Leading fish researchers are trying to calm panic over the news that a Scottish company may take part in trials on genetically engineered super-salmon.

A number of environmental groups are alarmed that Otter Ferry Salmon is contemplating duplicating Canadian trials on fast-growing salmon, and warn that these could create havoc with native species if they escaped into the wild.

Norman Maclean, professor of genetics and head of the biology department at Southampton University, who is himself leading research on transgenic fish, stressed that the Department of the Environment had legislation blocking experimentation unless the fish were adequately contained. "Mechanisms for control are already in place," he said. "People should be reassured that it's not a matter of opening the floodgate to disaster."

David Penman, research lecturer at Stirling University's institute of aquaculture, said each stage of transgenic work had to be carefully assessed. Outdoor testing controls in North America, where research was more advanced than in Britain, included very heavily screened ponds with filters, chemically treated water which would kill any fish which escaped, and even downstream predators - although there should be no possibility of escape in the first place.

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Transgenic fish are part of a strictly controlled technological revolution in which transgenic plants and animals are already having an agricultural and medical impact. Breeding by selection allowed the genetic composition of animals to be altered by choosing their parents, while the new technology provided an alternative by introducing one gene at a time, Professor Maclean said.

"In general, that means results would be less dramatic, more precise and often faster. Often people are unnecessarily alarmed by the idea of manipulating genes, and fail to remember that breeding by selection inevitably results in genetic rearrangement," he said.

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People also forgot that many animal and plant species in the United Kingdom, including pheasants, little owls, and horse-chestnut and sycamore trees, had been introduced from other countries.

"There's a long history of animals and plants moving round the globe, and transgenic animals will probably be less of a threat than a new species," he said.

About 40 laboratories worldwide were involved in putting novel genes into fish, most of which were used purely for research. "But there is some potential for acquaculture in terms of improved disease resistance or improved growth, so a number of labs, including my own, are also working with that end in mind," said Professor Maclean.

Salmon were already being overproduced, so there was little need for faster growth rates, he said. "It is much more intelligent to modify them so that they are more disease resistant."

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