Journal Article Feeding habit of juvenile fishes associated with drifting seaweeds in the East China Sea with reference to oceanographic parameters

Hasegawa, Takamasa  ,  Manda, Atsuyoshi  ,  Takatsuki, Naoki  ,  Kawabata, Yuuki  ,  Nishihara, Gregory N.  ,  Fujita, Shinji  ,  Kawabe, Ryo  ,  Yamada, Misato  ,  Kinoshita, Tsukasa  ,  Yamawaki, Nobuhiro  ,  Morii, Yasuhiro  ,  Sakakura, Yoshitaka

64 ( 2 )  , pp.157 - 172 , 2016 , 日本水産増殖学会
ISSN:03714217
Description
Many commercially important fishes associate with drifting seaweeds in their juvenile stage, however, the ecological significance of drifting seaweeds for juvenile fishes is still unclear. We postulated that the following two hypotheses may be applicable for juvenile fishes associate with drifting seaweeds, the “concentration of food supply” hypothesis: juvenile fishes are attracted by phytal animals on the drifting seaweeds and the “indicator-log” hypothesis: fish use accumulations of drifting seaweed as an indicator of productive areas (e.g. frontal areas) for food. We investigated the frontal areas, zooplankton abundance around the drifting seaweed, and the food availability of fish juveniles associated with drifting seaweed accumulations in the East China Sea in 2012 and 2013. A total of 14 drifting seaweed mass and 22 species (n = 408) of fish juveniles were collected. We found that 49.7 - 99.7 % of the individual fed on planktonic food and the feeding incidence on phytal animals was less than 50 %. Although drifting seaweeds were aggregated around the frontal areas of surface currents, the zooplankton abundance was not significantly different between these frontal areas and other areas. Our findings indicate that ecological significance of drifting seaweeds as feeding habit is relatively low for juvenile fishes associated with drifting seaweeds.
流れ藻には多くの水産上重要種の稚魚が付随するが,流れ藻の稚魚にとっての生態学的意義は明らかにされていない。筆者らは次の2仮説のいずれかが流れ藻付随稚魚に当てはまると考え,“concentration of food supply hypothesis”(流れ藻葉上生物を摂餌するため)と“indicator log hypothesis”(流れ藻をフロント域のような餌豊度の高い海域の目印とするため)を検証するため,2012年と2013年に東シナ海の流れ藻周辺の海洋環境,フロント域,動物プランクトン豊度,流れ藻付随稚魚の摂餌個体率を調べた。流れ藻は表層流の収束帯に集積されていたが,収束帯のプランクトン豊度は高くなかった。合計14個の流れ藻を採集し,合計22種(408尾)の稚魚の胃内容物を調査した結果,稚魚の49.7 - 99.7 %の個体はプランクトンを選択的に摂餌していたが,葉上生物の摂餌個体率は高くなかった(50 %未満)。以上の結果から流れ藻の稚魚にとっての生態学的意義は摂餌場でないことが示唆された。
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http://naosite.lb.nagasaki-u.ac.jp/dspace/bitstream/10069/36666/1/AquaSci64_157.pdf

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