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Journal of International Wildlife Law and Policy, 10:1–27, 2007
Copyright C
Taylor & Francis Group, LLC
ISSN: 1388-0292 print / 1548-1476 online
DOI: 10.1080/13880290701229838
Comparative Review of the Regional
Marine Mammal Mitigation Guidelines
Implemented during Industrial Seismic
Surveys, and Guidance Towards a
Worldwide Standard
CAROLINE R. WEIR1
SARAH J. DOLMAN1
1. INTRODUCTION
Marine mammals rely on sound for all of the fundamental biological and
ecological aspects of their lives including navigation, prey location and
capture, predator avoidance, and communication (including during migration
and reproduction). There is increasing concern regarding the potential effects
of the airgun sound produced during geophysical seismic surveys on marine
mammals. Airgun arrays typically produce high amplitude sound with source
levels in the region of 220–248 dB re. 1 µPa @ 1 m.2The acoustic output has
highest energy at relatively low frequencies of 10–200 Hz, which overlaps
extensively with the low frequency sound produced by baleen whales in
the 12–500 Hz bandwidth.3Airgun arrays may alsoproduce significant high
1Caroline Weir, Ketos Ecology, 4 Compton Road, West Charlton, Kingsbridge, Devon TQ7 2BR, UK.
Sarah J. Dolman, Whale and Dolphin Conservation Society (WDCS), Brookfield House, 38 St Paul
Street, Chippenham, Wiltshire SN15 1LJ, United Kingdom. E-mail: sarah.dolman@wdcs.org. Many
thanks to Ross Compton for help with several aspects of this article, and to Liz Burgess, Alison Gill,
Cristiano Vilardo Guimaraes, John Lane, and Helen McConnell for assistance with providing guidelines.
Thanks to Ken Findlay, Jonathan Gordon, Michael Jasny, Mark Simmonds, and Lindy Weilgart for their
valuable input on draft versions.
2Charles R. Greene, Jr. & W. John Richardson, Characteristics of Marine Seismic Survey Sounds
in the Beaufort Sea Canada USA. J.ACOUST.SOC.AM., 83 (1988); W. John Richardson & Bernd
W¨
ursig, Influences of Man-Made Noise and Other Human Actions on Cetacean Behaviour.M
ARINE AND
FRESHWATER BEHAVIOUR AND PHYSIOLOGY, 29 (1997); Gulland, Jim A. & C.D.T. Walker, Marine Seismic
Overview,in: Mark L. Tasker, & C.R. Weir (eds.), PROCEEDINGS OF THE SEISMIC AND MARINE MAMMALS
WORKSHOP, London, 23–25 June 1998 (2001).
3Thompson, T.J.,Winn, H. E., & Perkins, P.J. Mysticete Sounds, in Behaviour of Marine Animals,VOLUME
3: CETACEANS, (H.E. Winn & B. J. Olla, eds. (1979); W. John Richardson et al.MARINE MAMMALS AND
NOISE. (1995).
1
2WEIR AND DOLMAN
frequency sound energy, with airgun sound dominating frequencies up to 22
kHz within a few kilometres of the source.4
Since small odontocete species utilise and are sensitive to sound in the
0.5–20 kHz range,5both odontocete and mysticete species may potentially be
adversely affected by airgun sound. Reviews have identified several potential
levels of impact on marine mammals from seismic airgun sound, including
physical injury (such as tissue damage, temporary and permanent hearing
loss), indirect physical damage (e.g., “the bends”), physiological effects
(e.g., stress), masking of echolocation signals, behavioural impacts (including
displacement from migratory, feeding, and breeding habitat), and indirect
effects from displacement of prey species.6
Although the oil and gas industry conducts seismic surveys throughout
the world, the potential acoustic impact upon marine mammals from seismic
airguns has not yet been addressed on a worldwide scale. However, the last
decade has seen the regulatory agencies of several countries introduce marine
mammal mitigation guidelines for use during industrial seismic surveys,
aimed at reducing the impacts from seismic airgun sound. In 1998, the
UK’s Joint Nature Conservation Committee (JNCC) was the first regulatory
body to issue statutory marine mammal mitigation measures for use during
industrial seismic surveys in their national waters.7Australia’s Department
of Environment and Heritage (formerly Environment Australia) followed in
2001,8and a number of other countries have since developed guidelines (or
are in the process of doing so). Most of these guidelines are statutory and are
included by the regional industrial regulatory bodies within their oil and gas
licensing agreements.
Limited seismic surveys are also carried out annually for academic
research purposes, and the legislation governing these surveys is less specific
and often managed on a case-by-case basis. In some regions, particularly in
the US, the marine mammal mitigation procedures utilised during research
seismic surveys have a more stringent permitting procedure, are prepared
4John C. Goold & P.J. Fish. Broadband Spectra of Seismic Survey Air-Gun Emissions, with Reference to
Dolphin Auditory Thresholds. JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, 103 (1998).
5Arthur N. Popper. Sound Emission and Detection by Delphinids in CETACEAN BEHAVIOUR:MECHANISMS
AND PROCESSES, (L.M. Herman, ed. 1980); W. John Richardson, Charles R. Greene, Jr., Charles I.
Malme & Dave H. Thompson. Effects of Noise on Marine Mammals. OCS Study MMS 90–0093. LGL
Rep. TA834-1. Report from LGL Ecological Research Associates Inc., Bryan, TX for U.S. Minerals
Management Serv., Atlantic OCS Reg., Herndon, VA. NTIS PB91-168914 (1991).
6Jonathon C.D. Gordon et al.The Effects of Seismic Surveys on Marine Mammals, in Tasker, M.L. &
Weir, C.R., eds, PROCEEDINGS OF THE SEISMIC AND MARINE MAMMALS WORKSHOP, London, 23–25 June
1998 (1998); W. John Richardson et al., supra note 2 and 4.
7JNCC, Guidelines for Minimising Acoustic Disturbance to Marine Mammals from Seismic Surveys.
Joint Nature Conservation Committee, Peterborough, UK (1998).
8Environment Australia, Guidelines on the Application of the Environment Protection and Biodiversity
Conservation Act to Interactions Between Offshore Seismic Operations and Larger Cetaceans (2001).
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 3
specifically on a site basis and are considerably more precautionary than the
standard industrial guidelines.9However, some research seismic surveys, for
example in Antarctic waters, are apparently conducted with less protection
for marine mammals than the standard industrial guidelines.
This article reviews the types and effectiveness of marine mammal mit-
igation measures presently used during industrial seismic surveys worldwide.
We do not review the various levels of mitigation used during research-based
seismic surveys, since they are less standardised in nature. Many of the
protocols discussed here, however, apply to both types of survey. While many
developed countries now enforce statutory industrial guidelines within their
own national waters, the numerous seismic surveys occurring in the waters
of developing countries or elsewhere worldwide may not include marine
mammal mitigation measures. We make suggestions towards a minimum
worldwide mitigation standard, for use in unlegislated areas. The development
of each region’sstatutory guidelines is a continually evolving process, and this
comparative review is based on the best information available for each region
at this time. We also acknowledge that, although not available at present,
guidelines are currently being developed in several other geographic areas
(e.g., Alaska).
2. EXISTING MITIGATION MEASURES
There are three main methods currently used to mitigate the potential im-
pacts on marine mammals during seismic surveys: (1) implementation of
operational procedures (e.g., ‘soft start’—where sound levels are gradually
increased over time); (2) detection of animals close to airguns and implemen-
tation of real-time mitigation measures (e.g., shut-down), and (3) time/area
planning of surveys to avoid marine mammals. Detection of animals via
real-time monitoring, while not a mitigation measure per se, is an essential
component of marine mammal mitigation during seismic surveys and is
therefore discussed throughout this article in a mitigation context.
The mitigation measures in use worldwide are summarised in Table 1
on page 26 (which also identifies the sources of information used in this
chapter).
9Examples include NMFS Small Takes of Marine Mammals Incidental to Specified Activities; Seismic
Reflection Data off Southern California. Federal Register, 67, 42541–42547 (2002); NMFS Small
Takes of Marine Mammals Incidental to Specified Activities; Oceanographic Surveys in the Hess
Deep, Eastern Equatorial Pacific Ocean. Federal Register 68, 17909–17920 (2003); LGL Ltd. Marine
Mammal Monitoring During Lamont-Doherty Earth Observatory’s Acoustic Calibration Study in the
Northern Gulf of Mexico, 2003. LGL Rep. TA2822–12. Report from LGL Ltd. To Lamont-Doherty
Earth Observatory, Columbia University and the National Marine Fisheries Service, Silver Spring, MO
(2003).
4WEIR AND DOLMAN
2.1. Avoidance of Sensitive Areas
Most regional guidelines loosely define sensitive areas as breeding, feeding,
or migration habitat for marine mammals. While many guidelines request
more stringent mitigation procedures within such areas and suggest planning
surveys to avoid sensitive times/areas, the only regions for which seismic
survey closed seasons appear to be clearly defined and implemented are Brazil
where prohibited areas exist for breeding humpback Megaptera novaeangliae
(Jul–Nov) and southern right whales Eubalaena australis (Jun–Dec), nesting
areas for marine turtles (Oct–Feb) and manatee habitat (Sep–May, some
areas permanently closed) (reported in Brazilian Environmental Licensing
Guide),10 and Australia where the Marine Mammal Protection Zone in the
Great Australian Bight is permanently closed due to the sensitivity of southern
right whales and Australian fur seals Arctocephalus pusillus.11
2.2. Operational Procedures
2.2.1. Soft Start
Common to mitigation guidelines worldwide (Table 1) is the requirement
for a soft start or “ramp-up.” Soft start incorporates a gradual build-up of airgun
sound level over time, with the aim of warning marine mammals and allowing
them to depart the area of a seismic survey before sound levels peak. In most
regions it is stated that soft start should have at least 20 min duration and, in
some regions, an upper limit of 40 to 45 min is also provided to attempt to
minimise airgun disturbance.
2.2.2. Minimising Airgun Sound Propagation
The guidelines for the UK, Brazil, California, Sakhalin, and New Zealand
emphasise the requirement to use airgun arrays of lowest practicable volume
throughout. In the UK and New Zealand it is also requested that operators
minimise unnecessary high frequency sound and in Sakhalin it is required that
operators configure the airgun array to minimise horizontal sound propagation.
2.2.3. Restrictions on Airgun Use
Due to the ineffectiveness of visual monitoring at night there are vary-
ing requirements for using airguns during darkness. These range from the
continued use of airguns with no mitigation measures (UK), the use of night-
vision binoculars to carry our short-range visual monitoring (Australia and
California), the use of passive acoustic monitoring in sensitive areas (Canada)
and the use of a “warning” small volume airgun throughout night-time
10 IBAMA, Brazilian Environmental Licensing Guide. Atividades de S´
ısmica Mar´
ıtima na Costa
Brasileira, available at http://www.anp.gov.br/ibamasismica/ (Last viewed May 2006) (2005a).
11 Sarah J. Dolman. Noise Pollution and International Best Practise.J.INT.WILDLIFE LAW &POL’Y
(In press).
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 5
line changes (Gulf of Mexico, California, Brazil, and New Zealand). The
Californian guidelines include the possibility that airguns may operate only
during daylight hours. In most regions it is stated that airguns should be
shut-down completely (and a visual watch maintained) during daylight line
changes. In New Zealand and California, however, it is recommended that a
small airgun is active throughout all line changes.
2.2.4. Operational Shut-Downs
Seismic vessels occasionally need to stop firing airguns for operational
reasons including noise recordings, maintenance and repairs. In most regions
a period of acceptable shut-down has been stated, for which a full soft start
would not be required. In the UK and Brazil the permitted period is five
minutes. The Gulf of Mexico and New Zealand permit a 20 minutes shut-down,
while Canada allows the longest shut-down at 30 minutes. The California and
Sakhalin guidelines state that soft start is required following every power
down of the source.
2.3. Detection and Real-Time Mitigation Procedures
2.3.1. Visual Detection
Visual monitoring is the primary (and usually sole) method of animal
detection in all regions (Table 1). Notwithstanding external influences (such
as weather conditions), the efficacy of visual detection depends on factors
including the number of marine mammal observers (MMOs) present, their
experience, the regularity of their breaks, their dedication, their objectivity
(crew member or independent consultant), their enthusiasm, and their level
of training. The guidelines vary in their stated requirements for MMOs.
Those with stated shut-down procedures should require several MMOs to
ensure effective monitoring throughout all daylight hours. This is the case
in California, Brazil, the Gulf of Mexico, and Sakhalin (Table 1) where at
least two dedicated and trained MMOs must be on watch throughout the day.
Australia and Canada, however, do not require an MMO to be on watch all
daylight hours despite the prevailing shut-down policy.
Most regions accept the use of trained crew members to carry out MMO
duties, with the exception of sensitive areas where experienced biologists are
requested. The only regions where it is stated that a professional, experienced,
dedicated and trained MMO is required for all surveys are California and
Brazil. While most regions require a visual watch 360◦around an airgun
source prior to use, Australia appears to require visual observations only
forward and abeam of the survey vessel.
2.3.2. Species for Which Mitigation Applies
The UK, California, Brazil, New Zealand, and Sakhalin include all
marine mammal species within the mitigation measures (to varying extents).
6WEIR AND DOLMAN
In Australia, the Gulf of Mexico, and Canada, mitigation measures apply only
to whale species and exclude dolphins, porpoises, and pinnipeds.
2.3.3. Exclusion Zone
The exclusion zone (EZ) (or ‘safety zone’) is usually defined as the
radius around an airgun source within which real-time mitigation measures
are implemented if animals are detected. The UK, the Gulf of Mexico, and
Canada designate a 500 m EZ for all mitigation measures. Australia has the
largest designated EZ at 3000 m. In Brazil, the 500 m EZ is used for airgun
shut-down, but a more precautionary 1000 m EZ is used for delays to soft
start. In New Zealand, a 200 m EZ is used to delay soft start for most marine
mammals, but for stated species of concern a 1500 m EZ is used for delays and
a 1000 m EZ for shut-downs. In Sakhalin a 250 m EZ has been designated for
pinnipeds, while a standard 1000 m EZ is used for cetaceans. However where
feeding groups of western gray whales Eschrichtius robustus are observed,
an EZ of 6–7 km may be implemented.12 In California the EZ is defined as
the “radius of received sound levels believed to have the potential for at least
temporary hearing impairment,” and is calculated on a survey-specific basis
according to the calculated radius of the 180-dB re 1 µPa (rms) radius around
the source13 (all sound levels reported in this article are rms re 1µPa unless
otherwise stated).
2.3.4. Pre-Shoot Watch
The pre-shoot watch (the watch carried out for marine mammals prior
to starting up the airgun source) is required to be at least 30 min in all regions,
with the exception of Australia where a 90 minute pre-shoot watch is required
(Table 1).
2.3.5. Soft Start Delay
A delay to commencement of airgun operation if relevant marine mammal
species are observed within the EZ during the pre-shoot watch is a standard
mitigation measure applied in all regions. In Australia, the Gulf of Mexico,
and Canada, mitigation measures apply only to whales and airgun use is
permitted when dolphins, porpoises, or pinnipeds are within the EZ. After
implementing delays, it is generally stated that airguns may not be activated
until the animal is observed to depart the EZ (It is unclear in some guidelines,
12 SEIC, Western Gray Whale Environmental Impact Assessment. Draft 1. Chapter 7.2.4. Produced by
LGL Ltd for Sakhalin Energy Investment Company (2005).
13 HESS, (High Energy Seismic Survey) Review Process and Interim Operational Guidelines for Marine
Surveys Offshore Southern California.R
EPORT FROM THE HIGH ENERGY SEISMIC SURVEY TEAM FOR
THE CALIFORNIA STATE LANDS COMMISSION AND THE US MINERALS MANAGEMENT SERVICE PACIFIC OUTER
CONTINENTAL SHELF REGION, California (1999).
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 7
however, whether a further clearance delay is required or whether the soft start
can commence immediately that animals depart the EZ) or, if it submerges
and is not detected again, until a designated time after it was last observed
within the EZ (30 min in most regions).
2.3.6. Shut-Downs (Stop Work Procedure)
Most regions require a shut-down of the airguns whenever designated
species approach within the EZ. The exception is the UK, where no shut-down
procedure is required on the basis that animals “choose” to approach active
airguns of their own accord.14 In Brazil, California, and Sakhalin shut-down
occurs for all marine mammal species, while only whales warrant shut-down in
Australia and the Gulf of Mexico. In Canada and New Zealand, shut-downs are
requested only for stated species of concern. New Zealand is the only region
for which a larger shut-down EZ is designated when species of concern are
accompanied by calves. When shut-downs occur, all regions request a 20–30
min delay in gun use following the observation, or a delay until the animal is
observed outside of the EZ (again it is often unclear whether airguns can then
resume immediately or whether a further 30 min clearance period is required).
Most regions also require a full soft start procedure following marine mammal
shut-downs. It is unclear whether subsequent soft start is a requirement in all
guidelines, particularly in regions where airgun operations are permitted to
resume immediately that an animal departs the EZ and the total shut-down
period may be relatively short. For example, Canada states that a soft start
is only required for marine mammal shut-downs exceeding 30 min, and this
may also be the case in other areas.
2.3.7. Passive Acoustic Monitoring (PAM)
Although most guidelines acknowledge the potential value of real-time
passive acoustic monitoring (listening for vocalising animals) for mitigation,
it is not yet a mandatory procedure in any region. However, PAM may be
recommended by the regulating body as a back up to visual observation
in some sensitive areas, particularly deep water areas where sperm whales
Physeter macrocephalus are expected to occur (e.g., west of Scotland in the
UK).15 There are some specific mitigation measures relating to PAM in the
UK, the Gulf of Mexico, and Canada. In the UK, a delay to airgun use is
required if marine mammal sounds are detected within 500 m of the source
based on (a) software estimates or (b) judgement of the PAM operator. Canada
implements a similar delay to soft start when PAM is used, but applied only
to selected whale species. In the Gulf of Mexico, the use of PAM at night
14 JNCC, Guidelines for Minimising Acoustic Disturbance to Marine Mammals from Seismic Surveys.
Joint Nature Conservation Committee, Peterborough, UK (2004).
15 Id.
8WEIR AND DOLMAN
(or poor visibility) allows soft start to commence when it would otherwise
require visual monitoring or the continued use of a small airgun.
3. SEISMIC GUIDELINE LIMITATIONS
3.1. Operational Procedures
3.1.1. Soft Starts
Although the soft start procedure is the most widely used seismic
mitigation measure and, in some areas, comprises the sole measure used
at night, its effectiveness for at least some species has been the subject of
considerable debate. Beyond this basic shortcoming, the practice is also
limited by certain limitations in its application. The existing guidelines on
how to operate a soft start are ambiguous and state only that power should be
built up slowly over time, e.g., starting with the smallest airgun in the array
and gradually adding in others over 20 min. Only in the Gulf of Mexico,
Canada, and Brazil, is it stated that the smallest airgun means in terms of
energy output (dB) and volume (in3). The exact energy output requirement
for the first stage of soft start is not provided by any regional guidelines and
nor is there guidance on the level of acoustic output that should be added-in
during each subsequent stage of soft start, with the exception of the California
guidelines which request an energy increase of 6 dB per min.16
Soft starts are currently conducted in a variety of ways, varying from add-
ins of individual guns every 30 sec to add-ins of several guns simultaneously
every few minutes. The required minimum soft start duration of 20 min is
predetermined in all regional guidelines, and makes no allowance for variation
in airgun volume. Since the airguns used during modern 2D/3D/4D seismic
surveys vary from a few hundred to over 10,000 in3, the designation of single
soft start duration may be inappropriate. The requirement for soft start during
periods of gun testing (when only one sub-array might be active) is also poorly
defined in all guidelines.
Independent monitoring of the soft start procedure in the field is chal-
lenging since it is operated from the vessel’s instrument room and there is no
automated record. On most vessels soft starts are carried out manually (with
each gun(s) added in by switch at an appropriate time), and the precision of
the soft start procedure therefore relies entirely on the aptitude and interest
of individual seismic crew. On a minority of vessels the soft start is computer
automated (each gun(s) automatically added in at predetermined shot points),
providing a more reliable method of increasing sound level than manual
operation. Logging of soft starts (as required to ensure compliance with the
16 HESS, supra note 13.
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 9
20 min duration) is also carried out by seismic crew and cannot therefore be
independently monitored by an MMO who is required to be on watch for the
soft start.
3.1.2. Airgun Use
Some regional guidelines require airguns to be active 24 hr throughout
a survey (e.g., Department Of Conservation, New Zealand),17 while others
require a small gun to be active throughout the night.18 It is unclear how such
measures minimise acoustic impact on the environment, and in particular
there is no evidence that continual firing of a small gun acts as a deterrent to
marine mammals. In contrast, some studies suggest that some species such as
humpback whales may actively approach small volume airguns.19 Importantly,
although some guidelines suggest using airguns of “lowest practicable level”
during seismic surveys, it is unclear how or even whether this is regulated. It is
not stated that airgun use should be restricted to the allocated survey prospects.
In some regions weather downtime and maintenance may result in seismic
vessels straying far from their licensed prospect area (and sometimes into
more sensitive habitat), where airgun testing might occur. There are concerns
over the cumulative impact of time-sharing (two or more vessels operating in
adjacent areas, which take turns firing airguns to avoid interference with one
another), which may produce 24 hr airgun sound when one vessel commences
soft start as another ends a line.
3.1.3. Monitoring in Adverse Conditions
All of the current guidelines depend solely on visual monitoring to detect
animals at the surface. This means that effectively no mitigation is in place for
seismic surveys occurring at night. While JNCC “encourage all seismic survey
operators to ensure that, as far as possible, soft starts occur during daylight
hours,”20 this would greatly restrict seismic operation production time and to
our knowledge has not been implemented. Currently none of the guidelines
have an outright restriction on airgun use at night. Although airgun start-up
is not allowed during darkness in some regions, operations are allowed to
continue at full volume providing that a small gun is kept active during line
17 Department of Conservation, Reference Document: Guidelines for Minimising Acoustic Disturbance
to Marine Mammals from Seismic Surveys.D
EPARTMENT OF CONSERVATION, Wellington, New Zealand
(2005).
18 MMS, NTL No. 2004-G01. Implementation of Seismic Survey Mitigation Measures and Protected
Species Observer Program.U
NITED STATES DEPARTMENT OF THE INTERIOR,MINERALS MANAGEMENT SERVICE
(2004).
19 Rob D. McCauley et al.The Response of Humpback Whales (Megaptera novaeangliae) to Offshore
Seismic Survey: Preliminary Results of Observations about a Working Seismic Vessel and Experimental
Exposures. APPEA JOURNAL (1998). Rob D. McCauley et al.Marine Seismic Surveys—A Study of
Environmental Implications. APPEA JOURNAL (2000).
20 JNCC, supra note 14.
10 WEIR AND DOLMAN
changes. In Australia and California airgun operations continue at night with
visual monitoring via infra-red/night vision binoculars, despite an effective
range of only around 100 m.
With the exception of reduced visibility (which is treated the same as
night operations), the guidelines do not address adverse weather conditions.
It is well documented, however, that detection of marine mammal species
decreases significantly with increasing sea state (particularly porpoises, Kogia
whales, beaked whales, minke whales Balaenoptera acutorostrata).21 Envi-
ronment Australia notes that the “upper limit for practical whale observation
is sea state 5, corresponding with the operational weather limit for most
seismic vessels.”22 But sea state 5 is not conducive to the detection of many
cetacean species. Furthermore, advancing seismic technology (e.g., OBC,
solid streamers) means that some seismic surveys frequently operate in sea
states greater than 5 with swell height representing the more usual operational
constraint. In the California guidelines there is some indication that when
weather deteriorates such that the MMO cannot effectively monitor the EZ
and there are known to be concentrations of animals in the area, a halt to gun
use might be imposed.23
3.2. Detection and Real-time Mitigation Procedures
3.2.1. Visual Detection
In addition to the limitations described above, visual detection is also
currently hindered by the lack of appropriate training programs for, and
independence of, MMOs. The regional guidelines vary considerably in their
requirements for MMOs, but none define the frequently used terms “trained,”
“experienced,” and “qualified.” At present the MMS guidelines are the only
ones to state the criteria for a “trained” MMO via the content of training
courses. Where stated, training involves attendance of a one-day theoretical
course,24 which does not include marine mammal field experience. It is not
a prerequisite to have any practical experience of marine mammals to work
as a MMO, and use of crew members is permitted in most areas. There is no
feedback or assessment of those MMOs working in the industry.
A further concern is the lack of independence of MMOs. This is most
apparent where MMOs are crew members or otherwise employed directly by
the seismic contractor, presenting a clear conflict of interests. Even when this
is not the case, provision of “independent” MMOs to the oil and gas industry
21 Clarke, R. An Index of Sighting Conditions for Surveys of Whales and Dolphins.REPORT OF THE
INTERNATIONAL WHALING COMMISSION, 32 (1982).
22 Environment Australia, supra note 8.
23 IBAMA, Guide for Monitoring Marine Biota During Seismic Data Acquisition Activities. IBAMA,
Brazil (2005b).
24 JNCC, supra note 14; MMS, supra note 18.
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 11
is usually controlled by industry-specific employment agencies, which does
not necessarily ensure that the most appropriate MMOs are used on each
survey. Direct reports from the MMO to the regulating body are a stated
requirement only in Brazil.25 In most regions it is usual for MMO reports to be
submitted to the regulator via the employment agency and oil/gas company,
thus compromising the independence of the reporting procedure.
Australia’s policy of visually monitoring for only 10 min every hour
cannot ensure adequate detection of cetacean species or effective implemen-
tation of the stated mitigation measures, particularly given the large exclusion
zone stated for this region.
3.2.2. Species Included
All marine mammals utilise sound and are potentially affected by seismic
surveys. Although some regions currently offer no protection to dolphins and
porpoises (Table 1), there is good evidence that small odontocetes experience
disturbance from seismic surveys.26 Emission of higher frequency sound
increases concern of the potential impact on toothed whales.27 All species
of marine mammal should therefore be included in seismic survey mitigation
measures.
3.2.3. Exclusion Zone
Defining an EZ is clearly a fundamental component of the real-time
mitigation measures used during seismic surveys. However, the basis for
defining EZs remains unclear in most cases. Some of the regional guidelines
attempt to provide a scientific basis for the determination of these EZs. For
example, the Canadian guidelines suggest that behavioural and harmful effects
may be produced in marine mammals by 160 dB re 1 µPa and 180 dB re 1 µPa
respectively,28 while the existing Sakhalin guidelines calculate EZs according
to received levels of 190 dB re 1 µPa for pinnipeds and 180 dB re 1 µPa
for cetaceans.29 We note, however, that a received level of 120 dB re 1 µPa
was recently identified at a scientific workshop as the appropriate EZ standard
for protecting critically endangered Western gray whales during construction
25 HESS, supra note 13.
26 For example, John C. Goold. Acoustic Assessment of Populations of Common Dolphin Delphinus
Delphis in Conjunction with Seismic Surveying.J
OURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE
UNITED KINGDOM, 76 (1996); Caroline J. Stone. The Effects of Seismic Activity on Marine Mammals in
UK Waters, 1998–2000.JNCCR
EPORT NO. 323. Joint Nature Conservation Committee, Aberdeen, UK
(2003).
27 Peter T. Madsen et al.Quantative Measures of Air Gun Pulses Recorded on Sperm Whales (Physeter
macrocephalus) Using Acoustic Tags During Controlled Exposure Experiments.P
APER PRESENTED TO
IWC SCIENTIFIC COMMITTEE (2006).
28 Department of Fisheries and Oceans. Statement of Canadian Practice: Mitigation of Seismic Noise in
the Marine Environment (2005).
29 SEIC, Supra note 12.
12 WEIR AND DOLMAN
activities off Sakhalin Island.30 The New Zealand guidelines state that, “It is
generally accepted that noise levels below 180 dB re 1 µPa (rms) are unlikely
to cause any loss of hearing (temporary or permanent) or physiological damage
to cetaceans”.31
The HESS panel was the first to introduce a scientific basis for the EZ
in 1999, defining the EZ by the 180-dB radius since this was the received
sound level believed to have potential for auditory injury.32 The safety of this
level remains unverified, however, and recent evidence suggests that physical
injury and strandings may be induced at received sound levels far lower than
180 dB re 1 µPa.33 Except in California, none of the guidelines that use an
isopleth-based standard provide information on the distance that the isopleth
extends from the source, and none of the guidelines that use a radius-based
standard take into account the properties of individual survey areas (water
type, depth), or airgun arrays (volume) when determining the EZ.
Rather, the same generic value for EZ (from 200 m for some species
in New Zealand to 3000 m for whales in Australia) applies regardless of
whether airgun array volume is 10 in3or 10,000 in3, or the survey area in
deep, shallow or shelf edge waters. For example, the New Zealand guidelines
state that, “based on vessels operating 2000–3000 in3arrays at full power,
several studies indicate that the 180 dB re 1 µPa (rms) threshold correlates
well with a 1 km distance in most scenarios.”34 If 1 km has been calculated
as the 180 dB EZ for this region, then the basis for the 500 m EZ designated
by the UK, Gulf of Mexico and Canada should be questioned. And given that
airgun arrays reach volumes four times larger than the 2000–3000 in3quoted
in this statement, there is clearly a need to incorporate the effect of varying
airgun volume on EZ calculations.
Only in California is a considered evaluation of the basis for the EZ
provided, where a site-specific EZ is calculated during the survey application
process based on the specific survey parameters provided by the operator.
The mitigation guidelines implemented during some research-related seismic
surveys do take into account the variation in airgun volume on the EZ. For
example, modelling has shown that the 180 dB re 1 µPa (rms) EZ for a
relatively small 210 in3airgun array is expected to extend to only 50 m around
the source, but may comprise a 950 m radius around an 8600 in3airgun
30 IUCN. 2006. Report of the interim independent scientists group (IISG) on mitigation measures to protect
Western gray whales during Sakhalin II construction operations in 2006. Workshop convened by the
IUCN, Vancouver, British Columbia, 3–5 April 2006.
31 DOC. 2005. Draft Guidelines for Minimising Acoustic Disturbance to Marine Mammals from Seismic
Survey Operations. Department of Conservation, Wellington, New Zealand. November 2005.
32 HESS, supra note 13.
33 Dolman, S.J. and Simmonds, M.P. 2005. Noise pollution—some thoughts on mitigation and wider
protection. Paper SC/57/E9 presented to the Scientific Committee of the International Whaling
Commission.
34 DOC, supra note 31.
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 13
array.35 Models and subsequent field measurements in the Gulf of Mexico
clearly showed that the EZs for the received sound levels relevant to current
marine mammal mitigation (160 to 190 dB) increase markedly with airgun
volume.36 The effect of variation in water depth on received sound levels from
airgun arrays has also been studied using modelling and field verification,
indicating that the EZ for a 20-gun array at a measured precautionary sound
level of 160 dB re 1 µPa (rms) may be around 2.5 km in deep water (∼3200
m) but extends to over 12 km in a shallow water (∼30 m) area.37 Clearly, the
use of a single standard EZ value for all seismic surveys regardless of airgun
volume or water depth is inappropriate.
Although these field calibrations were conducted during a research-
related seismic survey,38 both the California and Sakhalin mitigation guidelines
recognise that exact sound levels can be relatively easily measured in the field
using existing industrial seismic equipment, and the EZs subsequently revised
according to measured sound levels. A recent study of sperm whales exposed
to seismic pulses found that the received sound level of the first pulse was
similar at ranges of 2 to 12 km from a seismic array, with secondary pulse
arrivals having higher received levels at 5 to 12.6 km from the source than
at closer range.39 This emphasises a need for measurements to be made at
extended distances from the source vessel and appropriate EZs designated.
3.2.4. Pre-Shoot Watch
The 30 min pre-shoot watch was originally defined by the JNCC for
the UK’s continental shelf (<200 m) waters. Only Australia has designated
a longer pre-shoot watch period (90 min), with all other areas retaining the
30 min watch regardless of water depth. Although 30 min might be adequate
for detecting shallow-diving shelf species, it is not necessarily appropriate in
deep water areas where the known dive times of some species (e.g., sperm
whale, beaked whales) regularly equals or exceeds this duration.
3.2.5. Soft Start Delays
The soft start delay for animals observed within the EZ is now standard
practice within the seismic industry and there are relatively few problems with
its implementation. However some of the regional guidelines remain unclear
on the required duration of the delay, and whether soft start can commence
immediately after animals depart the EZ or whether a 30 min clearance period
is required. Some operators now commence soft start much earlier in a line
35 LGL, supra note 8.
36 Tolstoy, M. et al. Broadband Calibration of R/V Ewing Seismic Sources.GEOPHYSICAL RESEARCH LETTERS,
31 (2004).
37 Id.
38 Id.
39 Madsen, supra note 27.
14 WEIR AND DOLMAN
change than is required operationally, in order to allow for potential delays
due to marine mammals and avoid circling. This tactic results in increased
airgun noise in the environment and should be prohibited.
3.2.6. Shut-downs
Only Brazil, California, and Sakhalin implement shut-downs for all
marine mammals. Given the evidence that small odontocetes may be sensitive
to disturbance from seismic surveys,40 it is appropriate for all regions to
apply shut-down for all cetaceans. As in New Zealand, specific shut-down
procedures should be considered for calves, which might be more sensitive
to anthropogenic sound than adults. While shut-down is a straightforward
mitigation technique, it is only possible to implement the procedure during
daylight as it relies upon visual detection. Following a shut-down procedure,
it is unclear in many of the regional guidelines whether airgun use can resume
immediately that the animals depart the EZ or whether a further 30 min
clearance period is required. While most guidelines stipulate that a full soft
start is required following shut-down for marine mammals, Canada requires
a soft start only if the shut-down exceeds 30 min duration. Potentially, this
means a temporary pause in airgun use simply as an animal passes through the
500 m EZ, with the guns suddenly activated again at full volume. This does
not appear to be a precautionary use of airguns given that animals may be only
500 m from the guns when they are activated again at full power. Similarly,
the period of accepted shut-down for “operational reasons” currently ranges
from 5 to 30 min according to region.
While the UK and Gulf of Mexico guidelines specify that operational
shut-down periods are only permitted if a visual watch is maintained, the
other guidelines omit this clause and therefore allow such shut-downs at night
when no monitoring can occur. Where shut-down procedures are required, it is
logical that several dedicated MMOs are used to cover all daylight hours and
to ensure detection and species identification of animals out to the required EZ
ranges of up to 3000 m. Australia’s policy of monitoring for only 10 min every
hour cannot allow effective implementation of the shut-down procedure.
3.2.7. Passive Acoustic Monitoring
Although passive acoustic monitoring is recognised as a potentially
valuable detection technique within most of the regional guidelines, its full
potential use in seismic mitigation is not yet realised. There are a variety
of PAM systems that can be used to detect cetaceans (e.g., towed arrays,
bottom-mounted hydrophones, sonobuoys). The system usually employed
during seismic surveys is the towed array, since airguns are mobile and require
a mobile mitigation system.
40 Goold, supra note 26; Stone, supra note 26.
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 15
The essence of existing seismic survey mitigation is to detect animals
within the EZ and implement the relevant measures, and PAM will become
more successful as a mitigation tool if it is able to: (a) reliably detect a
significant number of vocalising marine mammal species within the EZ, (b)
reliably identify each marine mammal species (where guidelines are species
selective), and (c) provide a reliable range measurement to the animal. Use
of PAM as a seismic mitigation tool is currently limited by the fact that
animals are not always vocal, the seasonality in vocal activity of some species
(e.g., baleen whales), lack of knowledge regarding sounds produced by some
species (e.g., beaked whales), difficulty in species identification, the variable
detection range between species, lack of accurate range estimation (currently
often based on operator interpretation) and the regular masking of lower
frequencies (those used by baleen whales) by vessel noise. To date PAM
towed arrays have usually been deployed from the chase (guard) vessel which
is often positioned over 1 km ahead of the seismic vessel itself so that PAM
monitoring occurs too far from the airguns to be effective.
The use of PAM is also constrained by the lack of guidance for its imple-
mentation and the lack of training programmes in its use. Establishing whether
a marine mammal is within 500 m of the airgun array often depends on the
judgement of the PAM operator rather than on objective software.41 As pointed
out by Barlow and Gisiner,42 acoustic detection improves tremendously if an
observer knows what to listen for, and the development of training programs
for the use of PAM should be a priority.
3.3. General Issues
3.3.1. Sensitive Areas
All of the regional guidelines recognise sensitive areas for marine
mammals, but there is little rigorous definition of these areas and how they
apply to seismic survey applications. Only Brazil (reported in Environmental
Licensing Guide)43 and Australia44 have allocated defined prohibited areas for
seismic surveys due to marine fauna. Avoidance of seismic surveys in sensitive
habitat is the most effective and straightforward mitigation measure that can be
applied to protect marine mammals and more regions should define this option.
3.3.2. Other Sources of Disturbance
Seismic surveys often incorporate a range of vessels, including chase
(guard) vessels, supply boats, undershoot vessels, workboats, and crew boats.
41 JNCC, supra note 14.
42 Jay Barlow & R. Gisiner. Mitigating, Monitoring and Assessing the Effects of Anthropogenic Sound on
Beaked Whales.J
OURNAL OF CETACEAN RESEARCH AND MANAGEMENT 7 (2006).
43 IBAMA, supra note 10.
44 Dolman, supra note 11.
16 WEIR AND DOLMAN
These vessels also have the potential to disturb marine mammals, and guide-
lines for minimising impact to marine mammals need to address all activities
related to seismic surveys and not simply airgun noise. Only the Brazilian
guidelines state that it is prohibited to attempt to deliberately move animals
out of the EZ,45 a matter that has arisen in other areas.
3.3.3. Ineffectiveness of Existing Mitigation Techniques
While visual detection is a reasonable method for detecting some marine
mammals in the vicinity of a seismic survey (given favourable weather and
daylight), it remains ineffective for certain species such as beaked whales46 and
small inconspicuous animals such as Kogia whales and porpoises. These same
species may be difficult to detect acoustically, for example the vocalisations
of beaked and Kogia whales are poorly known. All marine mammal species
are currently poorly protected at night. Where visual observations do occur at
night47 they are only realistically likely to detect bow-riding dolphins due to
limitations of night vision equipment. The use of acoustic monitoring at night
will detect only vocalising animals and is therefore very limited for species
that are largely non-vocal or which aren’t vocalising at the time. The use of
the currently available acoustic equipment is also hindered by ship-produced
noise.
A further inefficiency of the existing mitigation methods is that the MMO
must visually observe the marine mammal entering the EZ before mitigation
can be requested. This does not adequately mitigate for deep-diving species
such as sperm and beaked whales that may dive ahead of the survey on the
vessel’s trackline. For example, since sperm whales typically dive vertically
during the first portion of their dive,48 animals seen to fluke and commence a
dive ahead of the ship may remain submerged on the trackline and enter the EZ
without being visually detectable within the EZ by the MMO. No mitigation
measures could be applied to probable submerged animals under the present
regional guidelines. The MMS guidelines alone define the EZ as “the area
at and below the sea surface within a radius of 500 meters surrounding the
centre of an airgun array and the area within the immediate vicinity of the
survey vessel.” Mitigating for animals below the sea surface is clearly limited
using only visual methods.
3.3.4. Enforcement of Mitigation Methods
While the mitigation measures outlined within the guidelines in Table 1
are a licensing requirement for operators working in those particular regions,
there is little obvious enforcement by the regulating bodies. There appears
45 IBAMA, supra note 23.
46 Barlow, supra note 42.
47 For example, Environment Australia, supra note 8.
48 Hal Whitehead. SPERM WHALES:SOCIAL EVOLUTION IN THE OCEAN. (2003).
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 17
to be no onboard monitoring (or feedback system) of the effectiveness of
guidelines, no evaluation of the mitigation procedures and no repercussions
for operators that fail to comply with the guidelines, e.g., soft starts below the
required duration. This is partly a result of the reporting procedure in most
regions, whereby MMO reports are relayed via the contractor/agency before
reaching the regulating body. Mitigation measures would be better enforced
if the regulating body (or equivalent independent body) was responsible for
providing MMOs to industry, and if those independent MMOs were required
to report directly to the regulating body, as is the case in Brazil.
3.3.5. Regional Application of Guidelines
Although the guidelines summarised in Table 1 are now being used
within those particular geographic regions, the majority of the world’s oceans
are still open to seismic surveying without any marine mammal mitigation
procedures in place. Some of the regional guidelines are selective regarding
inclusion of their own waters, for example in most of the Gulf of Mexico the
MMS guidelines apply only to water depths greater than 200 m49 providing no
protection for marine mammals in shelf waters. In regions where no statutory
legislation exists for the protection of marine mammals, many seismic surveys
occur within sensitive habitats without any consideration of marine fauna.
4. ADDITIONAL MITIGATION MEASURES
Although there are a number of mitigation measures (e.g., acoustic deterrent
devices, bubble screens) currently used to mitigate the effects of other an-
thropogenic sound sources on marine mammals, many of these are unsuitable
for use during seismic surveys due to the mobility of the airguns. There are
several other technologies/measures, however, that could be developed for
seismic surveys in the future.
4.1. Closed Areas
The simplest way to mitigate the effects of seismic surveys on marine fauna
is to avoid animals either in space or time. This measure requires knowledge
on the distribution, density and seasonal occurrence of cetaceans in an area,
which is lacking for many parts of the world. In some regions the occurrence
of marine mammals is well documented, and simple closed (temporary or
permanent) areas could be implemented to ensure protection. For example,
humpback whales are a predictable species that return annually to traditional
breeding and feeding grounds. Brazil is the only country for which designated
closed areas are clearly defined, and a seasonal closed area to protect breeding
humpback whales exists between July and November. There are other areas
49 MMS, supra note 18.
18 WEIR AND DOLMAN
worldwide where similar breeding humpback whale populations are currently
offered little or no protection from seismic surveys, notably on the west coast
of Africa where the Angola and Gulf of Guinea breeding grounds overlap
with an area of increasing seismic survey activity.
The designation of closed areas is most effectively implemented at the
government level in each region as part of standard statutory guidelines,
where the legislation applies to and is adopted equally by all licensees.
Regional authorities can also recommend closed areas (e.g., regional seas
agreements), though their recommendations may have only limited force of
law. In some regions worldwide there is little awareness of the potential effects
of seismic activity on marine mammals, and such countries should be strongly
encouraged to consider marine mammal issues during the licensing procedure.
4.2. Passive Acoustic Monitoring
Although various types of acoustic monitoring are available, only the towed
array is currently used during seismic surveys due to the mobility of the
source. The limitations of the current towed array equipment have been
considered above, but with advancing technology it is likely that PAM will
provide improved detection ability in future years. Both the UK and Canadian
guidelines note that improvements in technology are likely to make PAM a
requirement in the future. It has been suggested that marine mammal PAM
equipment could eventually be incorporated into the standard seismic cables
towed behind a seismic ship to solve current deployment problems.
4.3. Active Sonar
Active sonar comprises emission of a sound signal that reflects off submerged
objects and back to a signal receiver to produce a 3D image of the water
column. There is potential for the use of high-frequency active sonars for the
detection of marine mammals within a short distance of an airgun array. But
the system requires further work to reduce false triggers and increase species
identification, and there are important concerns over the potential adverse
effects from this additional sound energy on cetaceans.
4.4. Equipment Modification / Development
The development of new technology as an alternative to airgun sound should be
encouraged. For example, there is a marine vibrational device being developed
as an alternative to airgun arrays, which has a lower peak amplitude, slower
rise time and significantly less energy above 100 Hz.50 Operators should aim
to reduce unnecessary output of incidental high frequencies from airguns, and
50 Smith, J.G. & M.R. Jenkerson. Acquiring and Processing Marine Vibrator Data in the Transition Zone.
Mobil Exploration and Producing Technical Centre (1998).
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 19
ensure that airguns are configured so that horizontal propagation of sound is
minimised.51 Equipment to improve visual monitoring during night and poor
visibility should also be developed, with potential uses of infrared equipment
and millimeter waves radar.52 While some engineering modifications have
been encouraged for years in some regions (e.g., baffling of higher frequency
sound requested by the JNCC), there have been no statutory requirements to
do so or to conduct relevant research.
4.5. Additional Monitoring Platforms
The Californian, Australian, and Sakhalin guidelines mention the use of aerial
surveys before, during, and after seismic surveys in sensitive areas to monitor
for concentrations of whales. This information can subsequently be used in
real-time planning of seismic data acquisition and assessing marine mammal
responses to the sound source. The use of additional, dedicated research
vessels may also be useful to survey the areas ahead of seismic vessels and
provide advice on the occurrence of animals.
5. GUIDANCE TOWARDS A WORLDWIDE INDUSTRIAL
STANDARD
As reviewed above, the statutory marine mammal mitigation guidelines in
use during industrial seismic surveys worldwide show significant variation
in most parameters between regions. This lack of consistency needs to be
addressed so that a minimum “best practice” with a scientific basis offering
adequate protection to all marine mammal species is adopted worldwide.
Guidance is also needed for the management of industrial seismic surveys
in waters where no statutory guidelines currently exist, for example in the
Indian Ocean and off West Africa. In the absence of standard international
guidelines, industrial seismic surveys in such areas are presently carried out:
(a) without any mitigation measures in place, or (b) using guidelines from
other countries. The UK guidelines are often perceived as incurring least
disruption to a survey,53 and are most commonly adopted by operators in those
regions without statutory guidelines (e.g., West Africa). However, the JNCC
guidelines do not constitute best practice for protecting marine mammals,
since they have no scientific basis and were developed for the UK’s shallow
continental shelf area54 which may not be appropriate for deep-water areas or
for marine mammals (and turtles) found in other regions.
51 JNCC, supra note 14.
52 HESS, supra note 13.
53 IAGC Statement of Principles. Marine Mammal Protection (2006).
54 JNCC, supra note 14.
20 WEIR AND DOLMAN
The marine mammal mitigation procedures implemented during some
research-related seismic surveys are prime examples of exemplary adaptive
management, involving a rigorous application process and developing a vari-
ety of mitigation measures specific to the survey site, adopting a precautionary
approach, based on scientific data and embracing the full range of mitigation
procedures and technologies available.55 This process certainly comprises
current “best practice” for mitigating the potential effects of airgun sound on
marine mammals. This multi-faceted approach however, is not implemented
for industrial seismic surveys anywhere in the world; nor is it applied to
research seismic surveys in some areas. For example, Article 7 of the Protocol
on Environmental Protection to the Antarctic Treaty bans all mineral resource
activities in Antarctica,56 yet despite the sensitivity of the region, research
seismic surveys are permitted with only ad hoc marine mammal mitigation
in place that depends predominantly on the awareness and interest of the
individual operator.
In the absence of comprehensive mitigation procedures for many stan-
dard industrial seismic surveys and some research seismic surveys (par-
ticularly in regions where statutory guidelines do not exist), the following
points are recommended for inclusion as a minimal “best practice” mitigation
procedure.
5.1. Avoiding Densities of Animals
•Surveys should be planned so that entire habitats or migration paths
are not blocked, cumulative seismic sound is limited within any
particular area, and time-sharing is prohibited. In some areas there are
considerable scientific data supporting the occurrence of vulnerable
species and/or key marine mammal breeding/feeding/migratory habi-
tat. Where such evidence exists, closed areas (seasonal and/or year-
round as appropriate) should be designated similar to those existing in
Brazil (e.g., the Abrolhos Bank).57 Research should be prioritised in
those areas where the distribution, density and seasonality of cetaceans
in an area are not known.
•Closed areas should be surrounded by appropriate buffer zones. They
should be managed so that use of airguns is completely prohibited
within and adjacent to key habitats (spatial areas or water depths)
during particular seasons or on a year-round basis so that damaging
or disturbing noise levels are not created. Theycould also be managed
55 NMFS, supra note 9; LGL, supra note 9.
56 Protocol on Environmental Protection to the Antarctic Treaty (1991) available at http://www.cep.aq/
apa/legal docs/protocol.html (last visited 2/24/07)
57 Marcia H. Engel et al.Are Seismic Surveys Responsible for Cetacean Strandings? An Unusual Mortality
of Adult Humpback Whales in Abrolhos Bank, Northeastern coast of Brazil. Paper SC/56/E28 Presented
to the Scientific Committee of the International Whaling Commission (2004).
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 21
so that only very low noise output surveys (e.g., High Resolution, site
surveys) can be considered to occur within sensitive areas during key
seasons.
•Closed areas and buffer zones need to be defined clearly in the regional
mitigation guidelines, so that all operators and companies are equally
subject to and aware of restrictions.
5.2. Onboard Mitigation Procedures
•Mitigation measures should apply to all marine mammal species (and
turtles).
•At least one dedicated MMO should be on watch 24 hr (max 4 hr
shift), requiring at least two (and preferably three) dedicated and
qualified MMOs on every seismic vessel. While visual watches at
night are clearly limited in range, there are no other mitigation methods
available and visual observers would still detect those animals closest
to the ship where they are most vulnerable. Equipment including high
quality infra-red and night-vision binoculars should be provided to
the MMO for night time observations. Studies into their effectiveness
would be useful.
•Every seismic operator (irrelevant of geographical area and local
conditions) should implement a soft start procedure for every use
of the airguns. Soft start should commence with a small, individual
gun (i.e., <70 in3), and increase by stages of approximately 6 dB
per minute. Total soft start duration will therefore be proportionate to
airgun volume, with larger volume arrays taking longer to complete
soft start than small arrays. This procedure can be applied in an
easily interpreted manner to all gun testing. All soft starts should
be automated, to reduce potential operator inaccuracy. All soft starts
should commence as close to start of line as practical to minimise
airgun noise during line change.
•The use of the lowest practicable airgun volume should be defined and
enforced. Small airguns should not be kept active during line changes
(to avoid habituation or positive approach), and airgun use should be
prohibited outside of the licensed prospect area.
•There should be a scientific basis for the exclusion zone rather than an
arbitrary designation. Although a received level of 180 dB re 1 µPa
(rms) is generally considered to be the likely injurious sound level
for marine mammals, this may not be adequately precautionary and
protective.58 Marine mammal behavioural responses have occurred at
58 Sarah J. Dolman & M.P. Simmonds, Noise pollution—some Thoughts on Mitigation and Wider
Protection. Paper SC/57/E9 Presented to the Scientific Committee of the International Whaling
Commission (2004).
22 WEIR AND DOLMAN
received sound levels of at least 160 dB, and it is therefore recom-
mended that a precautionary received level of no more than 160 dB
re 1 µPa (rms) is used to calculate the EZ (this sound level may
need to be revised in the future should research indicate that animals
are more sensitive to sound than indicated at the present time). For
some endangered populations/species in important habitat that has
not been effectively closed (e.g., Western gray whales on their feeding
grounds off Sakhalin Island), a more precautionary lower sound level
should be used and EZs may be correspondingly greater. EZ values
should be calculated by the operator prior to the application process,
using site-specific transmission loss modelling based on airgun array
parameters and the bathymetry, water properties and sound velocity
profiles of the water column within the prospect area. The EZ value
should be verified in the field at the start of the survey. During long
duration surveys, the EZ should be regularly recalculated. We also
recommend that the criteria used to calculate exclusion zones should
regularly be reviewed.
•There should be a dedicated pre-shoot watch of at least 30 min. In
areas where water depths exceed 200 m, the watch should be at least
60 min to help increase the probability that deep-diving species are
detected.
•There should be a delay to commencement of soft start for all marine
mammal species (and marine turtles) observed within the 160-dB EZ.
Soft start may not begin until 30 min after the animals depart the EZ
or 30 min after they are last seen.
•There should be a shut-down of the airguns whenever a marine mam-
mal (or marine turtle) is seen to enter the 160-dB EZ. Constant radio
communication is required between the MMO and the Instrument
Room to ensure shut-downs are instantaneous. Following a shut-down,
a full soft start is mandatory. Soft start should not begin until 30 min
after the animals depart the EZ or 30 min after they are last seen. The
permitted shut-down of airguns for operational purposes should be no
longer than 5 min without requiring full soft start.
•Extra mitigation measures should be applied in deep water areas
for sperm and beaked whales seen diving on the vessel trackline.
Assuming an average survey speed of 4.5 kts and a 15 min mean
vertical descent period for sperm whales,59 a whale diving within 2 km
ahead of the airgun source may remain on the vessel trackline until
the ship draws level before it commences horizontal movement. It is
therefore recommended that for sperm and beaked whales, soft start
59 Whitehead, supra note 48.
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 23
delays and shut-down procedures are applied to animals seen diving
within 2 km ahead of the source, even if outside of the EZ at the time
of last visual confirmation.
•Ideally, airgun use should be prohibited at night since current mitiga-
tion techniques are inadequate to detect marine mammals. Restricting
airgun use to daylight hours should certainly be considered in particu-
larly sensitive areas (breeding, feeding and migratory zones). However
there is a trade-off between allowing continual 24 hr airgun use and
completing the survey earlier, or restricting airgun use to daylight
only and having a much longer survey duration and possibly greater
impact on the region. To ensure that seismic surveys have minimal
overall duration within an area, airgun use should be permitted at
night (outside of sensitive areas) on condition that visual watches are
maintained using night-vision / infra-red binoculars. PAM should also
be used as an additional night time mitigation measure in areas where
species suitable for acoustic monitoring occur (e.g., deep-water areas
inhabited by sperm whales). Soft starts remain mandatory, and periods
of extra gun use (such as testing) should be restricted to daylight hours.
•Because of the impact of adverse weather conditions on the visual
detection of marine mammals, airgun use during unfavourable condi-
tions (at least Beaufort sea state ≥4, swell ≥2 m, visibility ≤1km)
should be restricted (both night and day). This measure is particularly
important at night when visual observations are already hindered. In
relatively more sensitive areas, gun use should be prohibited alto-
gether, but especially in unfavourable detection conditions. In other
areas, gun use should be permitted only if animal density in the region
is low and at least two MMOs maintain visual watch. PAM should be
used as an additional adverse weather mitigation measure, particularly
in deep-water areas.
•Disturbance from other vessels associated with the seismic operation
(e.g., guard vessels, supply boats, work boats, undershoot vessels
etc) should be minimised. In particular, vessels should be prohibited
from directly approaching cetaceans with the aim of ‘herding’ them
away from the area of seismic operations to avoid mitigation. Those
vessels free to manoeuvre should aim to provide at least 300 m clear-
ance around cetaceans, in consistency with standard recommendations
elsewhere.60
•MMOs should report directly to the regulating body throughout and on
completion of each survey to ensure that reports are received without
other involvement(i.e. reports should not go via a third party or be
60 Carole Carlson. A Review of Whale Watch Guidelines and Regulations Around the World. International
Fund for Animal Welfare (2004).
24 WEIR AND DOLMAN
subject to any editing prior to receipt). Standardised reporting should
also be a requirement.
5.3. Other Recommendations
•Marine mammal mitigation guidelines should be adopted by all oil
and gas companies and contractors, to ensure that marine mammals
are protected worldwide and not simply in those (usually developed)
countries where adequate resources and structure are available to
implement protection as a licensing requirement.
•A system of automated logging of gun use should be developed so
that soft starts and use of the small gun at night can be independently
monitored. At present the onboard observer cannot properly assess
these key measures.
•MMOs must be qualified, dedicated and experienced. As a minimum
this should require that an MMO has no other role on the ship, that
they have field experience of the relevant marine mammal species in
an area and that they have completed an appropriate training scheme.
Training courses should incorporate an eye test, practical field training,
extensive theoretical training (including seismic survey, underwater
acoustics, marine mammal identification, and passive acoustic mon-
itoring modules), and assessments. Establishment of an independent
MMO body should be encouraged, with MMOs reporting directly to
regulating bodies during and after a survey.
•Seismic PAM towed array technology should be further developed
so that accurate ranges can be determined to vocalising animals, and
official PAM guidelines should be developed (and continually revised
according to data available) for implementing mitigation measures
based purely on acoustic detection. A PAM training scheme is re-
quired, particularly since mitigation measures may be based on the
PAM operators’ judgement.
•Alternative seismic technology should be developed, such as low
sound intensity replacements for airgun arrays and suppressor devices
to eliminate unwanted high frequency sound. Such research could be
required as a condition of permit.
•There should be improved and ongoing biological monitoring before,
during and after seismic surveys, to provide information on species
occurrence, seasonal/temporal distribution, and reaction to airgun
sound. Long-term research programmes are recommended in those
areas particularly prone to industrial activities.
•A commitment to investigate the effectiveness of mitigation measures
undertaken is long overdue. Effort should be also be made to measure
MARINE MAMMAL MITIGATION DURING SEISMIC SURVEYS 25
the efficacy of commonly used mitigation measures, particularly soft
start and the deterrent success of small guns.
6. CONCLUSIONS
The marine mammal mitigation measures currently in use worldwide show
considerable variation in parameters such as the exclusion zone radius, the
marine mammal species included in mitigation, and delay/shut-down proce-
dures. Relatively few aspects of current mitigation have a firm scientific basis
and proven efficacy in the field, and there remains a total lack of effective
mitigation during night and adverse weather. This review highlights a number
of shortcomings in the existing mitigation guidelines and makes recommen-
dations towards a standardised set of guidelines applicable worldwide. Marine
mammal mitigation measures should be utilised as standard procedure during
all worldwide seismic surveys, and not simply where regional legislation
requires them. Area closures and avoidance of key marine mammal habitat
remain the most effective and precautionary mitigation against seismic noise
and should be implemented in areas of importance for marine mammals.
TABLE 1. Statutory Marine Mammal Mitigation Measures Currently Used During Seismic Surveys Worldwide (Industrial Surveys Only, Not Including Site, Borehole or VSP Surveys)61
Location Species included
Observer
requirement
Required
observation
technique
Soft start /
ramp-up
Source exclusion
zone (EZ)
Duration of
pre-shoot watch
Soft start delay for
animal(s) within
EZ
Airgun shut-down
for animal(s)
within EZ
Night-time airgun
use
Airgun use during
line changes
Use of passive
acoustics
Time/area closed
zones?
UK62 All marine
mammal
species
1–2 dedicated and
trained MMOs
(can be crew)
Experienced in
sensitive areas
All 30 min
pre-shoot
watches
Other data
collection
optional
Compulsory.
20–40 min
500 m 30 min At least 20 min
delay after
animal last seen
No Permitted without
monitoring
Discouraged.
Shut-down
completely
between lines
Recommended in
some sensitive
areas
Seasonal
limitations in
some licence
blocks
California63 All marine
mammal
species
Two dedicated and
NMFS certified
MMOs (Three
MMOs for
surveys >7days)
One MMO on
watch 24 hr
(night and day)
Max. 4 hr watch
Compulsory. Time
not provided.
Increase by 6dB
per min
180-dB radius
(defined by
transmission
loss modelling)
Survey dependent
At least 30 min Not stated Yes for all marine
mammals
No details
provided
Permitted (with
visual watches)
MMO can abort
operations if
visibility
insufficient
Continue during
turns but at
lower level (in
Appendix 5)
Not generally
recommended
unless sperm
whales in area
Some prohibited
areas, e.g.,
Channel Islands
National
Marine
Sanctuary
Australia64 All whale species
(except Kogia ),
plus pilot and
killer whales
MMO should be
trained, dedicated
and preferably
independent
(compulsory in
sensitive areas)
All 30 min
pre-shoot
watches. 10 min
every hour or
continual in
sensitive areas
Compulsory. At
least 20 min
3000 m 90 min 30 min delay or
until whale(s)
seen outside EZ
Yes for whales
Soft start after
20 min delay or
whale(s) depart
EZ
Watches using
Infra-Red /
night-vision
binoculars
Either leave small
guns running,
or shut-down
completely and
use soft start
again.
Recognised as
back-up to
visual, but not
required
Closed area in
Great
Australian
Bight for
southern right
whales and
Australian fur
seals11
Gulf of
Mexico65
Whale species
only
Two dedicated
MMOs on watch
(can be crew)
MMO must be
trained
All daylight hours
(max. 4 hr on
watch)
Compulsory.
20–40 min
500 m 30 min Delay of at least
30 min after the
whale(s) have
been seen
Yes for whales
Soft start after
30 min ‘all
clear’ delay
Permitted only if
small gun (160
dB re 1 mPa-m)
firing in line
change
Daylight
shut-down. Soft
start at night
permitted only
if small gun
kept active.
Encouraged Use
of PAM allows
ramp-up during
darkness
(adverse
weather)
No
Brazil66 All marine
mammals
(turtles
included)
Min. of three
professional and
dedicated—either
experienced or
trained
Twoonwatch
continuously
throughout
daylight hours
20–40 min 1000 m for soft
start 500 m for
shut-down
30 min 30 min delay after
animal seen
outside EZ
Yes f or a ll
mammals /
turtles 30 min
delay after
animal seen
outside EZ,
then soft start
Not allowed to
start airguns at
night unless a
small gun (160
dB re 1 µPa-m)
is kept active
Shut-down during
daylight Small
gun can be kept
active at night /
poor visibility.
Not required
Trials
encouraged
Seasonal closed
areas for
breeding
humpback and
right whales,
turtle nesting
season and
manatee areas
.
Canada67 Whale species
only (turtles
included)
Use of a qualified
and DFO
approved MMO
(qualification not
stated)
All 30 min
pre-shoot
watches Other
data collection
optional
20–40 min 500 m 30 min 30 min delay or
until animal
seen outside EZ
Yes f or some
whale/turtles of
concern30min
delay or until
animal seen
outside EZ. Soft
start if
shut-down >30
min
Not allowed to
start the airguns
at night / low
visibility (can
keep small gun
active)
Either full
shut-down or
use of a single
energy source
Strongly
encouraged If
vocalising
whales are
heard, soft start
cannot
commence for
30 min
Recommends
planning
surveys to avoid
sensitive
areas/times
New
Zealand68
All marine
mammals Extra
measures for
Species of
Concern
(SoC)69
Use of dedicated
MMO (can be
crew).
Experienced and
trained MMO in
sensitive areas
Continuous
throughout
daylight hours
20–45 min 1500 m for SoC
200 m for other
marine
mammals
30 min 30 min delay or
until animal
seen outside EZ
Yes f or S oC
within 1000 m
EZ (1500 m for
calves) 30 min
delay or until
SoC seen
outside EZ,
then soft start
Small gun kept
firing during
night time line
changes
Continued use of
small guns
during all line
changes
required
Recommended for
poor visibility
Plan surveys to
avoid sensitive
areas/times
Extra measures
in sensitive
areas
Sakhalin70 All marine
mammals
2–3 trained and
dedicated MMOs
Twoonwatch
continuously
throughout
daylight hours
20 min 250 m pinnipeds
1000 m
cetaceans (6–7
km for gray
whales in
feeding areas)
Not reported Yes—suspension
of airgun
activity until
animals depart
EZ. No details
Yes—suspension
of airgun
activity until
animals depart
EZ. Details not
reported
Not allowed to
start the airguns
at night / low
visibility.
Details not
reported.
Not reported Not reported Seismic prohibited
within two gray
whale feeding
area ‘protection
zones’
Guidance for
best
practice
All marine
mammals
2–3 trained,
experienced and
dedicated MMOs
At least one
(preferably two)
on watch
continuously 24
hr
Duration
proportional to
total airgun
volume
160-dB radius
(defined by
modelling)
Survey
dependent
30 min, or 60 min
in waters deeper
than 200 m
Yes —3 0 mi n
delay after last
sighting /
departure of
animals from
EZ
Yes for all species
30 min delay
after animal
seen outside EZ
(or after last
sighting), then
full soft start
Permitted with
visual watches
(using night
vision aids) and
PAM .
Discouraged.
Shut-down
completely
between lines
Required,
especially in
deep water
areas.
Implement
mitigation
measures based
on acoustic
detections
Required for
breeding,
feeding,
migratory or
other key
habitats
61Presented data are based on the best information available.
62JNCC 1998, 2004 supra note 6, 13.
63HESS, supra note 12.
64Environment Australia, supra note 7.
65MMS, supra note 17; MMS. Implementation of Seismic Survey Mitigation Measures and Protected Species Observer Program. United States Department of the Interior, Minerals Management Service (2003).
66IBAMA, supra note 22.
67DFO, supra note 27.
68DOC, supra note 16.
69Species of Concern refers to all whale species, pilot Globicephala sp. and killer whales Orcinus orca,Hector’sCephalorhynchus hectori, and Maui’s dolphins C. h. maui.
70SEIC, supra note 11.
