Abstract

Harbour porpoise (Phocoena phocoena) bycatch for Norwegian commercial gillnet fisheries from 2006 to 2018 was estimated using a traditional ratio estimator and generalized additive linear mixed models, with weight of fish landed and number of gillnet hauls as proxies for fishing effort. Estimates were derived from data collected with a contracted reference fleet of small coastal vessels and scaled up to the whole fleet using data from landing statistics. Bycatch estimates exhibited large yearly variations, ranging from 1151 to 6144 porpoises per year. Bycatch estimates in 4 of the last 5 years were significantly less than in the preceding 2 years. The best ratio-based and model-based yearly bycatch estimates were 1580 porpoises [coefficient of variation, (C.V.) 0.10, 95% confidence interval (CI) 1302–1902] and 1642 porpoises (C.V. 0.15, 95% CI 1165–2142), respectively. About 75% of bycaught porpoises were taken in the cod (Gadus morhua) and monkfish (Lophius piscatorius) fisheries, while the rest were taken in a variety of different gillnet fisheries. Our results suggest that bycatch of harbour porpoise in Norwegian gillnet fisheries has been unsustainable for several of the last 13 years but are currently within international bycatch limits due to a recent reduction in monkfish fishing effort.

中文翻译：

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评估在动态的挪威刺网渔业中由偶然兼捕造成的与海豚海豚（Phocoena phocoena）有关的渔业相关死亡率的影响

摘要

使用传统的比率估算器和广义加性线性混合模型估算了2006年至2018年挪威商业刺网渔业的海豚（Phocoena phocoena）兼捕量，其中以落地鱼的重量和刺网拖拉的数量为捕捞努力的代表。估计值是从与小型沿海船只签约的参考船队收集的数据中得出的，并使用着陆统计数据将其扩大到整个船队。兼捕渔获物的年变化很大，每年从海豚1151到6144。最近5年中有4年的兼捕量估计数明显少于前2年。最佳的基于比率和基于模型的年度兼捕量估计数是1580只海豚[变异系数，（CV）分别为0.10、95 ％置信区间（CI）1302–1902]和1642海豚（CV 0.15，95 ％CI 1165–2142）。约有75％的海豚被捕到鳕鱼（Madhua morhua）和安康鱼（Lophius piscatorius）的渔业中，其余的则被捕捞到各种刺网渔业中。我们的结果表明，在过去的13年中，挪威刺网渔业中海豚的副渔获一直不可持续，但由于近来减少了安康鱼的捕捞努力，目前在国际副渔获物限制内。