Aquatic Mammals - The Center for Regulatory Effectiveness

122 Pages·2008·5.43 MB·English

Aquatic
Aquatic Mammals, Volume 33, Number 4, 2007 ISSN 0167-5427 A
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Marine Mammal Noise Exposure Criteria: Initial Scientific Recommendations a
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ic
Brandon L. Southall, Ann E. Bowles, William T. Ellison, James J. Finneran, Roger L. Gentry,
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Charles R. Greene Jr., David Kastak, Darlene R. Ketten, James H. Miller, Paul E. Nachtigall, a
W. John Richardson, Jeanette A. Thomas, & Peter L. Tyack m Mammals
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Contents a
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Overview ................................................................................. 411
Chapter 1. Introduction ...................................................................... 415
Objectives............................................................................. 415
Historical Perspective ................................................................... 416
Acoustic Measures and Terminology........................................................ 417
Sound Production and Use in Marine Mammals............................................... 419
Responses to Sound..................................................................... 420
Chapter 2. Structure of the Noise Exposure Criteria................................................ 427
Sound Types........................................................................... 427
Marine Mammal Functional Hearing Groups ................................................. 430
Exposure Criteria Metrics ................................................................ 434
Levels of Noise Effect: Injury and Behavioral Disturbance ...................................... 436
Chapter 3. Criteria for Injury: TTS and PTS...................................................... 437
Effects of Noise on Hearing in Marine Mammals: TTS Data..................................... 437
Injury from Noise Exposure: PTS-Onset Calculation........................................... 441
Criteria for Injury from a Single Pulse ...................................................... 442
Criteria for Injury from Multiple Pulses ..................................................... 444
Criteria for Injury from Nonpulses ......................................................... 444
Chapter 4. Criteria for Behavioral Disturbance.................................................... 446
Behavioral Response Data Analysis Procedures: Disturbance Criteria and Severity Scaling............. 448
Criteria for Behavioral Disturbance: Single Pulse.............................................. 451
Behavioral Response Severity Scaling: Multiple Pulses......................................... 452
Behavioral Response Severity Scaling: Nonpulses ............................................. 456
Chapter 5. Research Recommendations ......................................................... 474
Measurements of Anthropogenic Sound Sources and Ambient Noise .............................. 474
Marine Mammal Auditory Processes........................................................ 474
Behavioral Responses of Marine Mammals to Sound........................................... 477
Effects of Noise Exposure on Marine Mammal Hearing and Other Systems......................... 478
Particularly Sensitive Species ............................................................. 480
Necessary Progressions of Marine Mammal Noise Exposure Criteria .............................. 481
Acknowledgments .......................................................................... 482
Literature Cited ............................................................................ 482 Marine Mammal Noise Exposure Criteria:
Appendix A. Acoustic Measures and Terminology................................................. 498 Initial Scientific Recommendations
Appendix B. Studies Involving Marine Mammal Behavioral Responses to Multiple Pulses . . . . . . . . . . . . . . . . . 502
Supported through Joint Sponsorship by the European Association for
Appendix C. Studies Involving Marine Mammal Behavioral Responses to Nonpulses ..................... 509
Aquatic Mammals, the Alliance of Marine Mammal Parks and Aquariums,
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Aquatic Mammals olu and the International Marine Animal Trainer’s Association
m
e Founded by EAAM in 1974
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Papers dealing with all aspects of the care, 3
conservation, medicine, and science of aquatic mammals , N
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Editor and Copyright: Jeanette A. Thomas
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Department of Biological Sciences, Western Illinois University–Quad Cities, Moline, IL 61265, USA e
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Co-Editor: Kathleen Dudzinski 4
Dolphin Communication Project, Stonington, Connecticut 06378, USA , 2
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Prepared and published by Document and Publication Services, Western Illinois University, Macomb, IL 61455, USA 7
Established by the EAAM in 1974 AQUATIC MAMMALS
AQUATIC MAMMALS
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Marine Mammal Noise Exposure Criteria 
Marine Mammal Noise Exposure Criteria:
Initial Scientific Recommendations
Brandon L. Southall,1, 2 Ann E. Bowles,3 Wllam T. Ellson,4 James J. Fnneran,5
Roger L. Gentry,6 Charles R. Greene Jr.,7 Davd Kastak,2 Darlene R. Ketten,8, 9
James H. Mller,10 Paul E. Nachtgall,11 W. John Rchardson,12
Jeanette A. Thomas,13 and Peter L. Tyack8
1National Oceanic and Atmospheric Administration (NOAA), National Marine Fisheries Service, Office of Science
and Technology, Marine Ecosystems Division, NOAA’s Ocean Acoustics Program, 1315 East-West Highway #12539,
Silver Spring, MD 20910-6233, USA; E-mail: [email protected]
2Long Marine Laboratory, University of California at Santa Cruz, 100 Shaffer Road, Santa Cruz, CA 95060, USA
3Hubbs-Sea World Research Institute, 2595 Ingraham Street, San Diego, CA 92109, USA
4Marine Acoustics, Inc., 809 Aquidneck Avenue, Middletown, RI 02842, USA
5U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center–San Diego,
53560 Hull Street, San Diego, CA 92152-5000, USA
6ProScience Consulting, LLC, P.O. Box 177, Dickerson, MD 20842-0177, USA
7Greeneridge Sciences, Inc., 4512 Via Huerto, Santa Barbara, CA 93110, USA
8Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
9Harvard Medical School, Department of Otology and Laryngology, Boston, MA 02114, USA
10University of Rhode Island, Department of Ocean Engineering, South Ferry Road, Narragansett, RI 02882, USA
11Hawai’i Institute of Marine Biology, P.O. Box 1346, Kane’ohe, HI 96744, USA
12LGL Ltd., environmental research associates, P.O. Box 280, 22 Fisher Street, King City, ON L7B 1A6, Canada
13Western Illinois University–Quad Cities, Department of Biological Sciences, 3561 60th Street, Moline, IL 61265, USA
Contents
Overvew ........................................................................411
Chapter 1. Introducton .............................................................415
Objectves .....................................................................415
Hstorcal Perspectve ............................................................416
Acoustc Measures and Termnology ................................................417
Sound Producton and Use n Marne Mammals........................................419
Responses to Sound..............................................................420
Chapter 2. Structure of the Nose Exposure Crtera.......................................427
Sound Types....................................................................427
Marne Mammal Functonal Hearng Groups ..........................................430
Exposure Crtera Metrcs .........................................................434
Levels of Nose Effect: Injury and Behavoral Dsturbance ...............................436
Chapter 3. Crtera for Injury: TTS and PTS.............................................437
Effects of Nose on Hearng n Marne Mammals: TTS Data..............................437
Injury from Nose Exposure: PTS-Onset Calculaton....................................441
Crtera for Injury from a Sngle Pulse ...............................................442
Crtera for Injury from Multple Pulses ..............................................444
Crtera for Injury from Nonpulses ..................................................444
Chapter 4. Crtera for Behavoral Dsturbance...........................................446
Behavoral Response Data Analyss Procedures: Dsturbance Crtera and Severty Scalng......448
Crtera for Behavoral Dsturbance: Sngle Pulse.......................................451
Behavoral Response Severty Scalng: Multple Pulses..................................452
Behavoral Response Severty Scalng: Nonpulses......................................456
 Southall et al.
Chapter 5. Research Recommendatons ................................................474
Measurements of Anthropogenc Sound Sources and Ambent Nose .......................474
Marne Mammal Audtory Processes.................................................474
Behavoral Responses of Marne Mammals to Sound....................................477
Effects of Nose Exposure on Marne Mammal Hearng and Other Systems..................478
Partcularly Senstve Speces ......................................................480
Necessary Progressons of Marne Mammal Nose Exposure Crtera.......................481
Acknowledgments .................................................................482
Lterature Cted ...................................................................482
Appendx A. Acoustc Measures and Termnology........................................498
Appendx B. Studes Involvng Marne Mammal Behavoral Responses to Multple Pulses . . . . . . . .502
Appendx C. Studes Involvng Marne Mammal Behavoral Responses to Nonpulses ............509
Marine Mammal Noise Exposure Criteria 
Acronyms
Acronym Defnton
A-weghtng Frequency-selectve weghtng for aeral hearng n humans derved from the nverse of the dealzed
40-phon equal loudness hearng functon across frequences
ABR Audtory branstem response
ADD Acoustc deterrent devce
AEP Audtory evoked potentals
AHD Acoustc harassment devce
ANSI Amercan Natonal Standards Insttute
ASSR Audtory steady-state response
ATOC Acoustc Thermometry of Ocean Clmate program
CF Center frequency
C-weghtng Frequency-selectve weghtng for aeral hearng n humans derved from the nverse of the dealzed
100-phon equal loudness hearng functon across frequences
EFR Envelope followng response
EPA U.S. Envronmental Protecton Agency
ES Exploson smulator
f Estmated upper functonal hearng lmt
hgh
f Estmated lower functonal hearng lmt
low
HESS Hgh Energy Sesmc Survey
HPA Hypothalamc-ptutary-adrenal axs
IMAPS Integrated Marne Mammal Montorng and Protecton System
ISO Internatonal Standards Organzaton
JNCC U.K. Jont Nature Conservaton Commttee
L Equvalent-contnuous sound level over perod T
eqT
L Impulse equvalent-contnuous sound level over perod T
IeqT
LFA Low Frequency Actve (sonar)
M-weghtng Generalzed frequency weghtngs for varous groups of marne mammals, allowng for ther
functonal bandwdths and approprate n characterzng audtory effects of strong sounds
M Frequency weghtng for low-frequency cetaceans (mystcetes)
lf
M Frequency weghtng for md-frequency cetaceans (most odontocetes)
mf
M Frequency weghtng for hgh-frequency cetaceans (odontocetes specalzed for use of very hgh
hf
frequences)
M Frequency weghtng for pnnpeds, lstenng n water
pw
M Frequency weghtng for pnnpeds, lstenng n ar
pa
MMPA U.S. Marne Mammal Protecton Act
NIHL Nose-nduced hearng loss
NIPTS Nose-nduced permanent threshold shft
NIOSH U.S. Natonal Insttute for Occupatonal Safety and Health
NMFS U.S. Natonal Marne Fsheres Servce
v Southall et al.
Acronym Defnton
NOAA U.S. Natonal Oceanc and Atmospherc Admnstraton
NRC U.S. Natonal Research Councl
NRL U.S. Naval Research Laboratory
P Maxmum sound pressure
max
OBN Octave-band nose
PCAD Natonal Research Councl’s Populaton Consequences of Acoustc Dsturbance Model
PICE Porpose ncdental catch elmnaton
PTS Permanent threshold shft
REFMS A computer program for predctng shock-wave propagaton from underwater explosons
RL Receved level
RMS Root-mean-square
SEL Sound exposure level
SL Source level (receved level measured or estmated 1 m from the source)
SLM Sound level meter
SPL Sound pressure level
TS Threshold shft
TTS Temporary threshold shft
USC Unted States Code
VAFB Vandenberg Ar Force Base
Aquatic Mammals 2007, 33(4), 411-414, DOI 10.1578/AM.33.4.2007.411
Overview
A group of experts n acoustc research from and qualty. In many respects, data gaps severely
behavoral, physologcal, and physcal dscplnes restrct the dervaton of scentfcally-based nose
was convened over a several year perod. The pur- exposure crtera and, n some cases, explct
pose of ths panel was to revew the expandng lt- threshold crtera for certan effects are not appro-
erature on marne mammal hearng and on phys- prate gven the amount and type of data avalable.
ologcal and behavoral responses to anthropogenc Scentfc nqury nto acoustc communcaton
sound, and to propose exposure crtera for certan among marne mammals extends back more than
effects. The group employed all avalable relevant half a century, but most of the specfc data rel-
data to predct nose exposure levels above whch evant to the proposed crtera have been publshed
adverse effects on varous groups of marne mam- wthn the last two decades. Owng to the mount-
mals are expected. Recent advances n these felds ng publc, scentfc, and regulatory nterest n
and the pressng need for a scence-based para- conservaton ssues related to acoustcs, the aval-
dgm to assess the effects of sound exposure were able scence s progressng rapdly (e.g., see NRC,
the prmary motvatons for ths effort. Two cat- 2003, 2005).
egores of effects were consdered: (1) njury and Ths paper proposes, for varous marne mammal
(2) behavoral dsturbance. The proposed crtera groups and sound types, levels above whch there
for the onset of these effects were further segre- s a scentfc bass for expectng that exposure
gated accordng to the functonal hearng capa- would cause audtory njury to occur. Controlled
bltes of dfferent marne mammal groups, and measurements of hearng and of the effects of
accordng to the dfferent categores and metrcs underwater and aeral sound n laboratory settngs
of typcal anthropogenc sounds n the ocean. The have greatly expanded the ablty to assess aud-
group acheved many of ts objectves but acknowl- tory effects. Whle understandng of the hearng
edges certan lmtatons n the proposed crtera capactes among all marne mammals remans
because of scarcty or complete absence of nfor- admttedly rudmentary, there s a farly detaled
maton about some key topcs. A major component understandng of some key aspects of underwater
of these recommendatons s a call for specfc and aeral hearng n a few representatve speces
research on crtcal topcs to reduce uncertanty of odontocetes, pnnpeds, and srenans, although
and mprove future exposure crtera for marne hearng n mystcetes remans untested. Avalable
mammals. Ths publcaton marks the culmnaton data, along wth the compellng evdence of smlar
of a long and challengng ntal effort, but t also audtory processes among all mammals, enables
ntates a necessary, teratve process to apply and some reasonable extrapolatons across speces for
refne nose exposure crtera for dfferent speces estmatng audtory effects, ncludng the exposure
of marne mammals. levels of probable onset of njury. Recent evdence
The process of establshng polcy gudelnes suggests that exposure of beaked whales to under-
or regulatons for anthropogenc sound exposure water nose may, under certan (generally unknown)
(.e., the applcaton of these exposure crtera) wll condtons, result n non-audtory njury as well
vary among natons, jursdctons, and legal/polcy (e.g., Fernández et al., 2005). At present, however,
settngs. Such processes should carefully consder there are nsuffcent data to allow formulaton of
the lmtatons and caveats gven wth these pro- quanttatve crtera for non-audtory njures.
posed crtera n decdng whether suffcent data There are many more publshed accounts of
currently exst to establsh smplstc, broad crte- behavoral responses to nose by marne mammals
ra based solely on exposure levels. In many cases, than of drect audtory or physologcal effects.
especally for behavoral dsturbance, context- Nevertheless, the avalable data on behavoral
specfc analyses consderng prevous studes on responses do not converge on specfc exposure
speces and condtons smlar to those n queston condtons resultng n partcular reactons, nor do
mght, at least for the foreseeable future, be more they pont to a common behavoral mechansm.
approprate than general gudelnes. Even data obtaned wth substantal controls,
precson, and standardzed metrcs ndcate hgh
State of Current Knowledge varance both n behavoral responses and n expo-
The avalable data on the effects of nose on sure condtons requred to elct a gven response.
marne mammals are qute varable n quantty It s clear that behavoral responses are strongly
412 Southall et al.
affected by the context of exposure and by the an- and (5) pnnpeds lstenng n ar (M ). These cr-
pa
mal’s experence, motvaton, and condtonng. tera do not specfcally address srenans, the sea
Ths realty, whch s generally consstent wth otter, or the polar bear, n part because of the lack
patterns of behavor n other mammals (nclud- of key data n these speces.
ng humans), hampered our efforts to formulate The M-weghtng functons were defned based
broadly applcable behavoral response crtera for on known or estmated audtory senstvty at df-
marne mammals based on exposure level alone. ferent frequences rather than vocal characterstcs
per se. Owng to the paucty of relevant data, these
Frequency-Weighting Functions audtory functons are ntentonally precauton-
In humans, hearng processes n a large number ary (wde) and lkely overestmate the functonal
of male and female subjects of dfferent ages bandwdth for most or all speces. Ther prmary
have been tested to determne a basc audomet- applcaton s n predctng audtory damage rather
rc curve, equal-loudness curve, and the levels and than levels of detecton or behavoral response.
exposure duratons needed to nduce ether recov- Consequently, t s more approprate to use “flat-
erable hearng loss (called temporary threshold ter” functons than would be obtaned by employ-
shft or TTS) or permanent threshold shft (PTS). ng a smple nverse-audogram functon.
In addton, the manner n whch successve expo-
sures to nose contrbute to TTS growth has been Exposure Criteria Metrics
well-documented n humans (e.g., Kryter, 1994; To further complcate the dervaton of nose expo-
Ward, 1997). In assessng the effects of nose sure crtera, sounds can be descrbed wth varous
on humans, ether an A- or C-weghted curve acoustc metrcs, ncludng sound pressure levels
s appled to correct the sound-level measure- and sound exposure levels. The latter s a measure
ment for the frequency-dependent hearng func- of receved sound energy. Avalable lterature pro-
ton of humans. Early on, the panel recognzed vdes a mxture of both measures, but many sound
that smlar, frequency-weghted hearng curves sources have prmarly been descrbed n pressure
were needed for marne mammals; otherwse, level unts. To accommodate these two measures,
extremely low- and hgh-frequency sound sources and to account for all relevant acoustc features
that are detected poorly, f at all, mght be subject that may affect marne mammals, we developed
to unrealstc crtera. dual crtera for nose exposures n each of the fve
One of the major accomplshments n ths functonal hearng groups, usng both sound pres-
effort was the dervaton of recommended fre- sure and sound exposure levels.
quency-weghtng functons for use n assessng
the effects of relatvely ntense sounds on hearng Exposure Criteria for Injury
n some marne mammal groups. It s abundantly Another area n whch we provde substantve
clear from measurements of marne mammal hear- conclusons s n the determnaton of sound
ng n the laboratory, call characterstcs, and aud- exposures beleved to cause drect audtory njury
tory morphology that there are major dfferences to marne mammals. By all accounts, the nner
n audtory capabltes across marne mammal ear s the organ system most drectly senstve to
speces (e.g., Wartzok & Ketten, 1999). Most pre- sound exposure and, thus, the most susceptble to
vous assessments of acoustc effects ether faled sound-derved damage. We defne the mnmum
to account for dfferences n functonal hearng exposure crteron for njury as the level at whch
bandwdth among marne mammal groups or dd a sngle exposure s estmated to cause onset of
not recognze that the “nomnal” audogram mght permanent hearng loss (PTS). Data on TTS n
be a relatvely poor predctor of how the audtory marne mammals, and on patterns of TTS growth
system responds to relatvely strong exposures. and ts relaton to PTS n other mammals, were
The authors delneated fve groups of marne used to estmate thresholds for njury. Owng to
mammals based on smlartes n ther hearng, and the lmted avalablty of relevant data on TTS
they developed a generalzed frequency-weght- and PTS, the extrapolaton procedures underlyng
ng (called “M-weghtng”) functon for each. these estmatons are necessarly precautonary.
The fve groups and the assocated desgnators are To account for all of the potentally njurous
(1) mystcetes (baleen whales), desgnated aspects of exposure, dual crtera for njury were
as “low-frequency” cetaceans (M); (2) some establshed for each functonal marne mammal
lf
odontocetes (toothed whales), desgnated as hearng group based on nstantaneous peak pres-
“md-frequency” cetaceans (M ); (3) odontocetes sure (unweghted) and total energy (M-weghted).
mf
specalzed for usng hgh frequences (.e., por- Exposure crtera for njury are gven for two types
poses, rver dolphns, and the genera Kogia and of sounds, pulse and nonpulse, and for sngle and
Cephalorhynchus) (M ); (4) pnnpeds (.e., seals, multple exposures. The term pulse s used here to
hf
sea lons, and walruses) lstenng n water (M ); descrbe bref, broadband, atonal, transents (ANSI,
pw
Marine Mammal Noise Exposure Criteria 413
1986; Harrs, 1998, Chapter 12), whch are charac- to derve explct and broadly applcable numer-
terzed by a relatvely rapd rse-tme to maxmum cal threshold values for delneatng behavoral
pressure followed by a decay that may nclude a dsturbance. We dd develop a quanttatve scor-
perod of dmnshng and oscllatng maxmal and ng paradgm that numercally ranks, as a severty
mnmal pressures. Examples of pulses are sounds scalng, behavoral responses observed n ether
from explosons, gunshots, sonc booms, sesmc feld or laboratory condtons. We appled ths
argun pulses, and ple drvng strkes. Nonpulse approach to the approprate behavoral data for
(ntermttent or contnuous) sounds can be tonal, multple pulses and nonpulses. Some of these data
broadband, or both. They may be of short dura- suffer from poor statstcal power, lmted nfor-
ton but wthout the essental propertes of pulses maton on receved sound levels and background
(e.g., rapd rse-tme). Examples of anthropogenc, nose, nsuffcent measurements of all potentally
oceanc sources producng such sounds nclude mportant contextual varables, and/or nsuffcent
vessels, arcraft, machnery operatons such as controls. Some such data are analyzed here solely
drllng or wnd turbnes, and many actve sonar for llustratve purposes. Most behavoral studes
systems. As a result of propagaton, sounds wth suffered from at least some of these problems.
the characterstcs of a pulse at the source may lose Therefore, we do not ntend to gve unform sc-
pulsatle characterstcs at some (varable) dstance entfc credence to all of the cted data, and we
and can be characterzed as a nonpulse by certan expect future studes to gve greater attenton and
recevers. rgor to these crtcal requrements.
Regardless of the anthropogenc sound, f a Ths revew and scorng process, whle not a
marne mammal’s receved exposures exceed the formal meta-analyss for normalzng and pool-
relevant (pulse or nonpulse) crteron, audtory ng dsparate observatons, corroborated certan
njury (PTS) s assumed to be lkely. Chapter 3, nterestng aspects of marne mammal behavoral
“Crtera for Injury,” provdes detals regardng responses to sound exposure. Foremost was that
the exposure levels requred to cause TTS-onset a behavoral response s determned not only by
and the extrapolaton of those results to estmate smple acoustc metrcs, such as receved level
levels above whch PTS-onset may occur. For all (RL), but also by contextual varables (e.g., labo-
fve functonal hearng groups, we propose dual ratory vs feld condtons, anmal actvty at the
exposure crtera above whch audtory njury s tme of exposure, habtuaton/senstzaton to
lkely. the sound, etc.). Also mportant s the presence
or absence of acoustc smlartes between the
Exposure Criteria for Behavior anthropogenc sound and bologcally relevant
One challenge n developng behavoral crtera natural sgnals n the anmal’s envronment (e.g.,
s to dstngush a sgnfcant behavoral response calls of conspecfcs, predators, prey). Wthn
from an nsgnfcant, momentary alteraton n certan smlar condtons, there appears to be
behavor. For example, the startle response to a some relatonshp between the exposure RL and
bref, transent event s unlkely to persst long the magntude of behavoral response. However,
enough to consttute sgnfcant dsturbance. Even n many cases, such relatonshps clearly do not
strong behavoral responses to sngle pulses, other exst, at least when response data are pooled
than those that may secondarly result n njury across multple speces and contexts. Ths argues
or death (e.g., stampedng), are expected to ds- for a context-based approach to dervng nose
spate rapdly enough as to have lmted long-term exposure crtera for behavoral responses. That
consequence. Consequently, upon exposure to a concept, along wth our revew and scalng of the
sngle pulse, the onset of sgnfcant behavoral avalable observatonal data, provdes a founda-
dsturbance s proposed to occur at the lowest ton for establshng dose-response relatonshps
level of nose exposure that has a measurable for some specfc crcumstances and a startng
transent effect on hearng (.e., TTS-onset). We pont for future analyses when addtonal data are
recognze that ths s not a behavoral effect per avalable.
se, but we use ths audtory effect as a de facto
behavoral threshold untl better measures are Conclusions and Research Recommendations
dentfed. Lesser exposures to a sngle pulse are Ths process has resulted n several sgnfcant
not expected to cause sgnfcant dsturbance, advances. These nclude a revew and nterpre-
whereas any compromse, even temporarly, to taton of the avalable lterature on njury and
hearng functons has the potental to affect vtal behavoral data usng precautonary extrapola-
rates through altered behavor. ton procedures, dervaton of marne mammal
For other anthropogenc sound types (multple frequency-weghtng functons, specfcaton of
pulses, nonpulses), we conducted an extensve quanttatve crtera for audtory njury, and derva-
revew of the avalable lterature but were unable ton of a “severty scale” for behavoral responses.
414 Southall et al.
The nablty to dentfy broadly applcable, constranng mportant human actvtes n the
quanttatve crtera for behavoral dsturbance n oceans wll contnue to be challengng for the
response to multple-pulse and nonpulse sounds s foreseeable future. Wth sustaned and focused
an acknowledged lmtaton. research n key areas, future scentsts wll be
Our efforts to derve marne mammal nose equpped to make nformed mprovements to the
exposure crtera clearly llustrate the fact that, ntal scentfc recommendatons presented here.
at present, research n ths feld remans lmted These mprovements should deally be ntegrated
n many areas. The need for extrapolaton pro- nto scence-based rsk assessment models that
cedures and precautonary assumptons ponts consder all aspects of sound exposure and other
drectly to research needs n a varety of areas on a potental stressors on ndvdual marne mammals,
varety of speces. In certan condtons, proposed populatons, and marne ecosystems.
crtera for an entre marne mammal group are
based on the most precautonary measurement
or observaton for a speces wthn that group,
despte the fact that, for other speces wthn that
group, there are emprcal data ndcatng that
hgher exposures are requred to nduce the same
effect. We beleve t s approprate to use the most
precautonary data n proposng group-wde crte-
ra applcable for speces where there are no drect
measurements. We also feel t s approprate on
a case-by-case bass to apply the most relevant
emprcal data (.e., from the speces or genus of
concern) n settng the exposure thresholds spec-
fed n polcy gudelnes.
Fnally, we emphasze that exposure crtera for
sngle ndvduals and relatvely short-term (not
chronc) exposure events, as dscussed here, are
nsuffcent to descrbe the cumulatve and eco-
system-level effects lkely to result from repeated
and/or sustaned human nput of sound nto the
marne envronment and from potental nterac-
tons wth other stressors. Also, the njury crtera
proposed here do not appear to predct what may
have been ndrect njury from acoustc exposure
n several cases where cetaceans of several spe-
ces mass-stranded followng exposure to mltary
sonar.
The extensve research recommendatons gven
here (see Chapter 5) represent our collectve
vew of the concerted effort that wll be requred
over the comng decades. Hgh prorty catego-
res of research nclude (1) contnued expanson
of knowledge on basc marne mammal hearng
capabltes, ncludng sound localzaton, the
detecton of realstc sound sgnals, commun-
caton maskng, and audtory “scene analyss”;
(2) contnued expanson of knowledge on baselne
marne mammal behavoral patterns; (3) well-
controlled, drect measurements (usng appropr-
ate, standardzed acoustc metrcs) of the effects
of sound exposure on marne mammal hearng,
behavor, and physology; and (4) rsk-assessment
studes of the cumulatve and synergstc effects
of nose and other exposure(s) on ndvduals and
populatons.
Understandng and managng the effects
of nose on marne lfe wthout unjustfably