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Within the North Pacific, gray whales (Eschrichtius robustus) are recognized as distinct eastern and western populations. Although both populations were severely reduced by whaling, the eastern population is generally considered to have recovered while the western population has remained highly depleted. This study expanded on previous work supporting differentiation between eastern and western populations using mtDNA and utilized a panel of 13 microsatellite loci to provide additional insight into the population structure of gray whales. Comparison of microsatellite allele frequencies indicated that eastern and western populations are genetically distinct. Although highly statistically significant, the level of nuclear differentiation between the two populations was relatively low, and the results of sex-specific analyses and assignment testing suggested that some degree of male- biased dispersal may occur between populations. Within the set of samples collected from animals on the primary western feeding ground, relatedness analyses revealed that, consistent with field observations, the fidelity of females and their offspring to this area have been important in shaping the structure of the population. Furthermore, analysis of the paternity of animals first identified as calves, with known and sampled mothers, in the western population between 1995 and 2007 identified 18 males as putative fathers, providing evidence that many of the animals identified on the Sakhalin feeding ground interbreed with each other, presumably while sharing a common migratory route. However, the success of the paternity assignment was lower than expected given the high proportion of sampled animals in this population, suggesting that some males which are contributing to reproduction may not use the primary western feeding ground on a regular basis. The combination of these results suggests that the population structure of gray whales in the North Pacific is more complex than previously thought, and that some movements between the eastern and western populations may take place. However, the maintenance of genetic differences between the two populations supports their recognition as separate eastern and western populations. Future efforts should focus on elucidating the nature and extent of any dispersal which is occurring in order to better understand factors potentially influencing the recovery of the small western population

NOAA technical memorandum NMFS ; NOAA-TM-NMFS-SWFSC ; 617

The 2015 Pacific marine mammal stock assessments include revised reports for eight Pacific marine mammal stocks under NMFS jurisdiction, including five “strategic” stocks: Hawaiian monk seal, Southern Resident killer whale, Eastern North Pacific blue whale, Main Hawaiian Islands Insular false killer whale, and Hawaii Pelagic false killer whale. New abundance estimates are available for three stocks in the Pacific Islands region (Hawaiian monk seal, Hawaii Pelagic and Northwestern Hawaiian Islands false killer whales) and two U.S. west coast stocks (Southern Resident killer whale and California northern fur seal). The stock range and boundaries of the three Hawaiian stocks of false killer whales, which have overlapping ranges, were recently reevaluated based on new information on the occurrence and movements of each stock (Bradford et al. 2015). New information on fisheryrelated serious injury and mortality of false killer whales has also been updated. A stock assessment report for the Eastern Tropical Pacific stock of Bryde’s whale has been reinstated into the Pacific reports in response to a regular and increasing presence of this species in southern California waters (Kerosky et al. 2012, Smultea et al. 2012). The Eastern Tropical Pacific Bryde’s whale report last appeared in the Pacific stock assessments in 2007. The genus of Hawaiian monk seal has been updated from Monachus to Neomonachus to reflect recent genetic and skull morphology data (Scheel et al. 2014). The report for Eastern North Pacific blue whales includes significant new information on historic whaling removals, the population’s status relative to carrying capacity, and risk of ship strikes to the population (Monnahan et al. 2014, 2015). This is a working document and individual stock assessment reports will be updated as new information on marine mammal stocks and fisheries becomes available. Background information and guidelines for preparing stock assessment reports are reviewed in Wade and Angliss (1997). The authors solicit any new information or comments which would improve future stock assessment reports.

The 2014 Pacific marine mammal stock assessments include revised reports for 11 Pacific marine mammal stocks under NMFS jurisdiction, including six 'strategic' stocks: Hawaiian monk seal, Southern Resident killer whale, Main Hawaiian Islands Insular false killer whale, Hawaii Pelagic false killer whale, California/Oregon/Washington sperm whale, and Western North Pacific gray whale. New abundance estimates are available for three stocks in the Pacific Islands region and five U.S. west coast stocks. New estimates of abundance for the California/Oregon/Washington stock of sperm whales are based on a Bayesian trend analysis that utilizes previously collected line-transect data (Moore and Barlow, 2014), resulting in a more stable time series of abundance estimates. Mortality and serious injury estimates of California/Oregon/Washington sperm whales in California drift gillnets are updated, based on pooling additional years of data (>5 years) to reduce bias and improve precision in mean annual bycatch estimates (Carretta and Moore 2014). The combination of new abundance estimates and pooling of bycatch estimates over a longer time period for this stock of sperm whales results in mean annual bycatch estimates that no longer exceed PBR. In addition, a new stock assessment report for Western North Pacific gray whales is presented for the first time, prompted by new data showing that gray whales previously photographed in the western North Pacific utilize U.S. and Mexican waters. Stock Assessments for Alaska region marine mammals are published by the National Marine Mammal Laboratory (NMML) in a separate report.

The IWC Scientific Committee recently adopted guidelines for quality control of DNA data. Once data have been collected, the next step is to analyse the data and make inferences that are useful for addressing practical problems in conservation and management of cetaceans. This is a complex exercise, as numerous analyses are possible and users have a wide range of choices of software programs for implementing the analyses. This paper reviews the underlying issues, illustrates application of different types of genetic data analysis to two complex management problems (involving common minke whales and humpback whales), and concludes with a number of recommendations for best practices in the analysis of population genetic data. An extensive Appendix provides a detailed review and critique of most types of analyses that are used with population genetic data for cetaceans. Publisher PDF