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Abundance estimate for a threatened population of franciscana dolphins in southern coastal Brazil: uncertainties and management implications

Published online by Cambridge University Press:  11 November 2010

Daniel Danilewicz ,
Ignacio B. Moreno ,
Paulo H. Ott ,
Maurício Tavares ,
Alexandre F. Azevedo ,
Eduardo R. Secchi  and
Artur Andriolo
Daniel Danilewicz*
Affiliation:
Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul (GEMARS), Avenida Tromandaí, 476-CEP: 95625-000, Imbé, RS, Brazil and Pós-Graduação em Biociências, PUC-RS, Porto Alegre, RS, Brazil
Ignacio B. Moreno
Affiliation:
Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul (GEMARS), Avenida Tromandaí, 476-CEP: 95625-000, Imbé, RS, Brazil and Pós-Graduação em Biociências, PUC-RS, Porto Alegre, RS, Brazil
Paulo H. Ott
Affiliation:
Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul (GEMARS), Avenida Tromandaí, 476-CEP: 95625-000, Imbé, RS, Brazil and Pós-Graduação em Biociências, PUC-RS, Porto Alegre, RS, Brazil Universidade Estadual do Rio Grande do Sul (UERGS), Cidreira, RS, Brazil
Maurício Tavares
Affiliation:
Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul (GEMARS), Avenida Tromandaí, 476-CEP: 95625-000, Imbé, RS, Brazil and Pós-Graduação em Biociências, PUC-RS, Porto Alegre, RS, Brazil CECLIMAR/UFRGS, Avenida Tramandaí, 976, Imbé 95625-000, RS, Brazil
Alexandre F. Azevedo
Affiliation:
Laboratório de Mamíferos Aquáticos (MAQUA)/UERJ, Rio de Janeiro, RJ, Brazil
Eduardo R. Secchi
Affiliation:
Instituto de Oceanografia and Museu Oceanográfico ‘Prof. E.C. Rios’, Universidade Federal do Rio Grande, FURG, Rio Grande, RS, Brazil 96201-900
Artur Andriolo
Affiliation:
Departamento de Zoologia, ICB, Universidade Federal de Juiz de Fora, MG, Brazil
*
Correspondence should be addressed to: D. Danilewicz Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul (GEMARS), Avenida Tramandaí, 976-CEP: 95625-000, Imbé, RS, Brazil and Pós-Graduação em Biociências PUC-RS, Porto Alegre, RS, Brazil email: daniel.danilewicz@gmail.com
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Abstract

The franciscana dolphin has been considered the most threatened small cetacean in the south-western Atlantic Ocean due to gillnet by-catch. The estimation of the species' abundance has been recommended as the highest research priority. A line transect aerial survey to estimate franciscana abundance in Rio Grande do Sul, southern Brazil, was carried out in February 2004. The overall surveyed area comprised 13,341 km2 and at least 20 transect lines. Abundance was estimated using distance sampling methods and assuming g(0) = 0.304. The corrected density is 0.51 franciscanas/km2, resulting in an abundance estimation of 6839 franciscanas (CV = 32%; 95% CI = 3709–12,594) for the surveyed area in Rio Grande do Sul. To improve this estimate: (a) perception bias should be determined; (b) the parameters influencing availability bias should be identified and quantified; and (c) survey sample size should be increased. While the lack of data to correct for perception bias and group size underestimation in this aerial survey is likely to yield an underestimate of franciscana abundance, the use of surfacing and diving time data from boat and land-based surveys to correct for availability bias is likely to cause its overestimation. Alternative values of the g0 group-size estimates and rates of increase were incorporated in the analyses, creating 240 different estimates of annual increment for this franciscana population. Even in the most optimistic scenario, the annual increment of franciscanas is not sustainable with the current levels of by-catch in Rio Grande do Sul, and fishery management to reduce by-catch must be initiated promptly.

Keywords

Pontoporia blainvilleiaerial surveydistributionsouthern Brazilline transect
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 90 , Special Issue 8: Marine Mammals , December 2010 , pp. 1649 - 1657
Copyright
Copyright © Marine Biological Association of the United Kingdom 2010

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References

REFERENCES

Andriolo, A., Piovezan, U., Costa, M.J.R.P., Laake, J and Duarte, J.M.B. (2005) Aerial transect survey to estimate abundance of marsh deer (Blastocerus dichotomus) (Illiger, 1815). Brazilian Archives of Biology and Technology 48, 807–814.CrossRefGoogle 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 of humpback whale (Megaptera novaeangliae) to estimate abundance in the breeding ground, Brazil. Journal of Cetacean Research and Management 8, 307–311.CrossRefGoogle Scholar
Ancrenaz, M., Goossens, B., Gimenez, O., Sawang, A. and Lackman-Ancrenaz, I. (2004) Determination of ape distribution and population size using ground and aerial surveys: a case study with orangutans in lower Kinabatangan, Sabah, Malaysia. Animal Conservation 7, 375–385.CrossRefGoogle Scholar
Barlow, J., Oliver, C.W., Jackson, T.D. and Taylor, B.L. (1988) Harbor porpoise, Phocoena phocoena, abundance estimation for California, Oregon, and Washington: II. Aerial surveys. Fishery Bulletin 86, 433–44.Google Scholar
Bertozzi, C. and Zerbini, A.N. (2002) Incidental mortality of franciscana (Pontoporia blainvillei) in the artisanal fishery of Praia Grande, São Paulo state, Brazil. Latin American Journal of Aquatic Mammals 1, 153–160.CrossRefGoogle Scholar
Bordino, P., Thompson, G. and Iñiguez, M. (1999) Ecology and behaviour of the franciscana (Pontoporia blainvillei) in Bahia Anegada, Argentina. Journal of Cetacean Research and Management 1, 213–222.CrossRefGoogle Scholar
Bravington, M.V. and Bisack, K.D. (1996) Estimates of harbour porpoise by-catch in the Gulf of Maine sink gillnet fishery, 1990–1993. Report of the International Whaling Commission 46, 567–574.Google Scholar
Brownell, R.L. Jr (1984) Review of reproduction in platanistid dolphins. Report of the International Whaling Commission 6, 49–158.Google Scholar
Buckland, S.T., Anderson, D.R., Burnham, K.P. and Laake, J.L. (2001) Distance sampling: estimating abundance of biological populations. 2nd edition. London, UK: Chapman and Hall.Google Scholar
Burnham, K.P., Andersonm, D.R. and Laake, J.L. (1980) Estimation of density from line transect sampling of biological populations. Wildlife Monographs 72, 1–202.Google Scholar
Corcuera, J. (1994) Mortality of Pontoporia blainvillei in Northern Buenos Aires Province: the threat of small fishing camps. Report of the International Whaling Commission 15, 291–294.Google Scholar
Crespo, E.A., Harris, G. and González, R. (1998) Group size and distributional range of the franciscana, Pontoporia blainvillei. Marine Mammal Science 14, 845–849.CrossRefGoogle Scholar
Danilewicz, D. (2003) Reproduction of female franciscana (Pontoporia blainvillei) in Rio Grande do Sul, southern Brazil. Latin American Journal of Aquatic Mammals 2, 67–78.CrossRefGoogle Scholar
Danilewicz, D. (2007) A toninha, Pontoporia blainvillei (Mammalia: Cetacea), no litoral norte do Rio Grande do Sul: mortalidade acidental em redes de pesca, abundância populacional e perspectivas para a conservação da espécie. Doctoral thesis. Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil.Google Scholar
Di Beneditto, A.P.M. and Ramos, R.M.A. (2001) Biology and conservation of the franciscana (Pontoporia blainvillei) in the north of Rio de Janeiro State, Brazil. Journal of Cetacean Research and Management 3, 185–192.CrossRefGoogle Scholar
Firchow, K.M., Vaughan, M.R. and Mytton, W.R. (1990) Comparison of aerial survey techniques for pronghorns. Wildlife Society Bulletin 18, 18–23.Google Scholar
Guenzel, R.J. (1986) Pronghorn ecology in southcentral Wyoming. MSc thesis. University of Wyoming, Laramie, USA.Google Scholar
Guenzel, R.J. (1994) Adapting new techniques to population management: Wyoming's pronghorn experience. Transactions of the North American Wildlife and Natural Resources Conference 59, 189–200.Google Scholar
IUCN (2008) IUCN Red List of Threatened Species: A global species assessment. Gland, Switzerland and Cambridge, UK: IUCN. Pontoporia blainvillei. Available from http://www.iucnredlist.org/search/details.php/41761/allGoogle Scholar
Johnson, B.K., Lindsey, F.G. and Guenzel, R.J. (1991) Use of aerial line transect surveys to estimate pronghorn populations in Wyoming. Wildlife Society Bulletin 19, 315–321.Google Scholar
Kinas, P.G. and Secchi, E.R. (1998) Modelling truncated data to estimate incidental kills of franciscana, Pontoporia blainvillei, by gillnets. Report of the International Whaling Commission 48, 533–536.Google Scholar
Kinas, P.G. (2002) The impact of incidental kills by gill nets on the franciscana dolphin (Pontoporia blainvillei) in southern Brazil. Bulletin of Marine Science 70, 409–421.Google Scholar
Laake, J.L., Calambbokidis, J.C., Osmek, S.D. and Rugh, D.J. (1997) Probability of detecting harbor porpoise from aerial surveys: estimating g (0). Journal of Wildlife Management 61, 63–75.CrossRefGoogle Scholar
Marsh, H. and Sinclair, D.F. (1989) An experimental evaluation of dugong and sea turtle aerial surveys techniques. Australian Wildlife Research 16, 639–650.CrossRefGoogle Scholar
Moreno, I.B., Ott, P.H. and Danilewicz, D. (1997) Análise preliminar do impacto da pesca artesanal costeira sobre Pontoporia blainvillei no litoral norte do Rio Grande do Sul, sul do Brasil. In Pinedo, M.C. and Barreto, A.S. (eds) Anais do 2°. Encontro sobre a Coordenação de Pesquisa e Manejamento da Franciscana. Rio Grande, Brazil; FURG, pp. 31–41.Google Scholar
Ott, P.H. (1998) Análise das capturas acidentais de Pontoporia blainvillei (Gervais and D'Orbigny, 1844) (Cetacea, Pontoporiidae) nas comunidades pesqueiras do litoral Norte do Rio Grande do Sul, Sul do Brasil. MSc dissertation. Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil.Google Scholar
Ott, P.H., Secchi, E.R., Moreno, I.B., Danilewicz, D., Crespo, E.A., Bordino, P., Ramos, R., Di Beneditto, A.P., Bertozzi, C., Bastida, R., Zanelatto, R., Perez, J.E. and Kinas, P.G. (2002) Report of the Working Group on Fishery Interactions. Latin American Journal of Aquatic Mammals 1, 55–64.CrossRefGoogle Scholar
Pinedo, M.C. and Polacheck, T. (1999) Trends in franciscana (Pontoporia blainvillei) stranding rates in Rio Grande do Sul, Southern Brazil (1979–1998). Journal of Cetacean Research and Management 1, 179–189.CrossRefGoogle Scholar
Praderi, R., Pinedo, M.C. and Crespo, E.A. (1989) Conservation and management of Pontoporia blainvillei in Uruguay, Brazil and Argentina. In Perrin, W.F., Brownell, R.L., Zhou, K. and Liu, J. (eds) Biology and conservation of the river dolphins. Gland, Switzerland: IUCN Occasional Papers, pp. 52–56.Google Scholar
Praderi, R. (1997) Análisis comparativo de estadísticas de captura y mortalidad incidental de Pontoporia blainvillei en Uruguay durante, 20 años. In Pinedo, M.C. and Barreto, A.S. (eds) Anais do 2°. Encontro sobre a Coordenação de Pesquisa e Manejamento da Franciscana. Rio Grande, Brazil: FURG, pp. 42–53.Google Scholar
Reeves, R.R., Smith, B.D., Crespo, E.A., Notarbartorlo di Sciara, G. and the Cetacean Specialist Group (2003) Dolphins, whales, and porpoises: 2003–2010 conservation action plan for the world's cetaceans. In IUCN Species Survival Commission. Gland, Switzerland, IUC.Google Scholar
Rosas, F.C.W., Monteiro-Filho, E.L.A. and Oliveira, M.R. (2002) Incidental catches of franciscana (Pontoporia blainvillei) on the southern coast of São Paulo state and the coast of Paraná state, Brazil. Latin American Journal of Aquatic Mammals 1, 161–167.CrossRefGoogle Scholar
Seber, G.A.F. (1982) The estimation of animal abundance and related parameters. 2nd edition. London: Charles Griffin and Company Ltd.Google Scholar
Secchi, E.R. (1999) Taxa de crescimento potencial intrínseco de um estoque de franciscanas, Pontoporia blainvillei (Gervais and D'Orbigny, 1844) (Cetacea, Pontoporiidae) sob o impacto da pesca costeira de emalhe. MSc dissertation. Fundação Universidade Federal do Rio Grande, Rio Grande, Brazil.Google Scholar
Secchi, E.R. (2006) Modelling the population dynamics and viability analysis of franciscana (Pontoporia blainvillei) and Hector's dolphins (Cephalorhynchus hectori) under the effects of bycatch in fisheries, parameter uncertainty and stochasticity. PhD thesis. University of Otago, Dunedin, NZ.Google Scholar
Secchi, E.R., Zerbini, A.N., Bassoi, M., Dalla Rosa, L., Moller, L.M. and Roccha-Campos, C.C. (1997) Mortality of franciscanas, Pontoporia blainvillei, in coastal gillneting in southern Brazil: 1994–1995. Report of the International Whaling Commission 47, 653–658.Google Scholar
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, 95–100.CrossRefGoogle Scholar
Secchi, E.R., Ott, P.H. and Danilewicz, D. (2002) Report of the fourth workshop for the coordinated research and conservation of the franciscana dolphin (Pontoporia blainvillei) in the western South Atlantic. Latin American Journal of Aquatic Mammals 1, 11–20.CrossRefGoogle Scholar
Secchi, E.R and Wang, J.Y. (2003) Pontoporia blainvillei (Rio Grande do Sul/Uruguay subpopulation). In 2003 IUCN Red List of Threatened Species. Available from www.iucnredlist.orgGoogle Scholar
Secchi, E.R., Danilewicz, D. and Ott, P.H. (2003a) Applying the phylogeographic concept to identify franciscana dolphin stocks: implications to meet management objectives. Journal of Cetacean Research and Management 5, 61–68.CrossRefGoogle Scholar
Secchi, E.R., Ott, P.H. and Danilewicz, D. (2003b) Effects of fishing by-catch and conservation status of the franciscana dolphin, Pontoporia blainvillei. In Gales, N., Hindell, M. and Kirkwood, R. (eds) Marine mammals: fisheries, tourism and management issues. Collingwood, Australia: CSIRO Publishing, pp. 174–191.Google Scholar
Secchi, E.R., Kinas, P.G. and Muelbert, M. (2004) Incidental catches of franciscana in coastal gillnet fisheries in the Franciscana Management Area III: period 1999–2000. Latin American Journal of Aquatic Mammals 3, 61–68.CrossRefGoogle Scholar
Siciliano, S., Di Beneditto, A.P. and Ramos, R.M.A. (2002) A toninha, Pontoporia blainvillei (Gervais and d'Orbigny, 1844) (Mammalia, Cetacea, Pontoporiidae), nos estados do Rio de Janeiro e Espírito Santo, costa sudeste do Brasil: caracterizações dos habitats e fatores de isolamento das populações. Boletim do Museu Nacional, Zoologia 476, 1–15.Google Scholar
Slooten, E., Dawson, S.M. and Rayment, W.J. (2004) Aerial surveys for coastal dolphins: abundance of hector's dolphins off the South Island west coast, New Zealand. Marine Mammal Science 20, 477–490.CrossRefGoogle Scholar
Van Erp, I. (1969) In quest of the La Plata dolphin. Pacific Discovery 22, 18–24.Google Scholar
Zar, J.H. (2000) Biostatistical analysis. 4th edition. Upper Saddle River, NJ: Prentice-Hall Inc.Google Scholar