Dopey Dick, the killer whale who lost his way, spent a placid day today frolicking in the River Foyle at Londonderry.

The 22-foot creature - really a large dolphin despite its name - refuses to swim back under the Craigavon Bridge to the open sea. It appears to have found a home in the waters that divide Ulster's most burned-out bombed-out city.

Royal Marine commandos and experts from the Foyle Fisheries Commission took to open boats yesterday in an effort to entice the animal back to the sea. It just played with them, however, so perhaps its nickname Dopey Dick is a misnomer after all.

Indeed, the salmon are now running in the Foyle, and any Derry visitor knows they are a rare treat for man or beast. The abundant salmon are further proof that Derry's killer whale is "very intelligent," in the judgment of Catherine Burnside, a Fisheries Commission aide.

Dick probably swam in from the sea and under the Craigavan bridge on Sunday night, skillfully negotiating the pet placed there to defeat terrorists. He was first spotted Monday - the white patch on his dorsal fin stamps him as unmistakably male - and ever since has provided Derry residents with something to talk about besides the "troubles."

Men, women and children have flocked to the river banks and crowded the bridge to watch Dick dive and surface every few minutes. Cars have halted on the Craigavan, creating monster traffic jams.

Tie-ups there familiar, but they are usually caused by army weapons searches or mobs of Protestants and Catholics exchanging stones, insults or deadlier missiles.

The Fisheries Commission has called on Martin Sheldrick, curator for Marine mammals at the Natural History Museum for advice. After yesterday's futile efforts to lead Dick out to sea, Sheldrick said, "They would be doing OK by leaving him alone."

Sheldrick, a matter-of-fact cetologist - or whale expert - thinks Dick came to Derry for one of two reasons. Either he swam in after the fish or his sonar blacked out in the shallow waters and mud bottom of Lough Foyle, the opening to the sea.

Sheldrick thinks Dick won's swim back under the bridge simply because there is a deep pool on the downstream side and the salmon are so think there they have been seen leaping into the air.

When the fish stop running, Sheldrick believes Dick will try to head back out. He should be helped only if he heads the wrong way, downstream toward Belfast.

Meanwhile, Burnside says the Fisheries Commission is getting all sorts of unsolicited advice from whale experts, real or presumed. The BBC solemnly reported that one scheme would involve tying a side of beef to a boat and leading Dick out like a hound after a hare. Unhappily, whales have no sense of smell so that plan never left the studio.

The Fisheries Commission has been urged to play sweet music or the recorded sounds of other whales to lure Dick from Derry.

Cetologist Sheldrick is contemptuous of all this.

"He hasn't panicked. he isn't stranded. Leave him alone," Sheldrick says.

Derry is a town where most Catholics live on one bank of the river in the Bogside and Greggan while most Protestants cluster on the other. It is a suspicious place.

Some of the overnight experts who consulted their encyclopedias found that killer whales eat fellow mammals like seals and porpoises and even attack larger whales for their tongues. This has led a few residents to suspect that Dick is on a mission, trying to signal either the irish Republican Army or its Protestants paramilitary analogues.

Sheldrick is indignant at those who demean the beast. He acknowledges that killer whales will attack small boats and cautions those who go out on the river in them. But then he adds sternly: "You never hear about the small boats they don't attack."