Abstract: Conservation policies require the status of protected species to be monitored. The choice of monitoring methods may be constrained in situations in which there is concern about disturbance or in which sighting individuals is difficult. This study investigated the potential of using a computer-assisted photo-identification method to measure population size in adult harbour seals (Phoca vitulina). Pattern cells or combinations of pattern cells from photographs (i.e., ventral, flank, shoulder, and head) were used for computerized selection of potential matching pairs, and the pelage patterns of those pairs were then checked visually. There was monthly variation in capture-recapture population estimates, with the highest number of adult harbour seals in May (117, CV = 7.2). Around three times more individuals used the sampling area in northwest Scotland between April and October (268, CV = 0.04) than were estimated per month (mean = 86, CV = 0.07). Using computer-assisted photo-identification and capture-recapture methods may be the only practical way of obtaining a measurement of how many seals use a site. This approach has important implications for determining the effectiveness of designated conservation areas for protecting seals and will influence management decisions, including the size of management units.

Key Words: harbour seals, Phoca vitulina, abundance, management, pelage, protected areas, Scotland, photo-identification

Document Type: Research article

DOI: 10.1578/AM.35.3.2009.319

Page Numbers: 319-329