Date of this Version
A collaborative Russia-U.S. research program on western gray whales (Eschrichtius robustus) summering off northeastern Sakhalin Island, Russia, has been ongoing since 1995 and has produced important new information on the present day conservation status of this critically endangered population. This interim report reviews preliminary findings from 2007 research activities and combines such with data from previous years, in some cases ranging back to 1994. Photo-identification research conducted off Sakhalin Island in 2007 resulted in the identification of 83 whales, including nine calves and two previously unidentified non-calves. When combined with data from 1994-2006, a catalog of 169 photo-identified individuals has been compiled. Not all of these 169 whales can be assumed to be alive, however. The most current mark-recapture analyses conducted estimated the abundance for the population to be 98 (95% CI=89-110) in 2002 and 99 (95% CI = 90-109) in 2003. A recent population assessment using a Bayesian individually based stage-structured model fitted to the same photo-identification data as used in the markrecapture studies, but also including data from 2004 through 2006, estimated the median non-calf population size to be 110 in 2004 and, should current population and demographic trends continue, projected a median non-calf estimate of 121 (90% Bayesian CI = 112-130) in 2007. Of the 169 whales photo-identified, 142 (84%) have been biopsy sampled. From genetic analysis of samples (n = 129) collected through 2006, an overall sex ratio of 58% male and 42% female was determined. Clear genetic differentiation from the eastern gray whale population and negligible gene flow of either sex between populations, based on mitochondrial DNA haplotype frequencies and nuclear DNA, have been documented. A minimum of 24 reproductive females has been observed since 1995. Of the 83 whales observed in 2007, 7.2% (n = 6) were recorded as "skinny”. In addition to the biological difficulties that western gray whales are facing, the large-scale offshore oil and gas development programs near their summer feeding ground, as well as fatal net entrapments off Japan during migration, pose significant threats to the future survival of the population.