Fiberglass Whales Deter Seals' Meals

FROM the upturned hull blocking its entrance, you conclude that this unpretentious building in the remote and rocky northwest tip of the Scottish mainland belongs to a boat builder. You are right - up to a point. But once you enter the shadowy interior, you are confronted by a surprise: a life-size fiberglass replica of a killer whale, freshly painted.

So this is also a whale-builder's establishment.

Marty Mackay - the boat (and whale) builder - claims it took about three days for Charles Marsham, director of a large local salmon farm, to persuade him that he was serious. Mr. Marsham reckons it took more like three hours. Either way, Mackay was persuaded to manufacture killer whales as well as boats. He has now completed his 13th ''Whalley'' in a year.

Mr. Marsham's idea, inspired by a sequence on a TV program in which killer whales were filmed coming ashore to prey on seals, was that the Whalley might work as a kind of scarecrow for seals.

Seals eat the salmon vulnerably penned in the nets of a fish farm. The seals tend to push at the nets and bite the salmon. The fish then fall to the bottom of the net and are eaten through the netting.

Although seals look as lovable as ''labradors without ears,'' in Marsham's own words, ''in essence, they are voracious predators.'' Though university-sponsored research concluded last year that seals do not favor salmon in their diet, Marsham and his fellow salmon farmers are not convinced.

The Whalley is designed to be tethered underwater near salmon nets. The trial of a wooden prototype over a six-month period in 1994 showed a dramatic and sustained drop in salmon killed by seals. Whalleys have since been shipped to Maine and Seattle. Marsham does not claim 100 percent success. It depends on how the nets and the Whalley are sited. ''The deterrent is visual,'' he explains. ''The seal has got to see it. It has to be placed on the seals' route toward the sea-pens.''

In the two lochs where Marsham has used the Whalley, it proved most effective where the seals' approach was channeled. ''But when you have a set of pens in open water,'' he says, ''we haven't worked out yet how many 'scarecrows' you would need.''

Jorn Vad of Atlantic Salmon (Maine) Inc, one of the largest salmon producers in the United States, owns two fiberglass orca.

''I do believe they can work,'' he says, ''but they have not worked the way we have things set up because one killer whale per site will not do the job. If you had five or six of them, only a couple of hundred feet apart, then that would make the seals more alert.'' He estimates he loses up to half a million dollars of salmon yearly.

So the Whalley idea is something Mr. Vad means to pursue.

''We will probably get a few more, so we have at least three or four of them at every site. But that alone wouldn't solve this problem. It would be in combination with a lot of other things.'' These include sonar devices, and predator nets - extra nets outside the pens that help to make an additional barrier.