Waldy Diez

Hundreds of 6- to 9-inch carp were discovered floating dead along the perimeter of the lake, which is off Singley and Center avenues in the borough.

Though the lake also contains other species, including sun fish, bass and trout, only carp — and small ones at that — seem to be affected, according to Camden County spokesman Dan Keashen, who noted that several adult carp were swimming in the lake, seemingly healthy.

Larry Hajna, spokesman for the Department of Environmental Protection, speculated Thursday morning that the fish kill may be due to “pathogen … specific to this species of fish.”

“We had a biologist out there who is trying to collect a live sample to send to the labs,” Hajna said.

The DEP sent specimens to a fish pathologist to determine the cause of death. According to Hajna, if it is a pathogen, there is nothing that can be done but to let it run its course. He theorized that recent heavy rains might be responsible, possibly by carrying pesticide runoff into the lake or increasing natural pathogens.

Keashen said representatives from the Camden County Department of Health also took specimens from the lake for testing but results were inconclusive Thursday. The investigation will continue.

“The rest of ecosystem in the lake is fine,” including oxygen levels in the water, Keashen noted.

Carp, which are bottom-feeders, might be affected by some issue with their food source or by a water-borne illness specific to their species, he said. Keashen added the fish kill seems to be localized to the north side of the lake and preliminary testing does not seem to indicate an environmental cause.

The fins of fish killed due to environmental problems will have their fins facing forward, not the case in this instance.

A runner passing by the lake Thursday morning shook his head and continued on his way.

“It used to be a great lake,” he said.