Pinniped Research Program
AERD researcher Mike Goebel is co-Principal Investigator on joint National Science Foundation/NOAA's Undersea Research Program's Climate Science and Elephant Seal project.
In April 2007, Mike Goebel joined collaborators on 2-month survey in the Antarctic to deploy tracking instruments on crabeater_seals.
As upper trophic level predators, pinnipeds are a conspicuous component of the marine ecosystem around the South Shetland Islands. They respond to spatio-temporal changes in physical and biological oceanography and are directly dependent upon availability of krill for maintenance, growth, and reproduction during the austral summer. The Antarctic fur seal, Arctocephalus gazella, is the most abundant pinniped at Cape Shirreff and our studies are focused to a large degree on this species. Because of their current numbers and their pre-exploitation biomass in the Antarctic Peninsula and Scotia Sea regions, they are recognized to be an important krill-dependent upper trophic level predator. The general objectives for pinniped research at Cape Shirreff are to monitor population demography and trends, reproductive success, and status of pinnipeds throughout the summer months. Our studies focus on foraging ecology, diving, foraging range, energetics, diet, and reproductive success of fur seals rearing offspring.
The rate of fur seal pup production at Cape Shirreff and the South Shetland Islands has decreased substantially in the last decade which indicates that the recovery of fur seals from being driven to extinction in the late 1800s has slowed dramatically. The AERD will continue to monitor the status of the fur seal populations at Cape Shirreff. In addition, annual inshore surveys and oceanographic mooring buoys providing enhanced monitoring of oceanographic conditions at the site (both during summer and winter seasons) are needed. The over-winter dispersal and survival of pups and adult female fur seals is also necessary to understand their relationships to primary fishing areas. To this end, the AERD has initiated a study using satellite tags [aka PTTs] to monitor the overwinter tracks of fur seals.
To enhance our understanding of the age structure of the fur seal populations at Cape Shirreff, researchers use two methods. One is to tag a subset of pups the year they are born, and to follow the animals through time. Each subsequent year, researchers scan each animal in the study area, looking for seals tagged in previous years. This informaton is useful to determine the age structure of the local populations. However, this obviously can't be done for older animals - their age is unknown. To overcome this information gap, a post-canine is extracted from a subset of adult females. The tooth is sliced into thin strips, and stained (see image). Each layer of cementum represents on year of age for the seal. This method allows us to determine the age of the older animals seen in a rookery.
Approximately every five years, the AERD conducts surveys of fur seal colonies in the South Shetlands. Finally, we need to investigate leopard seal distribution and dispersal using satellite linked archival recorders to investigate the hypothesis that "top-down" factors are currently controlling recovery of fur seal populations in the South Shetlands.
Pinniped research is directed by Dr. Michael Goebel of the AERD.