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Undersökning av sälar insamlade 2015
Swedish Museum of Natural History, Department of Environmental research and monitoring.
Swedish Museum of Natural History, Department of Environmental research and monitoring.
Swedish Museum of Natural History, Department of Environmental research and monitoring.
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2017 (Swedish)Report (Other academic)
Abstract [sv]

Sedan 1970-talet har gråsäl (Halichoerus grypus), knubbsäl (Phoca vitulina) och vikare (Phoca hispida) insamlats och undersökts på Naturhistoriska riksmuseet (NRM). Majoriteten av de undersökta sälarna är gråsälar. Beroende på jakt under 1900-talet och nedsatt reproduktion under århundradets senare del så minskade sälpopulationerna i Östersjön. Under 1970-och 1980-talet noterades ett antal sjukliga förändringar som kallades Baltic Seal Disease Complex framför allt hos gråsäl och som misstänktes ha samband med höga halter av miljögifter som PCB och DDT. Förekomsten av flera av dessa förändringar liksom halterna av PCB och DDT har minskat sedan dess. Hos gråsäl har därefter förekomst av tarmsår ökat och minskat, späcktjockleken minskat och förekomst av leverparasiter ökat.

Under år 2015 insamlades och undersöktes sälar och prover från 137 gråsälar, 44 knubbsälar och 27 vikare. I övrigt inrapporterades 196 döda sälar funna på stränder av allmänheten.

Gråsälspopulationen ökar för närvarande med ca 8% per år och 85% av de undersökta honorna mellan 6-24 år var dräktiga. Knubbsälspopulationerna ökar för närvarande med 7-9% per år. Antal undersökta knubbsälar var visserligen betydligt färre än antal undersökta gråsälar men andel dräktiga honor i motsvarande åldersgrupp var endast 57%. Vikarepopulationen i Bottenviken ökar för närvarande med ca 4,5% per år. Hos vikare inkom endast en könsmogen hona från dräktighetsperioden och hon var dräktig.

Av de undersökta vikarna var 20 av 27 yngre än 4 år gamla. Två två-åriga vikarhonor hade missbildningar i form av diafragmabråck hos den ena och avsaknad av ett livmoderhorn hos den andra.

 

Sammanfattningsvis ser hälsosituationen för undersökta gråsälar i Östersjön delvis bättre ut än tidigare och populationstillväxten har varit stabil under de senaste 15 åren. Antal undersökta knubbsälar och vikare är för få för att redovisa patologiska trender men undersökta knubbsälar visade tendens till låg dräktighetsfrekvens som bör studeras närmare. De båda västliga bestånden av knubbsälar drabbades av epidemier 1988, 2002 och 2014 och populationstillväxten hos dessa bestånd har minskat efter 2002. Däremot har populationen av knubbsälar på östkusten visat på en stadig populationstillväxt sedan 1970-talet. Vikarepopulationen i Bottniska viken har en fortsatt låg tillväxt.

Abstract [en]

Since the 1970s, grey seals (Halichoerus grypus), harbour seals (Phoca vitulina) and ringed seals (Phoca hispida) have been collected and necropsied at the Swedish Museum of Natural History. Mostly have grey seals been examined. The effect of hunting during 19th century and reproductive failure during the latter half of the century decreased Baltic seal populations. In the 1970s and 1980s, pathological changes found mostly in grey seals was called the Baltic Seal Disease Complex and was thought to be related to high levels of PCB and DDT. Since then several pathological changes have decreased in prevalence as well as levels of PCB and DDT. Since then in grey seals, the prevalence of intestinal ulcers has increased and then decreased, blubber thickness has decreased and the prevalence of a zoonotic biliary trematode infection increased.

In 2015, whole bodies and samples from 137 grey seals, 44 harbour seals and 27 ringed seals were examined at the museum. The public reported 196 seals found dead along the Swedish coast. At present, the Baltic grey seal population increases with 8% each year and 85% of the examined females 6-24 years old were pregnant during the pregnant period (August-February) in 2015. The harbour seal populations presently increase with 7-9 % per year, although the numbers of examined harbour seals are much lower than the number of grey seals, the proportion of examined pregnant harbour seals in corresponding age group was only 57%. The ringed seal population in the Gulf of Bothnia presently increase with 4,5% per year. One mature female examined from the period of pregnancy was pregnant. Of the examined 27 ringed seals, 20 of them were younger than 4 years. Two two-year old females showed malformations as diaphragmatic hiatus in one of them and the other female lacked one of the uterine horns.

 

In conclusion, the health situation for examined Baltic grey seals is better and the increase in the population during the last 15 years is stable. The number of examined harbour seals and ringed seals is small for presenting trends but harbour seals showed a tendency to low pregnancy rate that needs further studies. The populations of harbour seals on the Swedish west coast were affected by epidemics in 1988, 2002 and 2014 and the development rate of these populations have decreased since 2002. The development of the harbour seal population on the Swedish east coast has a steady increase since the 1970s. The population of ringed seals has a low increase in the Gulf of Bothnia

Place, publisher, year, edition, pages
2017. , 17 p.
Series
Rapport, 6
National Category
Natural Sciences
Research subject
Man and the environment
Identifiers
URN: urn:nbn:se:nrm:diva-2438OAI: oai:DiVA.org:nrm-2438DiVA: diva2:1136468
Projects
Sälpatologi
Funder
Swedish Environmental Protection Agency, 2213-16-004Swedish Agency for Marine and Water Management
Available from: 2017-08-28 Created: 2017-08-28 Last updated: 2017-09-06Bibliographically approved

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