| Summary: | In the marine environment, underwater noise is introduced through a diverse set of industrial activities, including vessel traffic. Endangered Southern Resident killer whales (SRKW), as well as their critical habitat, are federally protected in Canada by the Species at Risk Act. Fisheries and Oceans Canada states in the SRKW recovery strategy that this population of killer whales is potentially vulnerable to underwater noise through loss of echolocation efficiency (masking) and/or behavioural responses. To date, many assessments of the potential effects of underwater noise on marine mammals have used static estimates of noise and animal density (e.g. long-term averages). However, behavioural responses and masking are driven by the short-term confluence of noise and animal density. We therefore developed a simulation model that incorporates short-term estimates of underwater noise and animal density in order to estimate the number of behavioural responses and masking that might occur for each individual SRKW during a year. The simulation inputs included predicted underwater noise levels from vessel traffic at five-minute intervals, and spatiotemporally-informed probabilities of occurrence of three pods of SRKW. Inputs were based on the statistical properties of the source data and varied based on location and time of year. The model was run for 365 days and repeated 1,000 times to generate estimates of the number and the severity of behavioural responses to vessel noise, as well as provide estimates of variability. This simulation model provides a potential management and decision support tool for assessing the likelihood of behavioural responses and masking in SRKW in response to different underwater noise scenarios.
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