Mark-recapture vs. line-transect abundance estimates of a coastal dolphin population: a case study of Tursiops truncatus from Laguna, southern Brazil


  • Fábio G. Daura-Jorge Universidade Federal de Santa Catarina
  • Paulo César Simões-Lopes Universidade Federal de Santa Catarina



abundance, mark-recapture, line-transect, monitoring program, trends, bottlenose dolphin, Laguna


Cetacean populations in coastal habitats are increasingly threatened by multiple anthropogenic impacts. Monitoring these populations to obtain robust estimates of abundance and detect trends over time is critical to achieve conservation goals. Here, we conducted a pilot study to evaluate the effectiveness of two commonly used abundance estimation methods: mark-recapture and distance sampling line-transect. Surveys were conducted to estimate the abundance of bottlenose dolphins in Laguna, southern Brazil. We implemented power-analysis models and compared both techniques in terms of cost, time and effectiveness to detect trends over a five-year period. Mark-recapture models were analyzed in MARK and resulted in an abundance of 50 individuals (CI = 39-64) with a coefficient of variation (CV) of 0.13. The line-transect models were implemented using the program DISTANCE and resulted in an estimate of 62 individuals (CI = 38-103), with a CV of 0.24. Comparing both approaches, mark-recapture resulted 1.30 time more expensive than line-transect for a single season of effort, but was twice as effective in terms of precision. As a consequence, the probability of detecting a 5% trend during a five-year period is 2.08 times higher with mark recapture. Conversely, the final cost to detect a trend with distance sampling is 1.19 time higher but considering six more years of effort. These results highlight the importance of selecting a-priori sampling design techniques that include developing pilot studies that evaluate the bias, precision and accuracy of estimates while considering costs involved. Considering the small population size estimated herein, the sensitivity of both approaches for detecting trends is not sufficient because the original population would be markedly reduced by the time a declining trend was detected. Thus, a precautionary approach is still imperative, even when robust estimates are obtained.

Author Biographies

Fábio G. Daura-Jorge, Universidade Federal de Santa Catarina

Laboratório de Mamíferos Aquáticos, Departamento de Ecologia e Zoologia

Paulo César Simões-Lopes, Universidade Federal de Santa Catarina

Laboratório de Mamíferos Aquáticos, Departamento de Ecologia e Zoologia


Bearzi, G., Agazzi, S., Bonizzoni, S., Costa, M. and Azzellino, A. (2008) Dolphins in a bottle: abundance, residency patterns and conservation of bottlenose dolphins Tursiops truncatus in the semi-closed eutrophic Amvrakikos Gulf, Greece. Aquatic Conservation: Marine and Freshwater Ecosystems 18: 130–146.

Beissinger, S.R. and McCullough, D.R. (2002) Population viability analysis. University of Chicago Press, Chicago, USA.

Buckland, S.T., Anderson, D.R., Burnham, K.P., Laake, J.L., Borchers, D.L. and Thomas, L. (2001) Introduction to Distance Sampling: Estimating Abundance of Biological Populations. Oxford University Press, Oxford, UK.

Burnham, K.P. and Anderson, D.R. (2002) Model selection and multimodel inference: a practical information-theoretic approach. Springer Verlag, New York, USA.

Burnham, K.P., Anderson, D.R. and Laake, J.L. (1985) Efficiency and bias in strip and line transect sampling. Journal of Wildlife Management 49: 1012-1018.

Burnham, K.P., Anderson, D.R., White, G.C., Brownie, C. and Pollock, K.H. (1987) Design and analysis of fish survival experiments based on release–recapture data. American Fisheries Society, Monograph 5, Bethesda, MD.

Calambokidis, J. and Barlow, J. (2004) Abundance of blue and humpback whales in the Eastern North Pacific estimated by mark-recapture and line-transect methods. Marine Mammal Science 20(1): 63-85.

Cantor, M., Wedekin, L.L., Daura-Jorge, F.G., Rossi-Santos, M. and Simões-Lopes, P.C. (2012) Assessing population parameters and trends of Guiana dolphins (Sotalia guianensis): an eight-year mark-recapture study. Marine Mammal Science 28(1): 63-83.

Chades, I., McDonald-Madden, E., McCarthy, M.A., Wintle, B., Linkie, M. and Possingham, H. (2008) When to stop managing or surveying cryptic threatened species? Proceedings of the National Academy of Sciences 105: 13936-13940.

Conroy, M.J. and Carrol, J.P. (2009) Quantitative Conservation of Vertebrates. Wiley-Blackwell Press, Georgia, USA.

Cremer, M.J. and Simões-Lopes, P.C. (2008) Distribution, abundance and density estimates of franciscanas, Pontoporia blainvillei (Cetacea: Pontoporiidae), in Babitonga bay, southern Brazil. Revista Brasileira de Zoologia 25: 397-402.

Cremer, M.J., Hardt, F.A.S., Tonello, A.J. and Simões-Lopes, P.C. (2011) Distribution and status of the Guiana dolphin, Sotalia guianensis (Cetacea, Delphinidae) population in Babitonga Bay, southern Brazil. Zoological Studies 60: 327-337.

Currey, R.J.C., Dawson, S.M. and Slooten, E. (2007) New abundance estimates suggest Doubtful Sound bottlenose dolphins are declining. Pacific Conservation Biology 13: 265-273.

Daura-Jorge, F.G. (2011) Quantos? Onde? Como? Múltiplos aspectos ecológicos de uma população do boto-da-tainha (Tursiops truncatus) em Laguna, sul do Brasil: implicações para a conservação. Ph.D. Thesis. Universidade Federal do Paraná. Curitiba, Brazil. 265 pp.

Daura-Jorge, F.G., Cantor, M., Ingram, S.N., Lusseau, D. and Simões-Lopes, P.C. (2012) The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen. Biology Letters

Daura-Jorge, F.G., Ingram, S.N. and Simões-Lopes, P.C. (2013) Seasonal abundance and adult survival of bottlenose dolphins (Tursiops truncatus) in a community that cooperatively forages with fishermen in southern Brazil. Marine Mammal Science 29(2): 293-311.

Dawson, S.M., Slooten, E., DuFresne, S.D., Wade, P.R. and Clement, D.M. (2004) Small-boat surveys for coastal dolphins: line-transect surveys of Hector’s dolphins (Cephalorhynchus hectori). Fishery Bulletin 102 (3): 441-451.

Evans, G.H. and Hammond, P.S. (2004) Monitoring cetaceans in European waters. Mammal Review 34: 131-156.

Flach, L., Flach, P.A. and Chiarello, A.G. (2008) Density, abundance and distribution of the Guiana dolphin, (Sotalia guianensis van Benéden, 1864) in Sepetiba Bay, Southeast Brazil. Journal of Cetacean Research and Management 10: 31-36.

Forcada, J., Gazo, M., Aguilar, A., Gonzalvo, J. and Fernandez Contreras, M. (2004) Bottlenose dolphin abundance in the NW Meditteranean: addressing heterogeneity in distribution. Marine Ecology Progress Series 275: 275-287.

Fruet, P., Secchi, E.R., Di Tullio, J.C. and Kinas, P.G. (2011) Abundance of bottlenose dolphins, Tursiops truncatus, inhabiting the Patos Lagoon estuary, southern Brazil: Implication for conservation. Zoologia 28: 23-30.

Fury, C.A. and Harrison, P.L. (2008) Abundance, site fidelity and range patterns of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in two Australian subtropical estuaries. Marine and Freshwater Research 59: 1015–1027.

Gerrodette, T. (1987) A power analysis for detecting trends. Ecology 68: 1364-1372.

Gerrodette, T. (1993) TRENDS: Software for a power analysis of linear regression. Wildlife Society Bulletin 21: 515-516.

Gormley, A.M., Dawson, S.M., Slooten, E. and Bräger, S. (2005) Capture-recapture estimates of Hector’s dolphin abundance at Banks Peninsula, New Zealand. Marine Mammal Science 21: 204-216.

Haase, P.A. and Schneider, K. (2001) Birth demographics of bottlenose dolphins, Tursiops truncatus, in Doubtful Sound, Fiordland, New Zealand - preliminary findings. New Zealand Journal of Marine and Freshwater Research 35: 675–680.

Hammond, P.S. (1987) Techniques for estimating the size of whale populations. Pages 225-245 in Harris, S. (Ed.) Mammal Population Studies. Symposia of the Zoological Society of London 58, Clarendon Press,Oxford, UK.

Hammond, P.S., Mizroch, S.A. and Donovan, G.P. (1990) Individual recognition of cetaceans: use of photoidentification and other techniques to estimate population parameters. Report of International Whaling Commission (Special Issue) 12: 135–139.

López, B.D., Shirai, J.A.B., Prieto, A.B. and Fernández, M. (2008) Diving activity of a solitary wild free ranging bottlenose dolphin (Tursiops truncatus). Journal of the Marine Biological Association of the United Kingdom 88: 1153-1157.

Lukoschek, V. and Chilvers, B.L. (2008) A robust baseline for bottlenose dolphin abundance in coastal Moreton Bay: a large carnivore living in a region of escalating anthropogenic impacts. Wildlife Research 35: 593-605.

Lusseau, D., Schneider, K., Boisseau, O.J., Haase, P., Slooten, E. and Dawson, S.M. (2003) The bottlenose dolphin community of Doubtful Sound features a large proportion of long-lasting associations: Can geographic isolation explain this unique trait? Behavioral Ecology and Sociobiology 54: 396-405.

McClintock, B.T., White, G.C. and Burnham, K.P. (2006) A robust design mark-resight abundance estimator allowing heterogeneity in resighting probabilities. Journal of Agricultural, Biological, and Environmental Statistics 11: 231–248.

O’Grady, J.J., Brook, B.W., Reed, D.H., Ballou, J.D., Tonkyn, D.W. and Frankham, R. (2006) Realistic levels of inbreeding depression strongly affect extinction risk in wild populations. Biological Conservation 133: 42-51.

Otis, D.L., Burnham, K.P., White, G.C. and Anderson, D.R. (1978) Statistical inference from capture data on closed animal populations. Wildlife Monographs 62: 1-135.

Pandolfi, J.M., Bradbury, R.H., Sala, E., Hughes, T.P., Bjorndal, K.A., Cooke, R.G., McArdle, D., McClenachan, L., Newman, M.J.H., Paredes, G., Warner, R.R. and Jackson, J.B.C. (2003) Global trajectories of the long-term decline of coral reef ecosystems. Science 301: 955-958.

Pollock, K.H. (1982) A capture–recapture design robust to unequal probability of capture. Journal of Wildlife Management 46: 757–760.

Read, A.J., Urian, K.W., Wilson, B. and Waples, D.M. (2003) Abundance of bottlenose dolphins in the bays, sounds and estuaries of North Carolina. Marine Mammal Science 19: 59-73.

Regalado, A. (2010) Brazilian science: riding a gusher. Science 330: 1306-1312.

Secchi, E.R., Ott, P.H., Crespo, E.A., Kinas, P.G., Pedraza, S.N. and Bordino, P. (2001) A first estimate of Franciscana (Pontoporia blainvillei) abundance off southern Brazil. Journal of Cetacean Research and Management 3(1): 95-100.

Silva, M.A., Magalhães, S., Prieto R., Santos, R.S. and Hammond, P.S. (2009) Estimating survival and abundance in a bottlenose dolphin population taking into account transience and temporary emigration. Marine Ecology Progress Series 392: 263-276.

Simões-Lopes, P.C. and Fabian, M.E. (1999) Residence patterns and site fidelity in bottlenose dolphins, Tursiops truncatus (Montagu) (Cetacea, Delphinidae) off southern Brazil. Revista Brasileira de Zoologia 16: 1017-1024.

Simões-Lopes, P.C., Fabian, M.E.and Menegheti, J.O. (1998) Dolphin interactions with the mullet artisanal fishing on Southern Brazil: a qualitative and quantitative approach. Revista Brasileira de Zoologia 15: 709-726.

Small, C. and Nicholls, R.J. (2003) A global analysis of human settlement in coastal zones. Journal of Coastal Research 19: 584-599.

Soulé, M.E. (1987) Viable populations for conservation. Cambridge University Press, Cambridge, United Kingdom.

Sutherland, W.J. (2000) The Conservation Handbook: research, management and policy. Blackwell Science,United Kingdom.

Taylor, B.L. and Gerrodette, T. (1993) The uses of statistical power in conservation biology: the Vaquita and the Northern Spotted Owl. Conservation Biology 7: 489-500.

Taylor, B.L., Marinez, M., Gerrodette, T., Barlow, J. and Hrovat, Y.N. (2007) Lessons from monitoring trends in abundance of marine mammals. Marine Mammal Science 23: 157-175.

Thompson, P.M., Wilson, B., Grellier, K. and Hammond, P.S. (2000) Combining power analysis and population viability analysis to compare traditional and precautionary approaches to conservation of coastal cetaceans. Biological Conservation 14: 1253-1263.

Wedekin, L.L., Da-Ré, M.A., Daura-Jorge, F.G. and Simões Lopes, P.C. (2005) The use of a conceptual model to describe the conservation scenario of the estuarine dolphin within the Baía Norte, southern Brazil. Natureza e Conservação 3: 162-170.

Wells, R. and Scott, M.D. (1990) Estimating bottlenose dolphin population parameters from individual identification and capture–release techniques. Report of International Whaling Commission (Special Issue) 12: 407–415.

White, G.C. and Burnham, K.P. (1999) Program MARK: survival estimation from populations of marked animals. Bird Study 46: 120-138.

Whitehead, H., Reeves, R.R. and Tyack, P.L. (2000) Science and the conservation, protection, and management of wild cetaceans. Pages 308–332 in Mann, J., Connor, R.C., Tyack, P.L. and Whitehead, H. (Eds) Cetacean Societies: Field Studies of Dolphins and Whales. The University of Chicago Press, Chicago, USA.

Williams, B.K., Nichols, J.D. and Conroy, M.J. (2002) Analysis and management of animal populations. Academic Press, San Diego, USA.

Williams, J.A., Dawson, S.M. and Slooten, E. (1993) The abundance and distribution of bottlenose dolphins (Tursiops truncatus) in Doubtful Sound, New Zealand. Canadian Journal of Zoology 71: 2080–2088.

Williams, R. and Thomas, L. (2009) Cost-effective abundance estimation of rare animals: testing performance of smallboat surveys for killer whales in British Columbia. Biological Conservation 142: 1542-1547.

Wilson, B., Hammond, P.S. and Thompson, P.M. (1999) Estimating size and assessing trends in a coastal bottlenose dolphin population. Ecological Applications 9: 288-300.;2

Würsig, B. and Jefferson, T.A. (1990) Methodology of photo-identification for small cetaceans. Report of the International Whaling Commission (Special Issue) 12: 43-53.




How to Cite

Daura-Jorge, F. G., & Simões-Lopes, P. C. (2017). Mark-recapture vs. line-transect abundance estimates of a coastal dolphin population: a case study of Tursiops truncatus from Laguna, southern Brazil. Latin American Journal of Aquatic Mammals, 11(1-2), 133-143.