DIVING BEHAVIOR AND PERFORMANCE OF HARBOR PORPOISES, PHOCOENA PHOCOENA, IN FUNKA BAY, HOKKAIDO, JAPAN |
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| Authors: | Seiji Otani Yasuhiko Naito Akito Kawamura Masahiro Kawasaki Shigetoshi Nishiwaki Akiko Kato |
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| Affiliation: | Department of Polar Science, The Graduate University for Advanced Studies, 1-9-10 Kaga, Itabashi, Tokyo 173, Japan;National Institute of Polar Research, 1-9-10 Kaga, Itabashi, Tokyo 173, Japan;Department of Bioresources, Faculty of Bioresources, Mie University, 1515 Kamihama-cho, Tsu, Mie 514, Japan;The Institute of Cetacean Research, 4-18 Toyomi-cho, Chuo, Tokyo 104, Japan;National Institute of Polar Research, 1-9-10 Kaga, Itabashi, Tokyo 173, Japan |
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| Abstract: | In order to monitor the diving behavior of free-ranging cetaceans, microdataloggers, with pre-programmed release mechanisms, were attached to the dorsal fins of two female harbor porpoises ( Phocoena phocoena ) in Funka Bay, Hokkaido, Japan, in 1994. The two loggers were successfully recovered and a total of 141 h of diving data (depth and water temperature in 4,671 dives) was obtained. Both porpoises dived almost continuously, rarely exhibiting long-term rest at the surface. Maximum dive depths were 98.6 m and 70.8 m, respectively, with more than 70% of diving time at 20 m or less. Most shallow dives were V-shaped with no bottom time. The V-shaped dives were significantly shallower in dive depth and shorter in dive duration than U-shaped dives. Descent rate was not constant during a dive. The deeper the dive depths, the faster the mean descent and initial descent rates. This suggests that porpoises have anticipated the depth to which they will dive before initiating the dive itself. |
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| Keywords: | harbor porpoise Phocoena phocoena diving behavior microdatalogger Japan |
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