Real-time PCR assays for the identification of harbor and gray seal species and sex: A molecular tool for ecology andmanagement

摘要

A large proportion of the European population of harbor seals (Phoca vitulind) live around the British coastline. Numbers of harbor seal have been decreasing at the majority of breeding sites around Britain (Lonergan et al. 2007). This decline may becaused by a number of different factors such as disease, changes in prey availability, environmental contamination (Hall et al. 2006), competition with gray seals (Halicboerus grypus), or a combination of different drivers (Thompson et al. 1996). In order to investigate factors linked to changes in the availability of prey, including competition with gray seals, information on the seal diet is required. Analysis of prey remains recovered from scat is often used to determine the diet of pinnipeds. This methodology is both noninvasive and allows large sample sizes to be collected (Pierce et al. 1991). Scat are often collected from mixed species haul-out sites that are used by both harbor and gray seals. Previous work in the Moray Firth, UK, has shown that 15 % of gray seal scat samples were misidentified as belonging to harbor seals (Reed et al. 1997), while other studies have reported even higher level of misidentification (Masland et al. 2010). As scat from the two species are visually indistinguishable, it has not been possible to investigate the dietary overlap, and hence the potential for competition, between sympatric populations of the two seal species. Conclusions drawn from samples collected at separate sites, or times, are confounded by knownspatial and temporal variation in diet (Hammond et al. 1994, Tollit and Thompson 1996). A recent study described the use of conventional polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) analysis to discriminate between harbor and gray seal scat (Masland et al. 2010), while other studies have used allele frequency distribution from microsatellite analysis to identify scat from these species (Reed et al. 1997).