HUMPBACK – or pink – salmon which have recently been caught in some of Scotland’s east coast rivers could pose a threat to Scotland’s native salmon, according to a local freshwater fisheries expert.

Professor Eric Verspoor, director of the Rivers and Lochs Institute at Inverness College University of the Highlands and Islands (UHI) said the species – oncorhynchus gorbuscha – most likely strayed from naturalised populations in the north-west Russian Kola Peninsula and White Sea regions far to the north of Scotland.

Writing on the UHI blog, he said these populations were established from the stocking of millions of eggs from Pacific Ocean rivers in eastern Russia in the mid-1950s, but could also originate from rivers in adjacent northern Norway, where small populations have arisen from natural straying. Some had been found to stray into adjacent parts of the Arctic.

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A number of self-sustaining populations had also flourished after their introduction into the Great Lakes of North America.

Verspoor said his institute was now considering DNA analysis to confirm that they are pink salmon.

“If it is confirmed, this suggests that the species, like some other salmonid species (eg brown and rainbow trout) has the ability to adapt successfully to new environments when transplanted outside its native range and to expand to adjacent areas,” he said.

“It clearly has a solid foothold in the Kola-White Sea region of Russia where it has historically sustained a small local fishery. Thus the presence of multiple individuals in Scottish rivers gives rise to the concern that these strayers may eventually be able to establish self-sustaining populations in Scotland as well.”

He said the implications for the native Atlantic salmon were no clear, as the two were not naturally found together.

“But exotic species seldom establish themselves without some impact on local species and biodiversity,” he cautioned. “It might be argued by some that another salmon species might be desirable in Scotland’s rivers. However, the potential for negative impacts on native species and the fact that they are the least desirable of the Pacific salmon from an angling and commercial fishery perspective suggests there are unlikely to be any positives from their doing so.”

Verspoor said the fact that the fish were running up Scottish rivers suggested that they intended to spawn.

He said he was also concerned that the numbers of pink salmon caught in UK rivers over the last decade appeared to be on the rise.

“What would be interesting to know is whether the fish caught encompass males and females, and whether they are reproductively mature or not,” he added.

“It is a situation which should be closely monitored in respect of the threat it poses to Scotland’s native salmon, given the latter’s great socio-economic value and biological uniqueness.”

Verspoor’s warning comes ahead of the launch of the second Scotland’s Salmon Festival in Inverness at the end of next month.

The event celebrates the “iconic” Atlantic salmon as a “flagship species symbolising efforts to conserve and enhance the economic, social, cultural, educational and ecological value of Scotland’s rich freshwater and natural resources”.