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Polar Ecosystems

Research Cruise Aboard the McArthur II in the Central Bering Sea, April-May 2010

ice seal cruise crew
Figure 4.  The 2010 McArthur II ice seal cruise crew included biologists from the Polar Ecosystems Program, California Current Ecosystems Program, Alaska Department of Fish and Game, and a veterinarian from the School of Veterinary Medicine, University of California, Davis.  Back row, left to right: Dave Withrow, Erin Moreland, Josh London, Gavin Brady.  Front row, left to right: Jay VerHoef, Jeff Harris, Tracey Goldstein, Lorrie Rea, Heather Ziel.

The Polar Ecosystems Program (PEP) participated in an ice-seal research cruise in the central Bering Sea this spring, 26 April-25 May 2010, aboard the NOAA ship McArthur II. Primary objectives for the cruise were to deploy satellite-linked tags on ribbon and spotted seals and to collect biological samples including blood, blubber biopsies, hair, whiskers, skin, and scats. Satellite-linked tags provide critical information on haul-out and dive behavior and seasonal movements; data collected this year will be combined with information collected during similar cruises conducted since 2005 to provide additional information on haul-out and dive behavior and seasonal movements. The biological samples will be used to establish baseline data for research projects (including diet, physiology, disease, and contaminant studies) being conducted with ribbon and spotted seals; current data about much of the biology of these seals are scarce.

Both ribbon and spotted seals have been petitioned to be listed under the U.S. Endangered Species Act, primarily out of concerns about global warming and the loss of sea-ice habitat. Information on the timing of haul out is critical for estimating abundance from previous and future aerial surveys, and data on movements and dive behavior will help to identify important habitat.

figure 5, ribbon seal pup
Figure 5.  A ribbon seal pup in the Bering Sea with satellite-linked transmitter attached to the back and orange flipper tags attached to the rear flippers.  Photo by Dave Withrow.

figure 6, spotted seal pup
Figure 6.  A spotted seal pup in the Bering Sea with satellite-linked transmitter attached to the back.  Photo by Dave Withrow.

The McArthur II departed Kodiak, Alaska, on the morning of 26 April and arrived at the ice edge and began research operations the morning of 30 April. A typical day consisted of survey observations from 9 am to 8 pm Hawaii-Aleutian Standard Time; observation times were centered close to local solar noon.

The survey observations were interrupted by small-boat excursions to capture and tag seals when we encountered sufficient concentrations of seals and suitable ice. Seals were captured on ice floes with large, hand-held landing nets.

The field crew consisted of seven biologists from NMML's PEP and California Current Ecosystems Program, one biologist from the Alaska Department of Fish and Game, and one veterinary technician from the Wildlife Health Center, School of Veterinary Medicine at University of California, Davis (Fig. 4 above). We conducted surveys and tagging operations daily until the evening of 22 May, and the McArthur II returned to Dutch Harbor, Alaska, on the morning of 25 May.

We captured 42 seals in all, comprising 23 ribbon and 19 spotted seals. We attached satellite transmitters to 17 ribbon and 8 spotted seals (Figs. 5, 6). We deployed 14 SPOT tags (Wildlife Computers, Redmond, WA), attached to the seals' hind-flippers, which will provide long-term movement data and haul-out timelines but only when the seals are hauled out with their flippers exposed.

We also deployed 11 SPLASH and 6 MK10 tags (Wildlife Computers); these tags provide more detailed information about the seals' locations at sea and diving behavior. These tags must be glued to the hair on the seal's back or head and, thus, could only be attached to seals that had sufficiently completed their annual molt. In addition to the satellite-linked tags, we attached a numbered flipper tag to the hind-flipper of each seal that identified it as being previously captured.

This year we expanded our sampling protocol compared to what we have done in the past. Sampling typically included length and girth measurements, mass, blood, a small piece of skin for genetics analysis, any fecal material present on the ice for diet analysis, and any urine on the ice for domoic acid analysis. This year, we also collected hair for mercury analysis, blubber for contaminants or fatty acid analysis, whiskers for stable isotope analysis, nasal swabs for disease analysis, and an ultrasound for blubber depth.

We also took many photos to document sampling for each animal; photos generally included teeth, claws, any tags attached, overall condition, the release of the seal, and anything else that was distinct or important. We obtained blood samples from 37 seals, from which we collected whole blood, serum, plasma, and red blood cells, and measured hematocrits and hemoglobin levels. We also collected 42 skin samples and nasal viral swabs, 33 whiskers, 18 blubber biopsies, 29 fecal samples, 29 hair samples, 14 urine samples, and 26 ultrasounds from captured seals. All of the samples, including those collected in the past and those added to the sampling protocol this year, will be helpful in establishing baseline data for a variety of analyses about the biological condition of these seals.

By Josh London and Heather Ziel

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