DNR continues effort battling invasive grass carp in Lake Erie Basin

[STWA]

Talk to anyone familiar with Michigan’s invasive species and you’re likely to hear their concern about carp—voracious, prolific, invasive carp. 

News of electric barriers and fish flying into boats by the dozens may sound like a big fish story. However, while they are sizable creatures, there is nothing exaggerated about the ecological and environmental damage that would occur if bighead and silver carp were ever to enter the Great Lakes.

Therefore, a good deal of attention is being paid to the work done by researchers and biologists in the Great Lakes states and Canada to help stop invasive bighead and silver carp from moving through the Chicago Area Waterway System toward Lake Michigan.

In addition to this ongoing work in Lake Michigan and its tributaries, Michigan Department of Natural Resources Fisheries Division staff and researchers are also focused on the problem of grass carp in the Lake Erie Basin.

Distinctions

Small numbers of grass carp have been caught in the Great Lakes and its tributaries since the 1980’s.

While bighead and silver carp are believed to have escaped from aquaculture ponds, grass carp were stocked intentionally in water bodies throughout many states for the purpose of aquatic plant control.

Since the mid-1980s, grass carp used in this manner were required to be sterilized so that they could not reproduce.

However, periodic captures of fertile – or diploid – grass carp and the discovery of grass carp eggs in the Sandusky River in 2015 suggest that either the methods used to sterilize these fish were not always effective or compliance with state regulations barring fish able to reproduce was not complete. 

It is illegal to possess or stock grass carp in Michigan. However, sterile – or triploid – grass carp may still be used for stocking water bodies in Ohio, Indiana, Pennsylvania and New York.

Though similar to silver and bighead carp in their breeding and habitat requirements, grass carp are different in two very important ways.

· Grass carp feed exclusively on plants, whereas bighead and silver carp devour large quantities of plankton – the same food source required by native and sport fish species. In large numbers, grass carp can cause significant damage to wetland ecosystems and waterfowl habitat.

· Unlike silver carp, grass carp do not jump out of the water at the sound of boat motors.

Varied research approach

Invasive species management is most effective at the early stages of an infestation, before a species becomes established.

The Michigan and Ohio Departments of Natural Resources have launched a collaborative research effort with Michigan State University and Central Michigan University to better understand the situation posed by grass carp in Lake Erie to then develop effective management measures.

In 2014, grant funding provided to Michigan through the Great Lakes Restoration Initiative was awarded to Central Michigan University and Michigan State University to study the biology and behaviors of grass carp, with the ultimate goal of working towards eradicating these invasive fish from the Great Lakes. Under the management of lead coordinator Seth Herbst with the Michigan DNR, Central Michigan University researchers are studying the fertility, diet and origins of grass carp captured in western Lake Erie. Michigan State University researchers are evaluating large-scale movement, seasonal tributary use and migratory patterns of grass carp.

“If eradication is not possible, the next goal is to use research information to develop and implement more effective control strategies,” Herbst said.

Outlook

When asked about the future of Lake Erie, Mahon and Brenden agreed that it is still too early to predict the potential severity of the issue, as so much depends on the feasibility and success of control or eradication methods.