Sea Lice, Salmon Fish Farm Production and Infestation of Sea Trout in Ireland

1. Sea Lice, Salmon Fish Farm Production and Infestation of Sea Trout in Ireland By John Joyce Queen’s University, Northern Ireland

2. Summary of Case Salmon Fish Farm Production & Sea Lice • Large-scale salmon (Salmo salar) fish farm production began on the west coast of Ireland in the late 1980’s • In the natural environment normally a small number of parasitic sea lice (Lepeophtheirus salmonis) attach themselves to salmon – causing little or no impact on the life cycle of the salmon Now, 3. Due to the high density of salmon in the farm pens, excessive growth in the sea lice population has occurred

3. Statement of Case Cont’d Sea Trout & Sea Lice • In 1989, soon after large-scale salmon fish farm production began on the west coast, the sea trout stock collapsed in key fisheries – with collapse of stocks linked with sea lice infestation and increased mortality (the wild sea trout migration path passes by the salmon pens where sea lice attach themselves to the wild trout and causes the premature return of juvenile sea trout (smolts) to freshwater and a corresponding collapse in the spawning stock) • Since 1989 due the lack of archival data on natural sea lice loadings on returning wild adult sea trout, controversy over the link exists, so salmon production continued and in the majority sea trout stock levels never recovered • Interestingly, marginal recovery in sea trout stock levels occurred temporarily in specific fisheries largely due to fish farm diseases contaminating the pens, resulting in zero production for a period of time, or where fish farms are sold and during operational transfer, production temporarily ceased

4. Statement of case cont’d Control measures to allow sea trout stock levels to recover • Reducing sea lice levels to “near zero levels” in the key period, pre and post sea trout smolt migration, would allow stocks to recover • “Sea Lice Monitoring and Control Protocol” - during the key migration stage, sea lice numbers are restricted to a range of 0.3-0.5 egg-bearing females per fish • all farms under inspection 14 times are year • if the sea lice numbers are exceeded, then sanctions are imposed (including a peer review process, conditional fish movement orders, and accelerated harvests) 3. During the critical period, 58.3% of inspections found that the Protocol levels had been exceeded

5. Excessive sea lice also impacts the salmon production Sea Lice reduces the aesthetic appearance of farmed salmon and market value Farmers have introduced measures to reduce these negative impacts, namely, • Spatially distancing pens from each other • Fallowing between crops • Introduction of Wrasse, who graze sea lice of the pens And, the predominate measure, d) Use of the following medicines, cypermethrin, enamectin benzoate & teflubenzourn

6. Significant societal costs and benefits related to this case

7. Benefits to Salmon Farm Producers from current situation

9. Research Questions • Experimental work to define better sanctions • license arrangements - heterogeneity • To develop methods to ‘transfer’ the science from other locations to specific sites… • ?