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Marine Ecology Progress Series

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MEPS 573:101-115 (2017)  -  DOI:

Continuous behavioral observation reveals the function of drifting seaweeds for Seriola spp. juveniles

Takamasa Hasegawa1,*, Naoki Takatsuki1,4,*, Yuuki Kawabata1,**, Ryo Kawabe2, Gregory N. Nishihara2, Atsushi Ishimatsu2, Kiyoshi Soyano2, Kotoe Okamura1,5, Seishiro Furukawa2,6, Misato Yamada3,7, Masako Shimoda3, Tsukasa Kinoshita3, Nobuhiro Yamawaki3, Yasuhiro Morii3, Yoshitaka Sakakura

1Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Bunkyo, Nagasaki 852-8521, Japan
2Institute for East China Sea Research, Organization for Marine Science and Technology, Nagasaki University, Taira-machi, Nagasaki 851-2213, Japan
3Faculty of Fisheries, Nagasaki University, Bunkyo, Nagasaki 852-8521, Japan
4Present address: IDEA Consultants Inc., Higashihama, Higashi-ku, Fukuoka 812–0055, Japan
5Present address: Japan Fisheries Research and Education Agency, Minato Mirai, Nishi-ku, Yokohama, Kanagawa 220-6115, Japan
6Present address: Japan Sea National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Suido-cho, Niigata 951-8121, Japan
7Present address: Nagasaki Branch, Japan Radio Co., Ltd., Asahi-machi, Nagasaki 852-8003, Japan
*These authors contributed equally to this work**Corresponding author:

ABSTRACT: A large number of fish species are associated with drifting seaweeds; however, the ecological significance of such seaweeds for fishes remains unclear. Here, we developed a raft equipped with a seaweed clump, interval still/video cameras, and a GPS satellite buoy. This novel monitoring system was used to monitor the schooling and associative behavior of Seriola spp. juveniles with seaweed for up to 1 wk in the East China Sea. We observed diel behavioral patterns of the fish, which swam around the seaweeds during the day and remained ‘attached’ to the seaweed or to conspecifics at night. This nighttime behavioral pattern suggests that the fish may use drifting seaweed to maintain schools at night when vision is less effective. Solitary individuals and those in smaller schools tended to remain close to the seaweed, whereas fish in larger schools were observed swimming actively around the seaweed. Additionally, some of the solitary fish and small schools escaped into the seaweed when potential predators appeared. As the school size of the fish increased over time, solitary individuals and small schools may have used drifting seaweeds as a shelter from predators until the fish could gather to form larger schools. We suggest that drifting seaweeds have multiple ecological functions for Seriola spp. and other seaweed-associated fishes, and the knowledge of these functions will be useful in designing conservation and management measures for the associated fishes.

KEY WORDS: Fish-aggregating devices · Floating seaweed · Seriola quinqueradiata · Yellowtail · Shelter from predator hypothesis · East China Sea · Time lapse camera · GPS satellite buoy

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Cite this article as: Hasegawa T, Takatsuki N, Kawabata Y, Kawabe R and others (2017) Continuous behavioral observation reveals the function of drifting seaweeds for Seriola spp. juveniles. Mar Ecol Prog Ser 573:101-115.

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