Status of harbour seals (Phoca vitulina) in Atlantic Canada

Harbour seals are associated with small islets, reefs and rocks exposed at low tide and estuarine habitats throughout eastern Canada. Evidence of harvesting by indigenous people has been found in pre-European contact archaeological excavations. A bounty harvest as well as subsistence and commercial hunting probably lead to a decline in the population from 1949 to the early 1970s. The bounty was removed in 1976, and harbour seals, in the southern parts of their range have been protected since then. There is little information available on total abundance and current population trend. Mitochondrial and microsatellite DNA research has shown separation between Northeast and Northwest Atlantic harbour seals. Within Canada, the subspecies Phoca vitulina concolor shows some population sub-structure with three distinct units that could be separated into Hudson Bay, Gulf of St. Lawrence and Sable Island. Urban development resulting in habitat degradation is probably the most important factor affecting harbour seal populations inAtlantic Canada, although other factors such as incidental catches in commercial fisheries and competition with grey seals may also be important. Hammill, M.O., Bowen, W.D. and Sjare, B. 2010. Status of harbour seals (Phoca vitulina) in Atlantic Canada. NAMMCO Sci. Publ. 8:175-190. NAMMCO vol 8 dok ingunn 2802:NAMMCO vol 5, dok-geir 08-03-11 09:05 Side 175


INTRODUCTION
The harbour seal (Phoca vitulina) has the most extensive breeding distribution of any pinnipeds with breeding colonies distributed over 16,000 km from the Baltic Sea to Japan (Stanley et al. 1996).Five subspecies are recognized, with P. v. richardii and P.v.stejnegeri occurring in the eastern and western Pacific respectively, P.v.vitulina occurring in the Northeast Atlantic, P.v.concolor in the Northwest Atlantic, eastern Canadian Arctic and Hudson Bay, and P.v.mellonae confined to a few freshwater lakes in northern Quebec (Rice 1998).

P.v. concolor has been reported throughout
Hudson Bay, along the Baffin Island coast, Labrador, Newfoundland, the St. Lawrence River Estuary and Gulf of St. Lawrence, along the Nova Scotia coast, Sable Island, and in the Bay of Fundy (Mansfield 1967).During the 1800s the species was also reported from as far west as Lake Champlain and Lake Ontario (Allen 1880).Harbour seals are also found along the northeastern United States coast (Katona et al. 1993).They are normally associated with coastal areas, isolated sandy beaches, small islets, rocks and reefs exposed at low tide (Boulva andMcLaren 1979, Lesage et al.2004).Harbour seals are relatively sedentary, although at times extensive movement does occur (Lesage et al. 2004).Movements appear to be coastal, and harbour seals seem to avoid deep water (Lesage et al. 2004).In ice-covered regions, they are excluded from fast ice areas (Lesage et al. 2004).

Biology
The first most extensive study of Atlantic harbour seals in Canada was carried out by Boulva and McLaren (1979).Field work was done at Sable Island, but questionnaires and interviews were used to gather regional information on the location and size of breeding colonies throughout eastern Canada.Males are sexually mature at 6 years of age, while the mean age of sexual maturity for females was 3-4 years old.
In the early 1970s on Sable Island, pupping began as early as 7 May and had finished by 10 June, with a mean date of pupping over three seasons of 25 May (Boulva 1975).During the late 1980s, the mean date of pupping occurred earlier (mean=22 May, SE=0.3, N=286), when the population was stable, but shifted to a later date in the early to mid-1990s (Mean=28 May, SE=0.3, N=390), coincident with a dramatic decline in the population (Bowen et al. 2003).Lactation lasts for 24 days (Bowen et al. 2003).Pup mortality prior to weaning is quite variable (12-21%), resulting in a mean survivorship for the pre-weaning period of 0.876.The sex ratio at birth is not significantly different from 1:1 and some pups are born with a white lanugo (12-25%).Birth mass of pups averages 10.9 kg (N=375) but increases with maternal age and maternal body mass.Pups of primiparous females were smaller at birth than those of multiparous females (Ellis et al. 2000).Pups gain Hudson Bay (HB). of 24 d and are weaned at an average body mass of 24.9 kg (N=52, Muelbert and Bowen 1993).During the initial post-weaning period pups loose body mass, but gain lean tissue mass indicating continued skeletal growth.Heavier pups were also relatively fatter than light pups (i.e.those below the median mass) and had significantly greater total body energy to sustain them during the transition to nutritional independence (Muelbert et al. 2003).
In the St Lawrence Estuary, pupping begins as early as 12 May and finishes by 21 June, with a mean date of pupping over three seasons of 26 May (Dubé et al. 2003).This is earlier than predicted by Temte et al. (1991), suggesting latitude may be less important along the Atlantic coast of North America, than along the Pacific coast where a latitudinal gradient has been found.Pup survival prior to weaning is quite variable (0.5-0.9), but survival is high during the 2 months following weaning (0.8-1.0) (Dubé 2002).The sex ratio at birth is not significantly different from 1:1 and, as elsewhere, some pups are born with a white lanugo (3-12%).Pups gained on average 544 (SE=141, N=110) g per day; and 50% of the pups were weaned after 33 (SE=1.8)days (Dubé et al. 2003).This is almost 10 days longer than that which has been reported in other studies, and is likely the result of the indirect method used to estimate duration of lactation (Dubé et al. 2003).
Harbour seal pups are capable of entering the water soon after birth to follow the female but their ability to follow and dive with their mother is limited in early lactation (Bowen et al. 1999).However, blood oxygen stores and ability to control heart rate develop quickly, although development of oxygen stores in muscle myoglobin continues after weaning (Lapierre et al. 2004, Greaves et al. 2004, 2005, Clark et al. 2006, Clark et al. 2007).Bowen et al. (2001a, b) examined factors affecting pup development among harbour seals on Sable Island.They found that females expended a constant proportion of stored energy reserves, rather than a constant amount of energy.Females supported the costs of lactation from stored reserves early in lactation, but diving activity increased as lactation progressed as females foraged more to support lactation (also see Boness et al. 1994).The fraction of total energy expenditure that was derived from food intake during lactation was inversely proportional to maternal body mass, indicating that larger females were better prepared to support lactation than smaller females (Bowen et al. 2001a, b).The duration of lactation was related to the rate of mass gain and weaning mass.Pups that grew faster had shorter lactation periods, while pups with larger weaning mass suckled for longer periods.Pups of older females grew faster than did pups of younger females, at least early in lactation.Lighter females had lighter pups at birth, their pups grew more slowly and these females invested relatively more in lactation than did heavier females.Pups from heavy females had higher survival than pups of light females.
Mating occurs in the water, during late May or June, during late lactation.The mating system appears to be more of a lek-type than a territorial or female-defence system observed among land-or ice-breeding pinnipeds (Boness et al. 2006).Boness et al. (2006) simultaneously used animal-borne video cameras, radio telemetry, time-depth recorders and DNA paternity analysis to describe the tactic used by males to secure mating.Males decreased time offshore feeding and increased time near shore during late lactation.Concomitantly they reduce foraging effort and food intake (Coltman et al. 1997(Coltman et al. , 1998a) ) and increased display behaviour and threats to other males.A multivariate analysis of phenotype and paternity showed that the most successful males were of moderate body size, were rarely sighted alone and were associated with many different groups of females (Coltman et al. 1998b).DNA paternities also suggested that females selected as mates were females that were fertilized less often than expected by males adjacent to their haulout location in the colony (Boness et al. 2006).

Diet and foraging behaviour
As in most pinnipeds, harbour seals consume a wide variety of prey.Species composition and importance show temporal and spatial variation.In an early sample made up of animals from the Bay of Fundy, Sable Island and southeastern Cape Breton Island, Atlantic herring (Clupea harengus), squid (Illex illecebrosus), flounder (Pleuronectidae), alewife (Alosa psuedoharengus), hake (Merluccius sp. and Urophycis sp.), smelt (Osmerus mordax) and mackerel (Scomber scombrus) accounted for 78% of the diet by percent occurrence.Cod (Gadus morhua), capelin (Mallotus villosus) and sand lance (Ammodytes sp.) were also consumed, but each accounted for less than 3% of the diet (% occurrence) (Boulva and McLaren 1979).In a more recent study, involving animals collected in the Bay of Fundy, the Eastern shore of Nova Scotia and Cape Breton Island (Bowen and Harrison 1996), Atlantic herring, squid, Atlantic cod, pollock (Pollachius virens) and hake accounted for 54% and 61% of the diet by % occurrence and % mass respectively.Alewife, flounder and capelin each accounted for less than 3% of the diet.In Newfoundland and Labrador waters winter flounder (Pseudopleuronectes americanus), Arctic cod (Boreogadus saida), shorthorn sculpin (Myoxocephalus scorpius), Atlantic cod and Atlantic herring accounted for 83.8% of the diet based on mass.However the key prey species consumed by seals varied regionally within the province (Sjare et al. 2005).In the St Lawrence Estuary, trophic relationships of harbour seals, harp seals (Phoca groenlandica), hooded seals (Cystophora cristata), grey seals (Halichoerus grypus) and beluga (Delphinapterus leucas) have been examined (Lesage et al. 2001).Harbour seals along with hooded seals occupied the highest trophic position.Limited diet information indicate that harbour seals in the estuary feed on capelin, sand lance, herring, some sculpins (Cottidae) and flatfish (Lesage et al. 2001).
Although relatively little is known about the foraging behaviour of pinnipeds, animal-borne video cameras have provided some insight into the tactics used by adult male harbour seals during the breeding season (Bowen et al. 2002).Foraging tactics used by males differed with prey type.Swim speed and handling time differed with prey type with the result that profitability of prey (i.e., the net energy gain per unit prey mass) also varies by prey type and prey size.
Dive shape analysis revealed temporal changes in the foraging behaviour and food intake of harbour seal adults during the breeding season and young of the year during the first month post-weaning (Baechler et al. 2002).Estimates of food intake form water turnover studies were positively correlated with the proportion of flat bottomed dives suggesting that such dives are predominately used during foraging.(Lebeuf et al. 2003).

Abundance
Little effort has been undertaken to determine harbour seal abundance in Atlantic Canada.Available estimates are from regional studies that have addressed specific concerns.These studies have used different methods and methods used within studies have changed over time.
Early work by Fisher (1949, cited in Boulva andMcLaren 1979) suggested that the population of harbour seals in the Maritimes (excluding Sable Island) was around 10,000-15,000 animals.In 1973, there were an estimated 5,500 in the same area (Boulva and McLaren 1979).However, estimates from both studies must be viewed cautiously.Estimates from Boulva and McLaren (1979) were based upon interviews, bounty reports and questionnaires sent to local fisheries officers, which according to the authors were more thorough than the earlier study by Fisher (1949), but nonetheless were not the result of actual counts.The estimated total population for Newfoundland, the Maritimes, the Gulf and estuary of the St. Lawrence from the study by Boulva and McLaren (1979) was around 12,700 in 1973.Throughout the 1970s the perception was that the Atlantic harbour seal population was declining and the population was projected to number as few as 4,000 by 1979 (Boulva 1973, McLaren 1977).
Count and tagging data are available for the number of pups , parturient females (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996) and juveniles, adult males and females (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998) on Sable Island (Boulva and McLaren 1979, Lucas and Stobo 2000, Bowen et al. 2003).Using the number of pups as an index of abundance, pup production numbered around 350 animals in the early 1970's.The number of pups increased beginning in 1978 reaching a maximum of just over 600 pups by 1989, then declined to around a dozen pups or less by 2002 (Bowen et al. 2003).A decline in the number of juveniles and adults did not occur immediately, but a decline was observed in these age classes as a result of the reduced number of pups moving into the older age classes.This decline appears to result from a combination of shark-inflicted mortality, on both pups and adult females and inter-specific competition with the much more abundant grey seal (Halichoerus grypus) for food resources (Bowen et al. 2003).
Elsewhere, a series of coastal aerial surveys were flown over parts of the Bay of Fundy and southwestern Nova Scotia during 1985Scotia during , 1986Scotia during , 1987Scotia during , 1991Scotia during and 1992.Surveys were flown during the pupping season (1985) and also during the moult (July-August, 1986-1992) (Stobo and Fowler 1994).The study design called for surveys to be flown within a 4 h window centred on a mid-morning to mid-afternoon low tide, but for various reasons this was not always possible to achieve.Total counts of hauled-out animals from these areas varied from 731 in 1985 to 3,534 in 1992.Although the authors concluded that the harbour seal population in this area was likely increasing, interannual differences in survey conditions and areas covered did not allow for this change to be quantified.
Helicopter surveys have also been flown to count hauled-out animals along the coast and around small islands in parts of the Gulf of St. Lawrence and the St Lawrence estuary at an altitude of 152.4 m, and a distance of 300 m offshore to minimize disturbance.In the estuary, surveys were flown during June 1995, 1996, and 1997, and in August during 1994, 1995, 1996and 1997, and in different parts of the Gulf during June 1996 and 2001 (Robillard et al. 2005).Trends in counts at 9 sites that were surveyed in June and in August under similar conditions revealed, that although all slopes were positive, only one was significant.Overall, the June surveys resulted in an average of 469 (SD=60, N=3) hauled-out animals, which is only slightly lower than a count of 621 (SD=41, N=3) hauled-out animals flown under similar conditions in August.Aerial surveys in the Gulf of St. Lawrence resulted in counts of 467 animals in 1996 and 423 animals in 2001 for a different area (Robillard et al. 2005).If the hauledout counts are corrected for animals in the water at the time the surveys are flown, and the densities from the surveyed areas are extrapolated to include the areas not surveyed in the Gulf of St. Lawrence, then there were about 4,000-5,000 harbour seals in the St Lawrence River Estuary and the Gulf of St. Lawrence (Robillard et al.2005).
In Newfoundland, Boulva and McLaren (1979) estimated a total of 2,010 seals in Newfoundland, from their questionnaire survey.Since then, as in other regions there has been little attempt to determine harbour seal abundance.Local boat and aerial surveys and interviews with fishermen were completed during May-September 2001-2003 to obtain more information on harbour seals in the province.Surveys were timed to be completed within 2-3 h of low tide (Sjare et al. 2005).Although direct comparisons with the earlier study (Boulva and McLaren 1979) are not possible because the methods differed, the impression was that distribution had changed little and that numbers at some haulout sites in the south and south-western part of the province may have increased, while abundance at some haulout sites in the northern and north-eastern part of the province have remained stable or may have declined (Sjare et al. 2005).Recent reports from hunters along the Labrador coast suggest that there has been little change in general the Table 2. Estimates of 217 adult harbour seals killed by hunters and recovered (Boulva 1973).NS stands for the province of Nova Scotia and NB stands for the province of New Brunswick (see Fig. 1).Assuming 4,000-5,000 harbour seals in the Gulf and estuary of the St Lawrence, and an estimate of 4,000 to 7,000 animals for the Bay of Fundy (3,534 from Stobo and Fowler (1994) corrected for animals in the water by multiplying by 1.2-1.9 and rounding to the nearest thousand) results in an index of 8,000 to 12,000 harbour seals in Atlantic Canada, excluding Newfoundland.This is probably a minimum estimate because the surveys are dated, and large areas have not been surveyed, but the degree of bias is not known.With the exception of Sable Island, where harbour seal abundance has increased and then declined since the 1970s, it is not possible to evaluate trend among harbour seals in Atlantic Canada.A comparison of recent geographic distribution, with that observed in the 1970s suggests that there has been little change (Boulva and McLaren 1979).

Stock structure
Harbour seals in eastern Canada are generally found in small, apparently isolated populations (Boulva and McLaren 1979).Tagging and telemetry data, as well as variability in pelage patterns and the number of post-canine teeth have been used to support the hypothesis that harbour seals tend to be sedentary and the small groups are semi-isolated, (Boulva and McLaren1979, Thompson 1993, Lesage et al. 2004).This relatively sedentary nature would also suggest that a degree of segregation could be detected using genetic markers either by examining the degree of separation through maternally inherited mitochondrial DNAor using microsatellite DNA analyses.Analyses of mitochondrial DNA show clear separation between harbour seals from the East Atlantic (P.v.vitulina) and the West Atlantic (P.v.concolor), and in the West Atlantic between samples from western Hudson Bay and the French island of Miquelon off the south coast of Newfoundland and Sable Island, but no differences were observed between animals sampled from Sable Island and Miquelon (Stanley et al. 1996).In a recent study, skin samples (N=290) were obtained from harbour seals in the St. Lawrence Estuary, the northern Gulf of St. Lawrence Table 3. Geographical origins, acronyms, sample size and collection dates of the samples analysed for microsatellite and mitochondrial DNA variability of harbour seal (Picaud, 2008).(Picaud 2008).These analyses supported findings that there are significant differences between Northeast and Northwest Atlantic populations (Stanley et al. 1996), and also point to significant sub-structure with three distinct units that could be separated into Hudson Bay, Sable Island and the Gulf of St. Lawrence.Little differentiation was observed between populations of the Gulf of St. Lawrence, Newfoundland and coastal Nova Scotia, including the Bay of Fundy, indicating significant gene flow at this scale.
Analyses of patterns and overall persistent organic pollutant levels in marine mammal tissues reflect contaminant levels in areas where animals are foraging.Comparisons of contaminant burdens between areas might also provide insights into possible population structure.Polychlorinated biphenyl (PCB), and polybrominated diphenylether (PBDE) levels were examined in 8 harbour seals from the St Lawrence estuary, 10 harbour seals from the southern Gulf of St Lawrence and 10 harbour seals from the south, southeast coast of Newfoundland (Lebeuf et al. 2003).Ninety percent of animals could be separated correctly into three groups (Fig. 2).Three animals were not correctly assigned to their sampling area, including a seal from the estuary that was assigned to the southern Gulf, a seal from Newfoundland that was assigned to the southern Gulf and a seal from the southern Gulf that was assigned to Newfoundland.

Exploitation
Harbour seals were harvested for subsistence throughout the Maritime Provinces prior to the arrival of Europeans.Skeletal or tooth remains have been identified from the Bay of Fundy dating from the Woodland period, during 3000 BC-1500 CE (Black 2003).In the north-eastern part of the Gulf of St. Lawrence, near the Strait of Belle Isle, and along the north shore of Quebec and in the St Lawrence Estuary, seals were an extremely important resource to Amerindian groups during the Archaic (8500-3500 BC) and Woodland (3000 BC-400 BC) periods, but this harvesting seems to have concentrated on harp seals, during the spring, while harbour seals were much less important and were likely hunted in late spring or early summer (Pintal 2003, Plourde andSt. Pierre 2003).
There is some documentation of commercial harvesting of seals in the St Lawrence beginning in the 1700s.Initially, harvesting was for both the oil and the skin.Harp seals again seem to be the most important resource, but harbour seals continued to be taken into the 1900s for both food and for commercial reasons (Castonguay 2003, Comtois 2003).Harvesting was concentrated during spring and early summer when animals were hauled-out near shore and likely when young seals were available.
Harvesting of harbour seals for their pelts continued into the early 1970s.In 1927, a bounty was placed on harbour seals in eastern Canada to reduce conflicts with inshore fishermen.Initially payments were for submission of harbour seal snouts.However, it was discovered that grey seals and some other animals were sometimes submitted, so the system was changed in 1949 to payments for jaws only (McLaren 1977).Some statistics are available for early harvests.In Nova Scotia and New Brunswick, a total of 16,326 bounty kills were recorded between 1950 and 1971, approximately 73% of these were pups (Table 1).The estimates of numbers of adults killed are likely underestimated, because some animals killed were likely not recovered.Boulva (1973) estimated that on average only 65% (SD=24, CV=36.5) of adults killed are recovered (Table 2).Taking into account the number of animals struck and lost, increases the number of adults estimated to have been killed from 4,368 to 6,723 and total kills to 18,681.Animals were also killed by hunters from the province of Quebec, but species were not recorded separately so it is not possible to distinguish the number of harbour seals killed from the other seal species taken.The bounty was removed in 1976 owing to concerns about declines in harbour seal abundance.

Legislation
Marine mammal management and conservation in Canada are the responsibility of the Department of Fisheries and Oceans, which manages marine mammal activities under the Marine Mammal Regulations of the Fisheries Act.In cases of particular conservation concern, marine mammals may also be protected under the Species At Risk Act.Under the Marine Mammal Regulations, the hunting of harbour seals is prohibited along the Atlantic coast of Canada from near the northern tip of Labrador, south to the Bay of Fundy and including the Gulf of St. Lawrence and the waters surrounding Sable Island off the east coast of Nova Scotia (Fig. 1).

Interactions with fisheries
Seals interact with fisheries in a variety of ways that have both positive (feeding on predators of commercially valuable species) and negative (feeding on target species or their prey; damage to gear) impacts (Hammill andStenson 2000, Morissette et al. 2006).Compared to harp, hooded and grey seals, harbour seals are thought to be only minor consumers in the Atlantic Canada ecosystem, owing to their low abundance (Hammill and Stenson 2000), but as outlined elsewhere, there is considerable uncertainty regarding harbour seal abundance in eastern Canadian waters.Harbour seals have been identified as problematic to salmon aqua-culture operations in the Bay of Fundy, but this impact has not been quantified.Harbour seals have been implicated in the loss of catches and gear damage in small coastal fisheries for smelt (Osmerus mordax) and gaspereau (Alosa pseudoharengus), but these impacts have not been separated from the impacts of grey seals (Cairns et al. 2000).Harbour seals are also caught in fishing gear, primarily small trap nets deployed in coastal fisheries, but incidental catch levels have not been quantified.

Limiting Factors
A significant decline in harbour seals has been observed on Sable Island.This decline has been associated with high mortality from shark predation and possibly competition with the much larger and more abundant grey seal for prey resources (Bowen et al. 2003).The large number of grey seals on this offshore island is likely what attracts sharks to the area, and harbour seals are likely secondary prey.Elsewhere, habitat loss is likely an important factor limiting harbour seals.Coastal development and shoreline activity has resulted in harbour seals abandoning certain beach areas (Lavigne 1978), and throughout much of their range, haulouts are limited to offshore islets, reefs and rocks and small isolated points.Harbour seals are taken incidentally in coastal fishing gear, but this is not likely to have large scale population impacts.High contaminant levels have been documented among harbour seals in the St. Lawrence Estuary (Table 4) (Bernt et al. 1999, Hobbs et al. 2002), but this is not likely to be a factor limiting the population.

Table 1 .
Bounty claims in the Maritime region of Atlantic Canada between 1950 and 1971(Boulva 1973).Numbers have not been correct for struck and loss as presented inBoulva  (1973).

Table 4 .
(Hobbs et al. 2002)n PCB and OC pesticide blubber concentrations (ng/g lipid) in adult male harbour, grey, harp and hooded seals from the North Atlantic and Arctic Oceans since 1988(Hobbs et al. 2002).