Presentation Abstract
Underwater noise may be impacting the population recovery of critically endangered Southern Resident Killer Whales (SRKW). This study used an SRKW-Noise exposure simulation model to compare noise effects from large (AIS-enabled) commercial vessels with whale watch boats during summer (May-September) within their principal Salish Sea habitat range use. It predicted moderate or low behavioural responses (BRs) using SRKW-specific dose-response relationships and, if no BRs were triggered, the extent of residual high frequency echolocation click masking. BRs were considered to result in lost foraging due to switches in behaviour or via strong masking effects. The Monte-Carlo simulation used a fine-scale acoustic model to predict broadband sound pressure levels (SPL, BR analysis) and power spectral density (PSD) at 50 kHz (click masking analysis) for AIS-enabled commercial vessels. To derive equivalent data from whale watch boats, we combined data from Holt et al. (2009), SoundWatch and Beam Reach Sustainable School. SRKW habitat used a 10-year synthesis of effort-correct observer sightings. Overall, noise from AIS-enabled vessels was estimated to contribute 93% of overall BR-related potential lost foraging time, with whale watch boats contributing the remaining 7%, despite mean estimates of 6.1hr of boats with each whale per day. Lower SPLs of slow moving boats had low probabilities of exceeding BR thresholds, while large commercial vessel often exceed these thresholds. Lost foraging time per whale was estimated as a median 3.2hr per day when whales were present (13.4% of day). Echolocation click masking effects accumulated an additional 1.7hr of lost foraging time and was strongly dominated by noise predicted from slow (2.5-8 knot) whale watch boats, noting high model uncertainty due to PSD, speed and proximity assumptions. Overall, lost foraging time totaled 20.3% of each whale day (4.9hr), with ~2/3 due to AIS-enabled commercial vessels, highlighting mitigation measures for both vessel types should be considered.
Session Title
Collaborating to Reduce Impacts of Underwater Noise from Vessels on SKRW: Biological Impacts of Underwater Noise from Vessels
Keywords
Underwater noise, Killer whales, Vessel noise
Conference Track
SSE14: Vessel Traffic: Risks and Impacts
Conference Name
Salish Sea Ecosystem Conference (2018 : Seattle, Wash.)
Document Type
Event
SSEC Identifier
SSE14-28
Start Date
6-4-2018 8:45 AM
End Date
6-4-2018 9:00 AM
Type of Presentation
Oral
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Killer whale--Effect of noise on--Salish Sea (B.C. and Wash.); Whale watching industry--Law and legislation--Salish Sea (B.C. and Wash.); Marine mammals--Effect of human beings on--Salish Sea (B.C. and Wash.); Ships sounds--Salish Sea (B.C. and Wash.); Whales--Behavior--Salish Sea (B.C. and Wash.); Whales--Food--Salish Sea (B.C. and Wash.)
Geographic Coverage
Salish Sea (B.C. and Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Included in
Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, Terrestrial and Aquatic Ecology Commons
Commercial ship versus whale watch boat noise: relative effects on Southern Resident killer whales
Underwater noise may be impacting the population recovery of critically endangered Southern Resident Killer Whales (SRKW). This study used an SRKW-Noise exposure simulation model to compare noise effects from large (AIS-enabled) commercial vessels with whale watch boats during summer (May-September) within their principal Salish Sea habitat range use. It predicted moderate or low behavioural responses (BRs) using SRKW-specific dose-response relationships and, if no BRs were triggered, the extent of residual high frequency echolocation click masking. BRs were considered to result in lost foraging due to switches in behaviour or via strong masking effects. The Monte-Carlo simulation used a fine-scale acoustic model to predict broadband sound pressure levels (SPL, BR analysis) and power spectral density (PSD) at 50 kHz (click masking analysis) for AIS-enabled commercial vessels. To derive equivalent data from whale watch boats, we combined data from Holt et al. (2009), SoundWatch and Beam Reach Sustainable School. SRKW habitat used a 10-year synthesis of effort-correct observer sightings. Overall, noise from AIS-enabled vessels was estimated to contribute 93% of overall BR-related potential lost foraging time, with whale watch boats contributing the remaining 7%, despite mean estimates of 6.1hr of boats with each whale per day. Lower SPLs of slow moving boats had low probabilities of exceeding BR thresholds, while large commercial vessel often exceed these thresholds. Lost foraging time per whale was estimated as a median 3.2hr per day when whales were present (13.4% of day). Echolocation click masking effects accumulated an additional 1.7hr of lost foraging time and was strongly dominated by noise predicted from slow (2.5-8 knot) whale watch boats, noting high model uncertainty due to PSD, speed and proximity assumptions. Overall, lost foraging time totaled 20.3% of each whale day (4.9hr), with ~2/3 due to AIS-enabled commercial vessels, highlighting mitigation measures for both vessel types should be considered.
