CHARLOTTE HARBOR -- They abound in the cappuccino-colored backwaters of Charlotte Harbor -- a small invader from afar that scientists worry could pose big problems for local fisheries.

The Mayan cichlid, an invasive species from Central America and Mexico, has made its way to the harbor, on Florida's southwest coast north of Fort Myers. Researchers from Sarasota's Mote Marine Laboratory documented it for the first time in July while surveying native fish populations in the area.

"It was a surprise," said Dr. Aaron Adams, manager of Mote's Fisheries Habitat Ecology Program. "We weren't expecting to find it here."

They did. Twenty-six were found in July and ever since they seem to be increasing in number, raising fears that the aggressive cichlid will cause a decline in the harbor's native game fish.

One day last week Adams and Mote biologists Kirby Wolfe and Maggie Newton trudged through the ankle-deep muck of a small pond in the Charlotte Harbor Buffer Preserve south of Punta Gorda, dragging a 150-foot seine net behind them.

Wolfe and Newton slapped their arms across the surface of the pond to scare fish from the mangrove fringes into the open water and then into the net.

No one knows how the cichlid -- known as Cichlasoma urophthalmus in scientific circles -- arrived in Florida, although some theorize that the fish may have been released from aquariums or escaped from fish farms.

What is certain is that they have taken hold in South Florida. Since they were first documented in Everglades National Park in 1983 they have proliferated, dominating the waters of the Everglades and Florida Bay, spreading as far east as Miami.

However, Mote's find is the first in Charlotte Harbor and it is the farthest north that the fish have been sighted in any numbers.

Dr. Leo Nico thinks it's likely that the fish, which have been documented in Lake Okeechobee, followed the Caloosahatchee River from the lake and into Charlotte Harbor.

What troubles scientists is not that they were found, but that they were found in such abundance. Adams and his team of scientists began surveying the populations of juvenile fish such as snook, redfish and tarpon in Charlotte Harbor two years ago. But until July, they had never captured the Mayan cichlid.

But now they are appearing more and more frequently. It appears that these freshwater fish have a surprising ability to thrive in the brackish estuaries. They may even be spawning, Adams said.

That would not be good for the ecosystem. Research in Mexico indicates that a single pair of Mayan cichlids can spawn up to 7,000 eggs as often as every few weeks.

The fish, which are natives of South America, are aggressive and multiply quickly, possibly forcing out native species.

What alarms Adams most is the cichlid's carnivorous ways. The mangrove-laden estuaries act as nurseries for juvenile snook, redfish and tarpon -- fish that are "economically important to Charlotte Harbor," Adams said.

Adams worries that the cichlids could be preying on these game fish and causing a decline.