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 (Seattle, WA : 2018)

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

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

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

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Apr 6th, 8:45 AM Apr 6th, 9:00 AM

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.