Fifty-four-year-old James Hancock - a sanitation worker for Prince George's County by night and a fanatical fishermen by day - sat fishing on a lonely stretch of beach in Southern Maryland's Eagle Harbor shaking his head and grumbling about both the fish and the fishing spot that got away.

Hancock was sporadically interrupted while explaining the nature of a dispute between fishermen and a nearby Potomac Electric Power Co. plant because his fishing pole would suddenly come to life, bobbing and wiggling, forcing him to blurt out: "Good God Almighty!" as he lunged for it.

With his dark blue fishing cap pulled down to his ears, Hancock pointed down into his empty five gallon fish bucket and then out to the Chalk Point Electric Power plant.

"This bucket would have been full by now if I'd been fishin' over in the canal. But they run us out of thera about a year ago and I ain't been back since."

"They" are the Pepco officials. Those officials - prompted both by irate local residents and by a concern that those fishermen would create safety problems and cause erosion of the canal banks - have begun strictuly enforcing Pepco No-Trespassing regulations to keep fishermen off the Chalk Point grounds.

Hancock explained that fishing was better in the canal situated on the Pepco electric plant's property because large rockfish were apparently attracted from the deep part of the river to the warm water discharged from the plant.

Pepco officials, who admit fishing is particurlarly good during the winter in the canal because of the warm flow of water, say it would cost too much money to make the area safe to public fishing.

"They (Pepco officials) never told us anything. They just called the police and told us to get off the property," said Hancock, who lives in Oxon Hill and has been fishing at Eagle Harbor during the winter for the last 10 years.

"We call it the poor man's fishing hole," explained Carl Morgan, a 54-year-old freight company wroker who drove from Hyattsville down to quiet and almost deserted Eagle Harbor situated about 45 miles south of the District of Columbia line.

Mortan explained that the Chalk Point canal has been "the poor man's fishing hole," because fishermen who could not afford and a boat could fish in the canal and catch large fish that usually swim in the deep part of the channel of the Patuxent River and require a boat to reach.

"Now all we catch are small fish like spots, perch and eels," said Morgan.

These fishermen and hundreds of others have been fishing for years in this sleepy section of Southern Maryland, which is still a summer resort for blacks who bought property there years ago.

This year, however, residents say they are surprised that only a few of the fishermen have shown up.

"I guess they have finally gotten the message," said 67-year-old Mary E. Coleman who was strolling along a road just outside her Eagle Harbor home.

Coleman explained how residents of Eagle Harbor went to Pepco and asked that they put a fence up to keep the fisherman out of the canal.

"We just got tired of them parking on our property and leaving empty beer cans and bait boxs all over the place," said Coleman, a retired government employee.

"As soon as Pepco put a fence, those fisherman cut a hole in it and they were back down here blocking our narrow roads and trespassing on our property," she said. "They would start fires out there and throw stuff in the water . . . it was really bad."

"We recognize the popularity that the grounds have enjoyed for winter fishing and it is with real regret that we have had to place the area off-limits," said Ellis T. Cox, Pepco executive vice president.

". . . It would be unfair to our non-fishing customers to make the sizable expenditures necessary to accomodate fishing when the cost would have to be reflected in the price of the electricity for all consumers," added Cox.

Disgrunted fisherman, who have driven all the way down to Eagle Harbor only to be turned away, point to the current Maryland Sportfishing Guide that lists the grounds of the Chalk Point electric generating station as open to the public.

Pepco officials say the listing is incorrect and that they have persuaded the editors of the Maryland Sportfishing Guide to omit the Chalk Point listing in next year's editions.

Meanwhile, security guards at the Chalk Point Power plant's front gate entrance have been given a press release to help explain Pepco's position to fishermen.