Updated Marine Mammal Distribution and Abundance Estimates in British Columbia

• Main Authors: Best, Benjamin D., Fox, Caroline H., Williams, Rob, Halpin, Patrick H., Paquet, Paul C.
• Format: Text
• Language: unknown
• Published: WBI Studies Repository 2015
• Subjects: survey-vessel; abundance estimate; distribution; conservation; British Columbia; Pacific Ocean; Humpback Whale; Killer Whale; Common Minke Whale; Fin Whale; Pacific White-Sided Dolphin; Steller Sea Lion; Elephant Seal; Harbour Seal; Harbour Porpoise; Dall's Porpoise; Northern Hemisphere; Animal Studies; Environmental Studies; Population Biology; Pacific; Balaenoptera physalus; Fin whale; Harbour porpoise; harbour seal; Megaptera novaeangliae; minke whale; Orca; Orcinus orca; Phoca vitulina; Phocoena phocoena; Killer whale
• Online Access: https://www.wellbeingintlstudiesrepository.org/popdhab/3; https://www.wellbeingintlstudiesrepository.org/cgi/viewcontent.cgi?article=1002&context=popdhab

Information relating to the distribution and abundance of species is critical for effective conservation and management. For many species, including cetacean species of conservation concern, abundance estimates are lacking, out of date and/or highly uncertain. Systematic, line-transect marine mammal surveys were conducted in British Columbia’s (BC) coastal waters over multiple years and seasons (summer 2004, 2005, 2008, and spring/autumn 2007). In total, 10,057km of transects were surveyed in an 83,547km2 study area. Abundance estimates were calculated using two different methods: Conventional Distance Sampling (CDS) and Density Surface Modelling (DSM). CDS generates a single density estimate for each stratum, whereas DSM explicitly models spatial variation and offers potential for greater precision by incorporating environmental predictors. Although DSM yields a more relevant product for the purposes of marine spatial planning, CDS has proven to be useful in cases where there are fewer observations available for seasonal and inter-annual comparison, particularly for the scarcely observed elephant seal. The summer abundance estimates (with lower and upper 95% confidence intervals; all DSM method unless otherwise stated), assuming certain trackline detection (underestimates true population size) were: harbour porpoise (Phocoena phocoena) 8,091 (4,885–13,401); Dall’s porpoise (Phocoenoides dalli) 5,303 (4,638–6,064); Pacific white-sided dolphin (Lagenorhynchus obliquidens) 22,160 (16,522–29,721); humpback whale (Megaptera novaeangliae) 1,092 (993–1,200); fin whale (Balaenoptera physalus) 329 (274–395); killer whale (all ecotypes; Orcinus orca), 371 (222–621); common minke whale (B. acutorostrata) 522 (295–927); harbour seal (total; Phoca vitulina) 24,916 (19,666–31,569); Steller sea lion (total; Eumetopias jubatus) 4,037 (1,100–14,815); and northern elephant seal (CDS method; Mirounga angustirostris) 65 (35–121). Abundance estimates are provided on a stratum-specific basis with additional estimates provided for ...