Norwegian Veterinary Institute, Elizabeth Stephansens vei 1, N-1433 Ås, Norway.
Aqualife R&D, Havnegata 9, 7010 Trondheim, Norway; Norwegian Computing Centre, P.O.Box 114 Blindern, N-0314 Oslo, Norway.
Int J Parasitol. 2024 Jul;54(8-9):463-474. doi: 10.1016/j.ijpara.2024.04.003. Epub 2024 Apr 10.
Parasitic salmon lice (Lepeophtheirus salmonis) are a constraint to the sustainable growth of salmonids in open net pens, and this issue has caused production to level off in recent years in the most aquaculture-intensive areas of Norway. The maximum allowed biomass at a regional level is regulated by using the so-called "traffic light" system, where salmon louse-induced mortality of migrating wild salmon post-smolts is evaluated against set targets. As a case study, we have investigated how a specific aquaculture-intensive area can reduce its louse levels sufficiently to achieve a low impact on wild salmon. Analyses of the output from a virtual post-smolt model that uses data on the reported number of salmon lice in fish farms as key input data and estimates the salmon louse-induced mortality of wild out-migrating Atlantic salmon post-smolts, suggested that female louse abundance on the local farms must be halved in spring to reach the goal implied by the traffic light system. The outcome of a modelling scenario simulating a proposed new plan for coordinated production and fallowing proved beneficial, with an overall reduction in louse infestations and treatment efforts. The interannual variability in louse abundance in spring, however, increased for this scenario, implying unacceptably high louse abundance when many farms were in their second production year. We then combined the scenario with coordinated production with other louse control measures. Only measures that reduced the density of farmed salmonids in open cages in the study area resulted in reductions in salmon louse infestations to acceptable levels. This could be achieved either by stocking with larger fish to reduce exposure time or by reducing fish numbers, e.g. by producing in closed units.
寄生性鲑鱼虱（Lepeophtheirus salmonis）是鲑鱼网箱养殖可持续发展的制约因素，近年来，在挪威水产养殖最密集的地区，鲑鱼虱问题导致鲑鱼产量趋于平稳。在区域层面上，允许的最大生物量是通过使用所谓的“红绿灯”系统进行调节的，该系统根据设定的目标评估鲑鱼虱对洄游幼鲑的致死率。作为案例研究，我们调查了一个特定的水产养殖密集区如何降低鲑鱼虱的水平，以减少对野生鲑鱼的影响。利用虚拟幼鲑模型的输出进行分析，该模型使用报告的鲑鱼虱在养殖场的数量作为关键输入数据，并估计野生洄游大西洋鲑幼鲑的鲑鱼虱诱导死亡率，结果表明，春季当地养殖场的雌虱数量必须减半才能达到红绿灯系统所暗示的目标。模拟协调生产和休耕新计划的建模方案的结果是有益的，总体上减少了虱类的侵扰和治疗工作。然而，这种方案导致春季虱类丰度的年际变异性增加，这意味着当许多养殖场进入第二年生产时，虱类丰度会高得不可接受。然后，我们将该方案与协调生产以及其他控制虱类的措施相结合。只有减少研究区域内开放式网箱养殖鲑鱼密度的措施才能将鲑鱼虱的感染降低到可接受的水平。这可以通过饲养更大的鱼来减少暴露时间来实现，或者通过减少鱼的数量来实现，例如通过在封闭单元中生产来实现。
