December 2007
Special Focus

Seismic acquisition vs. marine life: An update

Regulations to mitigate the effects of exploration on whales and other species have evolved rapidly, while research tries to identify those effects and to better detect whales.

Vol. 228 No. 12  


Seismic and marine life: An update

Regulations to mitigate the effects of E&P exploration on whales and other species have evolved rapidly, while research tries to identify those effects and to better detect whales.

David Michael Cohen, Production Engineering Editor

Recent years have seen a major paradigm shift in the way mankind relates to the sea, from treating the marine environment as an endless resource for human use to a gradual recognition that our interactions with it can have powerful and sometimes negative effects. Of particular concern have been sharp drops in fish stocks and populations of marine mammals and turtles. One of the areas of human activity that may damage these marine populations is the generation of underwater sound.

Military sonar use has been positively linked to mass whale deaths in 2000 and 2002, and regulations have been enacted in many countries to mitigate the possible dangers of this and other sources of manmade sound to marine life. Included in these highly regulated activities is the use of seismic airgun arrays for offshore oil and gas exploration.

Unlike naval tactical sonar, E&P seismic streamer operations have a relatively small acoustic footprint on the oceans. Naval sonar is directed outward, at mid-frequency ranges above 3,000 Hz, with pulses lasting seconds. Marine seismic emissions last less than 10 ms and are directed downward, at frequencies less than 10% of naval sonar’s levels. No studies to date have conclusively linked E&P seismic activity to decline in marine populations.

Nonetheless, worries about possible impacts have created a rapidly evolving regulatory environment for E&P seismic activity, and research into the subject by industry, academic organizations and government agencies has increased, focusing on improving detection of marine mammals and determining what, if any, effects E&P seismic has on marine life.


Worldwide, governmental interest in protecting marine mammals has remained high, and has led to the continuous evolution of requirements for E&P seismic operations.

In the US, the Minerals Management Service (MMS) petitioned the National Marine Fisheries Service (NMFS) in November 2004 for programmatic rulemaking to enable MMS to authorize the harassment of marine mammals incidental to seismic surveys for petroleum exploration. In response, NMFS announced its intention to produce an Environmental Impact Statement (EIS). That EIS is still pending, and is not expected to be available for public comment until July 2008 at the earliest. The rulemaking is necessary to allow MMS to authorize seismic surveys under the Marine Mammal Protection Act (MMPA). Currently, MMS regulates GOM seismic activity through a regularly updated Notice to Lessees and Operators, but the operators have no authorization for their activities under the MMPA.

In the GOM, NMFS requires seismic operators to use ramp-up procedures before all seismic surveys, including airgun testing, to warn any marine mammals and sea turtles in the vicinity of pending seismic activities and to allow them to leave the area. The required ramp-up procedure consists of gradually activating airguns, starting with the smallest in terms of energy output and volume, over a period of at least 20 min., until the desired operating level of the airgun array is reached. NMFS also requires seismic operators to visually monitor the water surface for 30 min. or, in times of low visibility, use Passive Acoustic Monitoring (PAM) to ensure that no marine mammals are within a radius of 500 m around the center of the airgun array before ramp-up.

Visual observation must continue for the duration of seismic operations, or until conditions such as fog, rain and darkness make surface observation impossible. At least two trained observers must be on watch during daylight hours when seismic operations are being conducted, and no observer can work more than 4 hr at a time, with a break of 2 hr required between shifts for any one observer. Observers may be assigned no other duties, besides brief alerts of maritime hazards, during their observation shifts. These regulations apply in water depths deeper than 200 m in GOM waters west of 88°W longitude, and in all depths in waters east of 88°W.1

Canada’s Department of Fisheries and Oceans (DFO) in February 2005 issued a Statement of Canadian Practice to formalize and standardize seismic mitigation measures to protect the marine environment. The statement was based on a number of scientific papers commissioned by DFO to examine past research on seismic sound’s possible effects on marine animals.2

As in the GOM, Canadian operators are required to establish a 500-m safety zone around the center of the seismic array. During high visibility, a trained observer must monitor the safety zone during seismic activities, and for 30 min. before startup, to ensure that no sea turtle or whale (other than a dolphin or porpoise) enters the safety zone. Gradual ramp-ups must also be conducted similarly to in the GOM. Additionally, seismic arrays must be shut down or reduced to a single energy source for line changes; ramp-up is not required for each line change.

Passive acoustic monitoring is required for 30 min. before ramp-up during low visibility in areas where a vocalizing whale of a threatened or endangered species is expected to be, though it is unclear how such expectation will be legally determined. Where there is no such expectation, seismic operations may be initiated in low visibility without PAM.

In the UK, the Department of Business Enterprise and Regulatory Reform (BERR, formerly the Department of Trade and Industry) has widened the possible liability of E&P companies for marine mammal disturbance. An amendment to the Habitat Regulations of 1994 and the new Offshore Marine Regulations 2007 went into force on Aug. 21, 2007. In these regulations, the definition of disturbance is broadened to include any activity that is “likely significantly to affect: (i) the ability of any significant group of animals of [a European Protected Species] to survive, breed, or rear or nurture their young; or (ii) the local distribution or abundance of that species.”3 In addition, the amended Habitat Regulations eliminate the “incidental result” clause in the original regulations, which provided a defense against the charge of deliberate disturbance if the disturbance resulted incidentally from an otherwise lawful activity and could not reasonably have been avoided. The regulations place the onus on operators to assess the likelihood that their operations will result in a disturbance offense and to decide whether a wildlife license is needed. Furthermore, the new Offshore Marine Regulations extend the applicability of the regulations for the first time to areas farther than 12 mi from shore.

Mitigation requirements for the UK remain similar to those in the Gulf of Mexico, including safety zones, marine mammal observers and ramp-up requirements. Certain seasons and areas have stricter requirements. BERR continues to encourage operators to use Passive Acoustic Monitoring (PAM) in addition to visual observation to check for marine mammals before firing airguns. In some particularly sensitive areas, PAM is required. BERR requires that PAM systems be able to accurately identify marine mammals within a 500-m radius, and seismic vessels must use either trained PAM operators or software that can distinguish marine mammals from other sounds.

BERR is currently reviewing its seismic survey mitigation requirements to ensure that they provide adequate protection to protected species under the new Offshore Marine Regulations.

Australian requirements for marine mammal observation remain among the world’s toughest. The country’s Environmental Protection and Biodiversity Conservation (EPBC) Act of 1999 requires 90 min. of observation before ramp-up procedures may begin and an observation zone of 3,000-m radius.4 If a whale enters the observation zone, it must be monitored to determine if it is approaching the low-power zone, which has a radius of 1,000 or 2,000 m, depending on the vessel’s acoustic signal strength. Once a whale enters the low-power zone, seismic activity must be powered down to the lowest possible setting. If a whale enters the shutdown zone (500-m radius), all seismic activity must be shut down immediately. After a whale sighting in the shutdown zone, 2 hr must pass before operations can begin or continue.


Current studies on marine acoustic mitigation focus on developing software to improve the effectiveness of passive acoustic monitoring, and on determining the actual effects of E&P seismic activity on marine mammals.

PAMGUARD. Industry partners continue to work toward the development of open-source software to process and analyze whale sounds for passive acoustic monitoring. The software, called PAMGUARD, is being developed by the E&P Sound and Marine Life Programme, a JIP of 15 companies focused on understanding and mitigating the effects of underwater sound on animals. The JIP spends about $8 million per year on research. In March 2007, it convened the second PAMGUARD conference to introduce, demonstrate and provide hands-on experience with the developing software. A report on the conference is currently in draft, and publication is expected in 2008.

PAMGUARD studies are being conducted at Harriot Watt University and the University of St. Andrews in the UK, and at Oregon State University and UC-San Diego’s Scripps Institute of Oceanography in the US. Some of these, which should be concluded in first quarter 2008, focus on the challenge of making PAMGUARD adaptable to the many different PAM systems in use on seismic vessels. This flexibility is not available in the proprietary PAM software packages currently in use, such as Ishmael, Rainbow Click and Logger. Longer-running field trials of the software are underway as well. Conclusion of this research in 2008 may soon make PAMGUARD an industry standard, simultaneously eliminating the need for specially trained PAM operators and launching a multitude of new regulations worldwide to require PAM on seismic surveys.

Sperm Whale Seismic Study. The US Minerals Management Service (MMS) recently completed its Sperm Whale Seismic Study (SWSS) conducted in conjunction with Texas A&M University, the International Association of Geophysical Contractors (IAGC) and others, Fig. 1. The final SWSS synthesis report has gone through MMS review and is expected to be published in early 2008. Preliminary results published in 2006 indicate both remote exposure of marine mammals to sound from seismic arrays and effects of this exposure on sperm whale behavior.5

Fig. 1

Fig. 1. Two sperm whales fluke up to begin a feeding dive near a Texas A&M University research vessel during a 2002 Sperm Whale Seismic Study cruise. Courtesy of the US Department of the Interior’s Minerals Management Service.

The preliminary SWSS results are mixed with regard to sperm whales’ behavioral reactions to seismic surveys. Experiments on eight tagged whales showed that the movement of whales exposed to sound from seismic arrays was distributed randomly relative to the seismic source bearing in both ramp-up and full-array conditions. This suggests that the whales did not avoid the airgun source or otherwise change their pattern of movement in response to the seismic stimulus. On one occasion, a whale delayed its regular deep foraging dive for an unusually long interval that coincided with the airgun operation, and commenced deep diving immediately after the operation ended. This behavior suggests that the whale may have delayed diving in response to the sound exposure; however, the other seven whales were all observed deep diving in both ramp-up and full-array conditions. Preliminary data from this experiment revealed little or no effect of seismic activity on sperm whale dive patterns.

However, those whales that made a dive during the airgun operation showed lower pitching movements (6.4%) during full-array exposure than during post-exposure control observations. The difference between these movements and those of 13 control whales that were not exposed to airgun sound was statistically significant. Thus, all eight experimental whales were observed to reduce their energy use for locomotion during airgun sound exposure.

Another behavior that may have been affected by the seismic operation is the rate at which the whales produced the echolocation click buzzes that accompany their prey capture. The seven whales that dove during exposure had 19% lower buzz rates while at the bottom of their dive during full-array conditions than during post-exposure control, but this was not a statistically significant difference from the rates of the control whales. The buzz rate reductions decreased with increasing distance from the airgun array but, interestingly, were not related to sound exposure as measured by the whales’ tags.

Clearly, further research will be required to determine if these behavioral changes or others can be conclusively linked to airgun sounds, and if they have a detrimental effect on the whale population. If seismic activity is found to have a detrimental effect on exposed animals, mitigation will prove to be a major challenge, as the research shows that whales dive in and out of areas of high and low exposure at considerable ranges. WO 


1 US Department of the Interior, Minerals Management Service, “Notice to lessees and operators (NTL) of federal oil, gas, and sulphur leases in the outer continental shelf, Gulf of Mexico OCS region: Implementation of seismic survey mitigation measures and protected species observer program,” Feb. 7, 2007.
2 Department of Fisheries and Oceans, Canada, “Mitigation of seismic noise in the marine environment: Statement of Canadian practice,” February 2005.
3 Joint Nature Conservation Committee, “The deliberate disturbance of marine European Protected Species: Interim guidance for English and Welsh territorial waters and the UK offshore marine area,” October 2007.
4 Department of the Environment and Water Resources, Australia, “EPBC Act policy statement 2.1: Interaction between offshore seismic exploration and whales,” March 2007.
5 Jochens, A. et al., Sperm Whale Seismic Study in the Gulf of Mexico: Summary Report, 2002-2004, US Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, La., OCS Study MMS 2006-034, 2006, pp. 235-255.


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