Dietary analysis of harbour seals (Phoca vitulina) from faecal samples and overlap with fisheries in Erimo, Japan
Dietary analysis of harbour seals (Phoca vitulina) from faecal samples and overlap with fisheries in Erimo, Japan
复制标题
对粪便样本中斑海豹 (Phoca vitulina) 的饮食分析以及与日本襟裳渔业的重叠
DOI：
10.1111/maec.12431
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Miyashita Kazushi
中科院分区：
文献类型：
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作者：
Hui Tabitha C. Y.;Morita Yuka;Kobayashi Yumi;Mitani Yoko;Miyashita Kazushi
自20世纪80年代中期开始保护以来，日本的斑海豹数量一直在反弹。随着海豹数量的增加，由于掠夺和认为海豹与渔业争夺猎物，与渔业的冲突也越来越多。然而，只有在知道海豹随时间消耗的猎物种类和数量的情况下，才能确定竞争。我们研究了2011年至2012年日本最大的海豹种群所在地Erimo的海豹饮食，并评估了猎物与当地渔业重叠的程度。我们使用了硬的部分和DNA技术来识别海豹粪便中的猎物项目，并将这些结果与当地的渔业数据进行了比较。这两种方法共检测到46个猎物的出现，其中17个匹配的技术之间至少在家庭层面。硬部件的方法确定了五个事件的猎物未被发现的DNA方法在五个粪便（每粪便一个发病率）。DNA方法在13个没有找到确凿证据的猎物中发现了24个额外的猎物，这比15个猎物中的猎物总数增加了一倍多。总体而言，最常见的斑海豹猎物是狭鳕（Theragra chalcogramma），杜父鱼和蜗牛。相比之下，渔业的前三大目标群体是鳕鱼、鲑鱼和无脊椎动物。许多在斑海豹的食物中常见的物种，如蜗牛鱼和比目鱼，并不是渔业的目标。小绿叶鱼、杜父鱼、岩鱼和日本鳀（Engraulis）等鱼类是海豹的常见食物，但在埃里莫的渔业渔获量中所占比例很小。其他猎物物种的重要性随季节而变化。在春季，以发生频率的百分比计算，雕刻鱼、青鱼和饲料鱼是海豹的前三大猎物群体，而以渔业捕获的百分比计算，最重要的目标群体是鳕鱼、头足类和其他无脊椎动物。在夏季和秋季，除了鳕鱼、蜗牛和比目鱼外，雕刻鱼和岩鱼仍然是斑海豹的重要猎物。相比之下，夏季渔业捕捞的主要群体是其他鱼类，特别是日本琥珀鱼（Seriola quinqueradiata）和各种鲨鱼和鳗鱼以及无脊椎动物。到了秋天，埃里莫渔业的重点是捕捞鲑鱼。在此期间，海豹也会捕食鲑鱼，但与其他猎物群体相比，频率相对较低。我们的研究结果表明，尽管斑海豹会吃掉渔业目标的几种猎物物种，但这些物种对海豹和渔业的相对重要性以及它们所针对的季节是不同的。
The number of harbour seals in Japan has been rebounding since protection began in the mid‐1980s. With the increase in seal numbers, increased conflict with fisheries has occurred through depredation and the belief that seals compete with fisheries for prey. However, competition can only be determined if the prey species and quantities seals consume over time are known. We studied the diet of harbour seals in Erimo, site of the largest population of harbour seals in Japan, from 2011 to 2012 and assessed the degree of prey overlap with local fisheries. We used both hard parts and DNA techniques to identify prey items in seal scats, and compared these results to local fisheries data. A total of 46 prey occurrences was detected by both methods, of which 17 matched between techniques at least to the family level. Hard parts methods identified five incidences of prey undetected by DNA methods in five scats (one incidence per scat). DNA methods identified 24 additional prey occurrences in 13 scats, for which no hard part evidence for that prey had been found. This more than doubled the total number of prey occurrences across the 15 scats compared. Overall, the most frequently occurring harbour seal prey were walleye pollock (Theragra chalcogramma), sculpins and snailfishes. In contrast, the top three groups targeted by fisheries were codfishes, salmon and invertebrates. Many species common in the harbour seal's diet such as snailfishes and blennies were not targeted by fisheries. Fishes such as greenlings, sculpins, rockfishes and Japanese anchovy (Engraulis japonicus) were common in the diet of harbour seals, but made up a very small proportion of fisheries catches in Erimo. The importance of other prey species varied between seasons. Sculpins, greenlings and forage fishes were the top three prey groups for harbour seals in spring by percent modified frequency of occurrence, whereas the most important target groups by percentage mass caught by fisheries were codfishes, cephalopods and other invertebrates. Sculpins and rockfishes remained as important prey items for harbour seals in summer and autumn, in addition to codfishes, snailfishes and blennies. In contrast, the main groups caught by fisheries in summer were other fishes, particularly Japanese amberjack (Seriola quinqueradiata) and various species of sharks and eels, and invertebrates. By autumn, Erimo fisheries had focussed on catching salmon. Salmon were taken by harbour seals as well during this period, but at a relatively lower frequency compared to other prey groups. The results of our study show that although harbour seals consumed several of the prey species targeted by fisheries, the relative importance of these species to seals and fisheries and the seasons in which they were targeted were different.