Show simple item record Danilewicz, Daniel Moreno, Ignacio Benites Ott, Paulo Henrique Tavares, Maurício Azevedo, Alexandre de Freitas Secchi, Eduardo Resende Andriolo, Artur 2012-08-15T15:47:49Z 2012-08-15T15:47:49Z 2010
dc.identifier.citation DANILEWICZ, Daniel et al. Abundance estimate for a threatened population of franciscana dolphins in southern coastal Brazil: uncertainties and management implications. Journal of the Marine Biological Association of the United Kingdom, v. 90, n. 8, p. 1-9, 2010. Disponível em: <>. Acesso em: 20 jul. 2012. pt_BR
dc.description.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) ¼ 0.304. The corrected density is 0.51 franciscanas/km2, resulting in an abundance estimation of 6839 franciscanas (CV ¼ 32%; 95% CI ¼ 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. pt_BR
dc.language.iso eng pt_BR
dc.rights restrict access pt_BR
dc.subject Pontoporia blainvillei pt_BR
dc.subject Aerial survey pt_BR
dc.subject Distribution pt_BR
dc.subject Southern Brazil pt_BR
dc.subject Line transect pt_BR
dc.title Abundance estimate for a threatened population of franciscana dolphins in southern coastal Brazil: uncertainties and management implications pt_BR
dc.type article pt_BR
dc.identifier.doi 10.1017/S0025315409991482 pt_BR

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