Pam J. Stacey and Robin W. Baird
Canadian Field-Naturalist 105:219-232. 1991.
Abstract
The Pacific white-sided dolphin (Lagenorhynchus obliquidens) appears to be an abundant permanent resident of the pelagic waters off the west coast of Canada and a regular visitor to inshore waters. This report summarizes the general biology and management of this species with special reference to its status in Canada. One hundred and fifty- six records from Canada's 320 km (200 mile) extended economic zone are presented. Group size ranges from 1 to 1000, with a mean, median and modal size of 62, 15 and 6 respectively. Depth of water from sighting locations ranges from 10 to 2000 fathoms, with mean, median and modal depths of 617, 400 and 100 fathoms, respectively. Sea surface temperature taken at 73 record locations had a range from 6 degrees to 17 degrees C, with a mean, median and mode of 12 degrees, 13 degrees and 15 degrees C respectively. The Pacific white-sided dolphin is taken directly and incidentally in small numbers in fisheries throughout its range. From 1985 through 1987 a total of 14 (four of which were released alive) were caught in an experimental driftnet fishery for flying squid (Ommastrephes bartrami) in offshore Canadian waters, the second most frequent incidentally taken cetacean. Small numbers are also taken incidentally in net fisheries in British Columbia, but a lack of comprehensive recording of net-induced mortality makes determination of the extent of this catch or its impact on populations difficult. Based on sighting records, the number of Pacific white- sided dolphins in Canadian waters is probably high. Exact determination of status, especially population trends, cannot be made at this time. With the presumed lack of serious threats, however, and until further studies elucidate population numbers and trends, the Pacific white- sided dolphin should be considered not in jeopardy and therefore not in any COSEWIC category.