Controlled source level measurements of whale watch boats and other small vessels.

 

Jennifer L. Wladichuk – jennifer.wladichuk@jasco.com

David E. Hannay, Zizheng Li, Alexander O. MacGillivray

JASCO Appl. Sci., 2305 – 4464 Markham St.

Victoria, BC V8Z 7X8, Canada

 

Sheila Thornton

Sci. Branch

Fisheries and Oceans Canada

Vancouver, BC, Canada

 

Popular version of paper 2pUWb8

Presented Tuesday afternoon, Nov 6, 2018

176th ASA Meeting, Victoria, BC, Canada

 

 

 

The Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat and Observation (ECHO) program sponsored deployment of two autonomous marine acoustic recorders (AMAR) in Haro Strait (BC), from July to October 2017, to measure sound levels produced by large merchant vessels transiting the strait. Fisheries and Oceans Canada (DFO), a partner in ECHO, supported an additional study using these same recorders to systematically measure underwater noise emissions (0.01–64 kHz) of whale watch boats and other small vessels that operate near Southern Resident Killer Whales (SRKW) summer feeding habitat. During this period, 20 different small vessels were measured operating at a range of speeds (nominally 5 knots, 9 knots, and cruising speed). The measured vessels were catagorized into six different types based primarily on hull shape: ridged-hull inflatable boats (RHIBs), monohulls, catamarans, sail boats, landing craft, and one small boat (9.9 horsepower outboard). Acoustic data were analyzed using JASCO’s PortListen® software system, which automatically calculates source levels from calibrated hydrophone data and vessel position logs, according to the ANSI S12.64-2009 standard for ship noise measurements. To examine potential behavioural effects on SRKW, vessel noise emissions were analyzed in two frequency bands (0.5–15 kHz and >15 kHz) corresponding to the whales’ communication and echolocation ranges, respectively (Heise et al. 2015). We found that generally, with increased speed, decibel levels increased across the different vessel types, particularly in the echolocation band (Table 1). However, the speed trends were not as strong as those of large merchant vessels. Of the vessels measured, monohulls commonly had the lowest source levels in both SRKW frequency bands, while catamarans had the highest source levels in the communication band and the landing craft had the highest levels in the echolocation band at all speeds (Figure 1). Another key finding was the amount of noise onboard echosounders produced; a significant peak at approximately 50 kHz was present in some vessels, which is within the most sensitive hearing range of SRKW.

Table 1. Average source level for each vessel type in the SRKW communication and echolocation frequency bands for slow, medium, and fast vessel speeds.

 

 

Figure 1. Average one-third octave band source levels for each vessel type for the slow speed passes (≤7 kn, ie. whale-watching speed). Due to non-vessel related noise at frequencies below approximately 200 Hz (grey vertical line), levels at those low frequencies cannot be associated with vessel source levels. The peak observed at around 50 kHz is from onboard echosounders.

 

Literature cited:

Heise, K.A., L. Barret-Lennard, N.R. Chapman, D.T. Dakin, C. Erbe, D. Hannay, N.D. Merchant, J. Pilkington, S. Thornton, et al. 2017. Proposed metrics for the management of underwater noise for southern resident killer whales. Coastal Ocean Report Series. Volume 2, Vancouver, Canada. 30 pp.

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