{"created":"2024-04-22T04:04:00.763406+00:00","id":2002227,"links":{},"metadata":{"_buckets":{"deposit":"556c2599-0351-4024-a208-7abeb73461f1"},"_deposit":{"created_by":10,"id":"2002227","owners":[10],"pid":{"revision_id":0,"type":"depid","value":"2002227"},"status":"published"},"_oai":{"id":"oai:fra.repo.nii.ac.jp:02002227","sets":["12:14:1716951513399"]},"author_link":[],"item_10002_biblio_info_7":{"attribute_name":"書誌情報","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"1989-03","bibliographicIssueDateType":"Issued"},"bibliographicNumberOfPages":"132","bibliographicPageEnd":"152","bibliographicPageStart":"21","bibliographicVolumeNumber":"26","bibliographic_titles":[{"bibliographic_title":"遠洋水産研究所研究報告","bibliographic_titleLang":"ja"},{"bibliographic_title":"Bulletin, Far Seas Fisheries Research Laboratry","bibliographic_titleLang":"en"}]}]},"item_10002_description_5":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"The yellowfin sole, Limanda aspera (PALLAS) is a commercially important flounder species distributing widely in the northern North Pacific. In the eastern Bering Sea, the species began to be exploited in 1930. The annual catch was at a low level through 1958 and then showed rapid increases to about 470 thousand tons in 1961, followed by sudden decreases to 90 thousand tons in 1963. The catch since 1964 had remained at relatively low level of 40-170 thousand tons. From such catch trends, the yellowfin sole was often regarded as a typical overfishing species. Stock assessments of the species using catch and fishing effort informations from the fishery could not be developped because of lacks in data during the early and largest catch years and because of changes of fishing in quality during the exploitation history. In recent years, large-scale trawl surveys indicated that the yellowfin sole biomass had reached to a very high level much over 2 million tons in 1983. For the best and long-term utilization of the yellowfin sole stock in the eastern Bering Sea, the author describes biological characteristics of the species, assesses the stock condition and evaluates influences of fishing to the stock, estimates optimum yields, and considers effective stock management measures in the present paper. The results obtained are summarized as follows. I. Biological characteristics 1. Yellowfin sole distributes widely in the North Pacific, north from Vancouver I., Hokkaido I., and Pusan, Korea, up to the Point Barrow, Alaska. In the eastern Bering Sea, yellowfin sole is the secondary important groundfish for fishery, following walleye pollock. 2. There is a single stock of yellowfin sole in the eastern Bering Sea, except a very minor group having small biomass and distributing in the U.S.S.R. waters. 3. The species inhabits edges of the continental shelf and upper slope area in winter and distributes in shallower areas than 100 m in summer. Male 4 . The spawning takes place in shallow areas of 30-60 m from the Bristol Bay to north of Nunivak I. mainly during July-August. 5. The author used otoliths for ageing and regarded all circuli as annuli including the first one formed in around 6 months after hatching. Annuli are formed during December-May. Using the sample collected in 1968, the relationship between number of annuli (i) and total-length (TL in mm) back-calculated from the otolith radius- TL relationship is expressed in the following Bertalanffy's growth equation. Male : TLᵢ = 440.4 (1-exp (-0.086 (i-0.522))) Female : TLᵢ = 478.2 (1-exp (-0.082 (i-0.502))) The relationship between age (t) in full and TL using 7 year samples and the relationship between t and body-weight (BW in g) are expressed as follows. Male : TLₜ = 416.3(1-exp (-0.105(t - 0.083))) Female : TLₜ = 421.0 (1-exp (-0.121 (t - 0.688))) Male : BWₜ = 864 (1-exp (-0.105 (t-0.083)))³·⁰⁹⁷⁷ Female : BWₜ = 941 (1-exp (-0.121 (t-0.688)))³·¹⁴²⁶ 6. The total-length and age at which 50% of individuals reaches sexual maturity are much different by sex as shown in the followings. Male in 1973: 130 mm in 1974 : 150-160 mm in 1978 : 125-130 mm Female in 1973 : 255-260 mm in 1974 : 255-260 mm in 1978 : 270-275 mm Male in 1978 : 4 years of age Female in 1978 : 11 years of age There is a possibility that the length at maturity might have changed according to stock levels. 7. The feeding activity is high during June-October and very low during the wintering season of January-March. The principal prey items are benthic animals such as bivalves, polychaetes, echiuroids, amphipods. There is a clear tendency that prey species change to larger ones according to the size of yellowfin sole. II. Fishery 1. The yellowfin sole fishery had such a peculiar history that the catch increased from 40 thousand tons to the maximum of 470 thousand tons and decreased to 86 thousand tons within 5 years, followed by relatively low catches at 42-167 thousand tons. The principal fishing countries were Japan and U.S.S.R. 2. During the history, type and size of fishing vessels, fishing season and ground, gears, fishing tactics, etc. were changed largely, and so, consistency in quality of fishing effort could not be maintained for a long period. 3. Age compositions of commercial catches changed largely during the exploitation years, indicating fluctuations of year class strength. III. Stock assessments 1 . Catch per unit effort (CPUE) from the fishery through 1973 did not necessarily reflect the stock trend because of substantial changes in quality of fishing effort as mentioned in Item II. 2. Since 1974 the fishery changed little in quality and the CPUE increased rapidly through 1979 or 1980 and then showed sharp declines through 1983. 2. Trawl survey data were used for biomass estimation by adopting an area-swept technique, which uses catch per unit area swept and size of survey area. (1) Annual surveys conducted during 1966-1978 by Japan were of rather small scale and in addition some surveys covered only a part of major concentrations of yellowfin sole. The surveys during 1979-1982, conducted under a Japan-U.S. joint program, were of large scale and covered a major portion of the yellowfin sole distribution. (2) A stratified systematic sampling scheme was adopted for the surveys and trawl stations were arranged in a equally spaced grid pattern. Analytical procedures and formulae for a stratified random sampling were applied for the data analysis. (3) A alternate tail attack method was tried to estimate the vulnerability of trawl (ratio of fish caught in an area swept) but no estimates were obtained because of difficulties in trawling, in which areas swept by two trawlers have to be overlapped. Therefore, the vulnerability was assumed to be 1.0. (4) The distance between wingtips of trawl (w) was estimated from the extending angle of trawl warps during trawling and it was confirmed that the w value changes substantially by depth. (5) The biomass estimate was 1.04 million tons for 1975 and then increased rapidly to around 2.0 million tons for 1979-1981, and to 3.79 million tons for 1982. The biomass for 1979-1981 should be underestimated because of less bottom contact of the trawl and bridles. Since the bottom contact was improved between 1981 and 1982 and consequently the herding effect of bridles might occur, it could not be judged whether the biomass of 3.79 million tons may be still underestimated or overestimated. 3. A cohort analysis was used for calculating the biomass by year. The estimates of natural mortality coefficient (M) were obtained between 0.12 and 0.26 by various methods, and so 3 levels of M value, 0.12, 0.20, and 0.25 were used for the analysis. A basic information for the terminal fishing mortality was the population in number by age estimated by the trawl survey in 1979. The biomass estimates obtained were rather stable during 1964-1972 and increased rapidly through 1979. 4 . The CPUE values from the fishery and biomass estimates from trawl surveys and cohort analysis indicate that the yellowfin sole abundance was stable at rather low levels through 1972 after the decreases during the heavy exploitation years of early 1960s, and then increased rapidly through 1979 or 1980. The CPUE values showed sharp decreases thereafter but biomass estimates continued to increase through 1983. From the fact that the trawl surveys covered the major distribution area and strong year classes had appeared successively in the population, it can be judged that the biomass still increased after 1980. 5. Fluctuations of the stock abundance were mainly caused by successive occurences of year classes having similar strength. The recent increases of stock abundance were also caused by strong year classes and the low level of catches expedited the increases. Ⅳ. Stock management 1. Yield-per-recruit (Y/R) curves against fishing mortality coefficient (F) were obtained by using the following equation for natural mortality coefficient (M) of 0.12, 0.20, and 0.25, taking account of recruit ratio by age (rₜ, age-specific selectivity by the fishery estimated from the cohort analysis). Y/R=E·tλ∑t=tʀ rₜ·wₜ·tIIx=tʀ+1 (rₓ₋₁·exp(-Z)+(1- rₓ₋₁)·exp(-M) where, E is rate of exploitation, Z=F+M, t is age, tʀ is age at first recruitment and capture (3). tλ is maximum age (18), and wₜ is body-weight. Since it is not certain whether the maximum yield on the curve would be sustainable, the optimum yield per recruit (OY/R) being expected to be sustainable was estimated by following procedures. At first, the number of adult females was calculated for various F values. Then, the optimum F value (Fₒₚₜ) was determined as the F value which would maintain adult female at one half of the level that is obtained at no fishing (F=0). The Y/R value on the curve against the Fₒₚₜ is regarded as OY/R. 2 . Recruit number (population in number at age 3, estimated from the cohort analysis) was at high or low level during the period of 1964-1979. The optimum yield (OY) estimated from the OY/R and the recruit number was changed substantially according to the recruit level. The estimate of OY was 71,000 t, 81,000 t and 105,000 t for the M value of 0.12, 0.20 and 0.25 respectively at the low recruit level and 266,000 t, 240,000 t and 230,000 t for respective M value at the high recruit level. 3. The recent recruit level was relatively high successively, and therefore a yield over 230,000 t can be expected to catch a year. 4. Any specific relationships could not be found between the adult stock size and the recruit number, and so, long-term measures for stock management could not be established. In addition the influences of environmental factors on recruitment are unknown so far, and the prediction of recruit levels is not possible. When decreases of recruit would be detected, it should be necessary to reduce the catch according to the recruit level in order to secure the adult stock for recruitment. For the best and long-term utilization of the stock, the author emphasizes necessities to continue the Japan-U.S. joint trawl survey in order to monitor trends of recruit and stock levels and to promote exchanges of informations and views on the stock assessment and management among nations concerned.","subitem_description_language":"en","subitem_description_type":"Abstract"},{"subitem_description":"東部ベーリング海におけるコガネガレイ資源の開発は,1930年代に既に開始されていたが,1958年までの漁獲量は,4万トン以下の小規模なものであった。その後数年のうちに,漁獲量は約47万トンに急増し,また急激に低下するという特異な変化を示した。1963年以降の漁獲量は4~17万トンの低い水準にある。こうした漁獲量の変動から,コガネガレイはしばしば典型的な乱獲魚種とみなされてきた。しかし,漁業情報を用いた資源評価は,漁業が質的に大きく変化したこと,北洋底魚資源の組織的研究が漁業が衰退して後に開始され,それ以前の資料が充分でなかったことなどから進展しなかった。近年,トロール調査によって,資源量が増大し,1983年現在では200万トンを大幅に越える高い水準に達したと推定されるようになった。本論文は,東部ベーリング海におけるコガネガレイ資源について,生物学的特徴を明らかにし,長期的に安定した資源の有効利用をはかるため,資源状態と資源に及ぼす漁業の影響を解析し,資源の管理方策について考察したものである。得られた結果は以下のように要約される。I 生物学的特徴 1.コガネガレイは,バンクーバー島以北,釜山以北及び北海道以北の北太平洋に広く分布し,東部ベーリング海においてはスケトウダラに次いで漁獲量の多い産業的に重要な魚種である。2.東部ベーリング海には,ソ連水域に分布する資源量のごく小さい魚群を除き,単一の系統群が存在する。3.生息域は,冬期には大陸棚緑辺部から大陸斜面上部にかけての水域にあり,夏期には約100m以浅の大陸棚上に移る。4.産卵は,ブリストル湾からヌニバック島北側までの水深約30~60mの水域で,主に7-8月に行われる。5.年齢査定には耳石を用いた。輪紋は,12~5月の間に形成され,生後約半年で形成される第1輪を含め全て年輪とみなした。耳石半径一全長の関係から逆算した輪紋形成時全長(TL;mm)と輪紋数(i)の関係は,1968年の標本を用いて以下のように表わされる。雄:TLᵢ = 440.4(1-exp(-0.086(i-0.522))) 雌:TLᵢ = 478.2(1-exp(-0.082(i-0.502))) 満年齢(t)と全長及び体重(BW;g)の関係は,産卵期を中心に採取された7年間の標本を用いて以下のように表わされる。雄:TLₜ =416.3(1-exp(-0.105(t-0.083))) 雌:TLₜ =421.0(1-exp(-0.121(t-0.688))) 雄:BWₜ =864(1-exp(-0.105(t-0.083)))³·⁰⁹⁷⁷ 雄:BWₜ =941(1-exp(-0.121(t-0.688)))³·¹⁴²⁶ 6.性成熟は雌雄で相当異なり,50%成熟全長及び年齢は以下のとおりであった。雄,1973年:130mm 1974年: 150~160 mm 1978年:125~130mm 雌,1973年:255~260 mm 1974年:255~260 mm 1978年:270~275 mm 雄,1978年: 4歳 雌,1978年:11歳 成熟体長が資源水準に伴って変化した可能性が示唆された。7.主要な餌生物は、二枚貝類,多毛類,コムシ類,底生性端脚類等の底生動物であり,コガネガレイの体長が大きくなるに従って餌生物も大型の種へと変化している。摂餌活動は6~10月に活発となり,越冬期である1-3月には低下する。II 漁業の動向 1.漁業は,数年という短期間に急激に発展し,そして衰退した特異な開発の歴史をたどった。主要漁業国は日本,次いでソ連であった。2.漁法,漁期及び漁場は経年的に変化しており,また,主対象操業が長期にわたって中断したことから,漁獲努力量資料は質的一貫性が保たれていない。3.漁獲物年齢組成には,豊度の異なる年級群の出現が明瞭に示されており,構成される年級群によって年齢組成は経年的に大きく変化している。Ⅲ 資源評価 1.漁業から得られた単位努力当たり漁獲量(CPUE)は,漁獲努力量の質的年変化が大きく,1973年までは資源の動向を必ずしも反映していない。漁業の質的変化が少ないと判断された1974年以降のCPUEは,1979年ないしは1980年まで急激に上昇したが,それ以降1983年まで急激に低下した。2.トロール定点調査から得られた単位掃過面積当たり漁獲量と調査水域面積値とを用い,面積密度法によって資源量を推定した。(1) 1966-1978年の調査は,水域が狭く,コガネガレイの主要分布域と調査水域の重複度合が小さい年もあった。1979-1982年の調査は日米共同で実施され,主要分布域をほぼカバーし,また定点密度も高かった。(2) 調査設計は,層化系統抽出法を採用し,定点は間隔が等しくなるよう格子状に配置した。資料解析は,層化無作為抽出標本解析法を準用して行った。(3) トロール漁具の漁獲効率(vulnerability)の交互追尾法による推定を試みたが,操業上の困難から推定値は得られなかった。このため,漁獲効率は1と仮定した。(4) トロール袖先問隔は,トロールワープの走出角から推定し,トロールひき網水深との関係を明らかにした。(5) 資源量推定値は,1975年の米国調査に基づく104万トンから急激に増加し,1979-1981年には約200万トン,1982年には379万トンとなった。漁具の構造から,トロール網がひき網水域内の全個体を漁獲したとは考えられず1975-1981年の推定値は過小である。1982年には,高水準の加入によって1979-1981年より資源量は更に増加したと推定されたが,漁具の改良による手網等の駆集効果があったと推定され,379万トンの推定値がなお過小であるか,あるいは過大であるか判断できなかった。3.自然死亡係数Mは,0.12から0.26の範囲で推定された。ほぼ下限及び上限とその間の値である0.12, 0.20及び0.25の場合について,コホート解析法を用い,資源量を計算した。各年級群の端末年の漁獲死亡係数は,1979年のトロール調査による年齢別資源尾数推定値と漁獲尾数に基づいて数回の繰り返し計算で修正して用いた。得られた資源重量は,1964-1972年の期間比較的一定の値を示した後,1979年まで急激な増加を示した。4.CPUE,トロール調査及びコホート解析から,資源量は,大量漁獲のあった1960年代初期には低下し,1972年まであまり変化しなかったが,以後1979年又は1980年まで急激に増大したと推定された。その後CPUEは急激な低下を示したが,トロール調査による資源量推定値は1983年まで増加を続けた。トロール調査が主分布域をほぼカバーして実施されていること,また,豊度の高い年級群が連続して発生していることから,1980年以降も資源量は増加しているものと推定された。5.資源量の変動は,主に豊度の類似した年級群が連続して発生することによって起こっており,近年の資源量の急激な増加は,主に連続した卓越年級群の加入によっており,低水準の漁獲が増加を助長したと判断された。I 資源管理 1.加入当たり収量(Y/R)は,コホート解析結果から得られた年齢別加入割合を考慮に入れ,0.12, 0.20及び0.25のMについて計算した。加入当たり収量から得られる収量は持続することが保障されていないので,親魚量を漁獲が全くなかったと仮定したときのんの水準に減少させる漁獲死亡係数で得られるY/Rを最適値(OY/R)とし,親魚量と次代の加入量を確保するものとした。2.コホート解析で得られた加入尾数(3歳時の資源尾数)は,資料の得られた1964-1978年の期間,高低2水準が出現した。この2水準の加入尾数とOY/Rから期待される最適収量は加入量水準に応じて大きく変化する。加入量水準が低い時の最適収量はM=0.12 の場合の71,000トンからM=0.25の場合の105,000トンまで増加した。一方、加入量水準が高い時には,最適収量はMにしたがって減少し,230,000~266,000トンの範囲であった。3.近年における加入尾数水準は連続して高く,したがって,この高水準の加入が続く限り,年間23万トンを越える漁獲量が期待できる。4.加入尾数と親魚尾数の間に特定の関係を見出すことができず,長期的に安定した資源管理方策を示すことができなかった。また,加入量に及ぼす外的環境の影響も不明であり,加入量の予測はこれまでのところ不可能である。加入量水準の低下が観測された場合には,親魚尾数とそれから期待される加入量を確保するため,加入量に応じて漁獲量を減少させる必要がある。長期的に安定した資源の有効利用をはかるためには,資源量及び加入量の水準を継続して監視し,それらの変化に対応した適切な措置をとる必要がある。そのためには,1979年以来実施されてきた日米共同によるトロール調査をひき続き実施することが不可欠であり,また資源評価や資源の管理措置についての関係国間の意見や情報の交換を促進することが重要である。","subitem_description_language":"ja","subitem_description_type":"Abstract"}]},"item_10002_publisher_8":{"attribute_name":"出版者","attribute_value_mlt":[{"subitem_publisher":"遠洋水産研究所","subitem_publisher_language":"ja"},{"subitem_publisher":"Far 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Sea","subitem_title_language":"en"}]},"item_type_id":"10002","owner":"10","path":["1716951513399"],"pubdate":{"attribute_name":"PubDate","attribute_value":"2024-04-22"},"publish_date":"2024-04-22","publish_status":"0","recid":"2002227","relation_version_is_last":true,"title":["東部ベーリング海におけるコガネガレイの漁業生物学的研究"],"weko_creator_id":"10","weko_shared_id":-1},"updated":"2025-12-16T08:11:12.103972+00:00"}