Report of the NAMMCO-ICES Workshop on Seal Modelling (WKSEALS 2020)

  • Sophie Smout University of St Andrews
  • Kimberly Murray NOAA
  • Geert Aarts
  • Martin Biuw
  • Sophie Brasseur
  • Alejandro Buren
  • Fanny Empacher
  • Anne Kirstine Frie
  • James Grecian
  • Mike Hammill
  • Bjarni Mikkelsen
  • Arnaud Mosnier
  • Aqqalu Rosing-Asvid
  • Debbie Russell
  • Hans Skaug
  • Garry Stenson
  • Len Thomas
  • Jay ver Hoef
  • Lars Witting
  • Vladimir Zabavnikov
  • Tor Arne Øigård
  • Ruth Fernandez
  • Fern Wickson
Keywords: pinniped, management, population dynamics modelling, Bayesian, maximum likelihood, age-structured, pup production, MCMC, sequential importance sampling, particle filter

Abstract

To support sustainable management of apex predator populations, it is important to estimate population size and understand the drivers of population trends to anticipate the consequences of human decisions. Robust population models are needed, which must be based on realistic biological principles and validated with the best available data. A team of international experts reviewed age-structured models of North Atlantic pinniped populations, including Grey seal (Halichoerus grypus), Harp seal (Pagophilus groenlandicus), and Hooded seal (Cystophora cristata). Statistical methods used to fit such models to data were compared and contrasted. Differences in biological assumptions and model equations were driven by the data available from separate studies, including observation methodology and pre-processing. Counts of pups during the breeding season were used in all models, with additional counts of adults and juveniles available in some. The regularity and frequency of data collection, including survey counts and vital rate estimates, varied. Important differences between the models concerned the nature and causes of variation in vital rates (age-dependent survival and fecundity). Parameterisation of age at maturity was detailed and time-dependent in some models and simplified in others. Methods for estimation of model parameters were reviewed and compared. They included Bayesian and maximum likelihood (ML) approaches, implemented via bespoke coding in C, C++, TMB or JAGS. Comparative model runs suggested that as expected, ML-based implementations were rapid and computationally efficient, while Bayesian approaches, which used MCMC or sequential importance sampling, required longer for inference. For grey seal populations in the Netherlands, where preliminary ML-based TMB results were compared with the outputs of a Bayesian JAGS implementation, some differences in parameter estimates were apparent. For these seal populations, further investigations are recommended to explore differences that might result from the modelling framework and model-fitting methodology, and their importance for inference and management advice. The group recommended building on the success of this workshop via continued collaboration with ICES and NAMMCO assessment groups, as well as other experts in the marine mammal modelling community. Specifically, for Northeast Atlantic harp and hooded seal populations, the workshop represents the initial step towards a full ICES benchmark process aimed at revising and evaluating new assessment models.

References

Brasseur, S. M. J. M., van Polanen Petel, T. D., Gerrodette, T., Meesters, E. H., Reijnders, P. J. H. & Aarts, G. (2015). Rapid recovery of Dutch gray seal colonies fueled by immigration. Marine Mammal Science, 31, 405–426. https://doi.org/10.1111/mms.12160

Boveng, P. L., Ver Hoef, J. M., Withrow, D. E. & London, J. M. (2018). A Bayesian Analysis of Abundance, Trend and Population Viability for Harbor Seals in Iliamna Lake, Alaska. Risk Analysis, 38(9), 1988–2009. https://doi.org/10.1111/risa.12988

Coltman, D. W., Stenson, G., Hammill, M. O., Haug, T., Davis, C. S. & Fulton, T. L. (2007). Panmictic population structure in the hooded seals (Cystophora cristata). Molecular Ecology, 16(8), 1639–1648. https://doi.org/10.1111/j.1365-294x.2007.03229.x

den Heyer, C. E. & Bowen, W. D. (2017). Estimating changes in vital rates of Sable Island grey seals using mark-recapture analysis. (DFO Canadian Science Advisory Secretariat Research Document 2017/054). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2017/2017_054-eng.html

den Heyer, C. E., Bowen, D. W. & McMillan, J. I. (2014). Long-term changes in grey seal vital rates at Sable Island estimated from POPAN mark-resighting analysis of branded seals (DFO Canadian Science Advisory Secretariat Research Document 2013/021). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/publications/resdocs-docrech/2013/2013_021-eng.html

den Heyer, C. E., Lang, S. L. C., Bowen, W. D. & Hammill, M. O. (2017). Pup Production at Scotian Shelf Grey Seal (Halichoerus grypus) Colonies in 2016 (DFO Canadian Science Advisory Secretariat Research Document 2017/056). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2017/2017_056-eng.html

Frie, A. K., Stenson, G. & Haug, T. (2012). Long term trends in reproductive and demographic parameters of female Northwest Atlantic hooded seals (Cystophora cristata): Population responses to ecosystem change? Canadian Journal of Zoology, 90, 376–392. https://doi.org/10.1139/z11-140

Hammill, M.O. & Stenson, G. (2006). Abundance of Northwest Atlantic hooded seals (1960-2005) (DFO Canadian Science Advisory Secretariat Research Document 2006/068). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/publications/resdocs-docrech/2006/2006_068-eng.htm

Hammill, M. O., Gosselin, J-F. & Stenson, G. B. (2017a). Pup production of Northwest Atlantic grey seals in the Gulf of St. Lawrence (DFO Canadian Science Advisory Secretariat Research Document 2017/043). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2017/2017_043-eng.html

Hammill, M. O., den Heyer, C. E., Bowen, W. D. & Lang, S. L. C. (2017b). Grey Seal Population Trends in Canadian Waters, 1960-2016 and harvest advice (DFO Canadian Science Advisory Secretariat Research Document 2017/052). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2017/2017_052-eng.html

Hammill, M. O, Stenson, G. B., Doniol-Valcroze, T. & Mosnier, A. (2015). Conservation of northwest Atlantic harp seals: Past success, future uncertainty? Biology Conservation, 192, 181–191. http://dx.doi.org/10.1016/j.biocon.2015.09.016

Hammill, M. O., Stenson, G. B. & M. C. S. Kingsley. (2011). Historical Abundance of Northwest Atlantic harp seals (Pagophilus groenlandicus): influence of harvesting and climate (DFO Canadian Science Advisory Secretariat Research Document 2011/100). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2011/2011_100-eng.html

Hammill, M. O., Stenson, G. B., Mosnier, A. & Doniol-Valcroze, T. (2021). Trends in abundance of harp seals, Pagophilus groenlandicus, in the Northwest Atlantic, 1952–2019 (DFO Canadian Science Advisory Secretariat Research Document 2021/006). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2021/2021_006-eng.html

Han, G., Colbourne, E., Pepin, P. & Xie, Y. (2015). Statistical projections of ocean climate indices off Newfoundland and Labrador. Atmosphere-Ocean, 53, 556–570. https://doi.org/10.1080/07055900.2015.1047732

Han, G., Ma, Z., Long, Z., Perrie, W. & Chasse, J. (2019). Ocean and Sea-Ice Model Under an A1B Forcing Scenario 2011–2069. Atmosphere-Ocean, 57, 3–17.

Stenson, G. B. & Upward, P. (2020). Updated Estimates of Harp Seal Bycatch and Total Removals in the Northwest Atlantic (DFO Canadian Science Advisory Secretariat Research Document 2020/014). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2020/2020_014-eng.html

Stenson, G. B. & Hammill, M. O. (2014). Can ice breeding seals adapt to habitat loss in a time of climate change? ICES Journal of Marine Science, 71, 1977–1986. https://doi.org/10.1093/icesjms/fsu074

Stenson, G. B., Buren, A. D. & Koen-Alonso, M. (2016). The impact of changing climate and abundance on reproduction in an ice-dependent species, the Northwest Atlantic harp seal, Pagophilus groenlandicus. ICES Journal of Marine Science, 73, 250–262. http://dx.doi.org/10.1093/icesjms/fsv202

Stenson, G. B., Buren, A. & Sheppard, G.L. (2020). Updated estimates of Reproductive Rates in Northwest Atlantic Harp Seals and the influence of body condition (DFO Canadian Science Advisory Secretariat Research Document 2020/057). Retrieved from https://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocs-DocRech/2020/2020_057-eng.html

Thomas, L., Russell, D. J. F., Duck, C., Morris, C. D., Lonergan, M., Empacher, F., Thompson, D. & Harwood, J. (2019). Modelling the population size and dynamics of the British grey seal. Aquatic Conservation, 29(S1), 6–23. https://doi.org/10.1002/aqc.3134

Thomas, L. (2020). Estimating the size of the UK grey seal population between 1984 and 2019 (UK Special Committee on Seals Briefing Paper 20/01). Retrieved from http://www.smru.st-andrews.ac.uk/research-policy/scos/

Witting, L. (2013). Selection-delayed population dynamics in baleen whales and beyond. Population Ecology, 55, 377–401, https://doi.org/10.1007/s10144-013-0370-9

Published
2021-05-18
How to Cite
Smout, S., Murray, K. ., Aarts, G., Biuw, M., Brasseur, S., Buren, A., Empacher, F., Frie, A. K., Grecian, J., Hammill, M., Mikkelsen, B., Mosnier, A., Rosing-Asvid, A., Russell, D., Skaug, H., Stenson, G., Thomas, L., ver Hoef, J., Witting, L., Zabavnikov, V., Øigård, T. A., Fernandez, R., & Wickson, F. (2021). Report of the NAMMCO-ICES Workshop on Seal Modelling (WKSEALS 2020). NAMMCO Scientific Publications, 12(1). https://doi.org/10.7557/3.5794

Most read articles by the same author(s)

1 2 > >>