| Summary: | Masking by underwater noise can decrease prey acquisition rates in southern resident killer whales (SRKWs) by impeding communication and echolocation during foraging. SRKW increase the source level of their vocalizations when broadband underwater noise increases (in correlation with the number of nearby boats), and ship noise extends to higher frequencies of SRKW echolocation. On San Juan Island, WA, along the Haro Strait we operate hydrophones for the long-term measurement of underwater noise and we record all the Automatic Identification System (AIS) reports from passing boats and ships. Since late July, 2017, the NEMES Program at the University of Victoria, has operated a HD camera from the site taking photos of Haro Strait every few seconds. With AIS data from ships and small boat data from the on-site camera, we have developed noise models parameterized with these local data. We evaluate noise reduction strategies using a suite of metrics (decibels weighted and unweighted, communication range, foraging range) and discuss how these strategies impact the percentage of time that SRKWs are exposed to various levels of underwater noise (peak, minima, and quantiles). Noise reduction strategies we assess include: ship source level reductions (e.g. hull cleaning, maintenance, speed limits); small boat speed limits and no-go zones; and vessel scheduling scenarios.
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