Small cetaceans are by-caught in salmon gillnet fisheries in British Columbia (BC) waters. In Canada, there is currently no generic calculation to identify when management action is necessary to reduce cetacean bycatch below sustainable limits. We estimated potential anthropogenic mortality limits for harbour (Phocoena phocoena) and Dall’s (Phocoenoides dalli) porpoises and Pacific white-sided dolphins (Lagenorhynchus obliquidens) using quantitative objectives from two well-established frameworks for conservation and management (the United States’ Marine Mammal Protection Act and the Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas), which are similar to some management objectives developed for marine mammal stocks elsewhere in Canada. Limits were calculated as functions of (i) a minimum abundance estimate (2004–2005); (ii) maximum rate of population increase; and (iii) uncertainty factors to account for bias in abundance estimates and uncertainty in mortality estimates. Best estimates of bycatch mortality in 2004 and 2005 exceeded only the most precautionary limits and only for porpoise species. Future research priority should be given to determining small cetacean stock structure in BC and refining species-specific entanglement rates in these and other fisheries. The approach offers a quantitative framework for Canada to meet its stated objectives to maintain favourable conservation status of cetacean populations.
Pacific White-Sided Dolphins, also known as “Lags,” a shortened form of their scientific name Lagenorhynchus obliquidens, are offshore schooling dolphins that are becoming more common in the Salish Sea. They’re fast, they jump and leap from the water, and like most cetaceans, they have amazingly large brains.
Watch the video learn more about these fascinating animals and the cutting-edge research that is helping us better understanding their population dynamics.
Erin Ashe, a Ph.D student at the University of St. Andrews in Scotland, has had a SeaDoc-funded project to study Lags in the Salish Sea and the Broughton Archipelago for the past several years. Like killer whales, Pacific White-Sided Dolphins can be individually identified and she has developed a photo-identification database to track individuals and study their movements, life history, and population status.
Although not seen in these numbers in the Salish Sea, in some areas Pacific White-Sided Dolphins can congregate in groups as large as 1,000 animals. They enjoy bow-riding the wakes of boats, and even will ride the wakes of large whales. They can even been seen swimming with or harassing fish-eating Northern and Southern resident killer whales, even though transient killer whales prey upon them (for a video of this see: http://www.oceansinitiative.org/dolphins).
The 2012/13 Marine Science Lecture Series was presented by The SeaDoc Society and YMCA Camp Orkila. It was been made possible through generous sponsorship by Tom Averna (Deer Harbor Charters), Barbara Bentley and Glenn Prestwich, Barbara Brown, Audrey and Dean Stupke and West Sound Marina.
You can help us build a research database of Pacific white-sided dolphins in the Salish Sea.
While killer whales have captured the attention and focus of researchers in this region, we know relatively little about the Pacific white-sided dolphins. Is the population healthy? How many animals do we routinely see?
Pacific white-sided dolphins are individually identified from natural markings on the dorsal fin, just like killer whales are.
Thanks to private donations, SeaDoc is funding Erin Ashe, a PhD student at St. Andrews University, to study Salish Sea Pacific white-sided dolphins by using the same photographic-identification techniques used to study killer whales.
If you have photographs of Pacific white-sided dolphins (especially good dorsal fin shots) and are willing to share them for this study, please send them to Erin Ashe at firstname.lastname@example.org.
Please remember, though, it is ILLEGAL to approach within 100 meters of a Pacific white-sided dolphin (or any other marine mammal) in both the United States and Canada, even for the purpose of taking pictures.
While photographs of the dorsal fin most useful, any photos can be helpful to the study.
When were the dolphins seen? (Date and time)
Where were the dolphins seen? (place name and latitude and longitude if available)
About how many dolphins were in the group? (This can be a best guess.)
Where there calves (small babies) in the group? If so, how many?
Do you know if dolphins are new to this area? Have you seen dolphins here before?
Where there other cetacean species in the area?
Any additional comments:
As always, we still want you to also send your BC cetacean sightings and photos to the BC Cetacean Sighting Network at http://wildwhales.org/. The BC Cetacean Sighting Network is hosted by the Vancouver Aquarium and maintains long-term data on the abundance and distribution of cetaceans in the Pacific Northwest.
Keep up with periodic updates on the dolphin project at http://www.oceansinitiative.org/dolphins/