Norwegian Institute for Nature Research (NINA), P.O. Box PO 5685 Torgarden, 7485, Trondheim, Norway.
Norwegian Institute for Nature Research (NINA), P.O. Box PO 5685 Torgarden, 7485, Trondheim, Norway; Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences (SLU), SE-75007,Uppsala, Sweden.
Mar Environ Res. 2022 May;177:105625. doi: 10.1016/j.marenvres.2022.105625. Epub 2022 Apr 13.
Beachcast events, where a large number of seabird carcasses drift ashore, occur with irregular intervals. These events are due to specific situations where mass mortality of seabirds have occurred. Disentangling the cause of these events can provide valuable information on stressors impacting seabird populations. Following several mass mortality events involving gulls in northern Norway, an investigation of the probable cause of death was initiated. In total 75 dead gulls were collected at two occasions and necropsies were carried out. The findings from the necropsy of the gulls were consistent with drowning as the primary cause of death. Bycatch in coastal purse seine fishery was considered a potential cause of the mortality and monitoring of seabird bycatch in this fishery was thus initiated. The monitoring of fishing operations revealed that 10% of 91 fishing events observed led to bycatch, with a total of 32 bycaught seabirds. These bycatch events resulted in a total estimated bycatch rate of 0.356 (95% CI = 0.133-0.949) birds per haul. These findings are consistent with the hypothesis that the registered mortality events were caused by bycatch in the purse seine fishery. The highly episodic and unpredictable nature of these events makes it demanding to achieve solid estimates of the occurrence and extent of bycatch without a very high monitoring effort. Our study shows that systematic investigation following beachcast events can shed light on the occurrence of such extreme events.
海滩漂鸥事件是指大量海鸟尸体漂到岸上的现象，其发生具有不规则的间隔。这些事件是由于海鸟大量死亡的特定情况引起的。梳理这些事件的原因可以为影响海鸟种群的压力因素提供有价值的信息。在挪威北部发生了几起涉及海鸥的大规模死亡事件后，人们开始调查可能的死亡原因。总共在两个场合收集了 75 只死海鸥，并进行了剖检。对海鸥剖检的结果与溺水是导致死亡的主要原因一致。沿海围网渔业中的兼捕被认为是导致死亡的潜在原因，因此开始对该渔业中的海鸟兼捕进行监测。对捕捞作业的监测显示，在观察到的 91 次捕捞事件中，有 10%导致了兼捕，共有 32 只海鸟被兼捕。这些兼捕事件导致的总估计兼捕率为每拖网 0.356 只（95%置信区间=0.133-0.949）。这些发现与以下假设一致，即登记的死亡事件是围网渔业中的兼捕造成的。这些事件具有高度的偶发性和不可预测性，如果没有非常高的监测力度，很难对其发生和程度进行可靠的估计。我们的研究表明，在海滩漂鸥事件发生后进行系统调查，可以揭示此类极端事件的发生情况。
