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Estimating population status under conditions of uncertainty: the Ross seal in East Antarctica

  • Colin J. Southwell (a1), Charles G.M. Paxton (a2), David L. Borchers (a2), Peter L. Boveng (a3), Erling S. Nordøy (a4), Arnoldus Schytte Blix (a4) and William K. De La Mare (a5)...

The Ross seal (Ommatophoca rossii) is the least studied of the Antarctic ice-breeding phocids. In particular, estimating the population status of the Ross seal has proved extremely difficult. The Protocol on Environmental Protection to the Antarctic Treaty currently designates the Ross seal as a ‘Specially Protected Species’, contrasting with the IUCN's classification of ‘Least Concern’. As part of a review of the Ross seal's classification under the Protocol, a survey was undertaken in 1999/2000 to estimate the status of the Ross seal population in the pack ice off East Antarctica between 64–150°E. Shipboard and aerial sighting surveys were carried out along 9476 km of transect to estimate the density of Ross seals hauled out on the ice, and satellite dive recorders deployed on a sample of Ross seals to estimate the proportion of time spent on the ice. The survey design and analysis addressed the many sources of uncertainty in estimating the abundance of this species in an effort to provide a range of best and plausible estimates. Best estimates of abundance in the survey region ranged from 41 300–55 900 seals. Limits on plausible estimates ranged from 20 500 (lower 2.5 percentile) to 226 600 (upper 97.5 percentile).

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Ackley S.F., Bengtson J.L., Boveng P., Castellini M., Daly K., Jacobs S., Kooyman G.L., Laake J., Quetin L., Ross R., Siniff D.B., Stewart B.S., Stirling I., Torres J. & Yochem P.K. 2003. A top-down, multidisciplinary study of the structure and function of the pack ice ecosystem in the eastern Ross Sea, Antarctica. Polar Record, 39, 219230.
Akçakaya H.R., Ferson S., Burgmann M.A., Keith D.A., Mace G.M. & Todd C.R. 2000. Making consistent IUCN classifications under uncertainty. Conservation Biology, 14, 10011013.
Anonymous. 1994. Antarctic pack ice seal program. Draft Implementation Plan.
Bengtson J.L. & Cameron M.F. 2004. Seasonal haulout patterns of crabeater seals (Lobodon carcinophaga). Polar Biology, 27, 344349.
Bester M.N., Erickson A.W. & Ferguson J.W.H. 1995. Seasonal change in the distribution and density of seals in the pack ice off Princess Martha Coast, Antarctica. Antarctic Science, 7, 357364.
Blix A.S. & Nordøy E.S. 1998. Ross seal diving behaviour and distribution: a reassessment? Proceedings VII SCAR International Biology Symposium. New Zealand Natural Science, 23, Supplement 14.
Borchers D.L., Laake J.L., Southwell C. & Paxton C.G.M. 2006. Accommodating unmodelled heterogeneity in double-observer distance sampling surveys. Biometrics, 62, 372378.
Buckland S.T., Anderson D.R., Burnham K.P., Laake J.L., Borchers D.L. & Thomas L. 2001. Introduction to Distance sampling: estimating abundance of biological populations. Oxford: Oxford University Press, 448 pp.
Craven P. & Wahba G. 1979. Smoothing noisy data with spline functions. Numerische Mathematik, 31, 377403.
Eklund C.R. & Atwood E.L. 1962. A population study of Antarctic seals. Journal of Mammalogy, 43, 229238.
Erickson A.W. & Hanson M.B. 1990. Continental estimates and population trends of Antarctic seals. In Kerry K.R. & Hempel G., eds. Antarctic ecosystems: ecological change and conservation. Berlin: Springer, 253264.
Gilbert J.R. & Erickson A.W. 1977. Distribution and abundance of seals in the pack ice of the Pacific sector of the Southern Ocean. In Llano L., ed. Adaptations within Antarctic ecosystems. Washington, DC: Smithsonian Institute, 703740.
Hastie T.J. & Tibshirani R.J. 1990. Generalized additive models. London: Chapman and Hall, 352 pp.
Hedley S.L., Buckland S.T. & Borchers D.L. 1999. Spatial modelling from line transect data. Journal of Cetacean Research and Management, 1, 255264.
Horvitz D.G. & Thompson D.J. 1952. A generalization of sampling without replacement from a finite universe. Journal of the American Statistical Association, 47, 663685.
IUCN. 2006. IUCN Red list of threatened species.
Martin T.G., Wintle B.A., Rhodes J.R., Kuhnert P.M., Field S.A., Low-Choy S.J., Tyre A.J. & Possingham H.P. 2005. Zero tolerance ecology: improving ecological inference by modelling the source of zero observations. Ecology Letters, 8, 12351246.
Maxwell G. 1967. Seals of the world. London: Constable, 168 pp.
Mullahy J. 1986. Specification and testing of some modified count data models. Journal of Econometrics, 33, 341365.
Nordøy E.S., Folkow L. & Blix A.S. 1995. Distribution and diving behaviour of crabeater seals (Lobodon carcinophagus) off Queen Maud Land. Polar Biology, 15, 261268.
Nordøy E.S. & Blix A.S. 2001. The previously pagophilic Ross seal is now rather pelagic. Proceedings VIII SCAR International Biology Symposium, Abstract, Vrije University, Amsterdam, The Netherlands.
Nordøy E.S. & Blix A.S. 2005. Haulout behaviour of Ross seals in King Haakon VII Sea. Proceedings IX SCAR International Biology Symposium, Curitiba, Brazil.
R Development Core Team, 2005. R: a language and environment for statistical computing. Vienna: R Foundation for Statistical Computing.
Sato K., Tsuchiya Y., Kudoh S. & Naito Y. 2003. Meteorological factors affecting the number of Weddell seals hauling-out on the ice during the molting season at Syowa Station, East Antarctica. Polar Bioscience, 16, 98103.
Scheffer V.B. 1958. Seals, sea lions and walruses. a review of the Pinnipedia. Palo Alto, CA: Stanford University Press, 190 pp.
Scott P. 1965. Section XIII. Preliminary List of Rare Mammals and Birds. In Scott P., ed. The Launching of a New Ark. First report of the President and Trustees of the World Wildlife Fund. An International Foundation for Saving the World's Wildlife and Wild Places, 1961–1964. London: Collins.
Skinner J.D. & Westlin-van Aarde L.M. 1989. Aspects of reproduction in female Ross seals (Ommatophoca rossii). Journal of Reproduction and Fertility, 87, 6772.
Smith W.H.F. & Sandwell D.T. 1997. Global sea floor topography from satellite altimetry and ship depth soundings. Science, 277, 19561962.
Southwell C. 2003. Haulout behaviour of two Ross seals off eastern Antarctica. Antarctic Science, 15, 257258.
Southwell C. 2005a. Optimising the timing of visual surveys of crabeater seal abundance: haulout behaviour as a consideration. Wildlife Research, 32, 333338.
Southwell C.J. 2005b. Diving behaviour of two Ross seals in East Antarctica. Wildlife Research, 32, 6365.
Southwell C., de la Mare B., Borchers D.L. & Burt L. 2004. Shipboard line transect surveys of crabeater seal abundance in the pack ice off East Antarctica: evaluation of assumptions. Marine Mammal Science, 20, 602620.
Southwell C., Borchers D., Paxton C.G.M., Burt L. & de la Mare W.K. 2007a. Estimation of detection probability in aerial surveys of Antarctic pack ice seals. Journal of Agricultural, Biological and Environmental Statistics, 12, 4154.
Southwell C., de la Mare W., Underwood M., Quartararo F. & Cope K. 2002. An automated system to log and process distance sight-resight aerial survey data. Wildlife Society Bulletin, 30, 394404.
Southwell C., Kerry K., Ensor P., Woehler E. & Rogers T. 2003. The timing of pupping by pack ice seals in East Antarctica. Polar Biology, 26, 648652.
Southwell C., Paxton C.G.M., Borchers D.L., Boveng P. & de la Mare W.K. 2007b. Taking account of dependent species in management of the Southern Ocean krill fishery: estimating crabeater seal abundance off East Antarctica. Journal of Applied Ecology, 10.1111/j.1365-2664.2007.01399.x.
Williams B.K. 2001. Uncertainty, learning, and the optimal management of wildlife. Environmental and Ecological Statistics, 8, 269288.
Williams B.K., Nichols J.D. & Conroy M.J. 2002. Analysis and management of animal populations. modeling, estimation, and decision making. San Diego: Academic Press, 1040 pp.
Wood S.N. 2006. Generalized additive models. an introduction with R. Boca Raton, FL: Chapman and Hall, 416 pp.
Zorn C.J.W. 1996. Evaluating zero-inflated and hurdle poisson specifications. Midwest Political Science Association, April 1996, 116.
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Antarctic Science
  • ISSN: 0954-1020
  • EISSN: 1365-2079
  • URL: /core/journals/antarctic-science
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