Western Gray Whales off Sakhalin Island, Russia: A Joint Russia-U.S. Scientific Investigation July-September 2003

• Main Authors: Weller, David W., Burdin, Alexander M., Bradford, Amanda L., Ivashchenko, Yulia V., Tsidulko, Grigory A., Lang, Aimée R., Brownell, Robert L., Jr.
• Format: Text
• Language: unknown
• Published: DigitalCommons@University of Nebraska - Lincoln 2004
• Subjects: Environmental Sciences; Sakhalin
• Online Access: https://digitalcommons.unl.edu/usdeptcommercepub/72; https://digitalcommons.unl.edu/context/usdeptcommercepub/article/1065/viewcontent/Brownell_2004_Western_gray_whales_final.pdf

Research on the western gray whale (Eschrichtius robustus) population summering off northeastern Sakhalin Island, Russia, has been ongoing since 1995. This collaborative Russia-U.S. research program has produced important new information on the present day conservation status of this critically endangered population. This report reviews recent findings from 2003 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 2003 resulted in the identification of 75 whales, including 11 calves and two previously unidentified non-calves. When combined with data from 1994-2002, a catalog of 131 photo-identified individuals has been compiled. The population size is estimated to be approximately 100 individuals and non-calf and calf survival rates are 0.95 and 0.70, respectively. Of the 131 whales photo-identified, 108 (82.4%) have now been biopsy sampled. From genetic analysis of samples collected through 2002, an overall male biased sex ratio of 59.1% males and 40.9% females was determined. The sex ratio for calves was 68.0% male and 32.0% female. Previous genetic research on the western gray whale population documented clear genetic differentiation from the eastern population on the basis of mitochondrial DNA haplotype frequencies. Nuclear DNA markers used to measure the differentiation and relative levels of genetic diversity in the nuclear genome between the western and eastern populations confirm the earlier conclusion (based on mtDNA) that the two populations are genetically distinct and further suggests negligible gene flow of either sex between populations. A minimum of 23 reproductive females has been observed since 1995 and their most common (74.4%) calving interval is three or more years. Three whales were recorded as "skinny” in 2003, a total number lower than recorded in previous years. In addition to the clear biological difficulties that western gray whales are facing, the recent onset of ...