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Title: スケトウダラの年級群豊度に与える噴火湾の環境要因
Other Titles: Environmental Factors in Funka Bay, Hokkaido, Affecting the Year Class Strength of Walleye Pollock, Theragra chalcogramma
Authors: 中谷, 敏邦1 Browse this author →KAKEN DB
杉本, 晃一2 Browse this author
高津, 哲也3 Browse this author →KAKEN DB
高橋, 豊美4 Browse this author →KAKEN DB
Authors(alt): Nakatani, Toshikuni1
Sugimoto, Koichi2
Takatsu, Tetsuya3
Takahashi, Toyomi4
Keywords: walleye pollock
year class strength
Funka Bay
environmental factors
Issue Date: Jan-2003
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: 67
Issue: 1
Start Page: 23
End Page: 28
Abstract: The 1995-year-class of walleye pollock Theragra chalcogramma was dominant in and around Funka Bay. To understand the formation of dominant year classes of pollock in this area, annual changes in monthly fluctuation of density of pollock larvae, prey concentration at the initial feeding stage, and hydrographic conditions were investigated from 1991 to 1998. Pollock larvae occurred mainly from January to February. Warm water temperatures at 10 m depth in the bay, where pollock larvae were considered to be abundant, were observed from January to early February before the intrusion of the Oyashio Coastal Water (cold water). Thus the relatively warm water temperature in early winter appears to be necessary to produce the dominant year class of pollock in Funka Bay. From 1991 to 1998, no cold water temperature affecting the survival of larval pollock was observed. The densities of copepod nauplii as a primary food for larval pollock at the initial feeding stage were relatively high from January to February in 1991 (7.8-18.1 inds.・l^[-1]), 1994 (13.1-15.2 inds.・l^[-1]), 1995 (12.3-15.5 inds.・l^[-1]), and 1996 (13.8-17.2 inds.・l^[-1]), but the dominant year class occurred only in 1995. Therefore, the high density of copepod nauplii does not determine the year class strength of pollock in this area. These results suggest that the abundance of food for pollock larvae at the first feeding stage were enough to survival in early winter in this area. Pollock larvae and juveniles (7-30 mm in total length) mainly feed on small sized copepodites of Pseudocalanus spp., whose density was high from March to April and then decreases in early June. At that time, juveniles larger than 30mm in total length initiate to feed on larger sized copepodites of Neocalanus plumchrus. It is considered that pollock larvae hatching in March do not grow enough to feed on N. plumchrus in June. From this information, it is inferred that the spawning strategy of pollock in this area is concerned with the food conditions for juveniles at a transition period of food organisms. In Funka Bay, water temperature in early winter and food conditions for juvenile pollock might control the year class strength of pollock in and around Funka Bay.
Type: article
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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