scholarly journals Status of the harbour seal (Phoca vitulina) in Southern Scandinavia

2013 ◽  
Vol 8 ◽  
pp. 77 ◽  
Author(s):  
Morten Tange Olsen ◽  
Signe May Andersen ◽  
Jonas Teilmann ◽  
Rune Dietz ◽  
Susi Manuela Clermont Edrén ◽  
...  
Keyword(s):  
Harbour Seal ◽  
Current Status ◽  
Harbour Seals ◽  
Seal Population ◽  
Southern Scandinavia ◽  
Original Size ◽  
The Baltic ◽  
Further Development ◽  
Long Term Survey

The harbour seal population in Southern Scandinavia has experienced repeated declines caused by hunting and epizootics. These events have shaped the current distribution and abundance of the population. This paper assesses the current status of the population. We estimate trends in abundance of harbour seals from long term survey data, compare these with historic trends inferred from previously published material, and discuss past and potential threats to the harbour seal population of Southern Scandinavia. It is evident that harbour seals have disappeared from haulout areas along the Danish shores of Kattegat and in the westernmost part of the Baltic Sea, where they were previously numerous. In the 1920-30s, when abundance was at its lowest, the population is estimated to have been only a fraction of its original size. Following 30 years of protection the population is currently approaching historic abundance and might have reached the carrying capacity in some areas. Further development depends largely on effects of future epizootics, anthropogenic disturbance, and availability of suitable haulout sites.

scholarly journals Vulnerability of harbour seals, Phoca vitulina, to transient industrial activities in the Strait of Dover

2005 ◽  
Vol 85 (4) ◽  
pp. 1015-1016 ◽  
Author(s):  
Laurent J.J. Seuront ◽  
Perrine Prinzivalli
Keyword(s):  
Interannual Variability ◽  
Industrial Wastewater ◽  
Anthropogenic Activities ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Industrial Activities ◽  
Dramatic Decline ◽  
Harbour Seals ◽  
Seal Population ◽  
Number Of Individuals

The abundance of the harbour seal (Phoca vitulina) was recorded on a tidal bar in the Dover Strait off Calais, over a six-year period between 1999 and 2004. Despite clear seasonal and interannual variability in the number of individuals hauled out on the bar, underwater activities devoted to the installation of industrial wastewater pipes conducted during seven weeks 1 km away from the bar led to a dramatic decline in the number of seals hauling out. A full 19 months after the end of the operations the harbour seal population had not recovered their initial abundance. The results of this study have critical consequences on the conservation of P. vitulina in areas impacted by anthropogenic activities.

scholarly journals Introduction: The harbour seal (Phoca vitulina) - a global perspective

2010 ◽  
Vol 8 ◽  
pp. 7 ◽  
Author(s):  
Arne Bjørge ◽  
Geneviève Desportes ◽  
Gordon T Waring ◽  
Aqqalu Rosing-Asvid
Keyword(s):  
North Atlantic ◽  
Phoca Vitulina ◽  
Global Perspective ◽  
Harbour Seal ◽  
The North ◽  
Harbour Seals ◽  
The North Atlantic ◽  
The Baltic

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

scholarly journals The status of harbour seals (Phoca vitulina) in the United Kingdom

2010 ◽  
Vol 8 ◽  
pp. 117 ◽  
Author(s):  
Dave Thompson ◽  
Callan Duck ◽  
Mike E Lonergan
Keyword(s):  
Survey Methods ◽  
Harbour Seal ◽  
Rocky Shores ◽  
The North ◽  
Harbour Seals ◽  
General Decline ◽  
Seal Population ◽  
The Status ◽  
Thermal Imagers ◽  
The Uk

The UK holds approximately 40% of the European harbour seal population, with the majority found around the coasts of Scotland. Harbour seal populations in the UK have been monitored through a series of repeated aerial surveys of animals hauled out during the annual moult in early August. This moult count is used as a consistent index of population size. Survey methods and frequencies vary. The Scottish and English east coast populations mainly haul out in tidal estuariesand are surveyed annually, using fixed wing aircraft and digital photography. Populations in north and west Scotland often haul out on rocky shores and are surveyed less frequently, using helicopters fitted with thermal imagers. Overall, the most recent minimum estimate of the UK harbour seal population is 24,250 seals of which 19,800 are in Scotland, 3,200 in England and 1,250 in Northern Ireland. The results show that the number of harbour seals in eastern Englandwas increasing before the 1988 and 2002 phocine distemper (PDV) epizootic but has not increased since the end of the 2002 epizootic. There is also evidence of a general decline in most of the large harbour seal colonies around Scotland. The populations along the north and northwest mainland coast were an exception, with numbers appearing to be stable. Between 2001 and 2008, the population in Orkney declined by 67% and Shetland declined by 40%, indicating harbourseals in these areas experienced substantially increased mortality or very low recruitment over this period. The widespread declines, ranging from Shetland to The Wash, suggest that the causes may have been present over a large part of the North Sea and waters off western Scotland.

scholarly journals Sealworm (Pseudoterranova decipiens) infection in the benthic cottid (Taurulus bubalis) in relation to population increase of harbour seal (Phoca vitulina) in Skagerrak, Sweden

2001 ◽  
Vol 3 ◽  
pp. 47 ◽  
Author(s):  
Sven-Gunnar Lunneryd ◽  
Karl Inne Ugland ◽  
Paul Eric Aspholm
Keyword(s):  
Gadus Morhua ◽  
Final Host ◽  
Infected Fish ◽  
Harbour Seal ◽  
Population Increase ◽  
Threshold Size ◽  
Pseudoterranova Decipiens ◽  
Harbour Seals ◽  
Seal Population ◽  
Benthic Fishes

In Koster archipelago (northern Skagerrak, Sweden) the harbour seal population increased from approximately 350 to more than 1000 individuals between 1988 and 1998. During the same period, sealworm (Pseudoterranova decipiens) abundance in the most heavily infected fish species, bullrout (Myoxocepahulus scorpius) and sea scorpion (Taurulus bubalis), did not increase. Since harbour seals do not normally feed on those cottids an infection route via cod (Gadus morhua), which consume cottids, is proposed. The abundance of sealworm in the final host is therefore related to the probability of cod preying on infected cottids prior to being preyed upon by seals. Our model predictsthat the abundance of larval sealworm in benthic fishes is not related to the number of seals when the colony is over a specific threshold size.

scholarly journals Monitoring trends in the abundance of harbour seals (Phoca vitulina) in Icelandic waters

2010 ◽  
Vol 8 ◽  
pp. 227 ◽  
Author(s):  
Erlingur Hauksson
Keyword(s):  
Coastal Area ◽  
East Coast ◽  
Aerial Survey ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Northwest Coast ◽  
Coastal Regions ◽  
Harbour Seals ◽  
Seal Population ◽  
Icelandic Waters

Harbour seal (Phoca vitulina) numbers along the coast of Iceland were monitored by aerial survey in the period 1980-2006. Trends in the abundance of the harbour seal population on the whole coast and in coastal regions of Iceland waters were estimated using ANCOVA on the survey counts, corrected for the influence of several covariates. Harbour seals were found in every coastal area, but were most abundant in Faxaflói, Breiðafjörður and on the northwest coast inthe beginning of this study. Harbour seal numbers declined significantly at a rate of rest = -0.04 (SE 0.005) yr-1 during this period. Decline was highest in Faxaflói and at the south coast (≅7%), while the east coast experienced a significant but lesser (≅1%) decline. Other coastal areas did not show significant trends. The northwest coast was the richest harbour seal area in Iceland in 2006. In Icelandic waters seals are commercially harvested, and unreported but probably high numbers of harbour seals are killed intentionally by shooting and accidentally in fishing geareach year. These factors likely contributed to the overall observed decline in seal numbers.

Pathological findings in North Sea and Baltic grey seal and harbour seal intestines associated with acanthocephalan infections

2020 ◽  
Vol 138 ◽  
pp. 97-110 ◽  
Author(s):  
J Lakemeyer ◽  
K Lehnert ◽  
B Woelfing ◽  
I Pawliczka ◽  
M Silts ◽  
...  
Keyword(s):  
North Sea ◽  
Intestinal Inflammation ◽  
Clinical Signs ◽  
Harbour Seal ◽  
Grey Seal ◽  
The North ◽  
Associated Lesions ◽  
Harbour Seals ◽  
Tunica Muscularis ◽  
The Baltic

Grey seals Halichoerus grypus and harbour seals Phoca vitulina are common seal species in the North and Baltic seas and final hosts of Corynosoma acanthocephalans. C. strumosum and C. magdaleni infect the small intestines of both seal species. In contrast to harbour seals, Baltic grey seals in the past have regularly displayed severe C. semerme infections in the caecum and colon, with associated tunica muscularis hypertrophy, inflammation and ulcerations as part of the Baltic seal disease complex (BSDC). Pathogenesis and correlation of acanthocephalan infections with these lesions are still unknown. This study describes the intestinal pathology and parasitic distribution in each seal species. Grey seal (n = 83) and harbour seal (n = 1156) intestines of all age groups and sexes, collected in Poland, Germany and Estonia from 1998 to 2017, were investigated. Most harbour seals came from the North Sea, whereas grey seals were predominantly derived from the Baltic Sea. Both species featured mild to moderate small intestinal infections. Grey seals showed colonic infections not found in harbour seals and featured a chronic erosive to ulcerative, eosinophilic or lympho-plasmacytic colitis with tunica muscularis hypertrophy, indicating still prevailing clinical signs of the BSDC. Harbour seals displayed granulomatous, eosinophilic, lympho-plasmacytic or catarrhal enteritis. The prevalence of acanthocephalan infections in harbour seals increased from 2012 onwards. Furthermore, significant associations between acanthocephalan infection and the presence of intestinal inflammation were found for both seal species. This study suggests that the level of acanthocephalan infection and associated lesions are suitable seal population health indicators, with the colon being a specific target organ for Baltic grey seal health monitoring.

scholarly journals Dramatic decline of northern bat Eptesicus nilssonii in Sweden over 30 years

2020 ◽  
Vol 7 (2) ◽  
pp. 191754
Author(s):  
Jens Rydell ◽  
Marcus Elfström ◽  
Johan Eklöf ◽  
Sonia Sánchez-Navarro
Keyword(s):  
Climate Change ◽  
Red List ◽  
Mercury Vapour ◽  
Change Models ◽  
The Road ◽  
Dramatic Decline ◽  
The Baltic ◽  
Endangered Status ◽  
Long Term Survey

We monitored northern bat Eptesicus nilssonii (Keyserling & Blasius, 1839) acoustically along a 27 km road transect at weekly intervals in 1988, 1989 and 1990, and again in 2016 and 2017. The methodology of data collection and the transect were the same throughout, except that the insect-attracting mercury-vapour street-lights along parts of the road were replaced by sodium lights between the two survey periods. Counts along sections of the transect with and without street-lights were analysed separately. The frequency of bat encounters in unlit sections showed an average decline of 3.0% per year, corresponding to a reduction of 59% between 1988 and 2017. Sections with street-lights showed an 85% decline over the same period (6.3% per year). The decline represents a real reduction in the abundance of bats rather than an artefact of changed distribution of bats away from roads. Our study conforms with another long-term survey of the same species on the Baltic island of Gotland. Our results agree with predictions based on climate change models. They also indicate that the decline was caused directly by the disuse of the insect-attracting mercury-vapour street-lights, which may have resulted in lower availability of preferred prey (moths). In the 1980s, E. nilssonii was considered the most common bat in Sweden, but the subsequent decline would rather qualify it for vulnerable or endangered status in the national Red List of Threatened Species.

scholarly journals Harbour seals are regaining top-down control in a coastal ecosystem

2018 ◽  
Author(s):  
Geert Aarts ◽  
Sophie Brasseur ◽  
Jan Jaap Poos ◽  
Jessica Schop ◽  
Roger Kirkwood ◽  
...  
Keyword(s):  
North Sea ◽  
Marine Mammal ◽  
Wadden Sea ◽  
Demersal Fish ◽  
Fish Growth ◽  
Harbour Seal ◽  
Top Down ◽  
Harbour Seals ◽  
Seal Population ◽  
The Impact

ABSTRACTHistoric hunting has led to severe reductions of many marine mammal species across the globe. After hunting ceased, some populations have recovered to pre-exploitation levels, and may again act as a top-down regulatory force on marine ecosystems. Also the harbour seal population in the international Wadden Sea grew at an exponential rate following a ban on seal hunting in 1960’s, and the current number ∼38,000 is close to the historic population size. Here we estimate the impact of the harbour seal predation on the fish community in the Wadden Sea and nearby coastal waters.Fish remains in faecal samples and published estimates on the seal’s daily energy requirement were used to estimate prey selection and the magnitude of seal consumption. Estimates on prey abundance were derived from demersal fish surveys, and fish growth was estimated using a Dynamic Energy Budget model. GPS tracking provided information on where seals most likely caught their prey.Harbour seals from the Dutch Wadden Sea fed predominantly on demersal fish, e.g. flatfish species (flounder, sole, plaice, dab), but also sandeel, cod and whiting. Total fish biomass in the Wadden Sea was insufficient to sustain the estimated prey consumption of the entire seal population year-round. This probably explains why seals also acquire prey further offshore in the adjacent North Sea, only spending 13% of their diving time in the Wadden Sea. Still, seal predation was estimated to cause an average annual mortality of 43% and 60% on fish in the Wadden Sea and adjacent coastal zone, respectively. There were however large sources of uncertainty in the estimate, including the migration of fish between the North Sea and Wadden Sea, and catchability estimates of the fish survey sampling gear, particularly for sandeel and other pelagic fish species.Our estimate suggested a considerable top-down control by harbour seals on demersal fish. However predation by seals may also alleviate density-dependent competition between the remaining fish, increasing fish growth, and partly compensating for the reduction in fish numbers. This study shows that recovering coastal marine mammal populations could potentially become an important component in the functioning of shallow coastal systems.

scholarly journals Review on utilization and research on harbour seal (Phoca vitulina) in Iceland

2010 ◽  
Vol 8 ◽  
pp. 341 ◽  
Author(s):  
Erlingur Hauksson ◽  
Sólmundur T Einarsson
Keyword(s):  
Phoca Vitulina ◽  
Economic Resources ◽  
Harbour Seal ◽  
Legal Rights ◽  
Large Dataset ◽  
Harbour Seals ◽  
Seal Population ◽  
By Catch ◽  
Catch Statistics ◽  
Anisakid Nematodes

Harbour seals (Phoca vitulina) have been harvested in Iceland since the first settlers arrived in the 9th century. Pups were generally netted, clubbed and harpooned until 1875 when general use of guns for hunting began. Seal-hunting has been traditional amongst the farms legal rights. Seal hunting was an important supplement to other economic resources. Harbour seal skins, salted ordried, were exported and large dataset of catch statistics is available from trading logbooks since the late 19th century. In the early 20th century catch was about 6,000. In the ‘bounty’ period 1982 – 1989, maximum catches were of 4,000 animals with about 350 hunters participated; in 2006 catches were only about 100 animals with 18 hunters. After 1989 the population continued to decline even though catches decreased markedly. Unreported by-catch in fishing gear, hunt for local consumption and shooting of seals swimming in salmon rivers estuaries may have kept the total removal from the stock above sustainable levels. A considerable Icelandic knowledge base had been compiled about the biology of the harbour seal since the late 16th century, with the first written reference in 1588-1589. In the last decades, research on various aspects of its biology and monitoring have been intensified, with focus on abundance, distribution, diet and nematode infestation. The main results show that the Icelandic harbour seal population - has declined annually about 5% in the period 1980-2006, - was most abundant on the NW-coast, - feeds mainly on sand-eels and gadoids, - and was less infected with anisakid nematodes than grey seals. Seal watching, as a low-consumptive indirect utilization, may represent a new economical opportunity if properly regulated.

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