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Seasonal activity budget of adult baltic ringed seals.

Harkonen T, Jüssi M, Jüssi I, Verevkin M, Dmitrieva L, Helle E, Sagitov R, Harding KC - PLoS ONE (2008)

Bottom Line: Seals from three main regions showed explicit site fidelity and the distributions of animals tagged from different areas did not overlap, suggesting separate stocks.Seals spent 70% (females) to 85% (males) of their time diving in June and July which decreased to 50% in late autumn.The information on seasonal activity budget is crucial for developing population energetic models where interactions between ringed seals and other trophic levels can be evaluated.

View Article: PubMed Central - PubMed

Affiliation: Swedish Museum of Natural History, Stockholm, Sweden. tero.harkonen@nrm.se

ABSTRACT
Although ringed seals are important components in oceanic and fresh water ecosystems at high latitudes, little is known about how they exploit these harsh environments. Seasonal activity and diving behaviour of 19 adult Baltic ringed seals were studied by satellite telemetry. We elaborated an activity budget for ten months of the year, extending over the period from moult to the breeding season. Seals from three main regions showed explicit site fidelity and the distributions of animals tagged from different areas did not overlap, suggesting separate stocks. Both the mean duration and the mean depth of dives peaked in June and July. Seals spent 70% (females) to 85% (males) of their time diving in June and July which decreased to 50% in late autumn. Less than one percent of dives exceeded 10 min in females, while 10% of male dives lasted longer than 10 min in June to September. Less than one percent of dives lasted for more than 25 min. Both females and males were most active during day time and hauled out predominantly during the night. Activity patterns during the summer are suggested to be correlated to energy accumulation and prey availability. The information on seasonal activity budget is crucial for developing population energetic models where interactions between ringed seals and other trophic levels can be evaluated.

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Related in: MedlinePlus

The Baltic Sea area with names mentioned in text.Locations of adult ringed seals tagged with satellite transmitters in the Bothnian Bay (blue, 345 locations), the Gulf of Finland (red, 178 locations), and Estonian coastal waters (green, 812 locations). There was no overlap in the distribution of seals tagged in the different areas.
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pone-0002006-g001: The Baltic Sea area with names mentioned in text.Locations of adult ringed seals tagged with satellite transmitters in the Bothnian Bay (blue, 345 locations), the Gulf of Finland (red, 178 locations), and Estonian coastal waters (green, 812 locations). There was no overlap in the distribution of seals tagged in the different areas.

Mentions: Data on positions of tracked seals from the Bothnian Bay (345 locations of class 0 to 3) covered the period from November to March, and during this period the ringed seals were strictly found in the ice-covered areas in the north. None of five seals moved out of the Bothnian Bay (Fig. 1). The larger data set from Estonian coastal waters (10 seals, 812 locations) and the Gulf of Finland (4 seals, 178 locations) covering the period from mid May to mid March, indicate a similar behaviour, but also permits a more detailed analysis. In late May the seals left the shallow areas and most “at sea locations” during June and July were over deeper waters (>20 m) in the Gulf of Riga, and the Gulf of Finland. The positions from the deep off-shore waters were from the summer period, and in September and October all seals moved towards the main coast line. In December and January seals tagged in Estonia moved from the straits to the northern parts of the Gulf of Riga. This movement to the south coincided with the advancement of the fast ice edge in the straits. In years when the shallow Estonian coastal waters were covered by fast ice in February, none of the seals remained in the area. The males tagged in Russia showed a similar pattern and moved to the known breeding ice in the north-eastern part of the Gulf of Finland in November, and mainly stayed there through February, whereas both females stayed in the open waters of the Southern part of the Gulf. A more detailed analysis of seasonal movements and habitat selection will be given elsewhere.


Seasonal activity budget of adult baltic ringed seals.

Harkonen T, Jüssi M, Jüssi I, Verevkin M, Dmitrieva L, Helle E, Sagitov R, Harding KC - PLoS ONE (2008)

The Baltic Sea area with names mentioned in text.Locations of adult ringed seals tagged with satellite transmitters in the Bothnian Bay (blue, 345 locations), the Gulf of Finland (red, 178 locations), and Estonian coastal waters (green, 812 locations). There was no overlap in the distribution of seals tagged in the different areas.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2289877&req=5

pone-0002006-g001: The Baltic Sea area with names mentioned in text.Locations of adult ringed seals tagged with satellite transmitters in the Bothnian Bay (blue, 345 locations), the Gulf of Finland (red, 178 locations), and Estonian coastal waters (green, 812 locations). There was no overlap in the distribution of seals tagged in the different areas.
Mentions: Data on positions of tracked seals from the Bothnian Bay (345 locations of class 0 to 3) covered the period from November to March, and during this period the ringed seals were strictly found in the ice-covered areas in the north. None of five seals moved out of the Bothnian Bay (Fig. 1). The larger data set from Estonian coastal waters (10 seals, 812 locations) and the Gulf of Finland (4 seals, 178 locations) covering the period from mid May to mid March, indicate a similar behaviour, but also permits a more detailed analysis. In late May the seals left the shallow areas and most “at sea locations” during June and July were over deeper waters (>20 m) in the Gulf of Riga, and the Gulf of Finland. The positions from the deep off-shore waters were from the summer period, and in September and October all seals moved towards the main coast line. In December and January seals tagged in Estonia moved from the straits to the northern parts of the Gulf of Riga. This movement to the south coincided with the advancement of the fast ice edge in the straits. In years when the shallow Estonian coastal waters were covered by fast ice in February, none of the seals remained in the area. The males tagged in Russia showed a similar pattern and moved to the known breeding ice in the north-eastern part of the Gulf of Finland in November, and mainly stayed there through February, whereas both females stayed in the open waters of the Southern part of the Gulf. A more detailed analysis of seasonal movements and habitat selection will be given elsewhere.

Bottom Line: Seals from three main regions showed explicit site fidelity and the distributions of animals tagged from different areas did not overlap, suggesting separate stocks.Seals spent 70% (females) to 85% (males) of their time diving in June and July which decreased to 50% in late autumn.The information on seasonal activity budget is crucial for developing population energetic models where interactions between ringed seals and other trophic levels can be evaluated.

View Article: PubMed Central - PubMed

Affiliation: Swedish Museum of Natural History, Stockholm, Sweden. tero.harkonen@nrm.se

ABSTRACT
Although ringed seals are important components in oceanic and fresh water ecosystems at high latitudes, little is known about how they exploit these harsh environments. Seasonal activity and diving behaviour of 19 adult Baltic ringed seals were studied by satellite telemetry. We elaborated an activity budget for ten months of the year, extending over the period from moult to the breeding season. Seals from three main regions showed explicit site fidelity and the distributions of animals tagged from different areas did not overlap, suggesting separate stocks. Both the mean duration and the mean depth of dives peaked in June and July. Seals spent 70% (females) to 85% (males) of their time diving in June and July which decreased to 50% in late autumn. Less than one percent of dives exceeded 10 min in females, while 10% of male dives lasted longer than 10 min in June to September. Less than one percent of dives lasted for more than 25 min. Both females and males were most active during day time and hauled out predominantly during the night. Activity patterns during the summer are suggested to be correlated to energy accumulation and prey availability. The information on seasonal activity budget is crucial for developing population energetic models where interactions between ringed seals and other trophic levels can be evaluated.

Show MeSH
Related in: MedlinePlus