From giant goldfish the size of a basketball to round goby brought to the Great Lakes from the ocean, invasive fish species are a problem in Northeast Ohio.
Take a cruise down the Rocky River with a team from the Metroparks or along the Black River in Lorain with a team from the Ohio Division of Wildlife and you’ll hear a lot about the effects of invasive species.
While the number of invasive species has been more or less steady in recent decades, according to Mike Durkalec, aquatic biologist for Cleveland Metroparks, it is still an ongoing issue.
Durkalec and his team went on an outing in September to electrofish. The process involves a boat outfitted with a generator and anodes, or poles that stick out into the water, creating an electric charge. Durkalec said it was an important tool to root out invasive species in northeast Ohio waters.
“We’re stunning the fish,” Durkalec said of the process. “They float up, we net them. You can either remove them if they’re not native. You can measure them and weigh them if you’re doing a fish survey. But the fish do recover in the end.”
Common invasive fish species in Northeast Ohio
According to Durkalec, ballast water from ocean freighters has been one major factor in the spread of invasive species, but that it has waned in recent years due to success with regulations.
“But, in some cases, humans have purposefully introduced them as well, with good intentions that had ill consequences,” Durkalec said. “Common carp are one really good example of that.”
Becoming a bigger factor now are “individual actions.”
Durkalec cited “escaped ornamentals,” “unauthorized introductions” and “escapees from captivity (i.e. released pets) and anglers’ bait buckets” as examples.
Durkalec described some of the common invasive species in Ohio, including goldfish that were once pets.
“A goldfish in a small bowl could live its whole life and not grow very big,” Durkalec said. “You take that same fish and put it in an environment with unlimited space and a lot of resources, like Lake Erie or the Rocky River, it can grow to roughly the size of a basketball.”
Common carp and round goby are also problematic in Northeast Ohio waters.
“Invasive plants and animals are a huge ecological issue,” Durkalec said. “And just to put it in perspective, since European settlement, about 200 species of nonnative, just aquatic, species have been introduced to the Great Lakes alone.”
Durkalec said the best prescription for limiting invasive species is keeping the nonnative species out of Ohio waters in the first place.
“If they’re already here and established, electrofishing is one tool we can use to help keep their populations in check,” Durkalec said.
Efforts from the Ohio Department of Natural Resources
Crews from the Ohio Department of Natural Resources’ Division of Wildlife also recently electrofished on the Black River in Lorain.
“We have a shock box that we set the settings so that the fish are not harmed, they’re just stunned,” said Jason Gostiaux, a research technician at the University of Toledo’s Lake Erie Center. “It’s like a taser, so the fish is stunned. We’re able to grab it with our dip net, bring it on board.”
The crew caught some fish that are native to Northeast Ohio, such as freshwater drums. Native species are returned to the water, but invasive species, such as grass carp, are removed from the water before they can cause problems for other fish and vegetation.
According to John Navarro, the aquatic invasive species program coordinator with ODNR’s Division of Wildlife, grass carp are legal in Ohio as long as they’re sterile. The problem is that many of them aren’t, and so the “Grass Carp Strike Team,” as ODNR calls the sampling crew, is trying to find out what rivers in the state have reproducing populations of grass carp. The Sandusky and Maumee Rivers are both locations where grass carp reproduce.
“What we’re worried about is that they eat aquatic vegetation, hence the name grass carp,” Navarro said.
That’s why they were initially brought to Ohio, for use in controlling aquatic vegetation without chemicals, Navarro noted. But scientists are now concerned there could be too many of them.
“Our concern is that if they expand their population, they’ll impact the habitat for native species and also a food source for water fowl,” Navarro said.
While electrofishing doesn’t kill the fish, Navarro said grass carp that are captured must die in order to find out if they’re sterile or fertile.
The end game
Gostiaux said the ultimate goal for the team is to remove all grass carp from Lake Erie and its tributaries.
“I know in Ohio it’s legal to stock a sterile fish into your own pond or on a golf course,” Gostiaux said. “But you have to ask yourself, what is the actual risk involved? Is there a chance that this particular body of water could flood and then a fish could get into a tributary to Lake Erie?”
Navarro said that grass carp are edible and that ODNR pays fishermen for grass carp they collect. Fishermen can also sell grass carp. All of that is legal in Ohio.
“In Ohio, if you go out and you catch a round goby or a grass carp, we’re not going to write you a ticket,” Navarro said. “If you kept it alive and were gonna do something with it, then yeah, possession of live invasive species is illegal in Ohio. But if you caught a grass carp and you killed it properly, then we’re not going to write you a ticket cause it’s not a threat.”
Navarro noted that although grass carp is part of the Asian carp family, he and other scientists are relieved that bighead carp and silver carp have not come to Lake Erie because they could compete for food and have a larger impact on native fish.
For both ODNR and Cleveland Metroparks, removing invasive species is a priority to make sure they don’t crowd out Ohio’s native fish by competing for resources.
Durkalec said there are efforts between Canada and the United States to implement “early detection programs for aquatic invasive species” to help with this issue.