ABSTRACT: Salmon lice from fish farms in open net pens pose a threat to the survival of wild salmon post-smolts migrating through areas with high farm and lice densities. Reliable estimation of this mortality is fundamental for the sustainable management of aquaculture in such areas but is challenged by considerable uncertainty about several of the processes that link reported lice numbers in fish farms to post-smolt mortality. Utilising recent access to lice data from post-smolt trawling, we revised a virtual post-smolt model that estimates salmon lice-induced mortality of seaward-migrating wild salmon post-smolts. We also assessed the sensitivity of model results to model assumptions that differ among the virtual post-smolt models currently being used as management support in Norway. The spatiotemporal variation in infestation pressure along the entire Norwegian coast was calculated based on monitoring data for salmon lice, temperature and fish abundance in all Norwegian salmonid farm locations. The revised model integrates lice data from sentinel cage experiments and post-smolt trawling to quantify the spatiotemporal variation in infestation rate of wild post-smolts from the spatiotemporal infestation pressure, while also estimating the effect of calibration data type on infestation rate. Results show 10 times higher infestation rate in trawl-caught post-smolts than in post-smolts from sentinel cage experiments. Mortality estimates calibrated to trawl data are more sensitive to assumptions about possible density dependence in lice infestation rate than to assumptions about migration speed. These findings contribute to explaining why different virtual post-smolt models provide different estimates of salmon lice-induced mortality.

中文翻译：

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模拟三文鱼虱引起的野生三文鱼后鲑鱼死亡率对校准数据高度敏感

摘要：开放网围栏中来自养鱼场的鲑鱼虱子对在养殖场和虱子密度高的地区迁徙的野生鲑鱼后幼鱼的生存构成威胁。对这种死亡率的可靠估计对于此类地区水产养殖的可持续管理至关重要，但受到将养鱼场报告的虱子数量与二鲑鱼后死亡率联系起来的几个过程的相当大的不确定性的挑战。利用最近对二鲑后拖网捕捞的虱子数据的访问，我们修改了一个虚拟的二鲑后模型，该模型估计鲑鱼虱引起的向海迁移的野生三文鱼后二鲑的死亡率。我们还评估了模型结果对模型假设的敏感性，这些模型假设在挪威目前用作管理支持的虚拟后二孵化模型中有所不同。整个挪威海岸侵扰压力的时空变化是根据挪威所有鲑鱼养殖场地点的鲑鱼虱子、温度和鱼类丰度的监测数据计算出来的。修订后的模型整合了来自哨兵笼实验和二鲑后拖网捕捞的虱子数据，以根据时空侵染压力量化野生二鲑后侵染率的时空变化，同时还估计了校准数据类型对侵染率的影响。结果表明，拖网捕获的幼鲑后的侵染率比哨兵笼实验中的幼鲑高 10 倍。与对迁移速度的假设相比，根据拖网数据校准的死亡率估计对虱子感染率可能的密度依赖性假设更为敏感。