Transcript vessel noise and orca vocalization: implications for

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 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
• Soundwatch and
The Whale
Museum of San
Juan Island
• Guidelines for
boater behavior:
100 yard/meter nogo zone, slow zone
<7 knots from 100400 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)
Comparing noise level, speed
and boat types
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
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
• 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
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
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“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
Szymanski et al, 1999
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
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