THE CONTROL OF SEA LICE ON FISH FARMS IN SCOTLAND 2013-2015 A REPORT FOR SALMON AND TROUT CONSERVATION SCOTLAND DECEMBER 2015 EXECUTIVE SUMMARY 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, making the proper control of sea-lice on fish-farms essential to protect wild fish. Although analysis of control of sea-lice on Scottish fish-farms is severely hampered by the lack of farm-specific sea lice data, publicly available data for 2013 to 2015 shows that the number of Scottish fish-farming regions failing to keep adult female sea lice numbers below the CoGP threshold is on an upward trend. The industry- wide problem with sea lice is increasing and is certainly not under control. The proportion of the total Scottish farms salmon production exceeding CoGP thresholds shows a similar upward trend, with regions representing 60% of Scottish production being over the CoGP threshold of 0.5 adult female lice per fish in May 2015, at the peak of the wild smolt run. There is strong evidence that sea lice numbers on fish farms rise during the second year of production and, in much of Scotland, average adult female sea lice numbers per farmed fish appear to be linked to the cumulative biomass of farmed fish held on the farms. There is evidence of the considerable failure in some regions of available chemical sea lice treatments to limit sea lice numbers on farmed fish to below CoGP thresholds, strongly suggesting that resistance and tolerance to these treatments is becoming widespread. A number of regions appear to have experienced sea lice numbers persistently above CoGP thresholds, despite the use of wrasse as cleaner fish on some farms. There is some evidence of a failure by some operators to treat for sea lice on farmed fish despite sea lice numbers being over CoGP thresholds, contrary to CoGP requirements, and of the failure by fish-farmers to treat sea lice near the end of production cycles, both suggesting that little consideration is being given to the consequent negative effects on wild salmonids. Where there is evidence of early harvest or culling out of farmed fish, this appears only to be associated with unacceptable damage being caused to the farmed fish, causing either commercial losses or animal welfare issues for the farmed fish, rather than this occurring in order to protect wild fish. Action by Scottish Government is required urgently to address the sea lice issue as it affects wild fish. The major barrier to proper scrutiny of the fish farms - the lack of published farm- specific sea lice data - needs to be removed and further information concerning newer control methods for sea lice should be recorded and published to ensure that a complete picture is obtained of the sea lice control methods used. The voluntary CoGP should be made a statutory code, as provided for in the 2007 Act, and an upper tier sea lice threshold should be introduced, above which an immediate cull or harvest of farmed fish is mandated. It should not be possible for fish-farmers, where sea lice numbers have effectively gone out of control on their farms, to assert that they remain in compliance with the CoGP merely because they have instigated treatment, regardless of its efficacy in reducing lice numbers. 1 The Scottish Government should amend legislation with the express purpose of protecting wild fish from potential damage caused by fish-farms, with inspectors given a legal duty to control sea lice on fish-farms expressly in order to protect wild fish populations. Those farms consistently failing to control sea lice should be identified for closure and / or relocation. In parallel, Scottish Government should focus on alternative more sustainable production methods with the ultimate objective of moving to full closed containment of farmed salmon production in Scotland to eliminate the biological interaction between farmed and wild fish. 2 Contents Page 1. The threat to wild salmonids from sea lice emanating from fish-farms 4 2. Sea lice controls on fish-farms – legal and voluntary 8 3. How do fish-farms seek to control and treat sea lice? 10 4. Available data on sea lice on Scottish fish-farms between 2013 and 2015 12 5. Analysis of sea lice control on Scottish salmon farms 2014 to 2015 14 5.1 Inchard to Kirkaig North 16 5.2 Badachro to Applecross 18 5.3 Loch Long and Croe 21 5.4 Fyne 23 5.5 Isle of Lewis West 26 5.6 Harris 29 5.7 The Uists North 32 5.8 The Uists South 34 6. Discussion and conclusions 38 7. Recommendations 40 Annexes 42 3 1. The threat to wild salmonids from sea lice emanating from fish-farms Over many years, there has been considerable debate over the magnitude of the negative effects of sea lice, produced by salmon farms, upon wild salmonids. Despite this, the marine-cage salmon farming industry has accepted, for at least a decade, that the control of gravid adult female sea lice on farmed fish within salmon farms is essential, at least in part to minimise the impact of sea lice on wild salmonids. For example, the Strategic Framework for Scottish Aquaculture produced by the Scottish Executive in 2003, identified sea lice infestation as a significant factor which could impact upon the future sustainability of both aquaculture and wild fisheries. As Figure 1 shows, sea lice have both a free-swimming and a fixed parasitic stage in their life cycle. As they grow throughout these stages, they continue to molt. While salmon farming is conducted in the open sea, with fish held in nets suspended from floating cages, the risk to wild fish from large numbers of juvenile lice leaving the farms will remain. The sea lice life cycle comprises many stages, but during its planktonic stages, juvenile sea lice can be dispersed very long distances. Indeed, modelling scenarios suggest that sea lice can be dispersed up to 30km from fish-farms1. In effect, this means that the majority of the coastal waters of the west coast and western isles of Scotland - and the wild salmonids populations they contain - are potentially affected by sea lice emanating from Scottish salmon farms. An average sized salmon-farm can hold over half a million farmed fish. Even if just a single adult female louse is present on each fish, this would constitute an enormous production of juvenile sea lice. An adult female louse produces a pair of egg strings about every 20 days depending on temperature (and produces several pairs over its lifetime) with about 150 eggs on each string. This would mean roughly 150 million juvenile lice being released every 20 days by the adult female lice from such a farm of half a million fish. 1 NKG Salama, CM Collins, JG Fraser, J Dunn, CC Pert, AG Murray and B Rabe (2012) Development and assessment of a biophysical dispersal model for sea lice Journal of Fish Diseases Special Issue: Papers from the 9th International Sea Lice Conference Bergen, 20–23rd May 2012 Volume 36, Issue 3, pages 323–337, March 2013 4 If, as has been seen in 2013 to 2015, fish-farming regions on the Scottish west coast are consistently over CoGP thresholds for a whole year, this implies the production of tens, even hundreds of billions of mobile free-swimming stage lice. A report for the Norwegian Institute for Nature Research, Norway’s leading institution for applied ecological research, summarises the threat this poses to wild salmonids: “When large numbers of farmed salmon are introduced to the marine environment in open net cage salmon farms, three things are virtually inevitable for these fish. They will become hosts to sea lice since these occur naturally on wild host species in the vicinity of most farms; they will become part of a dynamic host‐parasite system involving wild hosts, because they can produce large numbers of infective larvae in a restricted spatial area if gravid females are allowed to develop; and because they carry sea lice, and because some of these fish may escape from the farms, the dispersal of parasites is likely to be even more widespread on occasion. Given the above, it may be concluded that it is next to impossible to (1) avoid infection of farmed fish, all of which go into the pens as clean smolts, and (2) also subsequently avoid infection of wild fish that are found in the vicinity (“infective field”) of an open cage farm2.” While adult wild salmon are perfectly adapted to coping with a few sea lice, and background levels of these parasites occur naturally in the sea, the negative impact of too many sea lice on wild salmonids (salmon and sea trout) is now widely accepted by fisheries scientists including the Scottish Government’s own Marine Scotland Science (MSS)3. A burden in excess of 13 pre-adult sea lice is known to compromise severely the survival of juvenile migratory salmonids. Sea lice feed by grazing on the surface of the fish and eating the mucous and skin and so large numbers of sea lice soon cause the loss of fins, severe scarring, secondary infections and, in time, death. Sea trout, which tend to remain in coastal waters, can pick up huge burdens of sea lice near salmon farms. As well as causing premature mortality, infestation at sub- lethal levels can trigger early returning behaviour in sea trout, with the fish moving back into freshwater prematurely, to rid themselves of sea lice.