Autumn Distribution of Epipelagic Fishes and Squids in the Okhotsk Sea and Western North Pacific Ocean off the Kuril Islands and Southeast Hokkaido

• Main Authors: Nagasawa, Kazuya, Ueno, Yasuhiro, Sakai, Junko, Mori, Junta
• Format: Article in Journal/Newspaper
• Language: English
• Published: 遠洋水産研究所 2014
• Subjects: ocean distribution; Pacific salmon; epipelagic fishes and squids; Okhotsk Sea; North Pacific Ocean; 分布; 北海道; 魚類; 太平洋; イカ類; オホーツク海; 秋; 480; Keta; Okhotsk; Pacific; okhotsk sea; Theragra chalcogramma
• Online Access: http://ir.lib.hiroshima-u.ac.jp/00030212; http://ir.lib.hiroshima-u.ac.jp/files/public/3/30212/2014101617412931444/BullNatResInstFarSeasFish_35_113.pdf

水産庁の調査船俊鷹丸と開洋丸により, 1996年8月下旬から11月下旬にオホーツク海および北海道・千島列島沖合の北西太平洋において, 表層トロール網を用いて表層生物の分布に関する調査を実施した. 漁獲された表層生物のうち, 種まで同定されたのは魚類33種(ヤツメウナギ類1種, サメ類2種, 硬骨魚類30種)とイカ類13種であった. 漁獲尾数をみると, サケ・マス類幼魚が最も多く漁獲され, サバ類, スケトウダラ幼魚、ハダカイワシ類, ホッケ幼魚, カタクチイワシが続いた。トガリイチモンジイワシ, マイワシ, テカギイカ類も多く漁獲された。本論文では, これら多獲された魚類とイカ類の分布を記述し, その特性を論じた. 秋前期のオホーツク海の表層水には, サケ・マス類幼魚, ホッケ幼魚, サンマ, 他の暖海性魚類が海面水温の差に応じて分布していた. 秋半ばから後期には, サケ・マス類幼魚はオホーツク海に分布したが、暖海性魚類の多くは南下し, ホッケ幼魚は沖合域から沿岸域に移動した. また夜間の表層水には, 深部から移動してきたハダカイワシ類とソコイワシ類, テカギイカ類が多く分布していた. これらの結果から, オホーツク海の表層水は, 深部から日周的に移動してくる魚類とイカ類に索餌域を提供するほか, ホッケ幼魚と暖海性魚類に夏～秋季, サケ・マス類幼魚に夏～秋・冬季の生育場を提供すると考えられる. Surface-trawl surveys were conducted in the central and southern Okhotsk Sea and in the western North Pacific Ocean off the Kuril Islands and southeast Hokkaido from late August to late November in 1996. A total of 33 fish species (one lamprey, two sharks, and 30 teleosts), 13 squid species, and some other unidentified species were collected. This paper describes and discusses the distribution patterns of abundant species. Salmonids (six species of the genus Oncorhynchus) were the most abundant (27 2048n number and 51-1073755312n weight of total catch), followed in number by mackerel (Scomber sp.), juvenile walleye pollock (Theragra chalcogramma), myctophids, juvenile arabesque greenling (Pleurogrammus azonus), and Japanese anchovy (Engraulis japonicus). Over 9814634472523f the salmonids collected were ocean-age 0 juveniles. Pink (O. gorbuscha) and chum (O. keta) salmon juveniles predominated. Northern smoothtongue (Leuroglossus schmidti), Japanese sardine (Sardinops melanostictus), and various gonatid squids were also abundant. In early autumn (August to September), juvenile salmonids, juvenile arabesque greenling, and migratory warm-water species were segregated according to sea surface temperature (SST) in the Okhotsk Sea: the salmonids occurred in more northern waters than did the others. With decreasing SST during mid- and late autumn (October to November), most of the warm-water species migrated southerly to the North Pacific Ocean and juvenile arabesque greenling moved to coastal waters. Juvenile salmonids moved southward but remained in the Okhotsk Sea. Vertically migrating myctophids and bathylagids were abundant in the evening. Gonatid squids were also numerous in the evening catches. We conclude that the surface water of the Okhotsk Sea is constantly utilized by the species vertically migrating from deep waters and also provides habitats for feeding and growth to various warm-water species and juvenile arabesque greenling from summer to autumn and to juvenile salmonids from summer to autumn or winter.