Vertical movement of dolphinfish <Emphasis Type="Italic">Coryphaena hippurus</Emphasis> as recorded by acceleration data-loggers in the northern East China Sea |
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Authors: | Seishiro Furukawa Ryo Kawabe Seiji Ohshimo Ko Fujioka Gregory N Nishihara Yuichi Tsuda Takashi Aoshima Hisao Kanehara Hideaki Nakata |
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Institution: | (1) Graduate School of Science and Technology, Nagasaki University, Bunkyo-machi, Nagasaki 852–8521, Japan;(2) Institute for East China Sea Research, Nagasaki University, Taira-machi, Nagasaki 851–2213, Japan;(3) Seikai National Fisheries Research Institute, Fisheries Research Agency, Taira-machi, Nagasaki 851–2213, Japan;(4) National Research Institute of Far Seas Fisheries, Fisheries Research Agency, Shimizu, Shizuoka 424–8633, Japan;(5) Fisheries Laboratory, Kinki University, Nishimuro, Shirahama 3153, Wakayama 649–2211, Japan;(6) Faculty of Fisheries, Nagasaki University, Bunkyo-machi, Nagasaki 852–8521, Japan |
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Abstract: | Environmental changes influence foraging behavior for most animals. Dolphinfish, Coryphaena hippurus, are epipelagic predators and have a cosmopolitan tropical to warm-temperate (>20°C) distribution. We simultaneously obtained
the ambient temperature and the foraging behavior (i.e., swimming speed, depth and tailbeat acceleration) of dolphinfish,
using an acceleration data-logger in May, September, October, November 2007, June 2008, May and July 2010 for 8 individuals.
Although the dolphinfish spent a mean ± standard deviation of 43.4 ± 27.7% of their time at the surface (0–5 m), dive excursions
from the surface (DES) were observed in all individuals and maximum DES depths ranged from 50.1 to 95.4 m. DES events resulted
dives below the thermocline for these dolphinfish, and there was a significantly positive relationship between the isothermal
layer depth (ILD) and DES depth. Our results demonstrate that dolphinfish avoided the rapid thermal change beyond the thermocline,
and their prey is most likely found in the upper layers of the thermocline. Gliding behavior during the DES phase was also
observed and dolphinfish gradually descended to deeper waters with gliding. The gliding time was longer when the ILD was deeper,
and fish tended to dive deeper. We suggest that dolphinfish adopt gliding behavior to search a broader range of depths for
prey, while minimizing energy use. |
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