Seismic Impacts on Sakhalin Gray Whales

Seismic Impacts on Sakhalin Gray Whales:

Summary and synthesis of recent studies.

31 July 2009

By Steve Nelson;

George Mason University and marine resource consultant

Introduction

In considering environmental impacts related to recent legislation, some observers claim that seismic operations associated with oil and gas operations do not harm marine mammals, when surveyors apply standard mitigation measures. For example, see: Jim Tozzi, “Comments on the Draft Proposed 5-Year Outer Continental Shelf Oil and Gas Leasing Program for 2010-2015.” Center for Regulatory Effectiveness (CRE), July 2009. The author cites several studies of acoustic sounds on whales, including those of gray whales near Sakhalin, Russia, fin blue whales off the California coast, and sperm whales in the Gulf of Mexico. Based on these data, Mr. Tozzi concludes that seismic activities do not affect feeding behavior in spermwhales.

To explore the issue in more detail and to provide a broader context, this paper reviews the Sakhalin study in greater depth. It summarizes and synthesizes six, industry-supported studies of gray whales off Sakhalin Island in the Russian Far East. These studies describe whale foraging, behavior, abundance, and distribution data during exploratory seismic studies in the summer of 2001. By reviewing all studies as a group, I avoid the perception of “cherry picking” specific data or conclusions to strengthen one point. In this case, I seek to evaluate feeding behavior in the broader context of other behaviors, such as swimming, breathing, and migration and to assess the impacts in a more holistic framework.

Published inEnvironmental Monitoring and Assessmentin 2007, the Sakhalin whale studies present recent, high-quality, international research findings that may not be readily available to U.S. policy makers. Scientists from industry and academia in Russian and the United States participated in the three year project and authored six scientific articles. This paper summarizes the result of those studies to evaluate the impacts of acoustic noise on marine mammals.

Overview

In considering the impacts of oil and gas activities on marine mammals, U.S. policy makers can benefit from recent international experiences and research findings. The Sakhalin project in the Russian North Pacific represents one of the world’s largest oil projects operating under a consortium of partners from Russia, Europe, and the United States. Moreover, Sakhalin oil resources lie close to critical feeding habitats for western grey whales (Eschrichtius robustus) and the project represents a potential conflict between development and conservation.

Led by Exxon Neftgas Limited, the Sakhalin -1 consortium is developing oil and gas reserves on the nearshore continental shelf off northeast Sakhalin Island, Russia. To survey potential reserves, DalMorNefteGeofizika (DMNG) conducted a 3-D seismic survey of the region during 17 August–9 September 2001. Due to harsh winter conditions, such surveys must take place in summer months during the whale feeding season. Seismic surveys use air guns to send acoustic waves through the water column that may interfere with marine mammals. When shot from large volume guns, these acoustic wavescan damage whale hearing at high levels (eg. > 163 decibels, (Dbrms)). In addition to immediate physical harm, acoustic noise can possibly disrupt important feeding, migration, and mating behaviors that could jeopardize population health.

To assess the impacts of seismic activities on gray whales, the Sakhalin -1 consortium monitored feeding, behavior, abundance, and distribution characteristics during the 2001seismic survey and for two additional years; 2002 – 2003. During the survey, researchers designed and implemented mitigation procedures, or “best management practices” to minimize adverse impacts from seismic air guns. Such practices included: 1) setting buffer zones between seismic operations and whales; 2) using lower air gun energies; and, 3) setting restrictions on survey times and space to avoid interactions with whales. Probably these practices greatly reduced adverse harm to the whales. We do not know impacts without these procedures.

The multi-year research and monitoring program combined six survey methods and several statistical analyses. Survey methods included: (1) aerial surveys; (2) vessel surveys; (3) shore-based surveys; (4) photo-identification; (5) shore-based behavior studies; (6) acoustics monitoring; and (7) benthic/epibenthic prey studies. Statistical techniques included ANOVA analysis and multiple regression equations fitted to key environmental and behavioral variables.

Western gray whales

Researchers describe two gray whale (Eschrichtius robustus) populations in North Pacific ocean: the Eastern Pacific (California–Chukotsk) and Western Pacific (Korea–Okhotsk). Commercial whaling reduced the number of western gray whales until the 1970s when some observers believed the species went extinct. Recent estimates put western gray whale numbers at approximately 123 individuals with less than 50 reproductively active adults in the population. The Red Book of the Russian Federation lists western gray whales as an endangered (category I) species and International Union for the Conservation of Nature and Natural Resources (IUCN) lists it as critically endangered (Yazvenko et al. 2007 a, b) Meier, et al.2007).

Gray whales arrive off northeast Sakhalin Island in late May to feed, after sea ice has left the area. Some remain as late as November or early December and migrate south when sea ice returns to the region. Scientists do not know winter calving and mating areas for this population nor do they know exact migration routes. Yet most researchers believe whales over-winter in the South China Sea or off the Korean peninsula (Yazvenko et al. 2007 a, b).

Earlier studies. Previous behavioral studies conducted in association with seismic experiments (Malme et al. 1986, 1987; Malme and Miles, 1985) provide earlier information about the effects of seismic surveys on gray whales. Richardson, et al. (1995) provides a good overview in his book “Marine Mammals and Noise.” Other studies observed feeding and migration behaviors of gray whales in the Bering Sea and off the California coast, respectively. Based on these findings, researchers conclude that high volume air guns (with acoustic energies greater than 163– 164 decibels (dBrms)) interfere with feeding behavior and displace about 10% of the gray whales from their normal distribution. In comparing other species, they assume that baleen whales do not suffer permanent hearing effects at noise levels below 180 dBrms.

Previous studies also indicated that lower sound intensities could affect behaviors related to swimming and respiration (Richardson et al. 1995; Rutenko, et al. 2007).

Figure. Map shows Sakhalin Island in the Russian Far East. Shallow waters around Piltun Bay on the northeast tip of the island represent he key western gray whale feeding grounds.

Feeding. Findings from the 2001 Sakhalin studies showed little direct impacts to whale feeding behavior resulting from the seismic survey. Since grey whales feed on the bottom by filtering sands and mud, observers tracked visible mud plumes on the surface as indicators of feeding behavior. In this way, mud plumes served as a proxy for feeding. However, such plumes cannot infer the quantity and qualityof food intake resulting from bottom dives. Based on aerial surveys conducted from 19 July–19November 2001, researchers did not find statistically significant correlations between seismic activity and the frequency of occurrence of mud plumes in the feeding area. In contrast, they correlated feeding behavior with environmental variables such as water depth and swell height of the sea. They concluded that the 2001 seismic survey had no measurable effect on bottom feeding activity of western gray whales off Sakhalin Island (Yazvenko, et al. 2007a).

Behavior. However, researchers measured statistically significant changes in whale behavior in response to low-level acoustic noise. According to research findings, seismic activity significantly affected five of eleven behavioral variables, including; leg speed, reorientation rate, distance from-shore, blow interval, and dive time. On the other hand, it had little effect on the linearity of whale movements, changes in swimming speed, mean direction of whale movement, mean number of whale exhalations per minute at the surface, mean time at the surface, and mean numberof exhalations per minute during a surface-to-dive cycle. (Gailey, et al. 2007, Yazvenkoet al. 2007b).

It is difficult to know if these impacts lead to long-term adverse consequences; or whether whales grow accustomed to industrial sounds and resume normal behavior. However, researchers found stronger behavioral impacts (correlations) from noise accumulated over a three-day period relative to noise on the scale of hours (Yazvenko, et al. 2007b). This suggests possible chronic, long-term impacts that cannot be measured in hours or weeks.

Distribution on feeding grounds. Survey results showed whale distributions in two areas: 1) in shallow coastal areas adjacent to Piltun Bay in waters less than 20 meters deep; and2) offshore areas from Chayvo Bay, with depths ranging from 30 to 65 meters. Scientists did not expect to find an offshore feeding ground and its discovery raised questions about feeding behavior, ecology, site-fidelity, memory, and possible responses to seismic operations(Meier, et al.2007).

During all three surveyed years, the distribution and abundance of whales changed in both coastal (north-south) and offshore (east-west) directions. Researchers believe these seasonal shifts correlate primarily to the distribution and abundance of prey. Whales follow the food. In this case, bottom-feeding gray whales return to known feeding grounds every year to strain amphipods and other benthic vertebrates from shallow sands and muds.

Although not proven, seismic activities could potentially shift feeding locations as some individuals move away from acoustic soundstransmitted through the water column. Statistical analyses of aerial survey data indicated that about five to ten gray whales moved away from waters near the seismic survey. Also, accumulated sounds over a three day period had more affect on whales than sounds issued on a single day. This suggests that marine noise affects whales more on the scale of days rather than hours and that noise will have greater affects when sustained over longer periods (Yazvenko, et al. 2007b).

Although earlier observers described the coastal region as the main summer feeding grounds, researchers discovered a new offshore feeding area in the 2001 study(Meier,et al. 2007). This discovery raised some important questions. Did earlier researchers overlook the area? Or did seismic activities drive some individuals to seek more peaceful feeding grounds? Whales remained in the core coastal area throughout the 2001 seismic survey season; but migration occurred from coastal to offshore areas. However, only males swam offshore while females and calves stayed in the shallower, more sheltered coastal habitat.

Benthic prey studies conducted from 2002–2003 revealed the richness of the offshore area as a bottom habitat dominated by tube-dwelling amphipods; a favorite whale food. After the seismic study concluded in 2001 whales continued to feed in the offshore area in subsequent years in absence of industrial activities. However females with calves stayed in coastal areas and observers did not see them feeding offshore. Age and gender stratification in habitat use has been reported in eastern gray whales and females with calves prefer shallow, coastal waters that offer more protection from potential predators, such as killer whales.

This suggests that the coastal area adjacent to Piltun Bay represents an important nursing habitat and the offshore area does not provide a comparable substitute for females and calves. However, the mechanism driving the movements of whales along the northeast coast of Sakhalin Island is likely very complex and influenced by a multitude of factors including not only prey density and seismic activities; but also memory, site-fidelity, and intra-species competition (Meier et al. 2007, Yazvenko, et al. 2007b). To avoid whale interactions, surveyors limited acoustic activities in shallow waters less than 20 meters.

Status and trends. Subsequent studies of western gray whale populations conducted in 2002–2005 indicate no apparent changes to numbers of whales, bodycondition, or reproductive success. Moreover, researchers observed no significant differences in population size between the year of industrial activity (2001) and subsequent years in which no industrialactivity took place. Recent estimatesof the size of the adult population indicate 123 individuals in thepopulation in 2005 compared to about 100 in 2001 (Meier et al. 2007, Yazvenko, et al. 2007b).

Mitigation strategies

The Sakhalin studies include the design and implementation of mitigation strategies to reduce possible adverse impacts of seismic activities to whale populations (Johnson, et al. 2007). In designing these best management practices, researchers reviewed and considered three sets of established mitigation guidelines including:

1. Guidelines/recommendations of the Joint Nature Conservation Committee (JNCC) of the United Kingdom;
2. Guidelines/recommendations of the Southern California High Energy Seismic Survey (HESS) Team; and
3. Guidelines/Recommendations of Environment Australia (Environment Australia 2001) and the Australian Petroleum Production and Exploration Association (APPEA).

Based on these guidelines, the seismic study established buffers between whales and active seismic air guns, set restrictions on air gun energies (or volumes); modified survey areas away from key habitats, and adapted survey times and methods to avoid interactions with whales.

(Johnson, et al. 2007)

Buffers. The study established a safety bufferto avoid any potential for physical injury; such as direct impacts to hearing. After calibration studies, the mitigation program set a air gun threshold of 163 dBrms used at a distance no closer than of four kilometers to whales. This ensured that received sounds at the 20 meter contour dropped below 163 dBrms at a distance of four kilometers. Moreover, the monitoring program required the seismic vessel to stay at or beyond the buffer distance from feeding gray whales (Rutenko, et al. 2007, Johnson, et al. 2007).

Time and space. The JNCC, HESS and Australian seismic survey guidelines recommend consideration of both seasonal and geographic restrictions to reduce impacts of seismic surveys on marine mammals. To minimize overlap with the whale feeding season, researchers rescheduled (pushed back) the seismic survey to the mid-August through mid-October period; even though this time poses greater risks of storms. Also, by eliminating surveys in all waters shallower than 20 meters, researchers reduced the overall survey area by 19 % (Johnson, et al. 2007).

Conclusion

In the most direct terms, these studies show that seismic activities do not significantly affect short-term gray whale feeding behavior. In this context, they support, but do not prove Mr. Tozzi’s conclusion that seismic operations do not harm marine mammals when surveyors apply mitigation techniques. Moreover, despite exposure to seismic noise, whale populations did not significantly decrease is size or health in subsequent years.

On the other hand, seismic activities affected some aspects of whale behavior and their distribution on feeding grounds. Previous research showed behavioral changes in about 10% of gray whales subject to acoustic signals. The 2001 studies measured statistically significant changes in 5 of 11 behavioral variables in response to acoustic noise and about five to ten whales moved away from the air gun sounds. Whales responded more to accumulated noise over a three-day period than to signals shot over a period of hours; indicating possible long-term, or chronic affects from sustained industrial operations. Although not proven, whale distribution may be affected by seismic activities and lead them to new feeding grounds.

Policy makers should stress the importance of mitigation measures in setting U.S. policy. We do not know adverse impacts resulting from more careless seismic studies; but we suspect it could cause significant harm. In the Sakhalin study, industry deserves credit for conducting seismic surveys with carefully researched mitigation practices to avoid adverse impacts. When combined with a robust monitoring program, it represents a significant scientific achievement conducted by collaborative industry and academic researchers.

In spite of these encouraging findings, the population remains severely endangered and its future is highly uncertain. Moreover, we do not know much about this animal; especially regarding mating and migration behavior. In addition to seismic activities, oil spills represent important threats to whale feeding grounds. Such an event could eliminate the species. In this context, oil developers and managers need to adopt the precautionary approach. They should adopt and implement best management practices and they monitor impacts and consequences of industrial activities.

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Steve Nelson is a researcher at George Mason University and an independent consultant to marine resource managers.
References

Gailey,G, B.Würsig, and T.L. McDonald. 2007. Abundance, behavior, and movement patterns of western gray whales in relation to a 3-D seismic survey, Northeast Sakhalin Island, Russia. Environmental Monitoring and Assessment. 134. Springer Science and Business Media.

Johnson, S.R., W. J. Richardson, S. B. Yazvenko, S. A. Blokhin, G. Gailey, M. R. Jenkerson, S. K. Meier, H. R. Melton, M. W. Newcomer, A. S. Perlov, S. A. Rutenko, B. Würsig, C. R. Martin, and D. E. Egging. A western gray whale mitigation and monitoring program for a 3-D seismic survey, Sakhalin Island, Russia. Environmental Monitoring and Assessment. 134. Springer Science and Business Media.

Malme, C. I. and P. Miles. 1985. Behavioral responses of marine mammals (gray whales) to seismic discharge. In G. D. Greene, F. R. Engelhardt, & R. J. Paterson (Eds.), Proc. Workshop on effects of explosives use in the marine environment, Jan 1985 (pp. 253–280). Tech. Rep. 5. Can. Oil and Gas Lands Adm., Inviron. Prot. Br.

Malme, C. I., B. Würsig, J. Bird and P. Tyack. 1986. Behavioral responses of gray whales to industrial noise: feeding observations and predictive modeling. Outer Continental Shelf Environmental Assessment Program, Final report of Principal Investigators, NOAA, Anchorage, AK 56(1988): 393–600. BBN Report 6265.