Narwhal Abundance in the Eastern Canadian High Arctic in 2013


  • Thomas Doniol-Valcroze Fisheries and Oceans Canada
  • Jean-François Gosselin Fisheries and Oceans Canada
  • Daniel G. Pike Esox Associates
  • Jack W. Lawson Fisheries and Oceans Canada
  • Natalie C. Asselin Fisheries and Oceans Canada
  • Kevin Hedges Fisheries and Oceans Canada
  • Steven H. Ferguson Fisheries and Oceans Canada



narwhal, Baffin Bay, summer stocks, abundance, aerial survey, double-platform, distance sampling, density surface modelling, fjords


In summer, narwhals (Monodon monoceros) migrate from Baffin Bay to northeastern Canada and northwest Greenland, where they are hunted by Inuit for subsistence. To prevent localized depletion, management of narwhals is based on summer stocks. The High Arctic Cetacean Survey (HACS), conducted in August 2013, was the first survey to estimate abundance of all 4 Canadian Baffin Bay narwhal summer stocks, as well as putative stocks in Jones Sound and Smith Sound, in the same summer. Narwhal abundance was estimated using a double-platform aerial survey. Distance sampling methods were used to estimate detection probability away from the track line. Mark-recapture methods were used to correct for the proportion of narwhals missed by visual observers on the track line (i.e., perception bias). We used a data-driven approach to identify single and duplicate sightings, using 4 covariates to compare differences in sightings made by front and rear observers based on: time of sighting, declination angle, group size, and species identity. Abundance in fjords was estimated using density surface modelling to account for their complex shape and uneven coverage. Estimates were corrected for availability bias (narwhals that are not available for detection because they are submerged when the aircraft passes overhead) using a new analysis of August dive behaviour data from narwhals equipped with satellite-linked time depth recorders. Corrected abundance estimates were 12,694 (95% CI: 6,324–25,481) for the Jones Sound stock; 16,360 (95% CI: 3,833–69,836) for the Smith Sound stock; 49,768 (95% CI: 32,945–75,182) for the Somerset Island stock; 35,043 (95% CI: 14,188–86,553) for the Admiralty Inlet stock; 10,489 (95% CI: 6,342–17,347) for the Eclipse Sound stock; and 17,555 (95% CI: 8,473–36,373) for the East Baffin Island stock. Total abundance for these 6 stocks was estimated at 141,908 (95% CI: 102,464–196,536). Sources of uncertainty arise from the high level of clustering observed, in particular in Admiralty Inlet, Eclipse Sound, and East Baffin Island, as well as the difficulty in identifying duplicate sightings between observers when large aggregations were encountered.


Asselin, N.C., Ferguson S.H., Richard P.R., & Barber, D.G. (2012). Results of narwhal (Monodon monoceros) aerial surveys in northern Hudson Bay, August 2011. DFO Canadian Science Advisory Research Secretariat Research Document, 2012/037. iii + 23 p.

Asselin, N.C., & Richard, P.R. (2011). Results of narwhal (Monodon monoceros) aerial surveys in Admiralty Inlet, August 2010. DFO Canadian Science Advisory Research Secretariat Research Document, 2011/065. iv + 26 p.

Brack, I.V., Kindel, A., & Oliveira, L.F.B. (2018). Detection errors in wildlife abundance estimates from Unmanned Aerial Systems (UAS) surveys: synthesis, solutions, and challenges. Methods in Ecology and Evolution, 9(8), 1864–1873. DOI:

Bröker, K.C.A., Hansen, R.G., Leonard, K.E., Koski, W.R., & Heide‐Jørgensen, M.P. (2019). A comparison of image and observer based aerial surveys of narwhal. Marine Mammal Science, 35, 1253–1279. DOI:

Buckland, S.T., Anderson, D., Burnham, K., Laake, J., Borchers, D., & Thomas, L. (2001). Introduction to distance sampling: estimating abundance of biological populations. Oxford University Press.

Burt, M. L., Borchers, D. L., Jenkins, K. J., & Marques, T. A. (2014). Using mark–recapture distance sampling methods on line transect surveys. Methods in Ecology and Evolution, 5(11), 1180–1191. DOI:

Cochran, W. (1977). Sampling techniques. New York: John Wiley & Sons.

Cope, J.M., & Punt, A.E. (2009). Drawing the lines: resolving fishery management units with simple fisheries data. Canadian Journal of Fisheries and Aquatic Sciences, 66(8), 1256–1273. DOI:

Dietz, R., Richard, P.R., & Acquarone, M. (2001). Summer and fall movements of narwhals (Monodon monoceros) from northeastern Baffin Island towards northern Davis Strait. Arctic, 54(3), 244–261. DOI:

Dietz, R., Heide-Jørgensen, M. P., Richard, P., Orr, J., Laidre, K., & Schmidt, H. C. (2008). Movements of narwhals (Monodon monoceros) from Admiralty Inlet monitored by satellite telemetry. Polar Biology, 31(11), 1295–1306. DOI:

Dunn, P. K., & Smyth, G. K. (1996). Randomized Quantile Residuals. Journal of Computational and Graphical Statistics, 5(3), 236–244. DOI:

Forney, K. A. (2000). Environmental models of cetacean abundance: Reducing uncertainty in population trends. Conservation Biology, 14(5), 1271–1286. DOI:

Gjertz, I. (1991). The Narwhal, Monodon monoceros, in the Norwegian High Arctic. Marine Mammal Science, 7(4), 402–408. DOI:

Hamilton, O.N.P., Kincaid, S.E., Constantine, R., Kozmian‐Ledward, L., Walker, C.G., & Fewster, R.M. (2018). Accounting for uncertainty in duplicate identification and group size judgements in mark–recapture distance sampling. Methods in Ecology and Evolution, 9, 354–362. DOI:

Hedley, S. L., & Buckland, S. T. (2004). Spatial models for line transect sampling. Journal of Agricultural, Biological and Environmental Statistics, 9, 181–199. DOI:

Heide-Jørgensen, M. P., Dietz, R., Laidre, K., & Richard, P. (2002). Autumn movements, home ranges, and winter density of narwhals (Monodon monoceros) tagged in Tremblay Sound, Baffin Island. Polar Biology, 25, 331–341. DOI:

Heide-Jørgensen, M. P., Dietz, R., Laidre, K. L., Richard, P., Orr, J., & Schmidt, H. C. (2003). The migratory behaviour of narwhals (Monodon monoceros). Canadian Journal of Zoology, 81(8), 1298–1305. DOI:

Heide-Jørgensen, M. P., Laidre, K. L., Burt, M. L., Borchers, D. L., Marques, T. A., Hansen, R. G., Rasmussen M., & Fossette, S. (2010). Abundance of narwhals (Monodon monoceros) on the hunting grounds in Greenland. Journal of Mammalogy, 91, 1135–1151. DOI:

Heide-Jørgensen, M. P., Hansen, R. G., Westdal, K., Reeves, R. R., & Mosbech, A. (2013). Narwhals and seismic exploration: Is seismic noise increasing the risk of ice entrapments? Biological Conservation, 158, 50–54. DOI:

Heide-Jørgensen, M. P., Richard, P. R., Dietz, R., & Laidre, K. L. (2013). A metapopulation model for Canadian and West Greenland narwhals: Narwhal metapopulation. Animal Conservation, 16(3), 331–343. DOI:

Heide‐Jørgensen, M. P., Hansen, R. G., & Strandler Sinding, M. H. (2014). Abundance and distribution of narwhals in Melville Bay in 2014. Report by the Greenland Institute of Natural Resources. Retrieved from

Hiby, L. & Lovell, P. (1998). Using aircraft in tandem formation to estimate abundance of harbour porpoise. Biometrics, 54, 1280– 1289. DOI:

Higdon, J. W., & Ferguson, S. H. (2017). Database of aerial surveys and abundance estimates for beluga whales (Delphinapterus leucas) and narwhals (Monodon monoceros) in the Canadian Arctic. Canadian Technical Report of Fisheries and Aquatic Sciences, 3211, 48.

Innes, S., Heide-Jørgensen, M. P., Laake, J. L., Laidre, K. L., Cleator, H., Richard, P., & Stewart, R. E. A. (2002). Surveys of belugas and narwhals in the Canadian High Arctic in 1996. NAMMCO Scientific Publications, 4, 169–190. DOI:

Kenyon, K. (2017). Movement patterns and winter habitat use of narwhal (Monodon monoceros) in the Eastern Canadian Arctic. (unpublished doctoral dissertation) University of Manitoba, Winnipeg, Manitoba, Canada. Retrieved from

Laake, J. L., & Borchers, D. L. (2004). Methods for incomplete detection at distance zero. In Advanced Distance Sampling (Eds. S.T. Buckland, D.R. Anderson, K.P. Burnham, J.L. Laake, D.L. Borchers and L. Thomas.) pp. 108–189. Oxford University Press: Oxford.

Laake, J.L., Borchers, D., Thomas, L., Miller, D., & Bishop, J. (2019). mrds: Mark-Recapture Distance Sampling. R package version 2.2.1.

Lydersen, C., Martin, A. R., Gjertz, I., & Kovacs, K. M. (2007). Satellite tracking and diving behaviour of sub-adult narwhals (Monodon monoceros) in Svalbard, Norway. Polar Biology, 30(4), 437–442. DOI:

Maling, D.H. (1992). Coordinate systems and map projections, 2nd edition. Pergamon Press. Oxford. 476 p. DOI:

Marcoux, M., Auger-Méthé, M., & Humphries, M.M. (2009). Encounter frequencies and grouping patterns of narwhals in Koluktoo Bay, Baffin Island. Polar Biology, 32(12), 1705–1716. DOI:

McLaren, I. A. (1961). Methods of determining the numbers and availability of ringed seals in the eastern Canadian Arctic. Arctic, 14, 162–175. DOI:

Miller, D.L. (2012). On smooth models for complex domains and distances. (unpublished doctoral dissertation). University of Bath, Bath, UK.

Miller, D. L., & Wood, S. N. (2014). Finite area smoothing with generalized distance splines. Environmental and Ecological Statistics, 21(4), 715–731. DOI:

Miller, D.L., Rexstad, E. A., Burt, M. L., Bravington, M. V., & Hedley, S. L. (2013). dsm: Density Surface Modelling of Distance Sampling Data version 2.2.17 from CRAN. Retrieved from

North Atlantic Marine Mammal Commission (NAMMCO). (2015). Report of the Joint Meeting of the NAMMCO Scientific Working Group on the Population Status of Narwhal and Beluga in the North Atlantic and the Canada/Greenland Joint Commission on Conservation and Management of Narwhal and Beluga Scientific Working Group In: NAMMCO Annual Report 2015; pp. 248–304. Retrieved from

North Atlantic Marine Mammal Commission (NAMMCO). (2018). Report of the NAMMCO Global Review of Monodontids. 13-16 March 2017, Hillerød, Denmark. Retrieved from

Pike, D., & Doniol-Valcroze, T. (2015). Identification of duplicate sightings from the 2013 double-platform High Arctic Cetacean Survey. DFO Canadian Science Advisory Research Secretariat Research Document, 2015/034. 27.

Priest, H., & Usher, P. (2004). The Nunavut Wildlife Harvest Study. Retrieved from

Quang, P.X., & Lanctot, R.B. (1991). A line transect model for aerial surveys. Biometrics, 47, 1098–1102. DOI:

Richard, P. R., Hall, P. A., Dueck, L., & Barber, D. G. (1994). Distribution and numbers of Canadian High Arctic narwhals (Monodon monoceros) in August 1984. Meddelelser Om Grønland, Bioscience, 39.

Richard, P. R., Laake, J. L., Hobbs, R. C., Heide-Jørgensen, M. P., Asselin, N. C., & Cleator, H. (2010). Baffin Bay narwhal population distribution and numbers: Aerial surveys in the Canadian High Arctic, 2002-04. Arctic, 63(1), 85–99. DOI:

Richard, P. R. (2010). Stock definition of belugas and narwhals in Nunavut. DFO Canadian Science Advisory Research Secretariat Research Document, 2010/022. iv + 14.

Richard, P. R., Weaver, P., Dueck, L., & Barber, D. G. (1994). Distribution and numbers of Canadian High Arctic narwhals (Monodon monoceros) in August 1984. Meddelelser Om Grønland, Bioscience, 39, 41–50.

Smith, T., Hammill, M. O., Burrage, D., & Sleno, G. A. (1985). Distribution and abundance of belugas, Delphinapterus leucas, and narwhals, Monodon monoceros, in the Canadian High Arctic. Canadian Journal of Zoology, 42(4), 676–684. DOI:

Southwell, C., de la Mare, B., Underwood, M., Quartararo, F., & Cope, K. (2002). An automated system to log and process distance sight-resight aerial survey data. Wildlife Society Bulletin (1973–2006), 30(2), 394–404.

Stevenson, B.C., Borchers, D.L., & Fewster, R.M. (2018). Cluster capture‐recapture to account for identification uncertainty on aerial surveys of animal populations. Biometrics, 1–11. DOI:

Thomas, L., Williams, R., & Sandilands, D. (2007). Designing line transect surveys for complex survey regions. Journal of Cetacean Research and Management, 9(1), 1–13. DOI:

Thomas, L., Buckland, S.T., Rexstad, E.A., Laake, J.L., Strindberg, S., Hedley, S.L., Bishop, J.R.B., Marques, T.A., & Burnham, K.P. (2010). Distance software: design and analysis of distance sampling surveys for estimating population size. Journal of Applied Ecology, 47(1), 5–14. DOI:

Watt, C. A., Marcoux, M., Asselin, N. C., Orr, J. R., & Ferguson, S. H. (2015). Instantaneous availability bias correction for calculating aerial survey abundance estimates for narwhal (Monodon monoceros) in the Canadian High Arctic. DFO Canadian Science Advisory Research Secretariat Research Document, 2015/044, 18.

Watt, C. A., Orr, J., Leblanc, B., Richard, P., & Ferguson, S. H. (2012). Satellite tracking of narwhals (Monodon monoceros) from Admiralty Inlet (2009) and Eclipse Sound (2010-2011). DFO Canadian Science Advisory Research Secretariat Research Document, 2012/046.

Williams, R., Hedley, S. L., & Hammond, P. S. (2006). Modeling distribution and abundance of Antarctic baleen whales using ships of opportunity. Ecology and Society, 11(1), art1. DOI:

Wood, S. N. (2001). mgcv: GAMs and generalized ridge regression for R. R News, 1.

Wood, S. N. (2003). Thin plate regression splines. Journal of the Royal Statistical Society: Series B (Statistical Methodology), 65(1), 95–114. DOI:

Wood, S. N. (2006). Generalized Additive Models: An Introduction with R. Second Edition. Boca Raton: Chapman and Hall/CRC. DOI:

Wood, S. N., Bravington, M. V., & Hedley, S. L. (2008). Soap Film Smoothing. Journal of the Royal Statistical Society: Series B (Statistical Methodology), 70(5), 931–955. DOI:




How to Cite

Doniol-Valcroze, T., Gosselin, J.-F., Pike, D. G., Lawson, J. W., Asselin, N. C., Hedges, K., & Ferguson, S. H. (2020). Narwhal Abundance in the Eastern Canadian High Arctic in 2013. NAMMCO Scientific Publications, 11.

Most read articles by the same author(s)