Invasive species threatening Maine waters

Posted June 06, 2010, at 6:12 p.m.
Last modified Jan. 29, 2011, at 11:38 a.m.

ENFIELD, Maine — Nels Kramer, a Department of Inland Fisheries and Wildlife regional biologist, has a photograph of a non-native, large northern pike whose stomach contents included a small duck.

While the photograph was not taken in Maine, the fact that the voracious predator has been illegally introduced into Maine bodies of water troubles him and other fisheries biologists. The fish has established a presence in the Belgrade Lakes region affecting the historic sport fisheries there and most recently has been documented in Pushaw Pond in Penobscot County and downstream in Mud Pond.

But northern pike aren’t the only problem facing Maine’s waters. In addition to largemouth bass, which recently were documented in Endless Lake in Penobscot County, there are 14 other fish species including black crappy, northern walleye, smallmouth bass, and even goldfish that have been introduced illegally into Maine waters.

“Invasive species are a big problem in the state,” Kramer said recently. “Any fish that grows to 20 or 30 pounds and has a mouth like an alligator” could destroy the fisheries in a pond or waterway. Even small non-native fish can disrupt an ecosystem, he said.

Biologists have seen thriving populations of native brook trout in certain ponds disappear or decline because of invasive species, according to Joe Dembeck, DIF&W fisheries management supervisor. In addition, native Arctic char “unique only to 11 Maine waters in the entire lower 48 states,” have been affected by illegal introductions, he said last week.

About 70 bodies of water in the state have had illegal introductions of fish species since 2006, according to Kramer.

These fish are making their way into the state either by the illegal transport of live fish across borders or through sales from private, out-of-state hatcheries, say state biologists. Once the invasive species establishes itself, the fish can move upstream or downstream affecting more bodies of water. In addition, there is the danger that a few people will move the fish from one pond to another, according to Dembeck.

“It’s a serious concern for the fisheries in Maine,” Dembeck said. These invasive species can do irrevocable harm to the ecosystem, he said. While the introductions have been statewide, the majority has occurred in waters in populated areas in eastern, central and southern Maine, he pointed out.

Invasive fish compete with and eat native fish populations thereby altering the food chain. In addition, there is the possibility of fish diseases being transferred into the state. “That’s a huge concern,” Dembeck said.

Biologists killed off a small population of goldfish last month that had been transported from another state to a Brownville hobby pond. While there was no inlet or outlet to the pond, biologists worried that a bird, animal or person could transfer the fish into nearby Schoodic Lake. The pond’s owner, who was not familiar with Maine law and was cooperative, could have faced a significant fine.

The biologists now are working on another investigation involving goldfish being transferred into Maine waters.

“It is never OK for anybody to release live fish in public or private water in Maine without a permit from the Department of Inland Fisheries and Wildlife,” Dembeck said.

Anyone who observes a person keeping live fish from a pond or dumping live fish into a body of water should call Operation Game Thief at 800-253-7887 or notify the warden service. In addition, people should be observant. Anyone who catches a fish that appears not right for a body of water should contact the regional fisheries office.

“Once an invasive fish species has been introduced to a water and begun to establish a breeding population, it is nearly impossible to eradicate the species,” despite complicated and costly strategies, Dembeck said.