Contributors and references


Karin Hårding, Britt-Marie Bäcklin, Charlotta Moraeus, Kaarina Kauhala, Tero Härkönen, Lena Avellan and Karl Lundström.



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

Nutritional status of seals HELCOM core indicator 2018 (pdf)

Earlier versions of the indicator are available at:

Core indicator report – web-based version December 2015 (pdf)

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

2013 Indicator Report



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.

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.

Bowen, W.D, den Heyer, C.E., McMillan, J.I., & Iverson, S.J. (2015) Offspring size at weaning affects survival to recruitment and reproductive performance of primiparous gray seals. Ecology and Evolution v.5(7): April 2015.

Boyd, I. L., Lockyer, C. & Marsh, H. D. (1999) Reproduction in marine mammals. In Biology of marine mammals (eds J. E. Reynolds & S. A. Rommel), pp. 218–286. Washington, DC: Smithsonian Institute Press.

Fedak, M., Anderson, S. (1987) The energetics of sexual success of grey seals and comparison with the costs of reproduction in other pinnipeds. Symp. Zool. Soc. Lond. 57: 319-341.

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.

Fowler, C.W. (1981) Density dependence as related to life history strategy. Ecology 62: 602-610.

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.

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European Commission (2016) Draft Commission Decision laying down criteria and methodological standards on good environmental status of marine waters and specifications and standardised methods for monitoring and assessment, and repealing Decision 2010/477/EU.

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Haller, M.A., Kovacs, K.M., Hammill, M.O. (1996) Maternal behaviour and energy investment by grey seals (Halichoerus grypus) breeding on land fast ice. Can. J. Zool. 74: 1531-1541.

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. (2000) Population dynamics of seals; the influences of spatial and temporal structure. Academic dissertation, Helsinki, Oy Edita Ab, ISBN 952-91-2794-4 (PDF).

Harding, K.C., Fujiwara, M., Härkönen, T., Axberg, Y. (2005) Mass dependent energetics and survival in harbour seal pups. Functional Ecology 19: 129-135.

Harding, K. C., Härkönen, T., Helander, B. and Karlsson, O. (2007) Status of Baltic grey seals: Population assessment and risk analysis. Nammco Scientific Publications. s. 33-56. No. 81986

Harding, K.C., Salmon, M. Teilmann, J., Dietz D. and T. Harkonen. (2018). Population wide decline in somatic growth in harbour seals – early signs of density dependence. Frontiers in Ecology and Evolution.

Härkönen, T., Heide-Jørgensen, M.-P. (1990) Density and distribution of the ringed seal in the Bothnian Bay. Holarctic Ecology13(2): 122-129.

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

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.

Harkonen, T., Bäcklin, B.-M., Barrett, T., 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.

Hauksson E., Bogason, V. (1997) Comparative feeding of grey (Halichoerus grypus) and common seals (Phoca vitulina) in coastal waters off Iceland, with a note on the diet of hooded (Cystophora cristata) and harp seals (Phoca groenlandica). J. Northwest Atl. Fish. Sci. 22: 125135. doi:10.2960/J.v22.a11.

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.

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.

Kauhala, K., Kurkilahti, M., Ahola, M.P., Herrero, A., Karlsson, O., Kunnasranta, M., Tiilikainen, R., Vetemaa, M. (2015) Age, sex and body condition of Baltic grey seals: Are problem seals a random sample of the population? Annales Zoologici Fennici52: 103–114.

Kauhala K., Bäcklin B.M., J. Raitaniemi and K.C. Harding. 2017. The effect of prey quality and ice conditions on the nutritional status of Baltic grey seals of different age groups. Mammal Research.

Kjellqwist, S.A., Haug, T., Øritsland, T. (1995) Trends in age composition, growth and reproductive parameters of Barents Sea harp seals (Phoca groenlandica). ICES J. Mar. Sci. 52(2): 197–208. doi:10.1016/1054-3139(95)80035-2.

Kovacs, K.M., Lavigne, D.M. (1986) Growth of grey seal (Halichoerus grypus) neonates: different maternal investment in the sexes. Can. J. Zool. 64: 1937-1943.

Krafft, B.A., Kovacs, K.M., Frie, A.K., Haug, T., Lydersen, C. (2006) Growth and population parameters of ringed seals (Pusa hispida) from Svalbard, Norway, 2002-2004. ICES Journal of Marine Science 63: 1136-1144.

Kunnasranta, M. (2010) Merihylkeet vuonna 2010. Riistajakalatalous. Selvityksiä 21/2010: 21–22.

McCann, T.S., Fedak, M.A., Harwood, J. (1989) Parental investment in southern elephant seals, Mirounga leonina. Behavioral Ecology and Sociobiology. 25: 81-87

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.

Mellish, J.-A.E., Horning, M., York, A. E. (2007) Seasonal and spatial blubber depth changes in captive harbor seals (Phoca vitulina) and Steller sea lions (Eumetopias jubatus). Journal of Mammalogy 88: 408–414.

Nilssen, K. T., Haug, T., Lindblom, C. (2001) Diet of weaned pups and seasonal variations in body condition of juvenile Barents Sea harp seals Phoca groenlandica. Marine Mammal Science 17: 926–936.

Oksanen, S. M., Niemi, M., Ahola, M. P. & Kunnasranta, M. 2015. Identifying foraging habitats of Baltic ringed seals using movement data. Movement Ecology 3: 33 (1–11). DOI 10.1186/s40462-015-0058-1

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.

Ryg, M., Lydersen, C., Markussen, N. H., Smith, T. G., Øritsland, N. A. (1990) Estimating the blubber content of phocid seals. Canadian Journal of Fisheries and Aquatic Sciences 47(6): 1223-1227.

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

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.

Stephens, P.A., Houston, A. I., Harding, K.C., Boyd, L., McNamara, J.M. (2014) Capital and income breeding in pinnipeds: the role of food supply. Ecology.

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.


Additional relevant publications

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

Bigg, M.A. (1969) The harbour seal in British Columbia (No. 172). Fisheries Research Board of Canada.

Boulva, J., McLaren, I.A. (1979) Biology of the harbor seal, Phoca vitulina, in eastern Canada. Fisheries Research Board of Canada.

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.

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:

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.

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., 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., 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., 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.

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:

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

Kokko, H., Helle, E., Lindström, 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.

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.

Olsen, M.T., Andersen, S.M., Teilmann, J., Dietz, R., Harkonen, T. (2011) Status of the harbour seal in Southern Scandinavia. NAMMCO Scientific Publications 8: 77-94.

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.

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.

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

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:



HELCOM core indicator report
ISSN 2343-2543