Discrimination between bycatch and other causes of cetacean and pinniped stranding Diseases of Aquatic Organisms

The challenge of identifying cause of death in discarded bycaught marine mammals stems from a combination of the non-specific nature of the lesions of drowning, the complex physiologic adaptations unique to breath-holding marine mammals, lack of case histories, and the diverse nature of fishing gear. While no pathognomonic lesions are recognized, signs of acute external entanglement, bulging or reddened eyes, recently ingested gastric contents, pulmonary changes, and decompression-associated gas bubbles have been identified in the condition of peracute underwater entrapment (PUE) syndrome in previous studies of marine mammals. We reviewed the gross necropsy and histopathology reports of 36 cetaceans and pinnipeds including 20 directly observed bycaught and 16 live stranded animals that were euthanized between 2005 and 2011 for lesions consistent with PUE. We identified 5 criteria which present at significantly higher rates in bycaught marine mammals: external signs of acute entanglement, red or bulging eyes, recently ingested gastric contents, multi-organ congestion, and disseminated gas bubbles detected grossly during the necropsy and histologically. In contrast, froth in the trachea or primary bronchi, and lung changes (i.e. wet, heavy, froth, edema, congestion, and hemorrhage) were poor indicators of PUE. This is the first study that provides insight into the different published parameters for PUE in bycatch. For regions frequently confronted by stranded marine mammals with non-specific lesions, this could potentially aid in the investigation and quantification of marine fisheries interactions. Grant no. NA12NMF4390144

辨识被丢弃的兼捕海洋哺乳动物的死亡原因存在多重挑战，该困境由多重因素共同导致：溺水所致病变缺乏特异性、潜水型海洋哺乳动物特有的复杂生理适应性、病例史缺失，以及渔具类型的多样性。目前尚无公认的急性水下被困综合征（peracute underwater entrapment syndrome, PUE）特征性病变，但过往海洋哺乳动物相关研究中，在PUE病例中已观测到以下征象：急性体表缠绕痕迹、眼球膨出或发红、近期摄入的胃内容物、肺部病变，以及减压相关气泡。
本研究回顾了2005至2011年间36头鲸类与鳍足类动物的大体尸检及组织病理学报告，其中包括20头经直接观测确认的兼捕个体，以及16头因病变符合PUE特征而被实施安乐死的活体搁浅动物。本研究确定了在兼捕海洋哺乳动物中检出率显著更高的5项判定标准：急性体表缠绕痕迹、眼球发红或膨出、近期摄入的胃内容物、多器官充血，以及尸检大体观察与组织学检测均发现的弥散性气泡。
与之相反，气管或主支气管内泡沫、肺部病变（如湿润厚重、存在泡沫、水肿、充血及出血）并非PUE的可靠指示指标。本研究是首次针对兼捕场景下PUE的各类已发表判定参数展开深入解析的研究。对于常遭遇病变非特异性搁浅海洋哺乳动物的区域而言，本研究结果可助力海洋渔业与海洋哺乳动物交互影响的调查与量化评估工作。资助编号：NA12NMF4390144