Table_2_Retrospective Study of Fishery Interactions in Stranded Cetaceans, Canary Islands.pdf

Estimating cetacean interactions with fishery activities is challenging. Bycatch and chronic entanglements are responsible for thousands of cetacean deaths per year globally. This study represents the first systematic approach to the postmortem investigation of fishery interactions in stranded cetaceans in the Canary Islands. We retrospectively studied 586 cases necropsied between January 2000 and December 2018. Of the cases with a known cause of death, 7.4% (32/453) were due to fishery interactions, and the Atlantic spotted dolphin (Stenella frontalis) was the most affected species [46.9% (15/32)]. Three types of fishery interactions were recognized by gross findings: bycatch [65.6% (21/32)], chronic entanglements [18.8% (6/32)], and fishermen aggression [15.6% (5/32)]. Among the bycaught cases, we differentiated the dolphins that died because of ingestion of longline hooks [23.8% (5/21)] from those that died because of fishing net entrapments [76.2% (16/21)], including dolphins that presumably died at depth due to peracute underwater entrapment (PUE) [37.5% (6/16)], dolphins that were hauled out alive and suffered additional trauma during handling [43.8% (7/16)], and those that were released alive but became stranded and died because of fishery interactions [18.7% (3/16)]. Gross and histologic findings of animals in each group were presented and compared. The histological approach confirmed gross lesions and excluded other possible causes of death. Cetaceans in good-fair body condition and shallow diving species were significantly more affected by fishery interactions, in agreement with the literature. Low rates of fishery interactions have been described, compared with other regions. However, within the last few years, sightings of entangled live whales, especially the minke whale (Balaenoptera acutorostrata) and Bryde's whale (B. edeni), have increased. This study contributes to further improvement of the evaluation of different types of fishery interactions and may facilitate the enforcement of future conservation policies to preserve cetacean populations in the Canary Islands.

评估鲸类与渔业活动的相互作用颇具挑战。全球范围内，兼捕（Bycatch）与慢性缠绕每年造成数千头鲸类死亡。本研究首次采用系统性方法，对加那利群岛搁浅鲸类的渔业相互作用开展死后调查。我们对2000年1月至2018年12月间完成尸检的586例病例进行了回顾性分析。在已知死亡原因的病例中，7.4%（32/453）的死因与渔业相互作用相关，其中大西洋斑海豚（Stenella frontalis）是受影响最严重的物种，占比达46.9%（15/32）。通过大体解剖观察（Gross findings），可识别出三类渔业相互作用类型：兼捕（65.6%，21/32）、慢性缠绕（18.8%，6/32）以及渔民攻击（15.6%，5/32）。在兼捕病例中，我们将致死原因分为两类：因误食延绳钓鱼钩死亡的海豚（23.8%，5/21），以及因渔网缠绕致死的海豚（76.2%，16/21）。后者又细分为三类：疑似因极急性水下被困（Peracute Underwater Entrapment, PUE）在深海死亡的海豚（37.5%，6/16）、被捞起后仍存活但在处理过程中遭受额外创伤的海豚（43.8%，7/16），以及被放生后仍搁浅并因渔业相互作用死亡的海豚（18.7%，3/16）。我们对各组动物的大体解剖与组织学（Histologic）检查结果进行了呈现与对比。组织学分析确认了大体解剖所见的病变，并排除了其他潜在致死原因。身体状况良好至中等的鲸类以及浅潜型物种受渔业相互作用的影响更为显著，这与已有文献的结论一致。与其他区域相比，加那利群岛的渔业相互作用发生率较低。但近年来，被缠绕的活体鲸类目击记录有所增加，尤其是小须鲸（Balaenoptera acutorostrata）和布氏鲸（Balaenoptera edeni）。本研究有助于进一步完善对不同类型渔业相互作用的评估工作，或可为未来制定保护加那利群岛鲸类种群的相关保护政策提供支撑。