Investigating high frequency underwater vessel noise and potential

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

Introduction n The Southern Resident Killer Whale n n Increase in WW boats over the years n n My study expand on aspects of this – boater cooperation! Look at specific vessel types using HF hydrophone n n n ‘ 98 -’ 05 consistently 20 vessels within ½ mile radius Erbe (2002) - underwater noise study of WW boats n n Endangered Sample up to 30 k. Hz at 44. 1 k sampling rate - HF samples up to 90 k. Hz at 192 k sampling rate WOW! Not done before measuring vessel noise new & novel! Echolocation clicks in these higher frequencies n Compare with boat noise to infer possible masking?

Spot the Orca

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

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

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

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

Sample sites Study site

Materials

Sampling

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

Results

More Results

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

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

Vessels vs. click vs. audiogram 2 vessels below echo Both 115. 5 d. B Higher spectrum level = higher mean RL? NO! MASKING All vessels above echo

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

Things to think about n KW Audiogram – is it representative of wild orcas? n n n Busy day in the Haro Strait - individual vessel noise might be indistinguishable to an orca Hard to quantify difference in vessel type n n n Individual tested reportedly partially deaf 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 n Does noise really bother them?

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

If we can lower noise of this

And better understand this

Then we can minimise impact on this

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

Questions?