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First abundance estimate of the Antillean manatee (Trichechus manatus manatus) in Brazil by aerial survey

Published online by Cambridge University Press:  04 August 2015

Maria Danise Alves ,
Paul Gerhard Kinas ,
Miriam Marmontel ,
João Carlos Gomes Borges ,
Alexandra Fernandes Costa ,
Nicola Schiel  and
Maria Elisabeth Araújo
Maria Danise Alves*
Affiliation:
Department of Oceanography, UFPE, Cidade Universitária, s/n, Recife-PE, 50670-901, Brazil Fundação Mamíferos Aquáticos, FMA, 17 de Agosto, Casa Forte, 2001, Recife-Pernambuco, 52061-540, Brazil Department of Biology, UFRPE, Dom Manoel Medeiros, Dois Irmãos, s/n, Recife-PE, 52171-900, Brazil
Paul Gerhard Kinas
Affiliation:
Instituto de Matemática Estatística e Física, FURG, Avenida Itália km 8, Rio Grande-RS, 93201-900, Brazil
Miriam Marmontel
Affiliation:
Instituto de Desenvolvimento Sustentável Mamirauá (IDSM), Estrada do Bexiga 2.584, Bairro Fonte Boa, Tefé: Amazonas, 69470-000, Brazil
João Carlos Gomes Borges
Affiliation:
Fundação Mamíferos Aquáticos, FMA, 17 de Agosto, Casa Forte, 2001, Recife-Pernambuco, 52061-540, Brazil Graduate Program in Tropical Animal Sciences, UFRPE, Dom Manoel Medeiros, Dois Irmãos, s/n, Recife-PE, 52171-900, Brazil
Alexandra Fernandes Costa
Affiliation:
Graduate Program in Aquatic Ecology and Fishery, UFPA, Cidade Universitária, Guamá-Belém-Pará, 66075-110, Brazil
Nicola Schiel
Affiliation:
Department of Biology, UFRPE, Dom Manoel Medeiros, Dois Irmãos, s/n, Recife-PE, 52171-900, Brazil
Maria Elisabeth Araújo
Affiliation:
Department of Oceanography, UFPE, Cidade Universitária, s/n, Recife-PE, 50670-901, Brazil
*
Correspondence should be addressed to:M.D. de Oliveira Alves, Department of Oceanography, UFPE, Cidade Universitária, s/n, Recife-PE, 50670-901, Brazil email: danisealves@hotmail.com
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Abstract

We estimated the abundance of Antillean manatees (Trichechus manatus manatus) through a large-scale project conducted in 2010 in north-eastern Brazil and evaluated the efficacy of an aerial survey for conservation purposes. Two observers conducted the survey via flights that maintained an altitude of 150 m and an air speed of 140 km h−1, covering over 2590.2 km2 of the coastline. Strip transects were flown in a zigzag pattern. A total of 67 manatees (on- and off-effort) were recorded in 55 sightings. Historical published records of occurrence were formally incorporated using a Bayesian approach. We estimated the manatee population for north-eastern Brazil in the form of a posterior distribution with a mean of 1104 individuals and a 95% posterior probability interval ranging from 485 to 2221 individuals, which indicates high uncertainty. More large-scale studies in the region are warranted to understand temporal trends, in addition to further studies in hotspot areas, with smaller spatial scales, to reduce the coefficient of variation and to allow the use of improved techniques for monitoring the manatees. A greater emphasis on species-specific characteristics and methods to enhance detection probability (e.g. dual observers) are also recommended. The conditions prevailing along the study area were not conducive to aerial surveillance; thus, the results are not a precise estimate of the manatee population. However, these highlight the importance of conservation efforts for the Antillean manatee, considered the most endangered aquatic mammal in Brazil.

Keywords

Antillean manateeabundanceaerial detectionstrip transectBayesian modelwater transparency
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 96 , Issue 4: Marine Mammals , June 2016 , pp. 955 - 966
Copyright
Copyright © Marine Biological Association of the United Kingdom 2015 

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References

REFERENCES

Ackerman, B.B. (1995) Aerial surveys of manatees: a summary and progress report. In O'Shea, T.J., Ackerman, B.B. and Percival, H.F. (eds) Population biology of the Florida manatee. Washington, DC: U.S. National Biological Service, pp. 13–33.Google Scholar
Albuquerque, C. and Marcovaldi, G.M. (1982) Ocorrência e Distribuição do Peixe-boi Marinho no Litoral Brasileiro (Sirenia, Trichechidade, Trichechus manatus, Linnaeus 1758). In Simpósio Internacional sobre a Utilização de Ecossistemas Costeiros: Planejamento, Poluição e Produtividade. Rio Grande: FURG/Duke University, p. 27.Google Scholar
Alves, M.D.O. (2007) Peixe-boi marinho, Trichechus manatus manatus: Ecologia e Conhecimento Tradicional no Ceará e Rio Grande do Norte, Brasil. PhD dissertation, Federal University of Pernambuco at Recife.Google Scholar
Alves, M.D.O., Borges, J.C.G. and Araújo, M.E. (2013a) Pilot aerial study of the marine megafauna in northern coast Alagoas, Brazil. Tropical Oceanography 41, 108–119.CrossRefGoogle Scholar
Alves, M.D.O., Schwamborn, R., Borges, J.C.G., Marmontel, M., Costa, A.F., Schettini, C.A.F. and Araújo, M.E. (2013b) Aerial survey of manatees, dolphins and sea turtles off northeastern Brazil: correlations with coastal features and human activities. Biological Conservation 161, 91–100.CrossRefGoogle Scholar
Alvite, C.M.C. and Lima, R.P. (2012) Antillean manatees in Brazil. Box 4.2. In Hines, E.M., Reynolds, J.E. III, Aragones, L.V., Mignucci-Giannoni, A.A. and Marmontel, M. (eds) Sirenian conservation – issues and strategies in developing countries. Gainesville, FL: University Press of Florida, pp. 42–43.Google Scholar
Andriolo, A., Kinas, P.G., Engel, M.H., Martins, C.C.A. and Rufino, A.M. (2010) Humpback whales within the Brazilian breeding ground: distribution and population size estimate. Endangered Species Research 11, 233–243.Google Scholar
Andriolo, A., Martins, C.C.A., Engel, M.H., Pizzorno, J.L., Más-Rosa, S., Freitas, A.C., Morete, M.E. and Kinas, P.G. (2006) The first aerial survey to estimate abundance of humpback whales (Megaptera novaeangliae) in the breeding ground off Brazil (Breeding Stock A). Journal of Cetacean Research and Management 8, 307–311.Google Scholar
Bauduin, S., Martin, J., Edwards, H.H., Gimenez, O., Koslovsky, S.M. and Fagan, D.E. (2013). An index of risk of co-occurrence between marine mammals and watercraft: example of the Florida manatee. Biological Conservation 159, 127–136.CrossRefGoogle Scholar
Borges, J.C.G., Vergara-Parente, J.E., Alvite, C.M.C., Marcondes, M.C.C. and Lima, R.P. (2007). Embarcações motorizadas: uma ameaça aos peixes-bois marinhos (Trichechus manatus) no Brasil. Biota Neotropica 7, 199–204.Google Scholar
Cardona, L., Revelles, M., Carreras, C., Félix, M.S., Gazo, M. and Aguilar, A. (2005) Western Mediterranean immature loggerhead turtles: habitat use in spring and summer assessed through satellite tracking and aerial surveys. Marine Biology 147, 583–591.Google Scholar
Castelblanco-Martínez, N. (2012) Relative abundance and conservation status of manatees (Trichechus manatus manatus) in French Guyana – preliminary analysis of the study area. France: Park National de la Guadeloupe, p. 29.Google Scholar
Castro, C.B. and Pires, D.O. (2001) Brazilian coral reefs: what we already know and what is still missing. Bulletin of Marine Science 69, 357–371.Google Scholar
Choi, K.F., Campos, T.M., Meirelles, A.C.O., Campos, A.A. and Fernandes, M.B. (2009) Desenho da área de um refúgio de vida silvestre para a conservação do peixe-boi-marinho. Natureza and Conservação 7, 82–89.Google Scholar
Costa, A.F. (2006) Distribuição espacial e status do peixe-boi marinho, Trichechus manatus manatus (Sirenia: Trichechidae) no litoral leste do Estado do Ceará. PhD dissertation. Federal University of Ceará, Fortaleza, Brazil.Google Scholar
Craig, B.A. and Reynolds, J.E. III (2004) Determination of manatee population trends along the Atlantic coast of Florida using a Bayesian approach with temperature-adjusted aerial survey data. Marine Mammal Science 20, 386–400.CrossRefGoogle Scholar
Cunha, I. (2005) Desenvolvimento Sustentável na Costa Brasileira. Revista Galega de Economia 14, 1–14.Google Scholar
Deutsch, C.J. (2008) IUCN Red List of Threatened Species, Trichechus manatus ssp. latirostris. IUCN 2013, Group Review. Gland: IUCN. http://www.iucnredlist.org.Google Scholar
Deutsch, C.J., Self-Sullivan, C. and Mignucci-Giannoni, A. (2008) IUCN Red List of Threatened Species, Trichechus manatus. IUCN 2013, Group Review. Gland: IUCN. http://www.iucnredlist.org.Google Scholar
Deutsch, C.J. and Reynolds, J.E. III (2012) Florida manatee status and conservation issues – a primer. In Hines, E.M., Reynolds, J.E. III, Aragones, L.V., Mignucci-Giannoni, A.A. and Marmontel, M. (eds) Sirenian conservation – issues and strategies in developing countries. Gainesville, FL: University Press of Florida, pp. 23–35.CrossRefGoogle Scholar
Domning, D.P. (1982) Commercial exploitation of manatees (Trichechus) in Brazil c. 1785–1973. Biological Conservation 22, 101–126.Google Scholar
Edwards, H.H., Pollock, K.H., Ackerman, B.B., Reynolds, J.E. and Powell, J.A. (2007) Estimation of detection probability in manatee aerial surveys at a winter aggregation site. Journal of Wildlife Management 71, 2052–2060.Google Scholar
Franklin, I.R. (1980) Evolutionary change in small populations. In Soule, M.E. and Wilcox, B.A. (eds) Conservation biology: an evolutionary ecological perspective. Sunderland, MA: Sinauer Associates, pp. 135–140.Google Scholar
Gonzalez-Socoloske, D. and Olivera-Gómez, L.D. (2012) Gentle giants in dark waters: using side-scan sonar for manatee research. Open Remote Sensing Journal 5, 1–14.Google Scholar
Gonzalez-Socoloske, D., Olivera-Gómez, L.D. and Ford, R.E. (2009) Detection of free-ranging West Indian manatees Trichechus manatus using side-scan sonar. Endangered Species Research 8, 249–257.Google Scholar
Hartman, D.S. (1979) Ecology and behavior of the manatee (Trichechus manatus) in Florida. Special Publication No. 5. Pittsburgh, PA: American Society of Mammalogists.Google Scholar
Hatt, R.A. (1934) Manatee collected by the American Museum Congo Expedition with observation on the recent manatees. Bulletin of the American Museum of Natural History 66, 533–566.Google Scholar
Hines, E.M., Ulyanukosol, K. and Duffus, D.A. (2005) Dugong (Dugong dugon) abundance along the Andaman coast of Thailand. Marine Mammal Science 21, 536–549.Google Scholar
ICMBio (2011) Plano de ação nacional para a conservação dos sirênios: peixe-boi-da-Amazônia: Trichechus inunguis e peixe-boi-marinho: Trichechus manatus. In Luna, F.O., Silva, V.M.F., Andrade, M.C.M., Marques, C.C., Normande, I.C., Velôso, T.M.G. and Severo, M.M. (eds) Série Espécies Ameaçadas, no. 12, Brasília, 80 pp.Google Scholar
Jiménez, I. (2005) Development of predictive models to explain the distribution of the West Indian manatee in tropical watercourses. Biological Conservation 125, 491–503.Google Scholar
Jolly, G.M. (1969) Sampling methods for aerial censuses of wildlife populations. East African Agricultural and Forestry Journal 34, 46–49.CrossRefGoogle Scholar
Katsanevakis, S., Weber, A., Pipitone, C., Leopold, M., Cronin, M., Scheidat, M., Doyle, T.K., Buhl-Mortensen, L., Buhl-Mortensen, P., D'Anna, G., de Boois, I., Dalpadado, P., Damalas, D., Fiorentino, F., Garofalo, G., Giacalone, V.M., Hawley, K.L., Issaris, Y., Jansen, J., Knight, C.M., Knittweis, L., Kröncke, I., Mirto, S., Muxika, I., Reiss, H., Skjoldal, H.R. and Vöge, S. (2012) Monitoring marine populations and communities: methods dealing with imperfect detectability. Aquatic Biology 16, 31–52.Google Scholar
Kempf, M., Coutinho, P.N. and Morais, J.O. (1970) Plataforma continental do Norte e Nordeste do Brasil. Trabalhos Oceanográficos 9, 95–110.Google Scholar
Kinas, P.G. and Andrade, H.A. (2010) Introdução à análise bayesiana (com R), 1st edn.Porto Alegre: maisQnada.Google Scholar
Langtimm, C.A., Dorazio, R.M., Stith, B.M. and Doyle, T.J. (2011) New aerial survey and hierarchical model to estimate manatee abundance. Journal of Wildlife Management 75, 399–412.Google Scholar
Lanyon, J.M. (2003) Distribution and abundance of dugongs in Moreton Bay, Queensland, Australia. Wildlife Research 30, 397–409.CrossRefGoogle Scholar
Lefebvre, L.W., Ackerman, B.B., Portier, K.M. and Pollock, K.H. (1995) Aerial survey as a technique for estimating trends in manatee population size – problems and prospects. In O'Shea, T.J., Ackerman, B.B. and Percival, H.F. (eds) Population biology of the Florida manatee. Washington, DC: National Biological Service Information and Technology Report 1, pp. 63–74.Google Scholar
Lefebvre, L.W. and Kochman, H.I. (1991) An evaluation of aerial survey replicate count methodology to determine trends in manatee abundance. Wildlife Society Bulletin 19, 298–309.Google Scholar
Lefebvre, L.W., Marmontel, M., Reid, J.P., Rathbun, G.B. and Domning, D.P. (2001) Status and biogeography of the West Indian Manatee. In Woods, C.A. and Sergile, F.E. (eds) Biogeography of the West Indies: patterns and perspectives. Boca Raton, FL: CRC Press, pp. 425–474.Google Scholar
Lima, R.P. (1997) Peixe-boi marinho (Trichechus manatus): Distribuição, status de conservação e aspectos tradicionais ao longo do litoral nordeste do Brasil. PhD dissertation. Federal University of Pernambuco, Recife, Brazil.Google Scholar
Lima, R.P. (2008) Distribuição espacial e temporal de peixes-bois (Trichechus manatus) reintroduzidos no litoral nordestino e avaliação da primeira década (1994–2004) do programa de reintrodução. PhD thesis. Federal University of Pernambuco, Recife, Brazil.Google Scholar
Lima, R.P., Paludo, D., Soavinski, R.J., Silva, K.G. and Oliveira, E.M.A. (2011) Levantamento da distribuição, ocorrência e status de conservação do Peixe-Boi Marinho (Trichechus manatus, Linnaeus, 1758) no litoral nordeste do Brasil. Natural Resources, Aquidabã 1, 41–57.Google Scholar
Luna, F.O., Bonde, R.K., Attademo, F.L.N., Saunders, J.W., Meigs-Friend, G., Passavante, J.Z.O. and Hunter, M.E. (2012) Phylogeographic implications for release of critically endangered manatee calves rescued in northeast Brazil. Aquatic Conservation: Marine and Freshwater Ecosystems 22, 665–672.Google Scholar
Luna, F.O., Lima, R.P., Araújo, J.P. and Passavante, J.Z.O. (2008) Status de conservação do peixe-boi marinho (Trichechus manatus manatus Linnaeus, 1758) no Brasil. Revista Brasileira de Zoociências 10, 145–153.Google Scholar
Magalhães, K.M. and Cazuza, S.M. (2005) Distribuição das angiospermas marinhas no litoral do estado de Pernambuco, Brasil – 1ª Parte: Levantamentos de herbários e literatura. Cadernos Fafire 4, 20–26.Google Scholar
Marsh, H. (1995) Fixed-width aerial transects for determining dugong population sizes and distribution patterns. In O'Shea, T.J., Ackerman, B.B. and Percival, H.F. (eds) Population biology of the Florida manatee. Washington, DC: National Biological Service Information and Technology Report 1, pp. 56–62.Google Scholar
Marsh, H., Ath, G., Gribble, N. and Lane, B. (2005) Historical marine population estimates: triggers or targets for conservation? The dugong case study. Ecologica Applications 15, 481–492.Google Scholar
Marsh, H., Lawler, I.R., Kwan, D., Delean, S., Pollock, K. and Alldredge, M. (2004) Aerial surveys and the potential biological removal technique indicate that the Torres Strait dugong fishery is unsustainable. Animal Conservation 7, 435–443.Google Scholar
Marsh, H., O'Shea, T.J. and Reynolds, J.E. III (2012) Ecology and conservation of the Sirenia – dugongs and manatees. Cambridge: Cambridge University Press.Google Scholar
Marsh, H. and Sinclair, D.F. (1989) Correcting for visibility bias in strip transect aerial surveys of aquatic fauna. Journal of Wildlife Management 53, 1017–1024.Google Scholar
Martin, J., Edwards, H.H., Burgess, M.A., Percival, H.F., Fagan, D.E., Gardner, B.E., Ortega-Ortiz, J.G., Ifju, P.G., Evers, B.S. and Rambo, T.J. (2012) Estimating distribution of hidden objects with drones: from tennis balls to manatees. PLoS ONE 7, e38882.CrossRefGoogle ScholarPubMed
McCarthy, M.A. (2007) Bayesian methods for ecology. Cambridge: Cambridge University Press.Google Scholar
Meirelles, A.C.O. (2008) Mortality of the Antillean manatee, Trichechus manatus manatus, in Ceará State, north-eastern Brazil. Journal of the Marine Biological Association of the United Kingdom 88, 1133–1137.Google Scholar
Miller, K.E., Ackerman, B.B., Lefebvre, L.W. and Clifton, K.B. (1998) An evaluation of strip-transect aerial survey methods for monitoring manatee populations in Florida. Wildlife Society Bulletin 26, 561–570.Google Scholar
Ministério do Meio Ambiente (MMA) (2014) Official list of Brazilian Fauna threatened with extinction. Portaria MMA nº 444 de 17 de dezembro de 2014. Brasília. 6 pp. http://www.icmbio.gov.br/portal/images/stories/biodiversidade/fauna-brasileira/portarias/PORTARIA_N_444_DE_17_DE_DEZEMBRO_DE_2014.pdf.Google Scholar
Morales-Vela, B. and Olivera-Gómez, L.D. (1994) Distribución espacial y estimación poblacional de los manatíes em la Bahía de Chetumal, Quintana Roo, México. Revista del Inventário Científico de la Universidad Autónoma 2, 27–32.Google Scholar
Morales-Vela, B., Olivera-Gómez, L.D., Reynolds, J.E. III and Rathbun, G.B. (2000) Distribution and habitat use by manatees (Trichechus manatus manatus) in Belize and Chetumal Bay, Mexico. Biological Conservation 95, 67–75.Google Scholar
Muehe, D. and Garcez, D.S. (2005) A plataforma continental brasileira e sua relação com a zona costeira e a pesca. Mercator 4, 69–88.Google Scholar
Oliveira-Filho, E.C., Pirani, J.R. and Giulietti, A.M. (1983) The Brazilian seagrasses. Aquatic Botany 16, 251–267.CrossRefGoogle Scholar
Olivera-Gómez, L.D. and Mellink, E. (2002) Spatial and temporal variation in counts of the Antillean manatee (Trichechus manatus manatus) during distribution surveys at Bahıa de Chetumal, Mexico. Aquatic Mammal 28, 285–293.Google Scholar
Olivera-Gómez, L.D. and Mellink, E. (2005) Distribution of the Antillean manatee (Trichechus manatus manatus) as a function of habitat characteristics, in Bahía de Chetumal, Mexico. Biological Conservation 121, 127–133.Google Scholar
Paludo, D. and Langguth, A. (2002) Use of space and temporal distribution of Trichechus manatus manatus Linnaeus in the region of Sagi, Rio Grande do Norte State, Brazil (Sirenia, Trichechidae). Revista Brasileira de Zoologia 19, 205–215.Google Scholar
Parente, C.L., Vergara-Parente, J.E. and Lima, R.P. (2004) Strandings of Antillean manatees, Trichechus manatus manatus, in northeastern Brazil. Latin American Journal of Aquatic Mammals 3, 69–75.Google Scholar
Plummer, M. (2013). Rjags: Bayesian graphical models using MCMC. R package version 3–10. http://CRAN.R-project.org/package=rjags.Google Scholar
Plummer, M., Best, N., Cowles, K. and Vines, K. (2006). CODA: convergence diagnosis and output analysis for MCMC. R News 6, 7–11.Google Scholar
Pollock, K., Marsh, H., Lawler, I.R. and Alldredge, M.W. (2006) Estimating animal abundance in heterogenous environments: an application to aerial surveys for dugongs. Journal of Wildlife Management 70, 255–262.Google Scholar
Powell, J.A., Belitsky, D.W. and Rathbun, G.B. (1981) Status of West Indian manatee (Trichechus manatus) in Puerto Rico. Journal of Mammalogy 62, 642–646.Google Scholar
Preen, A. (2004) Distribution, abundance and conservation status of dugongs and dolphins in the southern and western Arabian Gulf. Biological Conservation 118, 205–218.CrossRefGoogle Scholar
Preen, A.R., Marsh, H., Lawler, I.R., Prince, R.I.T. and Shepherd, R. (1997) Distribution and abundance of dugongs, turtles, dolphins and other megafauna in Shark Bay, Ningaloo Reef and Exmouth Gulf, Western Australia. Wildlife Research 24, 185–208.Google Scholar
Rajamani, L. and Marsh, H. (2010) Using parallel regional- and local-scale initiatives to inform conservation management of rare wildlife: a case study of the dugong Dugong dugon in Sabah, Malaysia. Endangered Species Research 13, 17–23.Google Scholar
Reynolds, J.E. III, Morales-Vela, B., Lawler, I. and Edwards, H. (2012) Utility and design of aerial surveys for sirenians. In Hines, E., Reynolds, J.E. III, Mignucci-Giannoni, A.A., Aragones, L.V. and Marmontel, M. (eds) Sirenian conservation: issues and strategies in developing countries. Gainesville, FL: University Press of Florida, pp. 186–195.Google Scholar
Reynolds, J.E. III and Powell, J.A. (2002) Manatees. In Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (eds) Encyclopedia of marine mammals. San Diego, CA: Academic Press, pp. 709–720.Google Scholar
Self-Sullivan, C. and Mignucci-Giannoni, A.A. (2008) IUCN red list of threatened species, Trichechus manatus ssp. manatus. IUCN 2012, Group Review. Gland: IUCN. http://www.iucnredlist.org.Google Scholar
Self-Sullivan, C. and Mignucci-Giannoni, A.A. (2012) West Indian manatees (Trichechus manatus) in the Wider Caribbean. In Hines, E.M., Reynolds, J.E. III, Aragones, L.V., Mignucci-Giannoni, A.A. and Marmontel, M. (eds.) Sirenian conservation – issues and strategies in developing countries. Gainesville, FL: University Press of Florida, pp. 36–46.Google Scholar
Su, Y. and Yajima, M. (2012) R2jags: A Package for Running jags from R. R package version 0.03–08. http://CRAN.R-project.org/package=R2jags.Google Scholar
Traill, L.W., Brook, B.W., Frankham, R.R. and Bradshaw, C.J.A. (2010) Pragmatic population viability targets in a rapidly changing world. Biological Conservation 143, 28–34.Google Scholar
UNEP (2010) Regional management plan for the West Indian Manatee ( Trichechus manatus ). Kingston: UNEP Caribbean Environment Programme.Google Scholar
Wright, I.E., Reynolds, J.E. III, Ackerman, B.B., Ward, L.I., Weigle, B.L. and Szelistowski, W.A. (2002) Trends in manatee (Trichechus manatus latirostris) counts and habitat use in Tampa Bay, 1987–1994: implications for conservation. Marine Mammal Science 18, 259–274.Google Scholar
Zerbini, A.N., Danilewicz, D., Secchi, E.R., Andriolo, A., Flores, P.A.C., Cremer, M., Ferreira, E., Alves, L.C.P.D.S., Perez, F.S., Castro, F.R., Pretto, D., Sartori, C.M., Schulze, B., Denuncio, P. and Laake, J.L. (2011) Assessing bias in abundance estimates from aerial surveys to improve conservation of threatened franciscana dolphins: preliminary results from a survey conducted off southern Brazil. In 63rd Annual Meeting of the International Whaling Commission, Jersey.Google Scholar
Zerbini, A.N., Secchi, E.R., Danilewicz, D., Andriolo, A., Laake, J.L. and Azevedo, A. (2010) Abundance and distribution of the franciscana (Pontoporia blainvillei) in the Franciscana Management Area II (southeastern and southern Brazil). Agadir: IWC Scientific Committee.Google Scholar