Introduction: The harbour seal (&lt;i&gt;Phoca vitulina&lt;/i&gt;) - a global perspective

Bjørge, Arne; Desportes, Geneviève; Waring, Gordon T.; Rosing‐Asvid, Aqqalu

doi:10.7557/3.2668

Cited by 16 publications

(14 citation statements)

References 6 publications

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“…Harbour seals are a relatively small species of Phocid seal averaging 1.5 m in length and around 70–100 kg in mass (Bjorge et al 2010). They are distributed widely in coastal waters of the North Atlantic and North Pacific, where they use a variety of habitats to haul-out and breed, moult or rest (Thompson et al 1997; Bjorge et al 2010).…”

Section: Methodsmentioning

confidence: 99%

“…They are distributed widely in coastal waters of the North Atlantic and North Pacific, where they use a variety of habitats to haul-out and breed, moult or rest (Thompson et al 1997; Bjorge et al 2010). In the UK, their annual life cycle comprises of aquatic mating (courtship and oestrous) in July, gestation, parturition and lactation in June–July and moult in August–September (Thompson and Rothery 1987; Thompson et al 1994).…”

Section: Methodsmentioning

confidence: 99%

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Dynamic habitat corridors for marine predators; intensive use of a coastal channel by harbour seals is modulated by tidal currents

Hastie

Russell

Benjamins

et al. 2016

Behav Ecol Sociobiol

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Previous studies have found that predators utilise habitat corridors to ambush prey moving through them. In the marine environment, coastal channels effectively act as habitat corridors for prey movements, and sightings of predators in such areas suggest that they may target these for foraging. Unlike terrestrial systems where the underlying habitat structure is generally static, corridors in marine systems are in episodic flux due to water movements created by tidal processes. Although these hydrographic features can be highly complex, there is generally a predictable underlying cyclic tidal pattern to their structure. For marine predators that must find prey that is often patchy and widely distributed, the underlying temporal predictability in potential foraging opportunities in marine corridors may be important drivers in their use. Here, we used data from land-based sightings and 19 harbour seals (Phoca vitulina) tagged with high-resolution GPS telemetry to investigate the spatial and temporal distribution patterns of seals in a narrow tidal channel. These seals showed a striking pattern in their distribution; all seals spent a high proportion of their time around the narrowest point of the channel. There was also a distinctive tidal pattern in the use of the channel; sightings of seals in the water peaked during the flood tide and were at a minimum during the ebb tide. This pattern is likely to be related to prey availability and/or foraging efficiency driven by the underlying tidal pattern in the water movements through the channel.Significance StatementTo maximise foraging efficiency, predators often make use of narrow constrictions in habitat to intercept prey using these corridors for movement. In the marine environment, narrow channels may act as corridors, and sightings of predators suggest that they may target these for foraging. Despite this, there is little information on how individual predators use such areas. Here, we investigate how individual harbour seals use a narrow coastal channel subject to strong tidal currents; results showed that seals spent the majority of their time at the narrowest point of the channel foraging during peak tidal currents. This highlights the importance of narrow channels for marine predators and suggests that this usually wide-ranging predator may restrict its geographic range to forage in the channel as a result of increased prey availability and/or foraging efficiency driven by water movements through the narrow corridor.Electronic supplementary materialThe online version of this article (doi:10.1007/s00265-016-2219-7) contains supplementary material, which is available to authorized users.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Dynamic habitat corridors for marine predators; intensive use of a coastal channel by harbour seals is modulated by tidal currents

Hastie

Russell

Benjamins

et al. 2016

Behav Ecol Sociobiol

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“…A similar proportion was also suggested by a previous study of five radiotagged female harbour seals in Orkney (Thompson and Harwood, ). An estimate, apparently primarily based on Norwegian data (ICES, ), that moult counts detect 0.55–0.7 of harbour seals has also been applied to other populations (Bjørge et al , ). However, none of these estimates come from a population undergoing a rapid and sustained decline in apparent abundance similar to that reported from Orkney.…”

Section: Introductionmentioning

confidence: 99%

Rescaling of aerial survey data with information from small numbers of telemetry tags to estimate the size of a declining harbour seal population

Lonergan

Duck

Moss

et al. 2012

Aquatic Conservation

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1. Estimates of both absolute abundance and trends in abundance are among the most basic pieces of information required for planning the conservation and management of wildlife populations. They are important for understanding both the current situation of species and potential risks to them.2. This study presents estimates of the size of the harbour seal (Phoca vitulina) population associated with the Orkney Islands, a part of northern Scotland that used to contain one of the largest concentrations of this species in Europe.3. The numbers of animals counted during aerial surveys of this area have decreased substantially over the period 2001-2010. ARGOS transmitters attached to flipper tags were used to rescale the counts into estimates of abundance and to confirm the rate of decline of this population.4. Females hauled out for more of the survey window (0.84; bootstrap 95% CI: 0.63-0.99) than males (0.61; bootstrap 95% CI: 0.34-0.86). The animals hauled out less during weekends (0.57; bootstrap 95% CI: 0.40-0.74) than during the week (0.76; bootstrap 95% CI: 0.58-0.91).5. The sex-ratios of this population is unknown. Assuming it was close to 1:1, then there were around 3586 (bootstrap 95% CI: 2970-4542) harbour seals in Orkney in 2010. A female-skewed sex-ratio would reduce the population estimate, and a changing sex-ratio might mean the counts understate the real decline.6. The mean annual rate of decline in the Orkney population of harbour seals, over the period 2001-2010, is estimated at 13% (95% CI: 10.8-14.8). Similar data for Arisaig, on the west coast of Scotland, shows an increase of around 2% (95% CI: 1.5-2.4) and, assuming an equal sex-ratio, 923 animals (95% CI: 765-1169) in 2007.

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“…In 1988 and again in 2002, a phocine distemper virus (PDV)-epizootic severely reduced the population of the Eastern Atlantic harbor seal, but it quickly recovered both times [ 33 , 34 ]. The total population of the Eastern Atlantic harbor seal has more recently been estimated at approximately 113,000 to 134,000 individuals [ 35 ]. Based on aerial surveys, the size of the sub-population from the Wadden Sea, to which the majority of the individuals analyzed in the present study belonged, was currently estimated at 38,100 animals [ 36 ].…”

Section: Introductionmentioning

confidence: 99%

Dental anomalies and lesions in Eastern Atlantic harbor seals, Phoca vitulina vitulina (Carnivora, Phocidae), from the German North Sea

et al. 2018

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Skulls of 1,901 Eastern Atlantic harbor seals (Phoca vitulina vitulina) were systematically studied for externally visible dental anomalies and lesions. The sample comprised 927 males and 974 female individuals, with age at death ranging between 1 week and 25 years. Most of the skulls originated from animals collected in 1988, when the population suffered from a mass mortality event caused by the phocine distemper virus (PDV). Mean age (± SD) of females (6.7 ± 6.4 years) was higher (p = 0.002) than that of males (5.9 ± 5.2 years). In 264 individuals, one or more teeth were missing either congenitally (n = 26 animals, 1.4%) or due to intravital loss (n = 238 animals, 12.5%). One male exhibited congenital absence of all teeth (anodontia). As this animal had been reported to be almost hairless, the condition was tentatively diagnosed as a case of hypohidrotic ectodermal dysplasia. Males were more frequently (p = 0.002) affected by intravital tooth loss (15.0%) than females (10.2%). Supernumerary teeth were found in 3.4% of the skulls, with females (4.7%) showing hyperodontia more frequently (p < 0.001) than males (1.9%). Fifty-nine individuals (3.1%; 28 males, 31 females, p = 0.84) exhibited abnormal tooth morphology. Tooth fractures were noted in 40 seals (2.1%), with males being more frequently affected than females (p = 0.017). Periapical lesions were diagnosed in 143 skulls, with a tendency (p = 0.05) for males (8.7%) to be more frequently affected than females (6.4%). Enamel hypoplasia was not observed in the study sample. Analyzing the occurrence of dental anomalies and lesions in wild mammals can substantially contribute to an assessment of population health and thereby broaden the basis for effective species conservation and informed management decisions.

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Introduction: The harbour seal (<i>Phoca vitulina</i>) - a global perspective

Abstract: Introduction to Volume 8: Harbour seals in the North Atlantic and the Baltic

Cited by 16 publications

References 6 publications

Dynamic habitat corridors for marine predators; intensive use of a coastal channel by harbour seals is modulated by tidal currents

Dynamic habitat corridors for marine predators; intensive use of a coastal channel by harbour seals is modulated by tidal currents

Rescaling of aerial survey data with information from small numbers of telemetry tags to estimate the size of a declining harbour seal population

Dental anomalies and lesions in Eastern Atlantic harbor seals, Phoca vitulina vitulina (Carnivora, Phocidae), from the German North Sea

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