Evidence of nighttime movement of finless porpoises through Kanmon Strait monitored using a stationary acoustic recording device
Article first published online: 5 OCT 2008
© 2008 Japanese Society of Fisheries Science
Volume 74, Issue 5, pages 970–975, October 2008
How to Cite
AKAMATSU, T., NAKAZAWA, I., TSUCHIYAMA, T. and KIMURA, N. (2008), Evidence of nighttime movement of finless porpoises through Kanmon Strait monitored using a stationary acoustic recording device. Fisheries Science, 74: 970–975. doi: 10.1111/j.1444-2906.2008.01614.x
- Issue published online: 5 OCT 2008
- Article first published online: 5 OCT 2008
- Received 2 October 2007. Accepted 10 March 2008.
- passive acoustics;
From March 2005 to March 2006, the presence of the finless porpoise Neophocaena phocaenoides in the Kanmon Strait, Japan was monitored using a stationary acoustic event recording device. A stereo acoustic event recorder (A-tag) recorded biosonar signals as well as sound source directions, which can be used to count the number of echolocating porpoises within a distance of 126 m. During 75 days of effective observation, 37 porpoises were detected acoustically. On average, one individual was detected every two days. Most of the finless porpoises appeared at night, and no porpoises were observed from 12:00 to 18:00 hours. Shipping traffic observed using the same acoustic system showed trends opposite to that of finless porpoise during the daytime. The tidal current did not affect the presence of the animals (up to 5.2 knots). However, porpoises were suggested to swim along the current direction. Finless porpoises appeared to be isolated and used relatively long-range sonar during the observations, suggesting that the porpoises passed through the Kanmon Strait rather than searched for prey.