Feeding events of Japanese lates Lates japonicus detected by a high-speed video camera and three-axis micro-acceleration data-logger
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The feeding events of wild animals have been widely researched in recent decades. The use of invasive methods to determine stomach contents in which the fish is killed can, however, be considered to be unjustifiable in the case of an endangered fish, such as the Japanese late. Here, we report on a method that can be used to verify feeding events of a fish species without the need for killing the fish through the use of a high-speed video camera and a three-axis micro-acceleration data-logger. High-quality images obtained by the video showed that the fish opens its mouth with a quick downward movement of the mandibles and ingests prey via suction feeding. The movement of the mandibles was also simultaneously recorded by changes in the three-axis accelerations obtained by the logger attached to the dorsum. We attached the logger with an automatic release system to the dorsum of one captive Japanese lates and two wild fish together with an acoustic transmitter and then released the fish in the Shimanto River in Japan. After retrieving the logger, the movement records of the fish obtained by the three-axis accelerometer showed the same pattern of feeding events as those in captivity. A total of 13 feeding events at night and five during the daytime were obtained for the three fish during a total 129.7 h of recording.
KeywordsBio-logging Feeding behavior Habitat use Telemetry
We thank Mr. T. Sugimura, Ms. S. Nomura, and the staff of the Shimantogawa Gakuyukan, Mr. K. Yamasaki and the staff of the Fisheries Cooperative Association of Shimanto River, Mr. T. Yasumitsu, Mr. T. Nishimura, Mr. K. Mouri, and Mr. K. Takimoto of the sport fishing experts team “Submarine”, Mr. T. Yamasaki and the staff of the Akamekan for their kind assistance in the field work and laboratory. We are grateful to Prof. Y. Naito of the National Institute of Polar Research for information about usage example of the loggers, Prof. R.W. Davis of Texas A&M University for commenting on a draft manuscript and contributing to improvements in the manuscript, and Dr. Y. Ropert-Coudert of the Institute Pluridisciplinaire Hubert for constructive criticism of the manuscript. This study was financially supported by the Japan Broadcasting Corporation, the Program of Bio-logging Science of the University of Tokyo (UTBLS), and Interdisciplinary Collaborative Research of Atmosphere and Ocean Research Institute, the University of Tokyo.
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