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.
Harbor porpoise (Phocoena phocoena) are one of the most frequently sighted cetaceans in the Salish Sea. Anecdotal information, possibly supported with stranding encounter rate data, suggests that harbor porpoise may have increased in Puget Sound, or have shifted their distribution back to Puget Sound relative to earlier decades.
On February 7, 2013, Pacific Biodiversity Institute, Cascadia Research Collective and the SeaDoc Society hosted scientists from Washington and British Columbia to determine the state of knowledge on this species and coordinate ongoing research efforts.
The group discussed what was currently known about harbor porpoise habitat needs, distribution, population trends, life cycle, genetics, behavior and role in the ecosystem. The workshop goals were to foster communication, identify the data that could be used to prepare manuscripts, determine the research that would most enhance our understanding of the harbor porpoise, seek opportunities for collaboration, and prioritize critical harbor porpoise conservation issues that need to be addressed.
In 2006–2007, an unusually high number of harbor porpoises (Phocoena phocoena) stranded along the Washington and Oregon coastlines. Spatiotemporal analyses were used to examine their ability to detect clusters of porpoise strandings during an unusual mortality event (UME) in the Pacific Northwest using stranding location data. Strandings were evaluated as two separate populations, outer coast and inland waters. The presence of global clustering was evaluated using the Knox spatiotemporal test, and the presence of local clusters was investigated using a spatiotemporal scan statistic (space–time permutation). There was evidence of global clustering, but no local clustering, supporting the hypothesis that strandings were due to more varied etiologies instead of localized causes. Further analyses at subregional levels, and concurrently assessing environmental factors, might reveal additional geographic distribution patterns. This article describes the spatial analytical tools applied in this study and how they can help elucidate the spatiotemporal epidemiology of other UMEs and assist in determining their causes. More than one spatial analytical technique should be used if the study objective is to detect and describe clustering in time and space and to generate hypotheses regarding causation of marine mammal disease and stranding events.
Although the harbor porpoise is the most abundant and widely dispersed cetacean species in the Salish Sea, we still know very little about its habitat needs, distribution, population trends, life cycle, genetics, behavior and role in the ecosystem.
Harbor porpoises feed primarily on fish and are among the smallest of the cetaceans, reaching an average size of about 5 feet and 120 pounds. They can dive deep, more than 655 feet, but usually stay near the surface, coming up regularly to breathe with a distinctive puffing noise that resembles a sneeze.
In the Salish Sea, harbor porpoises face a number of threats including pollution, noise, crowding, death due to bycatch, depleted stocks of forage fish, and habitat loss.
On February 7th, SeaDoc helped convene a US / Canadian workshop to bring scientists and managers together. This “think-tank,” co-sponsored by the Pacific Biodiversity Institute and Cascadia Research Collective, identified areas where more data are needed to better understand and manage the population, including things like doing a population stock assessment that will tell us if their numbers have grown or declined since the last one was conducted a decade ago.
This workshop is a good example of how SeaDoc works to bring US and Canadian scientists together to improve our management of the ecosystem. It’s a repeat performance on past successful SeaDoc “think tanks” focusing on rockfish, abalone and forage fish.
The meeting notes, including some consensus statements from the scientists involved, are available as a PDF. Click here to download.