State biologists last week pulled a three-pound koi, a non-native fish that resembles a giant goldfish, out of Pickerel Pond in Limerick, the Maine Department of Inland Fisheries and Wildlife announced today.

They believe there is at least one more of the exotic fish still at large in the lake.

"We're very concerned about the illegal introduction of this non-native, destructive species into one of Maine's lakes and have begun an all-out assault to minimize any harm it may cause," Commissioner Roland "Danny" Martin said in a written statement.

Koi is the Japanese term for carp. The fish, often kept as ornamental pets in tanks or outdoor fountains and garden ponds, are an invasive species that can survive and reproduce in Maine's waters and harm the state's native fish species, aquatic plant life and water quality, according to the state. They can grow to 50 pounds, according to the department.

It is illegal to possess koi in Maine without a special permit or to introduce them to the state's waters. The law generated local headlines in 2006 when the owner of the China Rose restaurant in Freeport had 10 koi seized from the restaurant and ultimately paid a $1,000 fine. The state eventually gave Cuong Ly a permit to display the fish and his koi were returned last year.

State officials said it's unknown how the koi got into Pickerel Pond. The fish, or fishes, were first noticed this summer by a neighbor, and town officials notified the inland fisheries and wildlife department.

State biologists caught the koi Sept. 10 with the help of an electric current that temporarily stuns nearby fish and allows them to be netted.

This koi pulled out of the pond was orange with a black spot on its head and had white-fringed fins. Observers have described a second koi as predominantly white in color. There could be others as well, according to the state.

The inland fisheries and wildlife department said it plans to ask shorefront property owners and town officials to remain on the lookout and help catch any remaining koi. It also plans to install a screen at the pond outlet to keep the invasive fish out of the Little Ossipee River and Lake Arrowhead.