Natl Res Inst Fisheries Engn, Fisheries Res Agcy, Kashima, Ibaraki 3140421, Japan; Natl Inst Polar Res, Tokyo 1738515, Japan; Chinese Acad Sci, Inst Hydrobiol, Wuhan 430072, Peoples R China
Dive-depth and swim-speed of a juvenile and an adult free-ranging, Yangtze finless porpoises (Neophocaena phocaenoides) were observed using velocity-time-depth recorders in an oxbow of the Yangtze River. In total, 8222 individual dives were recorded over 59 hours. Two dive types, deep-dive (greater than or equal to 2.7 m) and shallow-dive. were recognized. Horizontal travel distances of two finless pot-poises in a day were 94.4 km and 90.3 km, which were longer than those of oceanic relative species (harbor porpoises, Phocoena phocoena). Although the shallow water limited the maximum dive-depth, dive-duration, and bottom-time of finless porpoises were similar to the harbor porpoises. A sudden drop of swim-speed below 0.25 m s(-1) was frequently observed nearby the maximum dive-depth. This seemed to indicate "turning, around" behaviour, possibly during prey pursuit. (C) 2002 Published by Elsevier science Ltd on behalf of International Council for the Exploration of the Sea.
Tomonari Akamatsu; Ding Wang; Kexiong Wang; Zhuo Wei; Qingzhong Zhao; Yasuhiko Naito.Diving behaviour of freshwater finless porpoises (Neophocaena phocaenoides) in an oxbow of the Yangtze River, China,ICES JOURNAL OF MARINE SCIENCE,2002,59(2):438-443