Conservation group Salmon & Trout Conservation Scotland (S&TCS) has increased calls on the government to end a ‘business as usual’ approach to managing sea lice at farm sites.
In an open letter to Aileen McLeod — Minister for Environment, Climate Change and Land Reform — the group noted its concern at what it says is the Scottish government’s failure to protect wild salmonids from the damaging impacts of salmon farming, in particular the control of sea lice.
“Wild salmonids in the ‘aquaculture zone’ on the west coast are in trouble,” it said.
“This year, the Scottish government has published its classification of the country’s rivers’ salmon populations. This places all the rivers in the west Highlands and inner Hebrides in the worst-performing category, with wild salmon stocks not reaching their conservation limits, which are a measure of the overall health of the population.”
“No river within salmon farming’s heartland of the west Highlands and inner Hebrides has, according to the Scottish government’s own scientists, a sufficient stock of wild salmon. Sea trout populations too are under considerable threat with the number of sea trout returning to Scottish rivers in decline, with the 2013 rod catch being the lowest on record according to Marine Scotland Science.”
Alongside this evidence of such a major problem, fisheries scientists are increasingly firm in their conclusions that sea lice produced on fish-farms harm wild salmonids, both at an individual and at a population level, said S&TCS. However, this is not being translated into effective control of sea-lice on fish-farms.
Between 2013 and 2015, the number of fish–farming regions failing to keep adult female sea lice numbers below the industry’s voluntary code of good practice threshold is on an upward trend. The industry-wide problem with sea lice appears to be increasing and is certainly not under control, it said.
“Average adult female sea lice numbers per farmed fish appear to be linked to the cumulative biomass of farmed fish held on the farms – the greater the tonnage of farmed fish, the more adult female sea lice, and the greater the production of free-swimming juvenile lice into the surrounding sea lochs.””What is concerning is that the data shows that in much of the production of farmed salmon in Scotland and the Western Isles, adult female sea lice counts per farmed fish have risen often to levels well above CoGP thresholds, where they remain for many months.”
“This is not the case in just a few isolated cases – the regions examined in detail by S&TCS account for over 40% of production in Scotland and the Western Isles.”
The conservation group noted the use of wrasse as cleaner fish does not seem to have helped some sites.