AYER CREEK - As they have many times during the past three years, a team of Maryland scientists was trolling meandering, marshy waters yesterday, casting handnets for sick menhaden, the 2- to 3-inch silvery bait fish that have come to be seen as a potential warning sign of toxic Pfiesteria piscicida.
This time - for the first time - fish with bloody sores and ulcers have begun to turn up in the brackish waters of Maryland's coastal bays near Ocean City.
Department of Natural Resources researchers were quick to say there is no evidence the single-celled dinoflagellate, which in 1997 was blamed for one of the state's largest recorded fish kills, has transformed into its toxic form, believed capable of making people sick.
On Monday, routine sampling in this tributary of Chincoteague Bay found about one in four menhaden caught had lesions. Analysis of water samples at North Carolina State University did not reveal the dinoflagellate, but a separate test at a University of Maryland lab in Baltimore showed traces of it.
"We saw something unusual, not unprecedented, and we're following up with fish and water samples," said DNR spokesman John Surrick. "There's no indication of anything toxic. We haven't seen dead fish; in fact, we haven't had any reported fish kills in the state this year." The coastal bays have come under increased scrutiny as scientists study the first reported bloom of brown tide algae that occurred in the shallow waters last month.
Delaware officials are investigating two fish kills in small tributaries of Rehoboth Bay. On July 18, a half-million menhaden died because of a low level of oxygen in the water. A week later, 50,000 menhaden scarred with lesions were found dead, but scientists are not sure why.
"In these small tributaries, the water is shallow, it's warmer, it has all the conditions in small backwater areas of [Chesapeake Bay] where we have previously found Pfiesteria," said DNR biologist David Goshorn.
The state has established about 70 testing stations around the state where samples are collected from April through October, Goshorn said. Of 400 samples taken this year, nine have shown some kind of positive result for Pfiesteria, he said.
Yesterday, before the DNR crew arrived, Bethany Beach resident Brian Bomhardt, an avid fisherman who comes to the Ayer Creek bridge to collect menhaden for bait, said he's seen similar sores on fish.
"I have an environmental science degree myself, so I pay attention," Bomhardt said.
Yesterday, a three-member team collected 942 menhaden from three sites on Ayer Creek, finding 137 or about 15 percent, with lesions, said Charles F. Porcari, DNR communications director.
Tissue samples from the fish, along with water samples taken at four sites on the creek, were shipped overnight to labs in Maryland and North Carolina. Preliminary results are expected today, Porcari said.