- Kenney, Mary Kathryn
University of Maine
To document abundance and distribution of harbor seals (Phoca vitulina) in Maine, aerial surveys were flown along the coast between the Canadian and New Hampshire borders during pupping season of early June, 1993 and during the molting season in mid-August, 1993. Change in population size was determined by comparing the results of the June survey to censuses flown using the same techniques during the pupping seasons of 1981, 1982, and 1986. Characteristics of size, distance to mainland, and distance to boat launch were measured of potential haulout sites using a geographic information system (GIS). Chi square goodness of fit was used to test the hypothesis that seals use sites in proportion to their availability.
The 1993 spring census counted 28,810 seals including 4,250 pups. This represented an annual rate of increase of 8.7% between 1981 and 1993. A difference was observed between regions in productivity of pups. The percent of pups within the south region was 8%, in the middle region, 15% and within the downeast region, 20%. An increase in pup counts was observed in all regions since 1981. The August census was 26,054 individuals or 91% of the June count.
The smallest (< 0.3 ha) and largest (10-350 ha) size classes were used less than expected in all survey years and the tidal ledges (no substrate above high tide) were used more than expected for pupping sites and molting sites when compared with available sites. Use of islands for pupping within 0.25 km of the mainland was less than expected in all survey years while sites within the interval of 1-10 km were used more than expected in 1993. There was a significant shift in abundance away from the mainland between June and August. Site distance to boat launches was not significant for any year of use.