Fighting for Our Fisheries
In the Great Lakes, native fisheries are threatened by invasive species.
The open water fisheries of the Great Lakes are the foundation of a $4 billion commercial and recreational fishing industry, as well as a living indication of the health of the entire freshwater system. Yet, as with freshwater and ocean fisheries around the world, Great Lakes fish populations have grown unstable.
“Historically, Great Lakes fish were part of a thriving commercial fishery that regularly delivered more than 100 million pounds of fish each year and fish towns like Leland, Michigan lined our shores,” said Scott Sowa, director of science for the Michigan chapter. “But overfishing, degraded habitat and aquatic invasive species led to the extinction of some species and significant declines in many others like lake trout, lake whitefish and an entire suite of deepwater ciscoes.”
Today, more than 68 percent of the world’s fisheries are either overfished or afflicted by declining stocks. With the total population expected to reach nine billion in the coming decades, experts agree we need solutions that will ensure fisheries can produce the food the world needs, while doing so in a sustainable manner that protects nature. This includes figuring out how to rebuild depleted fisheries in the Great Lakes.
A crucial step to stabilize and rebuild Great Lakes fisheries involves restoring and growing native fish populations—particularly those that serve as prey to popular sport fish such as salmon, walleye and northern pike.
The arrival of non-native species—such as alewives and zebra and quagga mussels—have harmed native populations of cisco and other species at the middle of the food web. These invasions have destabilized fish populations at both the bottom and top of the web, leading to population crashes that have drastically affected the region’s commercial fishing industry.
The good news is that water quality and overall habitat conditions in the Great Lakes are improved enough that conditions are right for restoring key native fish species. To work at a scale as large as the Great Lakes, TNC is employing multiple science-based approaches.
Reducing Invasive Species Impacts
Scientists estimate the Great Lakes are currently home to 180 invasive species. Established invasives such as sea lamprey, round goby, rusty crayfish, and zebra and quagga mussels have disturbed the Great Lakes food web, leading to profound consequences for ecologically and economically important native fish species such as lake herring, lake whitefish and lake trout. For example, both the round goby and rusty crayfish hide in rocky areas and prey on eggs laid by native fish, limiting the growth of their populations.
The Chicago Area Waterways System connects the Mississippi River and Great Lakes, providing a key passageway for invasive species moving between the two systems. TNC is actively participating on the advisory committee to assist Congress and the U.S. Army Corps of Engineers in finding solutions to prevent the spread of invasives—most notably Asian carp—through this passage.
Early detection and rapid response is critical to reducing the impact of newly-arrived aquatic invasive species. Data-driven and well-tested surveillance methods are necessary in keeping up with the fight against invasives. TNC and partners have developed environmental DNA methods that detect the presence of different species in an area by extracting DNA from water samples. If an invasive species is detected, this evidence can inform and direct what action needs to be taken to contain the spread. In some cases, a quick response may entirely eradicate an invasive species from the vicinity.
Great Lakes Aquatic Invasive Species
Reconnecting Rivers and Streams
Rivers and streams are important for supporting the migration, spawning and foraging of at least 43 species of Great Lakes fish. Yet, less than 25% of the tributaries in the Great Lakes basin are connected to the lakes. Various barriers, including natural waterfalls, man-made road crossings, dams and culverts disconnect the natural flow of water and impede populations of native fish.
Conservancy scientists are working to prioritize which barriers if replaced or removed would have the best outcome for native fisheries. The benefits must be weighed against the expense of removal and risk of access for invasive species.
TNC also belongs to a consortium of groups dedicated to reconnecting rivers and streams to study and map priority habitat across the basin. This data is being used to power FishWerks, an optimization tool for habitat restoration projects.
Restoring Spawning Habitat
Locating and mapping spawning and nursery habitat is one step toward conserving fisheries. The next is to assess the quality of that habitat and restore key locations where spawning success could be improved. In 2015, after identifying rocky reefs in Lake Michigan where lake trout, lake whitefish and lake herring were known to spawn, The Nature Conservancy in Michigan undertook its first underwater restoration project in Grand Traverse Bay.
Partnering with the Michigan Department of Natural Resources and Central Michigan University, we restored an existing reef near Elk Rapids, Michigan, by adding 450 tons of special cobble rock to the site. This reef, degraded years ago by the iron ore industry, is one of three known spawning reefs in Grand Traverse Bay. The newly-added rocks provide nooks for lake herring and lake trout to lay their eggs and keep them safe through the harsh Great Lakes winters.
In addition to restoring the reef with new rock, scientists are also using the site to test new eradication tools for round goby and rusty crayfish—two invasive species who prey on the eggs laid there. This two-step approach has led to encouraging early results.
Working Together for Great Lakes Fisheries
The sheer size of the Great Lakes makes fisheries management a complex issue. Currently, each lake has a “lake committee” comprised of provincial, state and tribal agencies, with support from the Canadian and U. S. federal governments, that ensures the health of our fisheries. This means dozens of agencies, academic institutions, NGOs and businesses are collaborating to make decisions about fish stocking, harvesting and regulations. Now, these managers are looking for ways to work together on restoration and other environmental measures.
“Stakeholder cooperation will be key to success,” said Matt Herbert, an aquatic ecologist with the Michigan Chapter. “It will create a massive ripple effect throughout the system that leads to increased alignment of priorities, strategic allocation and leveraging of resources and coordinated management actions. And, that’s why we are working with so many partners from the public agencies, Great Lakes tribes, and the fishing industry.”
Now is the time for these myriad decision makers to come together around shared restoration goals. Our fisheries are at a critical conservation moment: water quality and habitat have improved enough to allow them to rebound. By working together to take advantage of this opportunity, we hope to achieve an overall 15 percent increase in availability of harvestable species, and to better protect the long-term health of our fisheries for both people and nature.