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CETACEAN STOCK ASSESSMENT IN RELATION TO EXPLORATION AND PRODUCTION INDUSTRY SOUND by Prepared for Joint Industry Programme 30 September 2009 LGL Report TA4582-1 CETACEAN STOCK ASSESSMENT IN RELATION TO EXPLORATION AND PRODUCTION INDUSTRY SOUND by LGL Limited, environmental research associates 22 Fisher Street, POB 280 King City, Ontario, Canada L7B 1A6 9768 Second Street Sidney, British Columbia, Canada V8L 3Y8 and LGL Alaska Research Associates Inc. 1101 East 76th Avenue, Suite B Anchorage, Alaska, United States 99518 Prepared for Joint Industry Programme 30 September 2009 LGL Report TA4582-1 Executive Summary Purpose and Objectives This project investigated the relationship between the oil industry‘s offshore E&P activities and trends in the distribution, abundance and rates of increase of key cetacean stocks found in three areas where E&P activities are intensive. The approach taken was to compare the status and population trends of stocks of key cetacean species in three areas with E&P activities―Alaska (subdivided into three regions, the Beaufort, Bering and Chukchi seas), Australia (Western and southeast regions), and Sakhalin Island, Russia―with corresponding parameters for stocks of the same species (where possible) in areas where E&P activities were absent or greatly reduced. The project involved a critical review of existing and historical data on cetacean stocks, and a compilation of data on E&P activities and non-industry factors that may have influenced stocks, in the areas of interest. Data were assessed in terms of quality, quantity, and temporal and spatial coverage to determine whether sufficient data were available for a reasonable assessment of correlations between cetacean populations and E&P activities. Where possible, data were examined to determine the extent of correlation between E&P activities and trends in stock abundance. The objectives of the project were to (1) evaluate changes in cetacean stocks as they may relate to sounds generated by offshore exploration and production operations; (2) determine the current status and trends of different cetacean stocks that were potentially exposed to sound generated by the oil and gas industry; (3) examine cetacean stock recovery rates and relate those to activity levels; (4) evaluate other key factors that may have influenced cetacean population growth rates; (5) identify key species that lend themselves to more detailed analyses/assessments or data collection for specific regions; (6) comment on existing literature and address data limitations; and (7) provide recommendations for future studies / assessments. Outcome of Comparative Approach for Those Stocks with Sufficient Information Of the key species and stocks considered, there were only two species (gray whale and humpback whale) for which sufficient information was available about both the stock(s) in our areas of assessment and the respective comparative stock. By sufficient information, we mean adequate information (for both stocks) concerning current abundance, trend in abundance, and extent of recovery. For two additional stocks, southern right whales in SE Australia and the Bering-Chukchi-Beaufort stock of bowhead whales, the available data are limited, but sufficient to warrant some evaluation. Gray whales―Data are available on both eastern and western stocks of gray whales. Although both have been exposed to E&P sound, the eastern gray whale has been exposed over a much longer period and in different key habitats than the western gray whale. The western gray whale has been heavily exposed to E&P activities during the summer feeding period, especially in recent years, whereas the eastern gray whale has had lesser and more infrequent exposure to E&P activities during the summer. Both populations appear to have been heavily exposed to shipping during their migrations to and from their respective feeding areas. However, this is poorly documented for the western gray whale. It may be presumed that the western stock encounters significant vessel and other activity along its migration route and in the presumed calving and calf-rearing area in the South China Sea. Nonetheless, in the absence of more specific information on seasonal distribution, the extent of exposure of the western gray whale to anthropogenic disturbance during the calving period is uncertain. In contrast, the eastern gray whale‘s calving areas have been extensively studied, and mothers and calves have been heavily exposed to anthropogenic activities in some calving areas. These anthropogenic activities have resulted in some changes in use of the calving lagoons (Bryant et al. 1984; Richardson et al. 1995). The comparison is further complicated by the fact that the western gray whale population is critically endangered and is a remnant population reduced to an extremely low level, so that its demographics may not be representative of a healthy population. In contrast, the eastern gray whale population has approached, and perhaps exceeded, the carrying capacity of its summer feeding range. Nonetheless, the eastern and western gray whale populations do show comparable growth rates (Table 6.1). Humpback whales―The Group D humpback whale stock that winters off Western Australia exhibited a relatively high rate of increase (~10% per year) over the period 1982–1994 (Bannister and Hedley 2001). Two very similar recent estimates of the abundance of this stock are available. Likewise, for the comparative Group E humpback whale stock, which winters off eastern Australia, robust estimates of abundance and trend are also available (e.g., Noad et al. 2006; Paton et al. 2006). Both stocks are recovering at rather rapid rates from historical exploitation. Group D has been exposed to extensive offshore E&P activities along its migration corridor whilst Group E has been exposed to little E&P activity but to more shipping, whale-watching, and recreational vessels. It appears that both stocks of humpback whales are very resilient to anthropogenic activities, including E&P industry activities. It does not appear that recovery of either stock subsequent to the whaling era has been seriously impeded by anthropogenic activities (E&P or otherwise) occurring in the ranges of the respective stocks. Southern right whales―The effect of E&P activities on the southern right whales wintering off southeast Australia is unclear. At present, there is no robust estimate of current abundance or rate of increase, but it is clear that the southeastern population is very small and there is no evidence of increasing numbers. The status of this stock is of concern. These whales are heavily exposed both to E&P activities and to other anthropogenic activities including extensive shipping and fisheries. It is likely that this population is less resilient to anthropogenic activities than are the larger stocks of southern right whales, such as the South African population. The latter stock is also exposed to high levels of E&P activities but is recovering at a rate close to the theoretical limit (Best et al. 2001, 2005). The western Australia/Head of Bight (HOB) population of southern right whales, which has been exposed to much less E&P and other anthropogenic activity, also has a high rate of population growth (Bannister 2008). E&P activities may not be the primary factor contributing to the apparent lack of recovery of the southern right whales in southeast Australia, but it is potentially one of the factors involved. Bowhead whales―As noted above, the population size and rate of recovery of the Bering-Chukchi- Beaufort (BCB) stock of bowhead whales are well documented. Commercial whaling of this stock ended almost a century ago (Bockstoce and Burns 1993). The stock is continuing to increase (Zeh and Punt 2005) despite an ongoing subsistence whale hunt each year and periodic exposure to E&P activities on the summering grounds and along the migration route. Data on stock sizes and population trends for other bowhead stocks are less reliable (or lacking altogether). However, the BCB bowheads have recovered better than other stocks despite the more consistent and ongoing exposure of BCB bowheads to human activities, including E&P activities and subsistence whaling. Conclusion The approach of comparing population size, rate of increase and health for stocks of selected key species in areas with different levels of E&P activity is of limited usefulness at this time. There are few pairs of key and comparative stocks with sufficient data on each stock. Also, for the few pairs of stocks with sufficient data, there are confounding (co-varying) factors that generally prevent ascribing between- stock differences specifically to E&P activity. Because of these considerations, generalisations are not possible. However, results from humpback whales in Australia show that rapid recovery is occurring in a humpback stock exposed to considerable E&P activity. Results from both western and eastern gray whales show population growth despite both populations being exposed to significant human activity. However, eastern population may have levelled off in recent year and may even have reached carrying capacity, and the status of the very small western population remains critical. There are major gaps in our knowledge of the distribution and movements of the western stock, and thus gaps in our knowledge of other pressures the population may be under. The southeastern Australian right whales are showing no signs of recovery, and they are exposed to both E&P activities and other anthropogenic activities. It is unknown whether the E&P activities are contributing to their lack of recovery. It is probable that additional pairs of stocks with robust population data could be identified by considering study areas other than the three addressed in this study. However, the number of cetacean stocks whose population biology has been studied systematically for extended periods is limited, and not all of these species include stocks in areas with significant E&P activity. It would be useful to review the results from the other JIP-funded stock-assessment projects to identify additional pairs of stocks that might be appropriate for consideration.