Note: You need to enable scripting and Javascript in your browser settings to best view and navigate our website. Otherwise use our keyboard navigation and search page. Our print link for screen media is scripted. Your computer's normal print command will print this page. Please contact us if you have difficulty in accessing our web pages.
  link to AFSC home page
Mobile users can use the Site Map to access the principal pages


link to NMFS home page link to AFSC home page link to NOAA home page

Project Description

The abundance of northern fur seals (Callorhinus ursinus) on the Pribilof Islands has declined in recent decades, yet the reasons for the decline are unclear. The estimated number of pups born on the Pribilof Islands in 2006 was approximately 9.1% less than the 2004 estimate and was comparable to the level observed in 1917. On-land mortality during the summer months may be a significant cause of mortality, particularly for new-born pups. Dead northern fur seal pups, juveniles and adults will be collected at selected sites on St. Paul Island during the summer of 2008, and necropsied by a veterinarian to determine the causes of mortality. The research will help to assess factors influencing mortality during the summer months, and to identify changes or trends in these factors. Additionally, it will allow for monitoring of unusual mortality events and the related causes.

Issues & Justification

Recent declines of northern fur seals on the Pribilof Islands may be affected or compounded by increased mortality during the summer months at the breeding islands. Fur seal population monitoring studies were conducted during 2004 on the Pribilof Islands, and indicate continued declines in the number of northern fur seals. The estimated northern fur seal pup production on the Pribilof Islands declined 24.6% between 2002 and 2006. Studies of mortality and causes of death of northern fur seal pups on the Pribilof Islands began in 1962, and at San Miguel Island in 1996. The most common cause of mortality among pups during the first 2 months of life is emaciation syndrome. However, the frequency of this and other causes of mortality, such as hookworm disease, tend to be cyclic. Continued evaluation of the factors which influence mortality of pups provides an early assessment of the parameters affecting cohort survival and potential for population growth. Additional studies of the causes of mortality among juvenile and adult fur seals provides a means of monitoring factors that may affect survival of these age classes during the summer months.

Goals

  • Assess the frequency and causes of pup mortality at selected rookery sites on St. Paul Island.
  • Assess the frequency and causes of juvenile and adult mortality at selected rookery sites on St. Paul Island.
  • Analyze long term data set (20 years) and write up the results for publication.

Methods

A veterinarian/pathologist will be contracted to collect and determine the cause of death of dead fur seals. Direct collection of dead northern fur seal pups will be conducted daily (from approximately July 1-August 10) from catwalks that are constructed through sections of Reef and Vostochni rookeries on St. Paul Island. Opportunistic collection of dead juvenile and adult fur seals will also be made. The researchers crawl on the catwalk, ~6-8ft above the rookery, from which dead pups can be collected using a long bamboo pole with attached noose line. All recently dead pups, juveniles and adults that are accessible within the selected sites are collected and necropsied by the veterinarian to determine the frequency and causes of mortality.

Webmaster | Privacy | Disclaimer | Accessibility