BERWICK – A goldfish hunt by state biologists at a storm-water retention pond has focused attention on the threat posed by non-native invasive fish.

Armed with backpack electrical fishing units and nets, biologists from the Department of Inland Fisheries and Wildlife set off Wednesday on a mission to remove goldfish from the pond, where they were introduced illegally.

The fear is that the 2-inch creatures can quickly grow into foot-long eating machines that turn ponds and lakes turbid and beat out Maine’s more delicate native species.

The biologists were working to stop the goldfish from making their way into the Little River in Berwick, and then to the Piscataqua River between New Hampshire and Maine, where they could pose an even bigger problem.

Invasive non-native aquatic plants, such as milfoil, have grabbed the public’s attention, but experts say the threat posed by invasive fish and other freshwater species is just as serious.

“This is much broader than milfoil,” said Francis Brautigam, a state regional fisheries biologist, referring to the aquatic weed that has choked many Maine water bodies.

The illegal goldfish in Berwick were discovered several weeks ago by a town public works employee who reported the find to state biologists.

The team first used the electrical-fishing units to stun the fish and then scoop them out with a net. The team then went over the pond with seiners to catch the stragglers. More than 100 fish, some up to 4 inches long, were removed. The team did not get them all and may try to obtain a permit from the town to drain the pond later in the summer.

Brautigam said the most effective measure would be an application of rotenone, an organic chemical used as a pesticide in gardens. “It also works really well on fish and other organisms with gills,” said Brautigam.

However, the environmental permit needed to use the chemical involves a review process that can take up to six months.

Two years ago, the state Department of Inland Fisheries and Wildlife used the same chemical to kill bass illegally introduced into a pond in Limestone.

Brautigam said there are another half-dozen goldfish-infested ponds in the region southwest of the Androscoggin River. He said goldfish and other non-native fish may be showing up in Maine waters because people who no longer want to keep them as pets are releasing them in the wild rather than destroying them.

It will be up to law enforcement wardens to decide whether to investigate how the fish wound up in Berwick and whether to pursue fines for stocking fish without a permit, Brautigam said.