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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.

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vessel noise and orca vocalization implications for policy

VESSEL NOISE AND ORCA VOCALIZATION: IMPLICATIONS FOR POLICY

ALEXANDRA KOUGENTAKIS

BEAM REACH FALL 2007 - beamreach.org/071

resident orcas highly social
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
Ambient Noise

Wind and waves

Vessels

Sonar

Offshore

construction

underwater sound propagation
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
2006 National Marine Fisheries Service Orca Recovery Plan

Endangered species status for SKRWs in 2005

Vessel 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
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
My Research Focus
  • Source levels of orca calls
  • Interaction between vessel noise and orca calls
  • Assessment of “Be Whale Wise” guidelines
  • Characterization of the noise of individual boats
  • Assessing vessel-amplified ambient noise
the research process
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
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
Findings
  • 19 Individual Vessel Recordings
  • Use of experimental spreading model to estimate source levels:

SL = RL + 23.263 x LOG(R)

cumulative vessel data
Cumulative Vessel Data

11 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
interactions between vessel noise and orca vocalization
Interactions between vessel noise and orca vocalization
  • Orca call SL increases when background noise goes up
  • This trend has also been previously found (Holt et al, 2007)
comparing noise power levels of vessels and orcas
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
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
possible areas for improvement
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
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
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.
orca hearing ability
Orca hearing ability

Orca hearing is most sensitive at 20 kHz

Calls are usually between 1 and 10 kHz, harmonics up to 30

Mean SL of orca call is 169.513 dB

Szymanski et al, 1999

number of boats and ambient noise
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