| Summary: | The summer habitat of the southern resident population of killer whales (Orcinus orca) in British Columbia and Washington experiences heavy traffic by vessels involved in whale-watching, sport fishing, other recreational activities, and shipping. Behavioural changes caused by vessel proximity and the impacts of vessel noise have been previously documented, but this is the first study to assess direct impacts of air pollutant emissions from vessel traffic. The concentration and composition of air pollutants from whale-watching vessels that southern resident killer whales are exposed to during the peak tourist season were estimated, as were the health impacts of the exposure. Specifically, the study a) estimated the output of airborne pollutants from the whale-watching fleet based on emissions data from regulatory agencies, b) estimated the vertical dispersion of such pollutants based on air stability data collected in the field and from climatological sources, c) used a dispersion model incorporating data on whale, vessel, and atmospheric behaviour to estimate exposure, and d) examined the likely physiological consequences of this exposure based on allometric extrapolation of data from other mammalian species. The results of these exercises indicate that the current whale-watching guidelines are usually effective in limiting pollutant exposure to levels just at or below those at which adverse health effects would be expected in killer whales. However, under ‘worst-case’ conditions and even under certain ‘average-case’ conditions the pollutant levels are much higher than those predicted to cause adverse health effects. With this information, recommendations are made for further studies that would fill in missing information, and increase confidence in the models, and the predicted impact on the southern resident killer whales. Recommendations for limiting killer whale exposure to air pollutants are also provided.
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