Pet fish pose potential lake problems

Leonard N. Fleming
The Detroit News

From his commercial fishing boat in Lake Erie, Nathan Newsome has seen all kinds of fish. And he will be the first to say he has an eye for something that doesn’t belong in Michigan waters.

The popular aquarium goldfish is native to east Asia that can grow to be as large as a person’s hand, according to the Michigan Department of Natural Resources.

From thousands of goldfish to varieties such as carp, the Great Lakes are full of invasive and non-invasive species — especially those apparently put there by pet owners who think there is no harm in freeing them into the state’s streams, rivers or lakes.

Newsome said he even caught a South American redtail catfish, which can grow up to five feet in length and 180 pounds in its native Amazon River. The one he caught was about 10 to 12 inches long and would be unlikely to survive a Michigan winter.

The Michigan Department of Natural Resources has received reports of “unique species” ending up in the state’s waterways and has issued warnings for owners not to release their pet fish back into nature. It follows sightings of all kinds, including a small squid.

“You never know how it’s going to affect all the other fish that are in there,” said Newsome, 30, who lives in Lambertville and works for the Erie-based Blair Fish Co. “It could possibly wipe out habitat or wipe out a whole fish species. If it doesn’t belong there, then we don’t know how it’s going to affect it.”

Releasing goldfish or other fish bought in pet shops or stores may seem harmless, state officials said. But they can become invasive, multiplying by the thousands, or struggle to survive and to fend off more aggressive predators, experts said.

Some pet species have become established and could cause problems “if they become overly abundant,” said Seth Herbst, a DNR aquatic invasive species biologist who studies the problem in Michigan’s waterways. He noted goldfish can grow to the size of a human hand.

There was one report that about 4,000 to 6,000 goldfish were in a small Metro Detroit ditch that connected to a couple of lakes, he said, adding that the average goldfish produces hundreds of thousands of eggs.

“You shouldn’t be releasing any of your pets, regardless of whether it’s a native species or a species that isn’t from Michigan,” Herbst said.

While Michigan has not yet suffered “detrimental impacts” from pet fish releases, the potential is there, Herbst said.

Other regions, particularly the East and Southeast, have run into problems with pet store releases. The Northern Snakehead has made inroads in those areas and is prohibited from being sold in Michigan because it preys on and displaces native species, such as largemouth bass, as well as would “likely cause significant harm to our fisheries,” Herbst said.

Even Russian sturgeon used to be sold as pets and could end up in Michigan waterways, according to the Michigan Department of Natural Resources.

The fish that tend to end up in Michigan’s lakes or rivers are Pacu fish, which had three different species reported in southeast Michigan, as well as Plecostomus, a warm water species that is an algae eater. Most of these fish won’t survive Michigan’s winters, experts say.

State officials and biologists take seriously the health of fish, especially in the Great Lakes.

A variety of fish in Lake St. Clair tested positive for a hemorrhagic virus, indicating the infection is likely to affect tens of thousands of fish, the Michigan DNR confirmed May 1. State officials in mid-April began investigating resident reports of several fish deaths in Lake St. Clair.

“Fish health is a big issue,” Herbst said.

Pet shop owners, too, are urging aquatic fish owners to properly dispose of an unwanted pet and are willing to take fish and look to get them adopted elsewhere.

Rick Preuss, the co-owner of Preuss Pets in Lansing, said although he has encountered less than a dozen people who have actively talked about releasing fish into the wild in the 35 years he has owned a pet business, it’s still a problem in Michigan.

It means “giving people the information and explaining to them that it can be unwelcome from the perspective of our ecosystem and from the perspective of our state officials,” Preuss said, “as well as any conscientious hobbyist or persons who are wanting to be responsible.”

The main reason why goldfish mostly are spotted in local waterways while other fish are spotted occasionally is because most fish sold at pet stores are tropical and “can’t survive more than a season in our waterways,” he said.

There are fish that may outgrow their tanks, prompting owners to toss the fish into the waterways without knowing the potential for doing harm, Preuss said. The proper thing to do is bring them to a pet store, he said.

Otherwise, some surviving fish can grow. Newsome said he’s seen former aquatic pets in local waterways that are “pretty big compared to what you’d have in a typical aquarium.”

One of them included the redtail catfish. One of those South American fish was reportedly caught near Portage, Indiana, in Lake Michigan in 2013 at a length of nearly two feet and weighing eight pounds.

Blair Fish Co. each year catches at least 30,000 pounds of a variety of goldfish, Newsome said. The company uses seine netting to catch and make money off the goldfish.

“We’re pretty much seeing the same fish all the time,” Newsome said. “Depending what species it is, it could be a big problem. Everybody’s got a goldfish they flushed down the toilet and probably winds up in the water.”

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