Study confirms impact of sea lice on sea trout (Photo: Salmon & Trout Conservation)

Sea lice on farmed salmon poses devastating consequences for wild fish populations

UNITED KINGDOM
Tuesday, September 04, 2018, 21:50 (GMT + 9)

A substantial proportion of this year’s wild adult salmon run, into one of the Hebrides’ most renowned rivers, has been killed by parasitic sea lice, apparently spread by farmed salmon.

The statement is based on the fact that at the end of July many dead, dying or distressed adult wild salmon were found in the tidal section of the lower part of the Blackwater River.

Blackwater River wild salmon, on their return journey from the Atlantic, must pass through Loch Roag where there are seven salmon farms, all operated by The Scottish Salmon Company (TSSC).

According to Salmon and Trout Conservation Scotland (S&TCS), there is strong evidence that sea lice numbers on farmed fish have been far too high in the farm cages this summer.

The NGO points out that lice breeding on the hundreds of thousands of farmed fish in Loch Roag will have released unimaginable numbers of juvenile lice into the waters of Loch Roag to infest wild fish.

Above: A dead wild adult Blackwater salmon, fatally wounded after its skin has been stripped away by hundreds of parasitic sea lice (Photo: salmon-trout.org)

“We believe that the explosion in lice numbers on the Loch Roag farms, spreading out into the wider sea loch environment, has had deadly implications for wild fish, as they were waiting to enter the Blackwater.

Adult salmon are well adapted to coping with a few lice but, when plastered with hundreds, they simply do not have a chance,” stresses Andrew Graham-Stewart, Director of S&TCS.

In his view, this episode represents exceptionally strong evidence of how lice on fish farms, where many hundreds of thousands of fish are packed close together in cages, can increase rapidly in number and release vast numbers of juvenile lice into the surrounding waters. This can have absolutely devastating consequences for wild fish populations.

S&TCS director explains that the loss of a very substantial proportion of the Blackwater River adult salmon run this year has severe implications for spawning and thus future salmon numbers and that on top of that, local rural businesses that rely on wild salmon are under threat.

For his part, Guy Linley-Adams, Solicitor for S&TCS, comments that as the Scottish Parliament’s Environment and Rural Economy Committees have both heard this year, the law is insufficient to protect wild fish from this sort of event.

“Currently, there is no regulatory body that is responsible for protecting wild salmon from the impacts of salmon farming and so one of Scotland’s most iconic species is under serious threat,” the solicitor states.

The Fish Health Inspectorate has been to the Roag farms, but the law means it is only able to involve itself in the health and welfare of the farmed fish, though the truckloads of mortalities that have been seen suggest that it has not been very successful.

Meanwhile, the Scottish Government and Scottish Society for Prevention of Cruelty to Animals (SSPCA) have received a video showing the evidence of the issue and have launched investigations.

The film of Vacasay was made by a photographer and fly fishing guide from Perthshire, Corin Smith. He filmed for 20 minutes, and a two-minute clip is being published by The Ferret.

“I was utterly shocked at the health of the stock and the very high proportion of fish in poor health with mortal sea lice infestation,” Smith said. “For fish to have reached this state of health as a result of sea lice parasites eating their flesh, this situation would have had to occur over a matter of weeks.”

He estimated that as many as 80 per cent of the salmon at Vacasay were suffering from lice damage. He said he saw “hundreds” of infested salmon in one part of one cage.

The Scottish Salmon Company, which runs Vacasay fish farm, has facilitated visits by SSPCA inspectors. The company said it had not had an opportunity to authenticate the video, but accepted that mortalities had been “exacerbated” by the warm summer.
 

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