Koi Spotted In Lake Bomoseen

Fisheries biologists are asking the public to keep an eye out this summer for a non-native fish in Lake Bomoseen.

The biologists are concerned about koi, a type of brightly colored ornamental fish. They are the same species of fish as the carp that have been in Lake Champlain since the 1800s. Koi are domesticated and much smaller, since they are raised in aquariums, but they have the same growth potential as the carp in Lake Champlain. Earlier this month, a Shoreham man shot a 44-pound carp with a compound bow. It’s the heaviest fish caught in the 45-year period that the state has recorded trophy fish catches.  

Last summer a Lake Bomoseen resident found koi swimming near the shoreline.

“Because they are a domesticated fish, they’re not spooky and they don’t run and hide at the first sound or sight of something, like a native fish would in Lake Bomoseen. These fish were just kind of lazily swimming around on the surface near somebody’s dock and they spotted them,” said Shawn Good, a fisheries biologist for the Vermont Department of Fish and Wildlife.  Unfortunately, by the time the fish were reported, they couldn’t be found again.

“When you put koi or any aquarium fish into the wild, it can have negative impacts or consequences on the native fish in that lake system.” – Shawn Good, state fisheries biologist

Good said the koi were most likely released by aquarium owners and it’s something that happens far too often when aquarium or pond owners can no longer maintain the fish, or the fish outgrow their enclosure.

“They think it’s good for both the fish and the environment, but it’s really not the case in both. But when you put koi or any aquarium fish into the wild, it can have negative impacts or consequences on the native fish in that lake system,” Good said.

In addition to crowding out native fish, carp are somewhat destructive. They are bottom feeders and eat snails, clams and insects off the bottom. They’ll also eat the roots and shoots of aquatic plants. And in feeding, they they can root up  and sir up the lake bottom, making the water murky.

Koi are also very hardy fish that can withstand low temperatures and low oxygen environments.  Good said lawn and garden shops sell small outdoor ponds that people put koi in, sometimes only 2 feet deep. “In the wintertime that will freeze, almost to the bottom, leaving only maybe six or eight inches of unfrozen water at the bottom, and those koi will stay there all winter in that little narrow band of unfrozen water in the bottom of those ornamental ponds.”

Good said it’s not the first time that domesticated koi have been found in Vermont waters.

“There’s a number of small ponds, mostly private waters and most of those ponds are connected to state waters through a small stream or something like that, so there have been instances in the past where we’ve seen these things get out and they haven’t really spread yet,” he said. “But it’s something that we’re always aware of and constantly trying to work to educate the public on.”

Lake Bomoseen Association has let its members know to be on the lookout for koi, and has asked people to call the Department of Fish and Wildlife right away if they are seen.

Meanwhile, officials are reminding people to never release unwanted aquarium fish into the wild because there’s always a chance that a population will establish which will always have some negative impact on native fish species.

Koi Spotted In Lake Bomoseen