The fishing in the Potomac River south of Fort Belvoir is as good as ever, but many fishermen aren't taking the bait these days, according to several people who make their living from river fishing.

Ever since news reports three weeks ago about thousands of dead fish washing up on the shores of Maryland and Virginia, fishermen have been afraid of the area, say the businesspersons, who argue that such fears are unwarranted.

"It hurt a number of businesses, including mine," said Ken Penrod, owner of Outdoor Life Unlimited, which has provided professional fishing guides on the Potomac since 1982.

Penrod said he got about 15 calls a day for a week from people planning fishing trips who were concerned about the fish kill.

Maryland officials, who have control over the Potomac, said the problem appears to be gone, because they are not finding dead fish anymore.

Because the dead fish were all large, it is unlikely the cause was a toxic spill, one of the early theories, said a spokesman for the Maryland Department for the Environment.

The cause is still undetermined, he said.

But news reports that a toxic spill may have occurred apparently had a significant effect on some businesses.

"That terrorized a lot of people. They panicked. They won't travel to the Potomac to fish," said Dave Ellis, co-owner of D&L Sports in Fort Washington, a fishing and hunting goods store.

Ellis said his business dropped off from an average of $1,300 a day to $250 a day, and he may have to lay off one or more of his four employees.

Ellis said a more likely theory of what happened was that a commercial fisherman left his nets out too long, the fish died and he dumped them back in the river.

The Maryland Department of the Environment estimates that 25,000 to 33,000 fish died over several days, said department spokesman John Goheen.

They were all large fish, including carp, white perch, gizzard shad, brown bullhead and channel catfish.

"It's still a mystery" what caused the kill, said Goheen.

"There isn't any one thing that we can go after."

He said neither a reduction in oxygen nor any of the dramatic natural causes usually responsible for fish kills, such as a sudden freeze or other radical changes in weather, seem to be responsible in this case.

"We also have no evidence of a toxic spill," Goheen said.

Very little actually has been ruled out, and the department still is waiting for the results of a fish tissue analysis and water testing, he said.

On the theory that a commercial fisherman may have dumped dead fish, Goheen said, "It could have been a factor, but that's an awful lot of fish."

Cynthia Sale, water resources manager in the Alexandria office of the Virginia Water Control Board, said all of Virginia's tests are completed and the agency was unable to determine a cause. The fish were badly decayed when the board analyzed them, hindering efforts to pinpoint a cause, she said.

The board is no longer receiving calls about dead fish being found.

"The large kill is over," Sale said.

The Potomac, which only two decades ago was described as an open sewer, has since been cleaned up and become a popular fishing spot. Officials on both sides say they see no reason for people not to fish in the area where the kill was.

"The fishing is still good in that area. There are plenty of fish," said Ed Mason, public information officer for the Maryland Department of Natural Resources.

Not all people in the fishing business have seen an impact.

"I don't think it had an effect, except in the first few days, because people could see the fish floating in the water," said Ken Shontere, manager of Bryans Road Sports on the Maryland side.