Alternative approaches to estimation of harbor seal numbers: the role of spatial scale ...

• Main Author: Gilbert, James R.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: ASC 2005 - R - Theme session 2024
• Subjects: Fisheries and aquaculture; Ecosystem observation, processes and dynamics; harbor seal; Phoca vitulina
• Online Access: https://dx.doi.org/10.17895/ices.pub.25350454.v1; https://ices-library.figshare.com/articles/conference_contribution/Alternative_approaches_to_estimation_of_harbor_seal_numbers_the_role_of_spatial_scale/25350454/1

No abstracts are to be cited without prior reference to the author.Complete counts of harbor seals (Phoca vitulina) hauled out during pupping season in Maine, USA, are expensive and logistically difficult. A complete aerial count of the haul-outs on the coast requires five to six days of flying. Given the short window of time around the peak of pupping, replicate counts are not feasible without considerable effort. Five previous coast-wide counts between 1981 and 2001 are evaluated to determine whether sample sites should be the same sites from year to year, or whether sites each year should be selected randomly. The information from previous counts is also used to define a sample unit and a sample design for the next aerial survey. Using previously observed haul-outs as sample units requires the assumption that no new haul-out sites will be colonized by harbor seals. In each of the previous surveys a substantial fraction of the sites where seals were observed were new haul-out sites. Also, some of the ...