scholarly journals Estimates of the size of the Baltic grey seal population based on photo-identification data

2007 ◽  
Vol 6 ◽  
pp. 163 ◽  
Author(s):  
Lex Hiby ◽  
Torkel Lundberg ◽  
Olle Karlsson ◽  
John Watkins ◽  
Mart Jüssi ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Population Based ◽  
Point Estimate ◽  
Grey Seal ◽  
The Baltic Sea ◽  
Photo Identification ◽  
A Value ◽  
Seal Population ◽  
The Baltic ◽  
Year 2000

The size of the year 2000 summer population of grey seals in the Baltic Sea was estimated using identification of individual seals from photographs taken over a period of 6 years. Photos were taken at haul-out sites within all major grey seal areas in the semi-closed Baltic Sea. The point estimate is 15,631, based on a value for annual survival of identification markings of 0.904, which was also estimated using the photo-id data, with 95% confidence limits from 9,592 to 19,005. The estimate is subject to an unknown, but probably small, upward bias resulting from the risk of failure to identify all individuals in the photographs used for the analysis. An estimated minimum of 15,950 seals were counted at moulting haul-outs in 2003, which thus provides a lower bound on the population size in that year and represents 80% of the photo-id point estimate.

scholarly journals Reconstructing the ecological history of the extinct harp seal population of the Baltic Sea

2021 ◽  
Vol 251 ◽  
pp. 106701
Author(s):  
Aikaterini Glykou ◽  
Lembi Lõugas ◽  
Giedrė Piličiauskienė ◽  
Ulrich Schmölcke ◽  
Gunilla Eriksson ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Harp Seal ◽  
The Baltic Sea ◽  
Ecological History ◽  
Seal Population ◽  
History Of ◽  
The Baltic

scholarly journals Decomposing Mean Sea Level Rise in a Semi-Enclosed Basin, the Baltic Sea

2019 ◽  
Vol 32 (11) ◽  
pp. 3089-3108 ◽  
Author(s):  
Ulf Gräwe ◽  
Knut Klingbeil ◽  
Jessica Kelln ◽  
Sönke Dangendorf
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Ocean Model ◽  
Spatial Variations ◽  
The Baltic Sea ◽  
Baltic Basin ◽  
Mean Sea Level ◽  
A Value ◽  
Regional Ocean Model ◽  
The Baltic

Abstract We analyzed changes in mean sea level (MSL) for the period 1950–2015 using a regional ocean model for the Baltic Sea. Sensitivity experiments allowed us to separate external from local drivers and to investigate individual forcing agents triggering basin-internal spatial variations. The model reveals a basin-average MSL rise (MSLR) of 2.08 ± 0.49 mm yr−1, a value that is slightly larger than the simultaneous global average of 1.63 ± 0.32 mm yr−1. This MSLR is, however, spatially highly nonuniform with lower than average increases in the southwestern part (1.71 ± 0.51 mm yr−1) and higher than average rates in the northeastern parts (2.34 ± 1.05 mm yr−1). While 75% of the basin-average MSL externally enters the Baltic basin as a mass signal from the adjacent North Sea, intensified westerly winds and a poleward shift of low pressure systems explain the majority of the spatial variations in the rates. Minor contributions stem from local changes in baroclinicity leading to a basin-internal redistribution of water masses. An observed increase in local ocean temperature further adds to the total basinwide MSLR through thermal expansion but has little effect on the spatial pattern. To test the robustness of these results, we further assessed the sensitivity to six different atmospheric surface forcing reanalysis products over their common period from 1980 to 2005. The ensemble runs indicated that there are significant differences between individual ensemble members increasing the total trend uncertainty for the basin average by 0.22 mm yr−1 (95% confidence intervals). Locally the uncertainty varies from 0.05 mm yr−1 in the central part to up to 0.4 mm yr−1 along the coasts.

scholarly journals The Role of Food Web Interactions in Multispecies Fisheries Management: Bio-economic Analysis of Salmon, Herring and Grey Seal in the Northern Baltic Sea

2021 ◽  
Author(s):  
Tin-Yu Lai ◽  
Marko Lindroos ◽  
Lone Grønbæk ◽  
Atso Romakkaniemi
Keyword(s):  
Baltic Sea ◽  
Food Web ◽  
Economic Model ◽  
Management Strategies ◽  
Management Approach ◽  
Grey Seal ◽  
Food Web Interactions ◽  
Seal Population ◽  
Salmon Fisheries ◽  
The Baltic

AbstractMultispecies bio-economic models are useful tools to give insights into ecosystem thinking and ecosystem-based management. This paper developed an age-structured multispecies bio-economic model that includes the food web relations of the grey seal, salmon, and herring, along with salmon and herring fisheries in the Baltic Sea. The results show that the increasing seal population influences salmon fisheries and stock, but the impacts on the harvest are stronger than on the stock if the targeted management policies are obeyed. If seal population growth and a low herring stock occur simultaneously, the salmon harvest could face a serious threat. In addition, scenarios of the multispecies management approach in this paper reveal a benefit that our model can evaluate the performance of different fisheries with identical or different management strategies simultaneously. The results show the most profitable scenario is that both fisheries pursuit aggregated profits and reveal a trade-off between herring fisheries and salmon fisheries. Our model indicates that the herring harvest level and the approaches to managing herring fisheries can influence the performance of salmon fisheries. The study also demonstrates a way to develop a multispecies bio-economic model that includes both migratory fish and mammalian predators.

scholarly journals Complementary methods assessing short and long-term prey of a marine top predator ‒ Application to the grey seal-fishery conflict in the Baltic Sea

PLoS ONE ◽  
2019 ◽  
Vol 14 (1) ◽  
pp. e0208694 ◽  
Author(s):  
Malin Tverin ◽  
Rodrigo Esparza-Salas ◽  
Annika Strömberg ◽  
Patrik Tang ◽  
Iiris Kokkonen ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Grey Seal ◽  
Top Predator ◽  
The Baltic Sea ◽  
Complementary Methods ◽  
Short And Long Term ◽  
The Baltic

The breeding and distribution of the grey seal ( Halichoerus grypus Fab.) in the Baltic Sea, with observations on other seals of the area

1972 ◽  
Vol 182 (1066) ◽  
pp. 37-58 ◽  
Keyword(s):  
Baltic Sea ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Last Deglaciation ◽  
The Baltic Sea ◽  
Eastern Canada ◽  
The North ◽  
Ice Coverage ◽  
Large Numbers ◽  
The Baltic

The grey seal ( Halichoerus grypus Fab.) is considered to be one of the rarest species of the seals. The area of greatest abundance is centred around the coasts of the British Isles where the species has been established for a considerable period. The Grey Seals Acts of 1914 and 1932 gave protection to the species in British waters during the breeding months of September to December. But this seal also occurs in other countries in the North Atlantic, notably in Eastern Canada, often on ice (figures 12, 13, plate 4), Iceland, the Faroes, Norway, the Kola peninsular and the Baltic Sea. The total population is estimated (Smith 1966) to be ca . 52500. Since the last deglaciation considerable changes have occurred in the Baltic region, but at the present time in this tideless sea – which embraces the Gulfs of Bothnia, Finland and Riga, and in waters of a salinity as low as 3.75 ‰, of an area of 400000 km 2 – the grey seal breeds in March on ice, as does the ringed seal in the same month and also on ice, though the common seal breeds in June on sandbanks or rocks. Within the area is a valuable and productive fishery and an inevitable conflict has for long existed between man and the seals, both predators of economically valuable fish, e. g. herring, cod, eel, salmon and other species, leading to the imposition of bounty payments for seals killed. Over the years very large numbers of grey and ringed seals have been killed, chiefly by fishermen in Sweden and Finland, to obtain bounties from the authorities. Unlike the planned culling and undertaken in some British colonies, the Baltic killings have been made at random and little is known of its effect upon the survival of the species. In the Baltic it is not possible to undertake counts of seals owing to the scattered nature of their breeding and the unpredictability of the winter ice coverage.

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