Presentation by Frances C. Robertson
SF Bay ACS Student Travel Grant recipient and Honorable Mention recipient of the National ACS conference Poster contest, University of British Columbia.
“A question of availability: The variable detectability of bowhead whales exposed to seismic sounds Bowhead whales (Balaena mysticetus) are known to alter their diving behavior when exposed to seismic sounds.”
Bowhead whales (Balaena mysticetus) are known to alter their diving behavior when exposed to seismic sounds. Variations in dive-cycle behaviors influence the probability of detecting whales during aerial surveys, so dive-cycle patterns are important when considering the availability of a bowhead for visual detection. The consequences of behavioral variations on assessments of distribution and abundance of bowhead whales are not well understood. Altered detectability could lead to under- or over-estimates of the numbers of whales present, as well as to incorrect conclusions about their distribution relative to seismic operations. To account for the altered probability of bowheads being at the surface and available for detection by observers, we examined the influence of factors such as age and activity state on their dive cycles. We used behavioral data collected by government- and industry aerial observation studies of bowhead whales conducted from 1980 to 2000 to calculate the mean surface and dive times for individuals of different reproductive states, engaged in different activities, and in summer and fall while exposed and not exposed to seismic operations. We found that the availability of bowhead whales for visual detection varied with exposure to seismic sounds. For example, travelling whales were less available for visual detection in the presence of seismic than in the absence of seismic. We provide correction factors for the altered availability of bowhead whales in the presence of seismic in the Beaufort Sea. Incorporation of these correction factors into analyses of aerial survey sighting data will provide more accurate assessments of bowhead density in the vicinity of seismic operations.
Frances C. Robertson is involved with a variety of research projects and works as a marine mammal observer to monitor and mitigate the impacts of industry activities on marine mammals and sea turtles. Her experiences with industry have widened her research interests and she now focuses her efforts investigating the impacts of human activities on marine mammals. She is currently working on a PhD in the Fisheries Centre at the University of British Columbia in Vancouver, Canada.
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