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Possible causes of annual change in the year class strength of flathead flounder Hippoglossoides dubius (Pisces, Pleuronectiformes) in Funka Bay, Hokkaido

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Title: Possible causes of annual change in the year class strength of flathead flounder Hippoglossoides dubius (Pisces, Pleuronectiformes) in Funka Bay, Hokkaido
Other Titles: 噴火湾におけるアカガレイ年級群強度の変動要因
Authors: Nakatani, Toshikuni1 Browse this author →KAKEN DB
Maeda, Tatsuaki2 Browse this author
Sugimoto, Kouichi3 Browse this author
Takatsu, Tetsuya4 Browse this author →KAKEN DB
Takahashi, Toyomi5 Browse this author →KAKEN DB
Authors(alt): 中谷, 敏邦1
前田, 辰昭2
杉本, 晃一3
高津, 哲也4
高橋, 豊美5
Keywords: Hippoglossoides dubius
Funka Bay
abundance of eggs
food availability of larvae
year class strength
water temperature
Issue Date: Nov-2002
Publisher: 水産海洋学会
Journal Title: 水産海洋研究
Journal Title(alt): Bulletin of the Japanese Society of Fisheries Oceanography
Volume: 66
Issue: 4
Start Page: 216
End Page: 223
Abstract: To elucidate the mechanism for the annual fluctuation of year class strength of flathead flounder Hippoglossoides dubius in Funka Bay, Hokkaido, annual changes in age composition, spawning period, egg abundance, food availability at the first feeding stage, and hydrographic conditions were investigated from 1988 to 1999. Strong year classes occurred in 1989, 1991, and 1995. Comparison between annual fluctuations of commercial catch of flathead flounder and the abundance of eggs suggests that there is no relationship between the spawning size and the resultant year class strength of flathead flounder in Funka Bay. The density of copepod nauplii, the primary food for larval flathead flounder, was 7.8 individuals・l^[-1] in January and then increased in February (18.1 individuals・l^[-1]) and March (12.9 individuals・l^[-1]) in 1991. High densities of copepod nauplii in January were also found in 1994 (13.1 individuals・l^[-1]), 1995 (12.3 individuals・l^[-1]), and 1996 (13.8 individuals・l^[-1]). However, the strong year class of flathead flounder did not occur in 1994 and 1996. Therefore, the high density of copepod nauplii does not determine the magnitude of the year class strength of flathead flounder in this area. During the study period the spawning period varied widely among years from January to March and early spawnings were found in the years when the high water temperatures were observed from November to December. The high water temperatures at the surface layer in January were observed in 1991. Relatively warm water were also observed from January to February in 1995, while temperatures during January and February were low in 1989. From the results, it is considered that the early spawning and relatively high water temperature affect the magnitude of the year class of flathead flounder in this area. For the 1989-yaer-calss, high water temperature in mid December 1988 might reduce the mortality during the early life period of flathead flounder in Funka Bay in spite of low temperature after the intrusion the Oyashio Coastal Water (cold water) in January.
アカガレイHippoglossoides dubiusは噴火湾における産業的重要種であり,顕著な年級群変動を示すことが知られており,1980年および1983年に卓越年級群が発生している.年級群強度を決定する要因を明らかにする目的で,1989年から1999年までの期間,噴火湾においてアカガレイを採集し,海洋環境を測定した.調査期間中,卓越年級群は1989,1991,および1995年に発生した.これらの年において年級群強度と産卵群の来遊量および産み出された卵の豊度との間に相関がみられないことから,当海域において年級群強度の決定に産卵来遊量および産卵量は大きな影響を及ぼさないと考えられる.摂餌開始期の仔魚の主要餌生物である橈脚類ノープリウスの豊度は1月から3月にかけて増加するが,その逆の年も認められた.橈脚類ノープリウスの豊度と年級群強度との関係から,生活史初期の餌生物環境が年級群強度を支配しているとは考えられない.調査期間中,産卵盛期は1月から3月まで変化しており,産卵直前の11月から12月にかけての海底水温が高い年には産卵期が早くなる傾向が確認された.卓越年級群が発生した年の産卵盛期はいずれも1月で,1月の表層水温は1991年で高く,1995年も比較的暖かかったが,1989年は低かった.過去の調査結果から卓越年級群が発生した1980年および1983年も冬期間の表層水温が高かったことから,摂餌開始期仔魚にとって水温が高いことが生き残りに重要な影響を持つと考えられる.1989年は沿岸親潮の流入が早く,1月の水温が低かったが,前年12月の水温が高かったことから,早期に産み出された仔魚の生き残りが高かったのではないかと予想される.
Type: article
URI: http://hdl.handle.net/2115/38882
Appears in Collections:水産科学院・水産科学研究院 (Graduate School of Fisheries Sciences / Faculty of Fisheries Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 高橋 豊美

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OAI-PMH ( junii2 , jpcoar )


 

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