Harbor Seal studies near Pederson and Aialik Glaciers

Withrow, Dave

The National Marine Mammal Laboratory (NMML) with support from the Kenai Fjords National Park, conducted research on ice-associated harbor seals (Phoca vitulina) from 5 to 20 August 1998. Harbor seals are censused from aircraft by photographing those on land during the molt period (August/September). These surveys miss an unknown number of animals that are at sea during the survey period. The NMML is involved in a multi-year study to determine a correction factor to estimate the relative proportion of seals that are at sea and thus not counted during these surveys. Our goal is to determine a correction factor for each haulout substrate (rocky, sand bars, ice, etc...) in each of the four general stock areas where harbor seals are found (SE Alaska, Gulf of Alaska, Aleutian Islands, and Alaska Peninsula/Bristol Bay). An unknown, but significant number of harbor seals haul out primarily or entirely on glacial ice. Nineteen seals (9 males and 10 females) comprising 8 adults, 7 sub-adults, 3 yearlings and 1 pup were captured by entanglement using gillnets placed near their haulout sites (ice flows). Fifteen seals were captured near Pedersen Glacier and 4 near Aialik Glacier. All seals were physically restrained during handling and tagging; no chemical sedation was required. Seals were initially given an external examination which included recording mass, standard length, sex, age class, stage of molt, and noting any external scars, wounds, or parasites. Approximately 50 cc of blood was drawn from the extradural intervertebral vein to assess health and condition. The seals were then tagged on the hind flipper with a Temple cattle-ear tag (1 x 1.5 x 5.0 cm) with a VHF transmitter attached (Advanced Telemetry Systems Inc. model 201, 165 MHZ). Weight of the tag and transmitter was approximately 25 gr. A small 0.7 cm diameter biopsy punch was taken from the left rear flipper (used for mitochondrial DNA studies) and the Temple tag was clipped in place through this small hole. A small plastic, orange, All-Flex tag (1.5 x 4.5 cm) was clipped to the right rear flipper. Seals were released immediately after tagging. A list of radio frequencies used, animal identification numbers, and other information appear in Table 1.