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Many valuable contributions to the biology and conservation of harvested or previously harvested species have come from examination of specimens obtained by lethal collections. The northern fur seal Callorhinus ursinus on the Pribilof Islands, Alaska, has a long history of exploitation, including a large (>320 000) experimental harvest of females from 1955 to 1968 when the population was at a peak (∼2 million seals). The decline caused by this harvest was followed in 1977 by another major decline, apparently unrelated to harvest, that has recently accelerated. To obtain current reproductive data that could be compared directly with historic estimates, we used imaging ultrasonography to estimate pregnancy rate in 171 adult fur seals captured on St. Paul Island, Alaska, in November, near the end of embryonic diapause. A modified logistic regression of pregnancy by date was used to estimate asymptotic pregnancy rate; a Bayesian hierarchical model based on date and size of embryonic vesicle was also used to account for pregnancies that were not detectable on the date of examination. Pregnancy rate was high [0·85 (SE = 0·05), 0·88 (SE = 0·05) or 0·92 (SE = 0·04), depending on method] and there was little statistical support for the hypothesis that the current pregnancy rate is lower than the pre-decline rate (0·84, SE = 0·012) or contributing significantly to the present decline. Synthesis and applications. Further study on intrauterine losses and pupping rates is necessary and ongoing, but reproductive ultrasonography provided an early comparative assessment important for the conservation management of this fur seal stock. It narrows the search for demographic and ecological causes of the population decline and allows research priorities to evolve in response to the likelihood of those causes. The field and analytic methods described have application to population assessments of other mammalian species, including those considered threatened or serving as ecosystem indicators. [ABSTRACT FROM AUTHOR]

The article presents a study which showed the role of global positioning system (GPS) in tracking the large-scale movements of marine species in Saint Paul Island, Alaska. The study, which was conducted from September to October 2007 and August to October 2008, evaluated the accuracy of a continuous-time correlated random walk model for spatial error and gap times associated Argos satellite (PTT) using GPS data. It included 42 adult female northern fur seals that were equipped with Wildlife Computers.

The article presents a study on the characterization of reproductive anatomy and early embryonic detection in the northern fur seal or Callorhinus ursinus using ultrasonography in Saint Paul Island, Alaska. The study's aim is to determine the feasibility of transrectal ultrasonography for assessing the reproductive status of female northern fur seals in the wild and to provide preliminary description of the reproductive tract and early embryo in situ. Subjects used were female northern fur seals of adult size, where ultrasonography was performed by an experienced operator with the use of a portable ultrasound unit. An overview of the results of the study is offered.