AcousticEcology.org Special Report
International Whaling Commission
Annex K of the Scientific Committee Report, from the Standing Working Group on Environmental Concerns.
A pdf document containing the latest research and recommendations on all environmental concerns, including noise and pollution. The Athropogenic Noise section is devoted to the pre-meeting workshop on seismic surveys and noise; it appears on pages 1-16 of the Annex K document.
[DOWNLOAD IWC58 SCIENTIFIC COMMITTEE REPORT ANNEX K(pdf)]
Anthropogenic Noise section of the State of the Cetacean Environment Report
SOCER is an annual survey of new research on all aspects of the cetacean environment, also compiled by the Standing Working Group on Environmental Concerns. It includes one-paragraph summaries of research reports, with citations for each; there is global coverage, as well as an annual focus on a particular region (this year, it was the Indian Ocean).
[DOWNLOAD SOCER SECTION ON ANTHROPOGENIC NOISE(doc)]
[MAIN IWC 2006 MEETING WEB PAGE]
[DOCUMENTS GENERATED FOR THIS YEAR'S MEETING]
[SCIENTIFIC COMMITTEE REPORT, AND ALL ANNEXES]
(the Annex on whale watching is also relevant to noise concerns)
[SOCER REPORTS FOR RECENT YEARS]
AEI Special Report: IWC 57 (2005) (includes link to 19p Word doc summarizing noise info)
AEI Speical Report: IWC 56 (2004) (includes summary of Anthropogenic Noise workshop)
Highlights of the 2006 Meeting Reports
While the press went crazy with the first majority vote to rescind the whaling ban, a move long urged by Japan and Norway, nations with cultural traditions of eating whale meat and still-ready whaling industries, there was also continued work on addressing the impacts of anthropogenic (human-made) noise on marine mammal health. As always, the Scientific Committee's Working Group on Environmental Concerns compiled the annual State of the Cetacean Environment Report (SOCER); it is always a treasure-trove of new findings. This year, there was also a pre-meeting extended workshop on the noise impacts of seismic survey airguns, which also included many important papers and discussions.
This year's presentations included several findings that warrant further research as soon as possible. One of the most striking findings was that infant Risso's dolphins have much greater hearing sensitivity than previously-tested adults; if this finding is confirmed and extended to other species, it could have major implications for setting appropriate thresholds of acceptible noise levels. Another study suggests wind farms add significant low-frequency noise to their local environments; further measurements in the field are urgently needed.
The following paragraphs offer very brief summaries of many of the papers presented at the seismic workshop and in this year's SOCER. The Working Group on Environmental Concerns main report (Annex K of the IWC Meeting Report) contains narrative summaries of all papers presented at the seismic workshop, as well as a complete list of papers presented. The SOCER report is always a good read; the full report is available from IWC, and the section dealing with anthropogenic noise is can be downloaded from AEI. See above for all links and downloads.
Among the issues discussed and findings presented this year:
Reports of two stranding events likely related to mid-frequency sonar exposure. One, off Spain's southern coast, coincided with a UK Navy exercise near Gibraltar; the other, offshore Indonesia, involved a large number of pilot whales while a joint US-Indonesian exercise was underway nearby.
Clear description of the physiological injuries associated with mid-frequency active sonar exposure; it's still unclear whether the bubble-caused lesions are caused by rapid surfacing or direct exposure to high-intensity sound while tissues are under high pressure (other research presented confirms that cetaceans of many species seem to exhibit such "decompression" tissue damage, and that direct bubble formation is possible in super-saturated cow tissues under high pressure exposed to hight intensity sound). The set of injuries, including congestion and bleeding in ears, brain, jaw fat and kidneys and unusual gas bubble lesions and fat emboli in several organs, including liver, has been named the "gas and fat embolic syndrome" and is becoming a standard diagnostic tool in determing whether strandings may be related to active sonar exposure.
Several papers looked at the reactions of dolphins to boat noise. In general, they found that smaller, faster boats elicit the most dramatic behavioral responses; personal power boats and jet-skis being the most disruptive, and large ships the least. Some mid-sized and mid-speed boats spurred engagement (bow-riding), and shrimp boats were always follwed by dolphins looking for a snack. One paper showed that acoustic behavior (clicks and whistles) did not change significantly, while behavior clearly did (shift from travelling to milling), suggesting that acoustic monitoring is not suffiicient to assess the impact of boating. Researchers stressed that subtle behvioral changes could accumulate to cause population-level impacts over the long term; for example, Sini et al noted that “[s]hort-term interruptions of normal activity could have long-term adverse effects on a population of dolphins, through reductions in the time available for foraging or resting, abandonment of favoured habitats, disruption of social bonds, or through physiological effects of stress.”
Wind farms add 80-110dB (re 1uPa) to the existing low-frequency ambient noise (under 400Hz); this could impact baleen whales communication and stress levels, and perhaps prey distribution.
A captive beluga was found to have suffered extreme hearing loss (90 dB) after treatment with antibiotics; if this effect is confirmed, it will raise questions about the possible shortcomings of using captive animals as a proxy for wild animals in auditory studies.
The International Council on Exploration of the Seas reported that worldwide beaked whale deaths from likely exposure to mid-frequency active sonar (40 over 9 years) is outpaced by by-catch in American fisheries (35 in 6 years). They concluded that sonar exposure is not likely to cause a major impact on global populations, though they noted it has had a significant impact on local abundance in some cases (eg Bahamas) and they cautioned that increasing sonar use does warrant continued refinement of mitigation measures. They also noted that the long-term increase in ambient noise levels in the sea (caused by non-sonar noise sources) may well impact communication and affect the life history of cetaceans (including reproduction), stating that long-term impacts on populations “could be worse than direct killing” (p. 39).
An infant Risso's dolphin was found to be much more sensitive to sound than adults of that species. At 100kHz, the infant could hear sounds 60dB quieter than the adult, and could also detect higher frequencies than adults have been known to hear. This could reflect age-related hearing loss (much as we routinely see in humans); it surely suggests that acoustic sensitivity data on older and/or captive animals may be underestimating potential impacts of anthropogenic sound on this species.
Workshop on seismic surveys
Among key results reported on and discussed during the pre-meeting workshop on seismic surveys:
Recent studies confirm more higher-frequency components of airgun sound than previously assumed. Two studies are underway (NSF and industry) to measure horizontal propagation of high-frequency sounds.
Trends: number of surveys peaked in the 1990s (100crews/month in 1994, 40 crews/month in 2004); now trending up but not likely to hit former peaks. 12 new vessels coming on line soon; about 90 ships currently operating. Highest concentration of activity in the world has been in the Gulf of Mexico, which averaged 25 crews/month over the past decade.
Chris Clark (Cornell) presented a paper suggesting that seismic survey activities produce very low frequency sound (under 100 Hz) that can ensonify large areas (10,000 square nautical miles) for considerable periods of time (weeks). Acoustic maps suggest that sound levels may reach thresholds at which fin whales stop singing during the surveys. Clark noted that if one assumes that such intrusions of anthropogenic sounds into an animal’s acoustic ecology are stressful, then these observations should be further considered within the context of synergistic effects from multiple stressors. The committee asked Clark to synthesize and analyze existing data that he presented and make final results available to the Standing Working Group for consideration. The Committee further recommended that research be undertaken to quantify the degree of ensonification at large ranges, and give special consideration to impacts on areas of special biological concern.
Ongoing Sperm Whale Seismic Study in the Gulf of Mexico, utilizing temporary (several hour) tags attached to whales, which can record the received sound and log swimming and acoustic activity; each year, they have increased the exposure level slightly. During the most recent year, whales received sound at 131-162dB peak-to-peak (111-147 RMS), at ranges of 1-13km. Results show a decrease in fluke strokes (a measure of foraging activity) in all whales observed during exposure to airgun sounds; also, no foraging dives during close approach by seismic ship,. Foraging echolocation clicks decreased by 20% during exposure; not enough to be statistically significant, but considered a likely affect. There was no observed avoidance (change in swimming course; horizontal movements were random with respect to seismic vessel); however, there were no approaches closer than 1km, and in one instance (the whale closest to the seismic ship), a whale waited unusually long at the surface, then commenced a foraging dive as soon as the airguns were turned off. (Two other related studies showed no measurable avoidance of seismic vessles at ranges of 5km to 100km). Another key set of results from the SWSS confirmed that sound propagation is not linear; for example, an animal 400m from the vessel but more than 50m below the surface was exposed to acceptably low sound levels, while an animal 6 km away was exposed to levels above the mitigation threshold (note: these levels are consistent with known physics of sound propagation; they are not a mystery). In this case the mitigation measures (assumed safety radius, and assumption that animals at risk would be observed) were ineffective because the sound prediction model was inappropriate. Therefore, the group recommended that readily available and appropriate sound propagation models for predicting sound exposure levels, although more complicated, should be employed and validated with empirical data, where available.
A new industry-funded research initiative was announced. The program as formalized just days before the seismic workshop, and currently is funded with over 7 million dollars. Two research efforts are already settled upon: one to characterize the source sound spectrum of a typical industry array in deep water, and one to futher develop PAMGUARD, a passive acoustic monitoring system. The program expects to fund cumulative effects studies in an ecosystem context, and the development of alternative sound sources and sound attenuation technologies.
Bowhead whale studies offshore Alaska indicate that the whales are extremely sensitive to noise during migration. While feeding, they were routinely seen in areas where the received level would be 160-170dB (rms), but during migration they avoided seismic vessels by about 20km, rarely exposing themselves to more than 120dB (rms).
A review of Marine Protected Areas suggested that MPAs could be an effective way to regulate noise around marine "hot spots," but that the current MPA networks are insufficient in size to encompass the ephemeral and large areas considered critical to marine mammals during migration and breeding. Seasonal protection and/or the creation of a larger network of areas would be needed.
Revisiting data from Brazil presented at IWC56 in 2004, while in 2004 there were an unusual number of strandings in areas with high seismic activity, total seismic activity peaked in 2001, with strandings increasing since 2002. Still, the group expressed appreciation of Brazil's decision to limit seismic activity during breeding season.
Gray whales near the Sakhalin oil and gas development in eastern Russia were displaced by surveys there; respiration and dive patterns also changed. Given the critically engangered status of this population (roughly 100 individuals remain), the group stressed the appropriateness of applying precautionary approach, and scheduling future surveys to avoid the key feeding months. There was considerable discussion about whether the analysis of changes in distribution in this paper adequately included the effects of naturally driven factors as was done in other papers cited in that document. It was suggested by several participants that these factors could have contributed to the effects observed. However, Weller pointed out a close overlap between the timing of seismic surveys and the observed change in distribution, thus arguing against the explanation of naturally driven factors being responsible. The group recommended that the authors conduct an analysis to evaluate the degree of change due to natural factors and to distinguish those effects from those due to exposure to sound from the seismic survey.
Standardized and transparent worldwide reporting system. minimum: location and time, number of vessels, size of array, mitigation measures used. ideally also time and location of start and end points of each line.
Host govts should put 5 and 10 year exploration plans in regional or national context, so IWC can better provide scientific guidance on species in the areas.
Potential effects on prey species should be considered.
Cumultative effects of multiple surveys on bowhead whales should be investigated. Need to look closer at biological significance of apparent sensitivity of bowheads to noise during migration, and identify sensitive areas for bowhead breeding, calving, feeding.
Further development of an incentive-based system of "exposure credits" suggested by Gordon. based on population density and effectiveness of observation and mitigation measures employed, adjusted based on actual measurements on site. (seen annex K, page 10-11).
Need to quantify the effectiveness (detection probability) of various observation techniques, singly and in various combinations. Recommends a broader approach to observation that includes independent observing platforms.
Measure behavior likely to affect vital rates (eg, rate of foraging or singing, disruption of mother-calf pairs or result in injury (rapid surfacing, stranding).
Research to improve seismic survey technology and reduce undesired transmission (including marine vibroseis, which would presumably apply sound at the seafloor rather than the surface, and research on reducing horizontal transmission).
The group identified the following critical attributes of effective mitigation and monitoring:
- Mitigation and monitoring programmes should be evaluated based on pre-established criteria.
- Mitigation and monitoring should employ techniques with measurable effectiveness.
- Mitigation procedures should be practical in that they should use data that can be readily collected by marine mammal observers during offshore surveys, account for operating conditions and constraints of seismic surveys and, as far as possible, minimize disruption of surveys while maximizing environmental protection.
- Procedures and protocols should be based on a conservative approach that reflects levels of uncertainty. They should include mechanisms that create an incentive for good practice.
Regarding monitoring, the group recommended:
- Procedures for collecting observational data should be standardized with reporting protocols defined.
- All whale observational data associated with seismic survey should be made available in the public domain. This could involve either central facilities for assembling and disseminating observational data collected during seismic surveys or standardizing a mechanism for distributing seismic monitoring data from each contractor.
- The use of long term monitoring programs in relation to marine development should be encouraged.
- Local research groups should be encouraged or education programs to develop local expertise should be initiated.
Regarding the need to develop methods to measure the effectiveness of mitigation and monitoring, and the biological effects of surveys, the group discussed:
- Continued development of new monitoring techniques, including active acoustics, LIDAR, infrared and hyper-spectral imagery, satellite imagery, and monitoring large spatial/long temporal scale changes is the autonomous seafloor-mounted instruments.
- Investigating and to the degree possible controlling for other factors besides sound that could account for observed changes in behavior or population densities. Control data could be biological information, such as sex or age of the target species, or prey/predator densities, or it could be environmental data, such as sea surface temperature, mixing layer, bottom depth or slope.
- Some mitigation procedures and criteria have not been scientifically validated. For example, the traditional use of ramp-up, the procedure in which the amplitude of the sound is steadily increased on the assumption that it avoids startling animals and gives them time to move away from the source before it reaches full volume, has never been validated as an effective mitigation measure. Therefore, the group recommended research to evaluate and quantify the effectiveness of existing mitigation procedures and any new mitigation measures. A criterion that has not been validated is the level at which injury occurs for either cetaceans or pinnipeds.