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北西太平洋におけるビンナガ竿釣漁業の漁況変動について
https://fra.repo.nii.ac.jp/records/2007260
https://fra.repo.nii.ac.jp/records/2007260bfd5abb9-724c-44df-9491-af2f64df834d
| Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2024-06-10 | |||||
| タイトル | ||||||
| タイトル | 北西太平洋におけるビンナガ竿釣漁業の漁況変動について | |||||
| 言語 | ja | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | departmental bulletin paper | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| その他（別言語等）のタイトル | ||||||
| その他のタイトル | 1977年青森県大型漁船による漁況の特長 | |||||
| 言語 | ja | |||||
| 著者 |
浅野, 政宏
× 浅野, 政宏 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Since 1971, the baitboat fishery has been the dominating producer of albacore in Japan, replacing the traditional longlining (Figure 1). Catch and effort statistics by 10-day period every month and one latitude-longitude degree square have been complied for the Japanese baitboat fishery in the western Pacific Ocean for ten years from 1968 to 1977. Here are analzyed the statistics to estimates measures of abundance of and amount of efficient effort on the species. They are: Japanese baitboat yield, Yi, in tons, in the i-th square taken in a 10-day period, amount of fishing effort, Xi, in terms of number of boat-days, in the i-th square operated in a 10-day period, extent of fishing ground, A, in terms of number of the one-degree squares where albacore were caught, in a 10-day period, index of stock size, P=∑ (Yi/Xi), in terms of ton per boat-day over given number of squares, in a 10-day period, density index, d=P/A, in terms of ton per boat-day, in a 10-day period, amount of effective effort, X=A∑Yi/P= ∑Yi/d, in terms of boat-day, in a 10-day period. The density indices, d's, are averaged for four months from April to July, to represent the yearly density. The other measures were summed up for the four months every year. The Japanese baitboat fleet have mainly exploited albacore in the northwest Pacific, north of Lat. 20°N, east of the date line. The waters are generally divided into three areas, A; Pacific waters north of Lat. 20°N, Long. 130°E-140°E, B: Lat. 20°N-35°N, Long. 140°E-180°, and C; Lat. 35°N-45°N, Long. 140°E-180° (Figure 2). The fishing grounds were limited to the Areas A and B until 1969. In 1970 and onwards the fleet have expanded the operating range eastwards, and the amount of catch in the Area C has exceeded 50 percent of total catch of albacore by the fleet. The yearly density index of albacore increased continuously from 1968 to 1974 and then rapidly decreased in the Areas B and C. The decrease of density occurred after 1971 in the Area A( figure 5). The maximum density is the highest in the Area C, 9.24, tons per boat-day 3.8 times as high as the maximum in the Area A, 2.4 tons per boat-day. In the Area B the maximum density was 3.86 tons per boat-day, 1.6 times as high as that in the Area A. The extent of fishing ground in the Areas B and C has widened year after year until 1973, and then stayed at that level (Figure 7). The fishing grounds formed between Long. 130°E-160°E in the early years under discussion, and then gradually expanded eastwards, having reached the date line in 1973. The expansion of fishing grounds resulted in not only increase of catch but also in extension of cruise period. In the early years around 1968, there occurred two major operation sites, the coastal ground around Long. 140°E and the offshore ground around Long. 150°E. The fishing activities declind in the coastal ground year after year, and the most prolific operations were limited in the waters of Long. 150°E-160°E in 1972, or of Long. 150°E-170°E in 1973 and onwards. Such eastward shift of major fishing grounds lead the areal catch on the decrease in the Area A since 1973 and in the Area B since 1976. For examination of body length composition of albacore caught by the livebait fishery, the Areas A, B and C are divided into two or three subareas (Figure 19). It is obvious that the small-sized fish are more frequently found in the northern subareas than in the southern subareas. More than one age group are often noted in the southern subareas (Kawasaki and Aizawa 1956). Resemblance in size composition is observed in the three sets of subareas; A1 and B1, A2 and B2, and C1 and C2. On the other hand the fish in the waters north of Lat. 35°N are found much smaller than those in the south. These geografical variation of size composition of catch confirms the east-west movement of the fish of the same ages, and the north-south segregation between different age groups. The year class strength also shows significant variation. For instance, the 1971 class dominated in 1973 as 2-age-old and were found abundant as 3-age-olds in 1974 and 4-age-olds in 1975 (Figure 28). According to Inoue (1959) the oceanographic conditions of the waters near central Japan are categorised into three types as: C type: the Kuroshio Current meanders to south of the cold water mass that appears off the Enshu Nada during the winter through summer, L type: the cold water mass does not appear and the Kuroshio flows along the southern coast of Japan, and, C-L type: the cold water mass appears only in the colder months of the year before April or May. He related the oceanographic conditions with success of fishing. For the C type, according to him, the catch is successful in the offshore waters but the fishing season ceases in April or May. In years of the L type, the fishing activities occurr in the nearshore waters, lasting for fairly long period from February to June. The intermediate C-L type corresponds to diverse types of fishing activities between the above two typical situations. Amoung the ten years under discussion, each of the C and L types occurs in four years, and the C-L type in the rest two years. Inoue's hypothesis agrees for some cases. In the Area A, the C type corresponds to both successful and poor years. In the Area B, the successful catch occurse frequently in years of the L type. Thus, it is still suggested that occurrence of the cold water mass off the Enshu Nada affects success of fishing in the Areas A and B. Change of catch in the Area C is explained in relation to the stock size and fishing intensity. The catch increased partly with rise of density since 1968 and partly with expansion of fishing activities since 1970. The unusually high catch appears to have been caused by high density in 1974 when the strong 1971 class was exploited as 3 age-olds, and by intensified fishing activity in 1976, both increase of number of boats and concentration toward the albacore. | |||||
| 言語 | en | |||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | 日本近海のビンナガ漁場を140°E及び35°N線で3つの水域に区分してA·B·C水域と名付け,1968年から1977年までの10ヶ年にわたって各水域毎に漁獲量,資源量指数,魚群密度等の値を旬別に,また漁期問を通しての年計値として求め,その動きについて比較検討を加えた.先ず漁期間を通しての年計値からこの間のビンナガ漁況の経過をみると,1969年以前にあってはもっぱらA・B2つの水域だけが操業されていたが,1970年頃からC水域での操業が増え,1974年以降はこの水城での漁獲が全漁獲量の50%を越えるに至っている.魚群密度はA水域を除いて何れも1974年まで一貫して増加を続け,その後急減している.ピーク時の値はC水域が最も高くてA水域の3.8倍,B水域が同じく1,6倍となっている. 漁場面積はB·C水域で1973年まで年々増加を続け,1973年をピークにその後横ばいに転じている.次に緯度·経度1度毎の年別及び月別漁獲量から年毎の漁場の推移をみると,当初漁場は130°~160°Eの範囲に形成されていたが,次第に東に延びて,漁場面積の最も拡がった1973年は 180°E付近に達している.この漁場範囲の拡大が年々の漁獲量の増大につながると同時に漁場の遠隔化ともなり,延操業日数の増大につながっている,また主漁場の位置も当初近海では140°E周辺,沖合では150°E周辺にあったが,次第に近海での漁場形成が少なくなり,1972年頃は150°~160°E,1973年以降は 150~170°E に形成をみるようになった,年漁獲量がA水域で1973年以降,B水域で1976年以降減少しているのはこのためである.さらにA水域をA1,A2,B水域をB1,B2,B3,C水域をC1,C2と,それぞれ2~3個づつの小水域に区分し,各水域別に漁獲物の体長組成を検討した,その結果一般的傾向として,漁場が北に移るに従って小型魚の割合が増加し,南の漁場では1~2個の大中型魚の年令構成による場合が多い、このことは川崎·相沢(1956)と一致する.A1水域とB1水域,A2水域とB2水域,C1水域とC2水域はそれぞれの組成に共通性が多く,東西の交流があり,同一の魚群が漁獲の対象になっているとみられる、反対に35°N線を境に以南と以北では魚群の交流はそれ程顕著ではないが,それぞれ別個の魚群を漁獲の対象としているようである,各年令群の出現の割合は年によって異なるが,1973年に2才魚が卓越し,1974年は3才魚の,さらに1975年は4才魚の比率が多くなるという傾向がみられ,卓越年級群の存在を示唆している.井上(1959) の海洋型の区分に従って考察の対象とした1968~1977年の10ヶ年を分類すると,C型及びL型はともに4ケ年,C-L型は2ケ年となる.この海洋型と漁況との関係をみると,A水域での豊漁年はC型に多いが,不漁年もC型となっている,一方B水域での豊漁年はL型が多くなっており,遠州灘沖冷水塊の出現の有無が,豊凶2つの面でA·B両水域の漁況に大きな影響を与えている.C水域では1968年以降魚群密度の急増によって, また,1970年以降は有効努力量の急増によって漁獲を年々伸ばしている.特に1974年は魚群密度が1976年は有効努力量が例年の2倍近くに急増したため,漁獲量も飛躍的に増加している.1974年の魚群密度の急増は漁獲の主対象である3才魚が卓越年級群として出現したため,また1976年の有効努力量の急増は実際の操業日数の増加とともに,漁獲努力のビンナガへの集中の度合がこの年特に大きかったためと考える. | |||||
| 言語 | ja | |||||
| bibliographic_information |
ja : 東北区水産研究所研究報告 en : Bulletin of Tohoku Regional Fisheries Research Laboratory 巻 41, 号 tnf_k_41_71, p. 71-102, ページ数 32, 発行日 1979-12 |
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| 出版者 | ||||||
| 出版者 | 東北海区水産研究所 | |||||
| 言語 | ja | |||||
| 出版者 | ||||||
| 出版者 | Tohoku Regional Fisheries Research Laboratory | |||||
| 言語 | en | |||||
| item_10002_source_id_9 | ||||||
| 収録物識別子タイプ | PISSN | |||||
| 収録物識別子 | 0049-402X | |||||
| item_10002_source_id_11 | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AN00167637 | |||||
| 情報源 | ||||||
| 識別子タイプ | Local | |||||
| 関連識別子 | tnf_k_41_71 | |||||
| 関連サイト | ||||||
| 識別子タイプ | URI | |||||
| 関連識別子 | https://agriknowledge.affrc.go.jp/RN/2010212444 | |||||
| 言語 | ja | |||||
| 関連名称 | 日本農学文献記事索引(agriknowledge) | |||||
