Seismic and the Marine Environment Q&A

PGS aims to generate high-quality seismic data with the least possible impact on the marine environment and those that have the oceans as their working place

This ambition is supported by our long-standing commitment to developing technology and improved practices that truly minimize the acoustic impact of our surveys on life below water. In a broader context, we will continue to support the collection and dissemination of oceanographic data that can further our collective understanding of the oceans.

The oceans are PGS’ workplace, and we are very much aware that we not alone out there. Conducting our work in a responsible manner means complying with applicable legal requirements, planning and executing our surveys in a manner that minimizes the impact on marine life and other users of the oceans, and using technology that enables the efficient and careful collection of high-quality data.

Minimizing the acoustic impact of our operations on life below water is a clear priority. We continuously examine our methods, carrying out modeling and advanced research into alternative seismic source technology. Our research and development teams are actively involved in several separate projects that each may lead to measurable reductions in the acoustic impact of seismic surveys on life below water.

We believe that improving common knowledge and understanding of the oceans is to our shared advantage. To this end, in 2017 we launched a global data-sharing initiative. Through this mechanism, we share oceanographic data collected during our surveys with academic institutions across the world.

As members of the International Association of Geophysical Contractors (IAGC), we support the ‘Ghost Net Initiative’ by actively removing marine debris like abandoned or damaged fishing gear. In 2017, we also proposed a novel approach to removing plastic pollution from the world’s oceans using our seismic vessels, competence, and experience from offshore work.

The Climate Change Challenge

The world is faced with the dilemma of meeting energy demands while avoiding climate change and reducing our impact on the environment. Climate change is a serious threat to society, the environment and to our own business. We are committed to reducing emissions from our own operations. By improving our energy efficiency, voyage planning, logistics and using modern technology, we strive continually to reduce emissions of greenhouse gases per unit of data collected.

Our operations technical team has a target of reducing drag from towed equipment to achieve a significant fall in vessel fuel consumption. This goal will be achieved through many incremental improvements in technology and towing practices. Looking ahead our goal is to develop new seismic sources that will further reduce the environmental impact of our seismic operations.

Q&A on Seismic and the Marine Environment

The below question and answer section is based on information from the International Association of Geophysical Contractors (IAGC).

Are there any long-term impacts on fish from seismic acquisition?

History shows that fisheries and seismic activities can and do coexist. There has been no observation of direct physical injury or death to free-ranging fishes caused by seismic survey activity. Any impacts to fish from seismic surveys are short-term, localized and have not led to significant impacts on a population scale.

Are there any physical impacts to fish from seismic activity?

There has been no observation of direct physical injury or death to free-ranging fishes caused by seismic survey activity. Seismic vessels move along a survey tract in the water creating a line of seismic impulses. A predominantly low-frequency sound-pulse is generated by releasing compressed air into the water as the vessel is moving. Each signal is short in duration, local and transient. Fish may react to these pulses by temporarily swimming away from the seismic air source. Fish that move away from a survey vessel often return to the area after the vessel has passed.

Since typical seismic surveys use a moving sound source, any potential effects on fish are inherently local and short-term. While some studies have shown that various life-stages of fish may be physically affected by exposure to seismic surveys, in all of these cases, the fish subjects were very close to the seismic source or subjected to exposures that are virtually impossible in free-ranging fishes.

Fish eggs, larvae and fry do not have the ability to move away from a sound source, and may be injured in the unlikely event they are within a few meters of the seismic source. The impact of this damage, however, is insignificant on a population scale compared to the high natural mortality rate of eggs, larvae, and fry.

Do seismic surveys affect fishing?

Active acoustic sound sources, such as seismic surveys, may result in fish temporarily moving away from the sound source. There is no conclusive evidence, however, showing long-term or permanent displacement of fish. Because the sound output from a seismic survey is immediate and local, there is no contaminate residue or destruction of habitat.

During seismic surveys, a vessel exclusion zone is maintained around the survey vessel and its towed streamer arrays to avoid interruption of commercial fishing operations, including the setting of fishing gear. These exclusion zones are dependent on the type of activity and national and local regulations in the area of operation.

Prior to conducting a seismic survey, operators work cooperatively with local fishing communities and regulatory bodies to avoid sensitive spawning grounds and mitigate any potential economic losses to fishermen. The geophysical industry works with fishermen to define and address potential concerns early in the permitting process.

How do seismic activities compare to other sources of risk to fish?

Separating the effects of sound from other environmental disturbances can be complex. The impacts of sound on fish stocks must be viewed in a wider context, considering how the effects of sound on populations compare to other natural and human influences on the marine environment. Those influences that are known to threaten marine life, such as overfishing, disease, habitat degradation, and pollution, have a greater impact from an overall risk perspective.

What is the seismic industry doing to improve knowledge about its impact on marine life?

For many years, the industry has invested in considerable research regarding the effects of seismic surveys on marine animals including fish. Research projects also address gaps in knowledge and assist in a more comprehensive understanding of potential environmental risks (see That investment continues today.

The industry employs various mitigation measures to decrease the potential impact of seismic operations on marine life, including

  • Research regarding the effects of seismic surveys on marine
  • Education regarding environmental risks associated with sound and marine life
  • Avoidance of important fish spawning grounds 
  • Soft-start/ramp-up procedures (a gradual build-up of the seismic sound source to allow fish to swim away).
Is seismic a reason for marine mammal strandings?

When dead marine mammals drift ashore or living mammals swim or float onto the shore and become beached or are unable to return to the water on their own, they are said to be stranded. Although this global phenomenon is not new, the causes of stranding are still not well understood. Natural occurrences of stranded marine mammals have been documented for centuries. The Greek philosopher Aristotle contemplated whale strandings phenomena more than 2300 years ago.

The direct cause of most strandings remains unknown due to the variety of uncertainties and phenomena in the marine environment. Scientists have identified a number of contributing factors, including illness and injuries, storms, predator attacks and even toxins from algae, just to name a few. Dramatic increases in the number of strandings in an area are typically connected to an outbreak of infection, such as red-tide or morbillivirus.

Does marine sound cause marine strandings?

Although beaked whales have shown strong evidence of stranding when exposed to tactical military mid-frequency sonars, the sound signals used during a seismic survey are quite different from sonars operations: in frequency, direction, and duration. No conclusive scientific link has been established between seismic surveys and any marine mammal strandings.

There have been a number of studies commissioned by governments around the world looking at stranding events. According to a March 2014 Federal Register Notice issued by the U.S. National Oceanic and Atmospheric Administration (NOAA), “To date, there is no evidence that serious injury, death, or stranding by marine mammals can occur from exposure to airgun pulses, even in the case of large airgun arrays.” Further, the Canadian Fisheries and Oceans Department have concluded, “…there is no conclusive evidence of cetacean, e.g. whales and dolphins, strandings as a result of exposure to seismic surveys."

What are seismic companies doing to mitigate strandings?

In spite of a lack of evidence linking seismic surveys to strandings, geophysical contractors have implemented industry-wide mitigation practices to avoid impacts on marine species. Regulators and seismic surveyors establish a marine mammal exclusion zone before beginning operations, and they hire trained observers with the authority to stop operations if a sensitive species is spotted within the exclusion zone. Operators also gradually ramp up sound emissions and move their vessels slowly, in order to allow marine mammals to move away from the area before the full operation begins.

What are seismic companies doing to protect the environment they operate in?

The seismic industry employs a number of measures to ensure that marine life is protected from direct or indirect harm from its operations.

Impact assessments

Environmental Impact Assessments (EIAs) are an integral part of developing and implementing a seismic survey. Many countries have environmental impact assessment requirements. The assessments include identification of marine species, including protected species, other environmental sensitivities and the human uses of the proposed area of operations. These assessments are conducted during the survey planning stage and evaluate the potential impacts and risks to marine life. The assessments also identify and consider measures to avoid or mitigate such potential impacts and risks. Seismic surveys are generally considered not to be harmful or damaging to the marine environment. Seismic surveys are comparable to many naturally occurring ocean sound sources, are temporary and transitory and the vast majority are conducted at frequencies below the hearing range of many marine species.

Mitigation and monitoring

Mitigation and monitoring must be proportionate to the potential risks identified by an environmental assessment and specific to the local environment and the operation being undertaken. Measures commonly used by the seismic industry include timing seismic surveys to avoid known areas of biological significance, such as whale foraging or breeding areas or avoiding seasonal marine life occurrences such as peak whale and dolphin activity seasons or migration.

Do you have any other precautionary measures in place?

Before a seismic operation begins, visual monitoring is undertaken to check for the presence of marine mammals and other marine species within a specified precautionary, or exclusion zone, often using dedicated marine mammal observers (MMOs) or protected species observers (PSOs).

Further monitoring may be done using passive acoustic monitoring technology (PAM), which may detect vocalizing marine animals, especially during low visibility and nighttime conditions. In the event marine animals are detected in the exclusion zone, the seismic operation will not begin for a certain time period until the marine animal moves away. Similarly, a seismic survey will shut down if the marine animal is observed entering the exclusion zone once operations have begun.

Soft-start or ramping-up procedures are undertaken by seismic vessels as a matter of general operational procedure. Soft starts involve activating a small section of the acoustic sound arrays over a period of time, gradually getting louder until the full acoustic array is operating. This measure also allows a marine animal to swim away before the acoustic source is activated at full strength.

Are there environmental protection guidelines in countries where you operate?

Many countries and regional authorities have established guidelines and regulations specific to seismic operations, which are then adapted for the specific location and operation for the permit.

In the absence of regulations or guidelines in a specific area, the industry has committed itself to a set of minimum mitigation measures as outlined in the 2011 International Association of Geophysical Contractors (IAGC) standards document, “Recommended Mitigation Measures for Cetaceans during Geophysical Operations.” IAGC has produced additional documents for mitigation and monitoring guidance for seismic operations, “Guidance for Marine Life Visual Observers” and “Guidance on the Use of Towed Passive Acoustic Monitoring during Geophysical Operations.”