Harbour seal (Phoca vitulina) COSEWIC assessment and status report: chapter 3

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Species Information

Name and classification

The scientific name of the harbour seal is Phoca vitulina (Linnaeus, 1758). Five subspecies are currently accepted (Rice 1998, Burns 2002, Reeves et al. 2002). The subspecies on Canada’s Pacific coast is P. v. richardsi, and that on Canada’s Atlantic and Arctic coasts is P. v. concolor (DeKay 1842). The subspecies confined to the area of Lacs des Loups Marins on Québec’s Ungava peninsula is P. v. mellonae (Doutt 1942). The English and French common names are harbour seal and phoque commun (loup marin), respectively. The term ranger seal is occasionally used, particularly in the Arctic. In Labrador, the term ranger seal is used for males, and dotter for females. The harbour seal is known to the Inuit as qasigiaq. The Cree of northern Québec refer to P. v. mellonae asnuchimu-achikw or achikunipi with the latter term being the older or more traditional name.

Morphological description 

The pelage colouration of harbour seals is extremely variable, ranging from nearly uniform brown or black to nearly uniform yellowish-white. Between these extremes there are many different variations of dark and light irregular spotting on dark or light backgrounds (Allen 1880; Doutt 1942; Bigg 1981) (Figure 1). Harbour seals usually lose their lanugo (prenatal pelage) in utero, though some exceptions have been reported (Boulva 1971; Oftedal et al. 1991).

Male adult harbour seals in eastern Canada reach a length of about 154 cm compared with about 143 cm for females (Boulva and McLaren 1979). Mean length at birth is approximately 80 cm and does not differ significantly between males and females (Boulva and McLaren 1979). Mature weight averages 90 kg for adult males, and 70 kg for females (Boulva and McLaren 1979). Males rarely exceed 100 kg and females rarely exceed 90 kg (Härkönen and Heide-Jørgensen 1990). In mature females, drastic changes in body condition and weight occur from pupping through lactation. On Sable Island, females lost 32% of postpartum body mass and 62% of body energy by late lactation (Bowen et al. 2001a).

Doutt’s (1942) subspecific description of P. v. mellonae was partly based on its unusually dark pelage and an enlarged coronoid process on the mandible. Though disputed by some authors (Mansfield 1967, Smith and Horonowitsch 1987), the craniological distinctiveness of P. v. mellonae was confirmed by Smith et al. (1994).

The Cree of northern Québec contend that P. v. mellonae is smaller and darker, behaves differently, and tastes different than oceanic harbour seals (Atkinson 1818; Doutt 1942; Posluns 1993; Petagumskum 2005). Historical references to the morphological dissimilarity between P. v. mellonae and oceanic harbour seals include Hendry’s (1828) mention of the “fine quality” (p. 84) of the freshwater seal skins, and the Hudson’s Bay Company’s distinguishing freshwater seal pelts in trade at its Little Whale River post (Smith 1999). Flaherty (1918) noted that the Inuit considered the pelt of the freshwater seal to be darker, softer and more lustrous than that of the saltwater variety. Based on his extensive work in Inuit communities, Graburn (1969) described freshwater seal skins as being the softest and most beautifully marked of all.

Genetic description

A study of worldwide patterns in harbour seal mitochondrial DNA (mtDNA), excluding P. v. mellonae, by Stanleyet al. (1996) indicated that harbour seal populations of the Atlantic and Pacific Oceans are significantly genetically differentiated, and have been isolated for 1.7-2.2 million years. There is also evidence of differentiation between subpopulations in the eastern and western Atlantic with the pattern of genetic divergence suggesting that colonization proceeded from west to north and then east. The degree of divergence between European and western Atlantic populations suggested that this colonization began between 0.9 and 1.3 million years ago (Stanley et al.1996).

Kappe et al. (1997) assessed harbour seal genetic variation in eastern Pacific (P. v. richardsi), western Atlantic (P. v. concolor), and European harbour seals (P. v. vitulina). They concluded that P. v. richardsi is clearly separated from the other two subspecies and is significantly more heterozygous. Two recent microsatellite DNA studies (Coltman et al. 1998a, 1998b) provide evidence of inbreeding-like effects in harbour seal pups from Sable Island and a low level of polygyny in this population. Recent studies of mitochondrial DNA in harbour seals along the west coast of North America have indicated substantial geographic substructure (e.g. Lamont et al. 1996; Burget al. 1999; Westlake and O’Corry-Crowe 2002); no similar data exist for harbour seals in the western North Atlantic.

Smith (1999) found a total of 14 different mitochondrial DNA haplotypes among 6 P. v. mellonae and 11 P. v. concolor samples (n = 17). Within the 480 b.p. examined the observed number of pairwise differences among haplotypes ranged from 1 to 19. Corrected DNA distances for comparisons between the 17 sequenced samples ranged from 0.008 to 0.05.

Lacs des Loups Marins had four haplotypes, three of which were similar and grouped together 64.7% of the time. The fourth Lacs des Loups Marins haplotype was more differentiated than those of the other harbour seals that were sequenced, with a mean of 16 ± 0.6 substitutions as compared to a mean of 6.6 ± 0.4 substitutions for all 17 samples.The P. v. concolor sample contained 10 haplotypes. No haplotypes were found in both groups.

When compared with the sequences from Stanley et al.(1996), all P. v. mellonae and the majority of the P. v. concolor samples examined by Smith (1999) grouped with other harbour seals from the western Atlantic. The number of pairwise substitutions in the combined sample of 17 sequences was very similar to that observed by Stanley et al. (1996) (1 to 23 substitutions in 435 b.p.). Burg et al. (1999) and Lamont et al. (1996) found higher numbers of pairwise substitutions in their sampling of Pacific animals (average of 2.6%-± 0.29%, and 1 to 16 among 320 b.p. respectively). 

Designatable units

The eastern Canadian harbour seal population is comprised of two designatable units (DUs), each attributed to a different subspecies by recent authors (Rice 1998; Burns 2002; Reeveset al. 2002).

One DU (P. v. mellonae) consists of the freshwater seals of the Lacs des Loups Marins area of Québec’s Ungava peninsula. Morphological, genetic, and behavioural evidence derived from both published and traditional Aboriginal sources supports the description of P. v. mellonae as a DU (Doutt 1942; Smithet al. 1994; Smith et al. 1996; Smith 1999; Petagumskum 2005; Smith et al. 2006). This DU is endemic to Québec and Canada.

The second DU (P. v. concolor) consists of the harbour seals found on the Canadian Atlantic and Arctic coasts. This DU ranges into the waters of southern and western Greenland (Teilmann and Dietz 1994), the northeastern United States (Waring et al. 2003), and Saint-Pierre and Miquelon (Linget al. 1974; Lawson 2006). Despite the conclusions of Temte et al. (1991) and Temte (1994) that birth timing in P. v. concolor implies one interbreeding stock, it is very likely that this unit, comprised of groups of harbour seals with high site fidelity distributed over an extremely large area, has within it significant geographic substructure. In their study of worldwide harbour seal genetic diversity, Stanley et al. (1996)suggested that harbour seal females are only regionally philopatric, which would support the notion of population or management units on the scale of a few hundred kilometres. On the Pacific coast of North America, extensive evidence of geographic substructure has prompted the United States National Marine Fisheries Service to recognize six harbour seal management units between California and Alaska (Angliss and Lodge 2004; Caretta et al. 2005). Though Boulva and McLaren (1979) speculated on geographic substructure within P. v. concolor based on variations in dental patterns, and more recent authors have provided further evidence supporting such substructure (see Lesage et al. 2004 for telemetry data; Lebeuf et al. 2003 and Sjare et al. 2005 for analyses of contaminant profiles; Gilbert et al. 2005 and Bowen et al. 2003 for region-specific differences in population dynamics), these data are not yet sufficient to define multiple DUs of P. v. concolor.