Invasive Grass Carp Threatens Georgian Bay

July 29, 2019 9:05 am Published by

By Mary Muter,

Chair, Georgian Bay Great Lakes Foundation

What is the biggest threat to Georgian Bay’s high quality wetlands and the fishery? Is it climate change? Is it low water levels? Is it development? Is it Phragmites? No – it is none of these. It is the voracious and invasive Grass Carp that are now present in Lake Erie and have been caught in Lake Huron. These large invasive fish once established in Georgian Bay can rapidly wipe out all the plants in a wetland, leaving nothing to nourish or protect native fish species.

The Invasion has started! Grass Carp is reproducing in two Ohio rivers that flow into Lake Erie, and 10 individuals have now moved upstream into Lake Huron.

Last June, when I attended the International Association of Great Lakes conference, it was clearly stated: “It will take fewer Grass Carp [than the other three types of invasive Asian Carp that are in rivers south of Chicago and being blocked by $Millions of electric barriers in the Chicago Sanitary Canal] to have a substantial impact on Great Lakes ecology.” Shockingly, I learned that Ohio and Michigan, with Great Lakes Restoration Initiative

$2 Million Funding, are working with Michigan State University researchers. They are catching these very large fish, inserting tracking devices, releasing them live, and then studying their movements in order to devise possible “management techniques” to “control” the population rather than eradicate it. With both Ohio and Michigan not planning to eradicate the Grass Carp, this wetlands destroyer is on the verge of becoming established in the Great Lakes. To stop this invasion, it is urgent to implement every possible eradication method now!

Dr. Nicholas Mandrak, Associate Professor at the University of Toronto, recently stated, “These tagging operations confirm what we already suspected, and do not change the basic need to eradicate these harmful invasive fish. They have an obligation to the entire Great Lakes community to begin effective eradication immediately.”

Canada is spending up to $20 Million over five years to prevent Grass Carp from establishing in the Canadian Great Lakes waters.  It is unacceptable that American agencies are putting the future of our Great Lakes ecosystems at risk by conducting “research projects” in areas already invaded by Grass Carp. They have a responsibility to begin a broad range of eradication methods: immediately.

Lake Erie commercial fishers are being paid $75 for each Grass Carp that they catch in their nets and last year turned in 116 to the Ohio Department of Natural Resources. The Grass Carp that they catch in their deep, open-water nets are ‘by-catch’, for these fish seldom frequent deeper waters. There must be much higher numbers along the shorelines, where there are wetlands. Commercial fishers know well that Grass Carp will ultimately destroy the essential wetland spawning and nursery habitats for the native fish they are catching and selling – walleye/pickerel and whitefish.

Tim Purdy, a Canadian Lake Huron commercial fishing operator, caught a metre-long Grass Carp in Lake Huron about a mile north of the Bluewater Bridge. A couple of years ago, Tim made a presentation to a Standing Committee in Ottawa indicating that his family’s fishery company has been operating since 1900 and he was hoping to be able to pass it on to his children. He expressed his concern that, if these Grass Carp get established, there will be nothing to pass on.

Compelling research by Professor Pat Chow-Fraser of McMaster University has already pointed out that Georgian Bay contains the highest quality, most diverse and extensive wetlands found anywhere in the Great Lakes.

We don’t want our wetlands destroyed by these very large invasive fish. Our native fish and other species that need wetlands for spawning, nursery and feeding habitat will be decimated.

An assessment carried out in 2017 found up to 1.2 million acres of wetlands including submerged aquatic plants in the five Great Lakes. Each acre of wetland provides $1,500 annually in ecological services. If all the Great Lakes are invaded by Grass Carp, the cost of the loss of these ecological services could mount to $16.5 Billion per year. Can we afford to let this happen?

What can be done?

We are asking Ohio and Michigan to rethink their study/management strategies and instead implement eradication methods immediately to target and remove all Grass Carp possible, and to employ barriers to prevent successful spawning and egg hatching. These fish spawn 2 to 3 times a year and each female lays 100,000 or more eggs at each spawn. When they swim up the Sandusky and Maumee Rivers in Ohio, they could be caught in nets and destroyed. Canada’s Department of Fisheries and Oceans stands ready to assist. Under a binational agreement Ohio and Michigan are obligated to ask for assistance whenever an invasion begins.

There is little time left to act. Have we not leaned from the sea lamprey release over 50 years ago? Some people thought they would not survive in the Great Lakes! The only way that population is kept under limited control is by discharging potent chemicals every spring in rivers where they spawn.

Can we not learn from our mistakes?

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