystem of the Great Lakes.
Freshwater mussels are bivalved mollusks that have a shell made up of two halves or valves to protect their soft body parts. They are commonly called freshwater clams and are often referred to as “ecosystem engineers” because they modify aquatic habitats, making them more suitable for themselves and other organisms.
Most freshwater mussels live in flowing waters like rivers and streams, and they have a close association with fish. In their life cycle, males release sperm into the water that is drawn in by the females. The fertilized eggs are brooded in the female mussel’s gills, where they develop into tiny larvae called glochidia. The glochidia are then released by the female mussels and attach to fish gills or skin as temporary parasites. If glochidia cannot find their host fish, they will not survive.
Over a few weeks to several months, the glochidia develop or metamorphose into juvenile mussels while attached to the host fish. When ready, the juveniles detach from the host, fall to the river bottom or lakebed, and begin their lives as free-living mussels.
The Difference Between Freshwater Mussels And Ocean Oysters
While there are similarities between freshwater mussels and ocean oysters, there are also significant differences. One of the most obvious differences is their habitat. Freshwater mussels are found in rivers, streams, and lakes, while ocean oysters live in saltwater or brackish water environments.
Another notable difference is their shell texture. Freshwater mussels have thin, mostly smooth shells, while oysters have very thick, rough, calcified shells. Additionally, the shape of their shells is different. Mussels have wedge-shaped shells that are longer than they are wide, while oysters have oval-shaped shells that can vary due to the presence of barnacles.
In terms of size, oysters are typically larger than mussels, weighing on average a full ounce more and growing half an inch longer. Oysters also tend to be more irregular in shape compared to clams or mussels.
Another significant difference is their method of feeding. Freshwater mussels are filter feeders, meaning they draw water into their bodies and filter out small particles like plankton and algae. Oysters also filter feed, but they do so in saltwater or brackish water environments.
Finally, their economic value differs as well. While both freshwater mussels and ocean oysters are commercially harvested for consumption or pearls, the value of commercially-harvested bivalve mollusks in the United States is estimated to be about $1 billion annually, with oysters accounting for a significant portion of that value.
The Importance Of Freshwater Mussels In The Great Lakes Ecosystem
Freshwater mussels are arguably one of the most important natural resources in the Great Lakes ecosystem. They are filter-feeding powerhouses that remove impurities, sequester heavy metals, and filter out nutrients as water flows by, making food sources more visible and available for other organisms to eat. Mussel beds also create habitat for other aquatic invertebrates, which in turn are eaten by fish. Empty mussel shells are a refuge for crayfish, snails, and fish, while decaying shells are a slow-release source of calcium, phosphorous, and nitrogen.
In addition to their ecological benefits, freshwater mussels also play an important role in the cultural history of the Great Lakes region. They have been used by indigenous peoples for thousands of years as a food source and for making tools, utensils, and jewelry. Today, they are recognized by Tribes as a “first food” of important cultural significance.
Unfortunately, many species of freshwater mussels in the Great Lakes are declining due to habitat loss, pollution, and over-harvesting. This has led to a decline in their ecosystem services and cultural significance. Restoring native freshwater mussels to the Great Lakes is an important step towards improving water quality and preserving cultural heritage.
Threats Facing Freshwater Mussels In The Great Lakes
Despite their important role in the ecosystem, freshwater mussels in the Great Lakes face a number of threats that have led to dramatic population declines. Habitat degradation is the most significant factor causing the decline of mussel species throughout North America. Dams, channelization, severe erosion, and dredging physically alter habitat conditions that these animals require to live. In addition, water pollution and the introduction of invasive species like zebra and quagga mussels have also contributed to their decline.
Native freshwater mussels in the Great Lakes have experienced significant population declines due to habitat degradation, water pollution, and the introduction of invasive species. The Detroit River is a prime example of this decline. However, there is still hope for these endangered and threatened species. A Central Michigan University Ph.D. student is focusing her dissertation on if and where native mussels remain in the Detroit and St. Clair Rivers and predicting other refuge areas for these imperiled species.
Freshwater mussels are also threatened by dams and other barriers that restrict movement of host plants and alter water levels. Water diversions that alter streamflow and function, changes to precipitation amounts and warming waters caused by climate change, exposure to toxic chemicals, and general degradation of freshwater ecosystems also pose significant threats to their survival.
The same characteristics that make freshwater mussels valuable to protecting water quality – their sedentary nature, ability to reach high density, and filtering lifestyle – also make them vulnerable to a wide range of stressors to which they may ultimately succumb. The introduction of invasive species, impacts to host fish populations, and other impacts to aquatic habitat also likely play a role in their decline.
In Michigan alone, 44% of mussel species are listed as either endangered or threatened under the Michigan Natural Resources and Environmental Protection Act of 1994. Five of these species are also federally listed and receive additional protection under the Endangered Species Act. It is crucial that we take action to protect these important ecosystem engineers before it’s too late.
Conservation Efforts To Protect Freshwater Mussels
Freshwater mussels are the most imperiled group of animals in North America, with 66% of species at risk. The factors contributing to these declines are habitat fragmentation and alteration, point- and non-point source pollution, navigation-related impacts, and exotic species introductions. The decline in mussel populations has led to conservation efforts to protect and restore them.
Conservation agencies and organizations work together to conserve and restore mussel populations. One of the current efforts is centered around quantifying the ecosystem services that native mussels provide. Freshwater mussels are known as “ecosystem engineers” because they modify aquatic habitats, making them more suitable for themselves and other organisms. By understanding the ecosystem services provided by freshwater mussels, we can better appreciate their importance and work towards their conservation.
Another effort is examining the sub-lethal effects of lampricides on native mussels. Lampricides are chemicals used to control sea lamprey populations in the Great Lakes. However, these chemicals can have negative effects on native mussel populations. Researchers are working to understand these effects and develop ways to minimize them.
Predicting the distribution and abundance of mussels from geomorphic indices is another conservation effort. Geomorphic indices are physical characteristics of river systems that can be used to predict where freshwater mussels are likely to be found. By understanding the distribution and abundance of mussels, we can focus conservation efforts in areas where they are needed most.
Finally, developing methods to assess the relative health of mussels in the Upper Mississippi River is also an important conservation effort. By monitoring the health of mussel populations, we can detect early warning signs of population declines and take action to prevent further declines.
How You Can Help Protect Freshwater Mussels In The Great Lakes
Freshwater mussels in the Great Lakes are facing threats from invasive species, pollution, and habitat destruction. However, there are several things you can do to help protect these important organisms:
1. Prevent the spread of invasive species: Invasive species like zebra and quagga mussels can harm native freshwater mussels by over-filtrating water and altering the food web. To prevent the spread of invasive species, always inspect your boat, trailer, and other recreational equipment that have been in contact with water. Remove all mud, plants, or animals, drain all bilge water, live wells, bait buckets, and all other water from your boat, engine and equipment. Wash all parts of your boat, paddles, and other equipment that have been in contact with water. Do not allow wash water to flow in any water body or storm sewer. Dry boats and trailers in the sun for five days before launching into another body of water.
2. Support restoration efforts: Restoration projects have the potential to improve mussel habitat, but mussels can be sensitive to management and construction activities. You can support restoration efforts by working with partners to improve aquatic restoration efforts to protect freshwater mussels. This includes assisting with pre-project surveys, providing guidance for restoration designs, and coordinating salvage and relocation efforts.
3. Advocate for funding: Programs like the Great Lakes Restoration Initiative (GLRI) are essential for protecting freshwater mussels in the Great Lakes. Each year, Congress needs to approve and fund the GLRI. In recent years it has maintained funding at $300M per year. The GLRI is needed, and needs to be fully-funded, to ensure that federal and regional programs are fully funded to stop the threat of invasive species.
By taking these actions, you can help protect freshwater mussels in the Great Lakes and ensure that they continue to play a crucial role in the ecosystem of this important region.
