UC San Diego

Overexploitation of Southern Ocean fish stocks has caused significant trophic restructuring in Antarctic marine ecosystems, forcing Antarctic fur seals (Arctocephalus gazella) to forage on alternative prey. As a species that has faced near extinction in the recent past, it is important to have accurate data to monitor the effects ecosystem changes may have had on their diet, health, and behavior. Stable carbon (δ13C) and nitrogen (δ15N) isotope analysis is a proven technique for reconstructing foraging ecology and migration patterns in marine mammals. Investigating whether the stable isotope values from Antarctic fur seal pup vibrissae grown in utero can provide valid data on their mothers' foraging ecology is useful as newborns are much more accessible research subjects than adults. Using samples collected at Cape Shirreff, Livingston Island in the South Shetland Islands during November to December 2012, I compared stable isotope values from vibrissae of 1- or 2-day-old pups with those from their mothers’ vibrissae. I determined whisker growth rates for all individual seals in the study, using known total gestational whisker growth for pups, and known annual growth for mothers. I used spatial data from some mothers to determine if isotopic data corresponded to known migration routes. No distinct patterns emerged for the δ13C values, whereas the δ15N data suggest a correlation with the Antarctic Polar Front. Pup and mother isotope data show the appearance of a correlation when normalized for individual growth rates, however further research with revised sample collection parameters would be ideal to conclusively establish this relationship.