VESSEL NOISE AND ORCA VOCALIZATION:

IMPLICATIONS FOR POLICY

ALEXANDRA KOUGENTAKIS

BEAM REACH FALL 2007 - beamreach.org/071

Resident Orcas: Highly Social• Vocalization types are echolocation, whistles

and pulsed calls.• Hunting, traveling, mating and social

behaviors all depend upon communication

•Pulsed call

•Echolocation click

•Whistle

Ambient Noise

Wind and waves

Vessels

Sonar Offshore construction

Underwater sound propagation

• Sound travels well in water: 1500m/sec in sea vs 343 m/sec in air

• Sound energy propagates from its source in a circle

• Distance and source level are most important to received level

• Also temperature, depth, bathymetry, salinity

2006 National Marine Fisheries Service Orca Recovery Plan

Endangered species status for SKRWs in 2005Vessel noise is one of the three “threats to orca survival”

•Noise level may mask orca calls•Risk of hearing loss

•Behavioral changes in presence of boats (Erbe, 2002)

Be Whale Wise and Ordinance #35–2007

• Soundwatch and The Whale Museum of San Juan Island

• Guidelines for boater behavior: 100 yard/meter no-go zone, slow zone <7 knots from 100-400 yards/meters

•2007 law: $750 fine for approaching orcas closer than 100m

My Research Focus

• Characterization of the noise of individual boats

• Assessing vessel-amplified ambient noise

•Source levels of orca calls•Interaction between vessel noise and orca calls•Assessment of “Be Whale Wise” guidelines

The Research Process

• Four weeks of data collection aboard the Gato Verde.

• Array of four hydrophones deployed

• Descriptive data collection for boats

• Beam Reach Analyzer and Ishmael software used for analysis

Modeling within the Study

• Sound propagation: SL = RL +TL x LOG(R) -Dinghy experiment

•Gato Verde as an orca–Measurement of ambient noise to simulate what orcas are cumulatively exposed to

Findings• 19 Individual Vessel Recordings• Use of experimental spreading model to estimate source levels: SL = RL + 23.263 x LOG(R)

Vessel Noise Level

161.6

167.5

173.4

179.3

185.2

150

160

170

180

190

200

-2 STDEV

-1 STDEV

Mean

+1 STDEV

+2 STDEV

Comparing noise level, speed and boat types

Correlation between noise level and boat speed

y = 0.519x + 170.13

R2 = 0.1371

y = 0.7467x + 166.66

R2 = 0.3827

160

165

170

175

180

185

190

0 5 10 15 20

Speed (knots)

Smallinflatables

Medium hard-bottom

Cumulative Vessel Data11 Data Points

•Data points reflect average RLs of 1-3 sequential recordings•Simulation of what orcas may experience under typical conditions•Sound propagation modeling not used here, potentially more accurate and/or informative

Average RL of Cumulative Boat Noise

111.7115.4

119.1122.8

126.5

100

110

120

130

140

Vessel Noise Level (dB re

-2 STDEV

-1 STDEV

Mean

+1 STDEV

+2 STDEV

Interactions between vessel noise and orca vocalization

Orca call SL increases when background noise goes upThis trend has also been previously found (Holt et al, 2007)

Orca Call Source Levels

153.0

161.6

169.5

177.5

186.7

125.0

150.0

175.0

200.0

-2 STDEV

-1 STDEV

Mean

+1 STDEV

+2 STDEV

Comparing noise power levels of vessels and orcas

• Power of vessel signal is close to that of orca call, direct competition• Substantially lower power level for ambient• Difference between ambient and orca SL determines hearing range

What the “Be Whale Wise” guidelines actually mean for orcas

•Meters for Canadian, yards for US vessels•Less than 1 dB difference between two units

Vessels at Be Whale Wise Distances

127.8

126.9

113.8

112.9

100 110 120 130 140

400m365.76m100m91.44m

Possible areas for improvement

• Vessel noise might be better assessed by further limiting distance for recording

• Communication with boat operators for more accurate assessment of the speed-noise relationship

• Observational data to corroborate orca range computer estimates

• Reexamination of sound spreading model used

What this research means for policy• Need to limit increase of ambient underwater

noise levels via multiple means• Ordinance # 35-2007 sets a minimum legal

distance• Limit speed close to orcas: Be Whale Wise• Number of boats at a time is also important

REFERENCES• “Be Whale Wise.” (2006) Soundwatch Boater Education Program. The Whale

Museum. Available www.whale-museum.org/downloads/ soundwatch/whaleBro5-26-06.pdf.

• Erbe, Christine (2002). “Underwater Noise of Whale-watching Boats and Potential Effects on Killer Whales (Orcinus orca), Based on an Acoustic Impact Model.” Marine Mammal Science. 18(2): 394-418.

• Holt, Marla M.; Veirs, Val; Veirs, Scott. “Noise Effects on the Call Amplitude of Southern Resident Killer Whales (Orcinus orca).” Presented at Nyborg Conference. August 2007.

• “Ordinance NO. 35-2007.” San Juan County Council. News. Available http://www.co.san-juan.wa.us/News/vesselwhaleord_final.pdf.

• “Proposed Recovery Plan for Southern Resident Killer Whales (Orcinus orca).” National Marine Fisheries Service Northwest Regional Office. November 2006. Available http://www.nmfs.noaa.gov/pr/pdfs/recovery/proposed_killerwhale.pdf

• Szymanski, M.D., D.E. Bain, K. Kiehl, S. Pennington, S. Wong, and K.R. Henry. (1999) Killer whale (Orcinus orca) hearing: Auditory brainstem response and behavioral audiograms. Journal of The Acoustic Society of America. 106 (2): 1134-1141.

QUESTIONS?

Orca hearing ability

Orca hearing is most sensitive at 20 kHzCalls are usually between 1 and 10 kHz, harmonics up to 30Mean SL of orca call is 169.513 dB

Szymanski et al, 1999

Number of boats and ambient noise

• Data plotted here excludes outlier of 4 boats that included a tanker

• Lack of strong linear relationship signifies importance of individual vessel qualities

Ambient RL vs. Boat Number

y = 0.5439x + 111.51R2 = 0.2259

113

114

115

116

117

118

119

120

121

122

123

6 8 10 12 14 16

Number of boats