The Alaska Fisheries Science Center's Marine Mammal Laboratory is conducting an ice-associated seal research survey in the central Bering Sea from April 2-29, 2016 aboard the NOAA Ship Oscar Dyson. The species being studied are ribbon, spotted, bearded and ringed seals.
A key objective is to attach satellite-linked tags on ribbon and spotted seals, which spend time either on or in the proximity of sea-ice during this time of year. Scientists plan to use data collected from the satellite-linked tags, together with information collected during similar surveys since 2005, to learn more about the timing of when these seals "haul out," that is come out of the water onto the ice. This information is critical for calculating abundance estimates from aerial surveys. Scientists also hope to learn more about dive behavior and seasonal movements (useful in identifying important habitat).
Eight biologists are on our field team: Gavin Brady, Michael Cameron, Shawn Dahle, Josh London, Dave Withrow and Heather Ziel from the Center, Charles Littnan from NOAA's Hawaiian Monk Seal Research Center and Markus Horning from the Alaska SeaLife Center. Our veterinarian is Deborah Fauquier from NOAA Fisheries' Office of Protected Resources. A typical day begins with transiting along the edge of, and within the, marginal pack ice looking for seals to tag.
We timed the survey to coincide with the whelping, nursing, and pup maturation season. Ribbon and spotted seals give birth to pups on the ice. Pups are nursed for 25-35 days before being weaned.
Seals prefer thicker, stronger ice floes that remain stable for this activity. However, at this time of the year, much of the marginal ice zone consists of young, thin ice formed late in the winter that is easily broken up and dissipated by ocean swells. This makes it difficult for seals to find stable places to haul out and challenging for our research team to capture them for tagging.
One way we find spotted seals is to look for a "triad." Adult male spotted seals will often find a mother and her pup on the ice and remain with them until the female is ready to breed. Collectively they are called a "triad."
To tag seals we attach satellite transmitters to their hind-flippers (SPOT tags, Wildlife Computers, Redmond, WA). These tags provide long-term movement data and haul-out timelines. However, the tags only transmit data when the seal is hauled-out and their flippers are exposed.
We will also try to attach head or back-mounted tags (SPLASH, Wildlife Computers, Redmond, WA) to most of the seals. This will provide more detailed information about locations at sea and seal diving behavior. These tags are adhered to the hair with super glue. Adult spotted and ribbon seals undergo an annual molt in May and June and so the SPLASH tags are expected to provide data for only a few weeks or months before being shed. In addition to location estimates, the SPLASH tags provide important behavioral data. Diving is an indicator of foraging activity and long periods at the surface indicate haul-out and resting behaviors.
The sampling for each seal typically includes morphometrics (i.e., length, girth and mass measurements) and the collection of numerous tissue and fecal samples for studies of pathology, genetic population structure, blood chemistry, diet, contaminants, health, and condition. These samples will begin to form a reference against which future impacts of climate disruption and loss of sea ice can be assessed. As the survey progresses, we plan to provide updates and photos that describe our research activities and more about what we are hoping to learn.