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Investigating High-Frequency Underwater Vessel Noise Impact on Killer Whale Echolocation Clicks

Explore the impact of vessel noise on killer whale echolocation clicks, sampling high frequencies up to 90 kHz to assess possible masking effects. Results indicate varying noise levels across vessel types but no clear masking effects on echolocation clicks. Considerations for future research and noise mitigation strategies are discussed.

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Investigating High-Frequency Underwater Vessel Noise Impact on Killer Whale Echolocation Clicks

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  1. Investigating high frequency underwater vessel noise and potential masking of killer whale echolocation clicks Tim HuntBeam Reach Marine Science and Sustainability SchoolFall 2007 - beamreach.org/071 Flinders University of South Australia

  2. Introduction • The Southern Resident Killer Whale • Endangered • Increase in WW boats over the years • ‘98-’05 consistently 20 vessels within ½ mile radius • Erbe (2002) - underwater noise study of WW boats • My study expand on aspects of this – boater cooperation! • Look at specific vessel types using HF hydrophone • Sample up to 30 kHz at 44.1k sampling rate - HF samples up to 90 kHz at 192k sampling rate WOW! • Not done before measuring vessel noise new & novel! • Echolocation clicks in these higher frequencies • Compare with boat noise to infer possible masking? • Relate to County Law and WW guidelines

  3. Spot the Orca

  4. Echolocation clicks in killer whales • What is an echolocation click? • What is it used for? • What does it sound like? • High frequency, range up to 80 kHz • Need a device to sample up to these high frequencies…

  5. 2 orcas in captivity Attached probes to melon Measured ABR Most sensitive 18-42 kHz Simplified from Szymanski et al. 1999 Killer whale audiogram

  6. Questions posed • Is a vessel cruising at high speeds (>18 knots) at 400m “louder” that a vessel slow motoring at low speeds (5-8 knots) at 100m? • Is there is a difference in frequency spectrum levels between different vessel propulsion types? • To what degree, if at all, do different vessel types mask echolocation clicks?

  7. Methods • Two speeds, two distances (relates to SJ County Law and BWW guidelines) • Slow Motor (SM) = speed of 5-8 knots • When within 400m of whales • Cruise (C) = 18-25 knots • When further than 400m • Test SM and C at 100m and 400m • Record echolocation clicks

  8. Sample sites Study site

  9. Materials

  10. Sampling

  11. Vessels measured • Business names kept anonymous, vessel classification based on propulsion system • Twin Inboard 400HP BioDiesel • Twin Outboard 150HP • Surface Piercing • Twin Inboard Diesel • Jet Drive • Also measured Gato Verde catamaran, Washington State Ferry, cargo ship and dinghy

  12. Results

  13. More Results

  14. Even more results • No sig. difference b/w SM 100m & C 400m • 3/5 vessels had difference in RL of 10 dB or greater (C 400m > SM 100m) • Twin OB 150HP opposite • Surface Piercing 1dB difference

  15. Sounds above echo, clicks masked Sounds below echo, clicks heard A killer whale echolocation click What in the bloody hell do all these lines mean?!

  16. 2 vessels below echo All vessels above echo Both 115.5 dB Vessels vs. click vs. audiogram MASKING Higher spectrum level = higher mean RL? NO!

  17. Discussion • Peaks in Jet Drive vessel, & Twin IB 400HP BioDiesel. Mmm…. • What is a significant dB difference? • 6 dB = twice as loud in human ear • Gato Verde – EM vs G, just propeller noise? • Echolocation click mean • Bimodal distribution 10-50 kHz • Similar to Au et al. 2003

  18. Things to think about • KW Audiogram – is it representative of wild orcas? • Individual tested reportedly partially deaf • Busy day in the Haro Strait - individual vessel noise might be indistinguishable to an orca • Hard to quantify difference in vessel type • Can’t really say one is better/worse than another • Can’t really say one is having more/less effect on echolocation • Personal observations – orcas swimming under ferries & riding bow wave of cargo ship • Does noise really bother them?

  19. Improvements/Future research • Make sample size bigger! • Sample vessels on separate days • More clicks, perhaps infer distance? • Measure vessels at more distances, build database, compare, infer, legislate? • Engine noise? Propeller noise? Combination? • Test these to aid in minimising underwater noise • More research = better understanding

  20. If we can lower noise of this

  21. And better understand this

  22. Then we can minimise impact on this

  23. Acknowledgements • Beam Reach and all the crew • Boat operators for driving-by • Whale watch operators for the good times on the radio • Team VaTo for putting up with my singing • Flight Of The Conchords for musical comic relief during times of hardship

  24. Questions?

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