Project Description
This is a collaborative study with the Alaska Ecosystems Program at NMML to document age and sex-specific, range-wide patterns in movements and migration of northern fur seals. Populations in the two regions express different population dynamics due to characteristics of their different ocean habitats. Recent comparative studies of the populations in Alaska and California indicated different migratory patterns of adult females and pups from Alaska and California colonies. While females and pups from the Alaska populations ranged widely in the open ocean of the North Pacific, the migratory routes of animals from California were restricted to the California Current. This study will document movements and migration of juveniles (1-2 years old) in California to compare with similar data from the Alaska populations to determine if these patterns are consistent among the age classes.
Issues & Justification
The northern fur seal was listed as 'depleted' under the MMPA in 1972. The Northern fur seal Conservation Plan in 1993 outlines research that will encourage the recovery of the population and includes all populations of fur seals in the U.S. Understanding habitat and food requirements of the populations during their breeding and migratory phases of the life cycle is a critical component of the conservation plan and is essential to meeting recovery goals. This project will support the conservation plan goal of defining the age and sex-specific habitat requirements of fur seals throughout their range. The northern fur seals at San Miguel Island, California represent the southern extent of the breeding range for the species and are managed under the MMPA as a separate stock. The population is small, about 10,000 animals and is vulnerable to catastrophic decline caused by environmental perturbations. The dynamics of the northern fur seal population at San Miguel Island over the past 25 years reflect the population's growth during warm oceanographic conditions in the California Current. A resurgence of sardine in the late 1990's as an energy-dense food resource and a colder oceanic regime in the California Current that began in 1999 should create a favorable environment for fur seals in California during the breeding and migratory phases of their life cycle. The effects of the higher nutritional plane of the population should result in higher survival and natality rates. Thus, the next 5 years will be an important time to monitor the population's foraging behavior and vital rates. The expansive range of northern fur seals requires a multi-ecosystem approach to understand factors affecting the U.S. northern fur seal population. We will collaborate with the Alaska Ecosystem Program at NMML to provide a comparative framework to evaluate environmental factors influencing northern fur seal populations in different population growth phases and ecosystems.
Goals
- Describe breeding and migratory foraging behavior of pups, juveniles, adult females, sub-adult males, adult males and compare to other populations and to shifts in environmental conditions.
Methods
In FY08 we will deploy satellite tags on 10 juvenile fur seals in late September or November 2008. Animals will be tracked for at least 8 months of their winter migration and the tracks and dive information will be compared with animals instrumented in Alaska.