A team of researchers that has kept close tabs on grass carp numbers are now sounding the alarm, saying more fertile specimens end up in fishing nets by the year. While at first this does not sound as much of a concern, grass carp have originally been brought from Asia to the U.S. in 1960 to control weed growth in waterways.
While other species feast on microscopic animals and plants, grass carp thrive on vegetation. With said vegetation gone, so would be spawning grounds and crucial habitat of native fish. An increase in the number of specimens has been observed mostly in Lakes Erie, Ontario, and Michigan, according to the joint team of Canadian and U.S. researchers. Even though the exact number of grass carp currently swimming in national waters is yet unknown, the general consensus suggests they are reproducing at alarming rates.
The presence of grass carp in Lake Michigan is nothing new, say the researchers. It had already been determined some migrated to the Great Lakes in the past. However, the individuals were bred in hatcheries and were sterilized before they were released back into the wild. Now that the number of fertile specimens is increasing, so if the researchers’ concern about an imminent invasion that could have a devastating effect on the native fish population.
Up until now, only one or two fertile specimens ended up in fishing nets. However, no less than 23 have been caught since 2012, including some in Toronto’s Lake Ontario.
“They’ve just been humming in the background”, says Great Lakes Fishery Commission’s spokesman Marc Gaden.
If they did not get much attention in the past, they surely do now, added Gaden. Because more fertile specimens pop up with each passing year, the researchers now fear an imminent invasion. Good news is that the population of sterilized grass carp currently outnumbers the number of fertile fish. However, this does not mean the researchers can leave the invasion prospect in the rearview mirror just yet.
At the moment, the researchers focus on preventing further reproduction of the grass carp before the scientists are faced with a full-fledged invasion, says the study’s author, Becky Cudmore.
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