NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries (LFI), Nygårdsporten 112, 5008 Bergen, Norway.
Department of Biological Sciences, University of Bergen, Bergen, Norway.
Aquat Toxicol. 2020 Jul;224:105519. doi: 10.1016/j.aquatox.2020.105519. Epub 2020 May 23.
Emamectin benzoate (EB) is a prophylactic pharmaceutical used to protect Atlantic salmon (Salmo salar) smolts migrating out of rivers and into the ocean against sea lice parasites. Randomized control trials comparing the marine survival of smolts treated with EB to a control group is used to calculate the fraction of marine mortality attributable to sea lice parasitism. However, it is assumed that there is no baseline difference in survival induced by the application of EB treatment. We used a combined laboratory and field study approach to investigate the potential impacts of EB treatment on behaviour and survival of hatchery-reared Atlantic salmon in western Norway. In aquaria experiments, EB-treated salmon smolts did not differ significantly in exploratory behaviour. Fish from treated groups responded similarly to simulated predator attack with spontaneous escape and elevated gill beat rate. Three rivers in the Osterfjord system of western Norway were selected for field experiments, Dale, Vosso, and Modalen. Dale River smolts were treated with intraperitoneal EB injections and had lower probability of detection in a wolf trap downstream of the release site than control smolts. Salmon smolts raised in the Vosso River hatchery were treated with EB delivered in their food and were detected on PIT antennas at the rivermouth of Vosso and Modalen at lower rates than control fish, but only when released at downstream sites. Calculation of risk ratios suggested that the bias in mortality caused by treatment with EB decreased the estimated survival of treated fish from an expected 18%to 46%, reducing the observable negative impact of sea lice on Atlantic salmon smolts in randomized control trials. The results suggest that estimates of the fraction of mortality attributable to sea lice may be underestimated due to lower baseline survival of treated fish caused by treatment and bring urgent attention towards a potential systematic underestimation of the impacts of sea lice on wild salmon.
苯甲醯胺（EB）是一种预防性药物，用于保护从河流洄游进入海洋的大西洋鲑（Salmo salar）幼鱼免受海虱寄生虫的侵害。将用 EB 处理的幼鱼与对照组的海洋存活率进行随机对照试验，以计算归因于海虱寄生的海洋死亡率的分数。然而，据假设，EB 处理引起的存活率没有基线差异。我们使用实验室和野外综合研究方法，调查 EB 处理对挪威西部养殖大西洋鲑行为和生存的潜在影响。在水族箱实验中，EB 处理的鲑鱼幼鱼在探索行为上没有显著差异。来自处理组的鱼对模拟捕食者的攻击有类似的反应，表现为自发逃避和提高的鳃拍动率。在挪威西部奥斯特峡湾系统中选择了三条河流进行野外实验，分别是戴尔河、沃索河和莫达伦河。戴尔河的幼鱼接受了腹腔内 EB 注射，在释放点下游的狼陷阱中被检测到的可能性低于对照组幼鱼。来自沃索河孵化场的鲑鱼幼鱼接受了 EB 喂养，在沃索和莫达伦河口通过 PIT 天线被检测到的比率低于对照组鱼类，但仅在下游释放时才会出现这种情况。风险比的计算表明，EB 处理引起的死亡率偏差降低了预期 18%至 46%的处理鱼的存活率，从而降低了随机对照试验中海虱对大西洋鲑幼鱼的可观察到的负面影响。结果表明，由于治疗引起的处理鱼的基线存活率较低，归因于海虱的死亡率的估计可能被低估，这引起了对海虱对野生鲑鱼影响的潜在系统性低估的迫切关注。
