Time flies when you’re busy having fun! I truly enjoyed being home on St. Paul Island this summer, conducting research for my Masters project and catching up with family and friends. Now that my field season is complete, I’ve returned to the University of British Columbia to begin analyzing my dive data and writing my thesis.
This summer I was busy working on a couple of projects. During the subsistence fur seal harvest in July, I collected body measurements and tooth (canine) samples from 254 juvenile males for an ongoing nutritional stress study. Recent measurements (in 2005 and 2006) continue to show stunted growth— evidence that fur seals are still experiencing nutritional stress resulting from inadequate diet. This ongoing study will determine whether the trend in body sizes of fur seals continues to decrease, levels out or begins to increase.
In August and September, I deployed dead-reckoner tags on 13 adult female fur seals. The focus of my study is to measure the degree of spatial overlap between fur seal foraging areas and commercial fishing activity in the eastern Bering Sea. It has been suggested that commercial fisheries may be playing a role in the decline of fur seals by affecting the abundance of their key prey.
Dive data from the dead-reckoner tags will provide detailed records of fur seal diving patterns and will be used to create habitat maps showing areas where fur seals are traveling and foraging. These maps will be overlaid with a grid showing habitat usage from high to low, and will be compared with annual and seasonal fisheries data to calculate overlap indices. Results will provide a better understanding of fur seal foraging behavior and will ultimately provide an improved assessment of critical habitat.
Studying fur seal foraging behavior at a fine scale is a necessary step towards addressing the question of potential interactions between fur seals and commercial fisheries operating in the vicinity of the Pribilof Islands. With the advent of new technology and increasing knowledge of fur seal foraging behavior, researchers can make recommendations to commercial fishery managers on where and when fur seals may be more vulnerable to fishing activity.
Future studies should look at fine-scale foraging behavior, as well as data on prey capture and diet, to better understand how fisheries may be affecting the fur seal population. In time, studies will also use tracking instruments that can measure acceleration and obtain location-at-sea within two meters accuracy (the error associated with satellite tags is much larger, between 150 and 1,000 meters).
So far it has been exciting to look at the detail of the data collected by the dead-reckoner tags, and to visualize the dive profiles of the different females tracked with these tags. I have months and months of data to analyze, but I hope to finish my Masters degree in the fall of 2007.
Both projects were made possible by the help of many individuals. The Tribal Government of St. Paul’s Ecosystem Conservation Office was supportive in collecting and processing canine samples collected from the subsistence fur seal harvest and in deploying instruments on female fur seals in 2006. The National Marine Mammal Lab in Seattle was instrumental in deploying instruments on fur seals in 2005 and 2006 and Stephen Insley was central to training a local capture team.
I am also grateful for the financial support of NOAA and the North Pacific Research Board to the North Pacific Universities Marine Mammal Research Consortium through the North Pacific Marine Science Foundation.
This is my final What’s New article. I would like to thank you for following my adventures in the Pribilofs, and I hope you enjoyed learning about my study and a little about my hometown.
4 December 2006
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previous installments from "Summer Field Season 2006