Project Description
Harbor seal branding and resighting effort will continue at Gertrude Island, Washington to develop age-specific survival and natality rates. Genetics samples have been sequenced for 526 unweaned pups from 10 sites (8 in the inland stock (including 2 areas in the Canadian transboundary waters); 2 from the coastal stock) using maternally inherited mtDNA. These samples will now be processed for microsatellites to compare biparentally inherited information. The microsatellite analysis is more likely to provide information on phylogenetic relationships because nuclear DNA evolves more slowly than mtDNA and the microsatellite data will provide male migration rates.
Issues & Justification
Analysis of resightings of 523 harbor seals branded between 1993 and 2003 has produced estimates for natality, age of first reproduction and survival. Data on the abundance of harbor seals in Washington, collected between 1978 and 1999 indicate that seals in both the coastal and inland waters stocks have reached OSP (Jeffries et al. 2003). Additional branding and resighting effort is necessary to determine natality for older females and to increase sample sizes for younger animals to refine survival rates for pups, yearlings and subadults. Analysis of sequencing data has been completed on genetic samples collected from 526 unweaned pups comparing 8 sites in the inland stock with 2 sampling sites from the coastal stock. The presence of two stocks has been confirmed and the present stock boundary appears appropriate based on mtDNA and pupping phenology. Direct sequencing of 526 samples defined 72 haplotypes resolving into 4 matrilines.
Goals
- Continue harbor seal branding and resighting effort to refine survival and age-specific natality rates for seals in Puget Sound.
- Continue genetic analysis comparing information from microsatellites and mtDNA direct sequencing to assess genetic differences among harbor seals in ten regions within Washington State.
- Compare information from microsatellite data to results from direct sequencing to confirm the appropriate boundary between Coastal and Inland stocks of Washington harbor seals.
Methods
Harbor seals of all ages will be captured and branded at Gertrude Island, Washington during the pupping season 2008. To date, 613 seals have been branded. Resighting observations 2-4 days/week during the pupping/breeding season (mid-June through October) will give information on survival and age-specific natality of branded seals in the south Puget Sound population as well as information on preweaning mortality. Data will be analyzed using the program MARK. During captures, genetic samples will be taken from unweaned and newly weaned pups. Differences in microsatellite frequencies among areas will analyzed using fixation index (Fst), inbreeding co-efficient (Fis), heterozygosity, and migration rate (MR) based on RST.