Genetic population structure of harbour seals in the United Kingdom and neighbouring waters

Olsen, Morten Tange; Islas, Valentina; Graves, Jeff A.; Onoufriou, Aubrie B.; Vincent, Cécile; Brasseur, S.M.J.M.; Frie, Anne Kirstine; Hall, Ailsa J.

doi:10.1002/aqc.2760

Cited by 23 publications

(46 citation statements)

References 33 publications

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“…As throughout the study the growth rate of the total Wadden Sea population did not exceed the intrinsic rate of increase for the species, it seems unlikely that the growth was influenced, let alone fuelled by immigration from colonies outside the Wadden Sea. This is supported by earlier findings that indicate the Wadden Sea harbour seal population being a distinct genetic population [ 34 , 35 ] though recent findings indicated there was a strong connection with harbour seals from France and southern UK [ 64 ]. In addition to this, the occurrence of virus epizootics did affect population growth temporarily, but did not prevent the population from continuing its recovery.…”

Section: Discussionsupporting

confidence: 83%

Echoes from the past: Regional variations in recovery within a harbour seal population

et al. 2018

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Terrestrial and marine wildlife populations have been severely reduced by hunting, fishing and habitat destruction, especially in the last centuries. Although management regulations have led to the recovery of some populations, the underlying processes are not always well understood. This study uses a 40-year time series of counts of harbour seals (Phoca vitulina) in the Wadden Sea to study these processes, and demonstrates the influence of historical regional differences in management regimes on the recovery of this population. While the Wadden Sea is considered one ecologically coupled zone, with a distinct harbour seal population, the area is divided into four geo-political regions i.e. the Netherlands, Lower Saxony including Hamburg, Schleswig-Holstein and Denmark. Gradually, seal hunting was banned between 1962 and 1977 in the different regions. Counts of moulting harbour seals and pup counts, obtained during aerial surveys between 1974 and 2014, show a population growth from approximately 4500 to 39,000 individuals. Population growth models were developed to assess if population growth differed between regions, taking into account two Phocine Distemper Virus (PDV) epizootics, in 1988 and 2002 which seriously affected the population. After a slow start prior to the first epizootic, the overall population grew exponentially at rates close to assumed maximum rates of increase in a harbour seal population. Recently, growth slowed down, potentially indicative of approaching carrying capacity. Regional differences in growth rates were demonstrated, with the highest recovery in Netherlands after the first PDV epizootic (i.e. 17.9%), suggesting that growth was fuelled by migration from the other regions, where growth remained at or below the intrinsic growth rate (13%). The seals’ distribution changed, and although the proportion of seals counted in the German regions declined, they remained by far the most important pupping region, with approximately 70% of all pups being born there. It is hypothesised that differences in hunting regime, preceding the protection in the 1960’s and 1970’s, created unbalance in the distribution of breeding females throughout the Wadden Sea, which prevailed for decades. Breeding site fidelity promoted the growth in pup numbers at less affected breeding sites, while recolonisation of new breeding areas would be suppressed by the philopatry displayed by the animals born there. This study shows that for long-lived species, variable management regimes in this case hunting regulations, across a species’ range can drive population dynamics for several generations.

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Section: Discussionsupporting

confidence: 83%

Echoes from the past: Regional variations in recovery within a harbour seal population

et al. 2018

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“…Moreover, recent tagging and genetic studies indicate that especially juvenile harbour seals undertake movements across much greater distances than previously reported, and thus potentially could have played a larger role in transporting PDV longer distances. For instance, Wadden Sea harbour seals have been shown to undertake foraging trips of a couple of hundred kilometres into the North Sea (Dietz et al, 2013;Tougaard et al, 2008;Aarts et al, 2016), and recent population genetic analyses suggested movements among the seals in southern England, France and the Dutch Wadden Sea (Olsen et al, 2017). Likewise, tagging of harbour seals in the fall and early winter of 2016 provided the first documented movements from a haul-out in southern Kattegat to the central Limfjord (Rune Dietz and collaborators, unpublished) by an animal that has now been genetically determined to originate from the Limfjord (Morten Tange Olsen, unpublished).…”

Section: Spread Of Pdv In 2002 Through Multiple Transmission Eventsmentioning

confidence: 99%

Phylogenomic insights to the origin and spread of phocine distemper virus in European harbour seals in 1988 and 2002

Stokholm

Härkönen²,

Hårding³

et al. 2019

Dis. Aquat. Org.

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The 1988 and 2002 Phocine Distemper Virus (PDV) outbreaks in European harbour seals (Phoca vitulina) are among the largest mass mortality events recorded in marine mammals. Despite its large impact on harbour seal population numbers, and three decades of studies, many questions regarding the spread and temporal origin of PDV remain unanswered. Here, we sequenced and analysed 7,123 base pairs of the PDV genome, including the coding and non-coding regions of the entire P, M, F and H genes in tissues from 44 harbour seals to shed new light on the origin and spread of PDV in 1988 and 2002. The phylogenetic analyses trace the origin of the PDV strain causing the 1988 outbreak to between May 1987 and April 1988, while the origin of the strain causing the 2002 outbreak can be traced back to between June 2001 and May 2002. The analyses further point to several independent introductions of PDV in 1988, possibly linked to a southward mass immigration of harp seals in the winter and spring of 1987-1988. The vector for the 2002 outbreak is unknown, but the epidemiological analyses suggest that the subsequent spread of PDV from the epicentre in Kattegat, Denmark, to haul-out sites in the North Sea through several independent introductions.

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“…A prime example of changing dynamics in a metapopulation is the UK harbour seal (Phoca vitulina), which has been monitored for decades to provide regional population trends, local movement and genetic datasets (15)(16)(17)(18). The UK-wide abundance of harbour seals is currently 42,100 seals (95% CI: 34,500 -52,300), which is comparable to the estimate 20 years ago at 45,550 (95% CI: 37,250 -60,750) (17).…”

Section: Introductionmentioning

confidence: 99%

Perturbation drives changing metapopulation dynamics in a top marine predator

et al. 2020

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Metapopulation theory assumes a balance between local decays/extinctions and local growth/new colonisations. Here we investigate whether recent population declines across part of the UK harbour seal range represent normal metapopulation dynamics or are indicative of perturbations potentially threatening the metapopulation viability, using 20 years of population trends, location tracking data ( n = 380), and UK-wide, multi-generational population genetic data ( n = 269). First, we use microsatellite data to show that two genetic groups previously identified are distinct metapopulations: northern and southern. Then, we characterize the northern metapopulation dynamics in two different periods, before and after the start of regional declines (pre-/peri-perturbation). We identify source–sink dynamics across the northern metapopulation, with two putative source populations apparently supporting three likely sink populations, and a recent metapopulation-wide disruption of migration coincident with the perturbation. The northern metapopulation appears to be in decay, highlighting that changes in local populations can lead to radical alterations in the overall metapopulation's persistence and dynamics.

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Genetic population structure of harbour seals in the United Kingdom and neighbouring waters

Cited by 23 publications

References 33 publications

Echoes from the past: Regional variations in recovery within a harbour seal population

Echoes from the past: Regional variations in recovery within a harbour seal population

Phylogenomic insights to the origin and spread of phocine distemper virus in European harbour seals in 1988 and 2002

Perturbation drives changing metapopulation dynamics in a top marine predator

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