The scientific, peer-reviewed study was led by Fisheries and Oceans Canada, coordinated by the Great Lakes Fishery Commission and authored by experts from Fisheries and Oceans Canada, the University of Toronto Scarborough, the U.S. Geological Survey and the U.S. Fish and Wildlife Service, according to a press release issued by Fisheries and Oceans Canada.
The study – “Binational Ecological Risk Assessment of Grass Carp for the Great Lakes Basin” concludes that unless actions are taken to curb the invasion of the grass carp, the ecological consequences would be devastating and would be extreme in the Great Lakes Basin within 50 years.
The voracious grass carp is one of four carp species threatening to invade the world’s largest surface freshwater system. The grass carp feeds on aquatic vegetation that provides spawning and crucial habitat while the bighead and silver carp are actually the most feared of the species. They compete with native fish and eat microscopic plants and animals.
The Canada-U.S. study
Between 2013 and 2016, Fisheries and Oceans Canada’s (DFO) Asian Carp Program recorded and examined 23 grass carps caught in Lake Erie and Lake Ontario. Nine of the fish were fertile grass carp, capable of reproducing. DNA analysis indicated all the fish had been born outside the Great Lakes and made their way into Canada.
And while many of the carp were sterile, the actual number of carp already in the lakes is unknown. According to ABC News, Becky Cudmore, Asian carp program manager for DFO and the report’s primary author said, “Right now, the sterile fish outnumber the fertile fish. This isn’t game over, but we are finding more of these fertile fish.”
It should be noted that some states in the US allow grass carp to be raised in fish farms, but they are required to be sterilized before they are released.
The report also concluded that Lakes Erie, Huron, Michigan, and Ontario will end up with an established population of grass carp within 10 years unless something is done to stem the invasion.
Grass carp introduced into U.S. during the 1960s
Grass carp were actually welcomed into the US during the 1960s to control weeds in waterways. And like other Asian carp, some escaped into the Mississippi River where they proliferated and spread northward to the Great Lakes. Marc Gaden, the spokesman for the Great Lakes Fishery Commission told Phys.Org that it has been known for a long time that some of the grass carp had made it into the Great Lakes.
There was evidence that some may have made their way into Lake Michigan through a waterway network running through the Chicago area until electric barriers were set up to stop them. And Gaden says other carp may have been intentionally or by accident, released. “They’ve just been humming in the background,” Gaden said. “They haven’t gotten a lot of attention. Once in a while, one would get captured.”
Researchers say they are studying ways to mitigate the invasion that appears to be growing. Tougher enforcement of laws governing fisheries releasing unsterilized fish, or bringing the fish into the region could help, but there is actually a need for additional input if we want to find a plan that will work.
Note: This writer would like to thank the Canadian press for letting readers know exactly which organizations and agencies conducted the studies on the grass carp invasion.
