Holyrood watchdog begins salmon farm inquiry
THE SCOTTISH Parliament has launched an inquiry into the environmental impact of Atlantic salmon farming in Scotland.
The Environment, Climate Change and Land Reform Committee, which scrutinises the Scottish Government’s policies and expenditure, took evidence from the Dunbeg-based Scottish Association for Marine Science (SAMS) on Tuesday. Earlier this month SAMS published its review of the scientific evidence.
‘The lochs, voes and sheltered coastal waters of the Scottish West Coast and Western and Northern Isles provide ideal conditions for growing salmon in floating cages,’ the report began. ‘The aquaculture industry creates jobs. Nevertheless, its growth during recent decades has encountered economic, societal and environmental challenges which are likely to increase as the industry expands from 163,000 tonnes in 2016 to about 200,000 tonnes in 2020, with the intention to produce up to 300,000 tonnes in 2030.’
The scientists identified many challenges ahead, including the potential for lice from salmon farms to infect wild salmon and damage their populations.
They said: ‘More farmed salmon implies more sea lice (and thus more costs for farmers and more impact on wild salmon), unless mitigation improves. Sea lice populations also appear to be developing resistance to many existing treatment[s].
‘There is some evidence some disease is transmitted between farmed and wild fish by direct infection [or] by escapees.
‘Increased numbers and sizes of farms could lead to increased risk of infection of wild fish unless improvements in farm biosecurity and disease prevention outpace the expansion of production.’ Salmon farm organic waste accumulating on the seabed can also significantly degrade communities of seabed (benthic) animals, the report said. ‘Sinking particulate organic matter results in a farm ‘footprint’ on the seafloor. Oxygen demand is much increased as the organic matter is degraded. Reduced oxygen levels, coupled to the physical smothering effect of the particulates, makes the diversity of the community of seabed (benthic) animals much reduced. This footprint has an area of about half a square kilometre beneath a 1,500-tonne farm. Increased salmon production will lead to increased organic waste.’
There are also concerns salmon escaping from farms could interbreed with wild salmon populations, harming the wild fish. The report said: ‘An average of 146,000 cultivated adult salmon are reported to enter the sea from salmon farms each year in Scotland. The number is likely to be under-reported. The number of survivors is estimated to be significant in relation to numbers of wild salmon in Scotland (about a third of a million).
‘Increase in numbers of farmed salmon is likely to result in more escapees, unless farming practices are change[d].’
Another issue is the deterrence of predators by netting, or acoustic methods, or by shooting of seals, might harm populations of protected marine mammals and seabirds. Birds and mammals, especially seals, may take, injure or frighten farmed fish, or damage nets leading to escapes.
‘Seals can be shot under Scottish government licence. Based on reported numbers of seals shot, current mortality levels represent a small proportion of Scottish seal populations.
‘Although current downward trends in seal shootings are encouraging, these may stabilise or reverse in case of significant future expansion of the industry.
‘Acoustic deterrent devices (ADDs), which produce a loud underwater noise, are widely used as non-lethal seal deterrents. There is, however, little evidence concerning the efficacy of ADD. Their use adds to underwater noise pollution, which is known to cause behavioural changes in acoustically sensitive marine mammals, in particular cetaceans.
‘A simple prediction is that effects on predators will increase as salmon production increases.
‘There is an urgent need to further develop and promote alternative non-lethal depredation prevention methods that do not also have such a widespread impact on the surrounding environment as ADDs.’