Contributors and references


Tero Härkönen, Anders Galatius, Morten Tange Olsen, Markus Ahola, Karin Hårding, Olle Karlsson, Mervi Kunnasranta, Lena Avellan, Petra Kääriä, Minna Pyhälä, Owen Rowe.



This version of the HELCOM core indicator report was published in July 2018:

Population trends and abundance of seals HELCOM core indicator 2018 (pdf)

Older versions of the indicator report are available:

Core indicator report - web-based version January 2016 (pdf)

Extended core indicator report – outcome of CORESET II project (pdf)

2013 Indicator report (pdf)



Anon. (1895) Svensk fiskeritidskrift 1895.

Bäcklin, B.-M., Moraeus, C., Roos, A., Eklöf, E., Lind, Y. (2011) Health and age and sex distributions of Baltic grey seals (Halichoerus grypus) collected from bycatch and hunt in the Gulf of Bothnia. ICES Journal of Marine Science 68: 183-188.

Bäcklin, B.-M., Moraeus, C., Kauhala, K., Isomursu, M. (2013) Pregnancy rates of the marine mammals - Particular emphasis on Baltic grey and ringed seals. HELCOM web portal.

Bergman, A., Olsson, M. (1985) Pathology of Baltic grey seal and ringed seal females with special reference to adrenocortical hyperplasia: Is environmental pollution the cause of a widely distributed disease syndrome. Finnish Game Res. 44: 47-62.

Bergman, A. (1999) Health condition of the Baltic grey seal (Halichoerus grypus) during two decades. Apmis 107(1‐6): 270-282.

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Caswell, H. (2001) Matrix population models: Construction, analysis, and interpretation. Second edition. Sinauer, Sunderland. Massachusetts, USA.

Dietz, R., Heide-Jørgensen, M.-P., Härkönen, T. (1989) Mass deaths of harbour seals Phoca vitulina in Europe. Ambio 18(5): 258-264.

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Fietz, K., Graves, J.A., Olsen, M.T. (2013) Control Control Control: A Reassessment and Comparison of GenBank and Chromatogram mtDNA Sequence Variation in Baltic Grey Seals (Halichoerus grypus). PLoS ONE 8(8): e72853. doi:10.1371/journal.pone.0072853.

Fietz, K., Galatius, A., Teilmann, J., Dietz, R., Frie, A.K., Klimova, A., Palsbøll, P.J., Jensen, L.F., Graves, J.A., Hoffman, J.I. & Olsen, M.T. (2016) Shift of grey seal subspecies boundaries in response to climate, culling and conservation. Molecular Ecology 25(17):4097-4112. doi:10.1111/mec.13748

Galatius, A., Ahola, M., Härkönen, T., Jüssi, I., Jüssi, M., Karlsson, O., Verevkin, M. (2014) Guidelines for seal abundance monitoring in the HELCOM area 2014. Available at:

Goodman, S.J. (1998) Patterns of extensive genetic differentiation and variation among European harbor seals (Phoca vitulina vitulina) revealed using microsatellite DNA polymorphisms. Molecular Biology and Evolution 15(2): 104-118.

Harding, K.C., Härkönen, T.J. (1999) Development in the Baltic grey seal (Halichoerus grypus) and ringed seal (Phoca hispida) populations during the 20th century. Ambio 28: 619-627.

Harding, K.C., Härkönen, T., Helander, B., Karlsson, O. (2007) Status of Baltic grey seals: Population assessment and risk analysis. NAMMCO Scientific Publications 6: 33-56.

Härkönen, T., Heide-Jørgensen, M.-P. (1990) Density and distribution of the ringed seal in the Bothnian Bay. Holarctic Ecology 13(2): 122-129.

Härkönen, T., Lunneryd, S.G. (1992) Estimating abundance of ringed seals in the Bothnian Bay. Ambio 21: 497-510.

Härkönen, T., Stenman, O., Jüssi, M., Jüssi, I., Sagitov, R., Verevkin, M. (1998) Population size and distribution of the Baltic ringed seal (Phoca hispida botnica). In: Ringed Seals (Phoca hispida) in the North Atlantic. Edited by C. Lydersen and M.P. Heide-Jørgensen. NAMMCO Scientific Publications 1: 167-180.

Härkönen, T., Harding, K.C., Goodman, S., Johannesson, K. (2005) Colonization history of the Baltic harbor seals: Integrating archaeological, behavioural and genetic data. Marine Mammal Science 21: 695-716.

Härkönen, T., Dietz, R., Reijnders, P., Teilmann, J., Harding, K., Hall, A., Brasseur, S., Siebert, U., Goodman, S., Jepson, P., Dau Rasmussen, T., Thompson, P. (2006) A review of the 1988 and 2002 phocine distemper virus epidemics in European harbour seals. Diseases of Aquatic Organisms 68: 115-130.

Härkönen, T., Brasseur, S., Teilmann, J., Vincent, C., Dietz, R., Reijnders, P., Abt, K. (2007) Status of grey seals along mainland Europe, from the Baltic to France. NAMMCO Scientific Publications 6: 57-68.

Härkönen, T., Harding, K., Rasmussen, T.D., Teilmann, J., Dietz, R. (2007) Age- and Sex-specific Mortality Patterns in an Emerging Wildlife Epidemic: the Phocine Distemper in European Harbour Seals. PLoS ONE 2(9): e887. doi: 10.1371/journal.pone.0000887. 

Harkonen, T., Bäcklin, B.-M., Barrett, T., Anders Bergman, A., Corteyn, M., Dietz, R., Harding, K., Malmsten, J., Roos, A., Teilmann, T. (2008) Mass mortality in harbour seals and harbour porpoises caused by an unknown pathogen. The Veterinary Record 162: 555-556.

Harkonen, T., Jüssi, M., Jüssi, I., Verevkin, M., Dmitrieva, L., Helle, E., Sagitov, R., Harding, K.C. (2008) Seasonal activity budget of adult Baltic ringed seals (Phoca hispida botnica). PLoS ONE 3(4): e2006.doi:10.1371/journal.pone.0002006.

Harkonen, T., Isakson, E. (2011) Historical and current status of harbour seals in the Baltic proper. NAMMCO Scientific Publications 8: 71-76.

Harwood, J., Prime, J.H. (1978) Some factors affecting the size of British grey seal populations. Journal of Applied Ecology: 401-411.

Heide-Jørgensen, M.-P., Härkönen, T. (1988) Rebuilding seal stocks in the Kattegat-Skagerrak. Marine Mammal Science 4(3): 231-246.

Helle, E. (1980) Lowered reproductive capacity in female ringed seals (Pusa hispida) in the Bothnian Bay, northern Baltic Sea, with special reference to uterine occlusions. Annales Zoologica Fennici 17: 147-158.

Hiby, L. et al. (2013) Estimates of the size of the Baltic grey seal population based on photo-identification data. NAMMCO Scientific Publications [S.l.] 6: 163-175. Oct. 2013. ISSN 2309-2491. Available at: <>. doi:

Jüssi, M., Härkönen, T., Jüssi, I., Helle, E. (2008) Decreasing ice coverage will reduce the reproductive success of Baltic grey seal (Halichoerus grypus) females. Ambio 37: 80–85.

Karlsson, O., Härkönen, T., Bäcklin, B.-M. (2008) Populationer på tillväxt. Havet 2008: 91-92.

Kokko, H., Helle, E.J., Ranta, E., Sipilä, T. (1999) Backcasting population sizes of ringed and grey seals in the Baltic and Lake Saimaa during the 20th century.  Annales Zoologici Fennici 36: 65-73.

Meier, H.E.M., Döscher, R., Halkka, A. (2004) Simulated distributions of Baltic Sea-ice in the warming climate and consequences for the winter habitat of the Baltic Ringed Seal. Ambio 33: 249–256.

Olsen, M.T., Andersen, S.M., Teilmann, J., Dietz, R., Harkonen, T. (2010) Status of the harbour seal in Southern Scandinavia. NAMMCO Scientific Publications 8: 77-94.

Olsen, M. T., Wesley Andersen, L., Dietz, R., Teilmann, J., Harkonen, T., Siegismund, H.R. (2014) Integrating genetic data and population viability analyses for the identification of harbour seal (Phoca vitulina) populations and management units. Molecular Ecology 23: 815-831

Teilmann, J., Riget, F., Harkonen, T. (2010) Optimising survey design in Scandinavian harbour seals: Population trend as an ecological quality element. ICES Journal of Marine Science 67: 952–958.

Sipilä, T. (2003) Conservation biology of Saimaa ringed seal (Phoca hispida saimensis) with reference to other European seal populations. PhD Thesis. Available at:

Stenman, O., Halkka, A., Helle, E., Keränen, S., Nummelin, J., Soikkeli, M., ... Tanskanen, A. (2005) Numbers and occurrence of grey seals in the Finnish sea area in the years 1970-2004. In Symposium on Biology and Management of Seals in the Baltic area. Kala-ja riistaraportteja nro 346: 58-61.

Svensson, C.J., Hansson, A., Harkonen, T., Harding, K. (2011) Detecting density dependence in growing seal populations. Ambio (2011) 40: 52–59. DOI 10.1007/s13280-010-0091-7.

Sundqvist, L., Harkonen, T., Svensson, C.J., Harding, K.C. (2012) Linking climate trends to population dynamics in the Baltic ringed seal - Impacts of historical and future winter temperatures. Ambio. DOI 10.1007/s13280-012-0334-x.

Vanhatalo, J., Vetemaa, M., Herrero, A., Aho, T., Tiilikainen, R. (2014) By-Catch of Grey Seals (Halichoerus grypus) in Baltic Fisheries—A Bayesian Analysis of Interview Survey. PLoS ONE 9(11): e113836. doi:10.1371/journal.pone.0113836.

Zohari, S., Neimanis, A., Härkönen, T., Moraeus, C., Valarcher, J.F. (2014) Avian influenza A(H10N7) virus involvement in mass mortality of harbour seals (Phoca vitulina) in Sweden, March through October 2014. Euro Surveill. 2014; 19(46):pii=20967. Available at:


Additional relevant publications

Harding, K.C., Härkönen, T., Caswell, H. (2002) The 2002 European seal plague: epidemiology and population consequences. Ecology Letters 5: 727-732.

Harding, K.C., Härkönen, T., Pineda, J. (2003) Estimating quasi-extinction risk of European harbour seals: a reply to Lonergan and Harwood. Ecology Letters 6: 894-897.

Härkönen, T., Harding, K.C. (2001) Spatial structure of harbour seal populations and the implications thereof. Can. J. Zool. 79: 2115-2127.

Harkonen, T., Harding, K.C. (2011) Predicting recurrent PDV epidemics in European harbour seals. NAMMCO Scientific Publications 8: 275-284.

Heide-Jørgensen, M.-P., Härkönen, T. (1992) Epizootiology of seal disease. J. Appl. Ecol. 29: 99-107.

Heide-Jørgensen, M.-P., Härkönen, T., Dietz R., Thompson, P. (1992) Retrospective of the 1988 European seal epizootic. Diseases of Aquatic Organisms 13: 37-62.

Mortensen, P., Bergman, A., Bignert, A., Hansen, H.J., Härkönen, T., Olsson, M. (1992) Prevalence of skull lesions in harbour seals Phoca vitulina in Swedish and Danish museum collections during the period 1835-1988. Ambio 21: 520-524.

Palo, J.U., Mäkinen, H.S., Helle, E., Stenman, O., Väinölä, R. (2001) Microsatellite variation in ringed seals (Phoca hispida): genetic structure and history of the Baltic Sea population. Heredity 86: 609–617. doi: 10.1046/j.1365-2540.2001.00859.x.



HELCOM core indicator report,

ISSN 2343-2543