An examination of variance and sample size for female Antarctic fur seal trip durations

This paper uses power analysis and bootstrap functions to examine the importance of sample size in detecting differences between two years of fur seal trip duration data. Female foraging trip duration for the first six trips to sea for 1997/98 (n = 30) and 1998/99 (n = 31) at Cape Shirreff, Livingston Island was used to calculate minimum sample sizes necessary to detect differences from year to year. A bootstrap function was used to examine the effect of sample size on variance. Currently CCAMLR-Ecosystem Monitoring Program Standard Method C 1.2 for measuring fur seal trip duration sets the sample size at 40 females. Based upon my results I propose incorporating some flexibility in sample size and suggest changing the protocol from 40 to 25 – 40 females.