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ESR 52:17-26 (2023)  -  DOI: https://doi.org/10.3354/esr01262

Distribution, population size and IUCN Red Listing of an isolated population of the threatened franciscana

Federico Sucunza1,2,3,*, Daniel Danilewicz2,3,4, Paulo H. Ott2,5, Mariana Neves6, Ana Paula C. Farro7, Agnaldo S. Martins8, Alexandre N. Zerbini3,9,10

1Laboratório de Ecologia Comportamental e Bioacústica, Programa de Pós-graduação em Biodiversidade e Conservação da Natureza, Universidade Federal de Juiz de Fora, Juiz de Fora, MG 36036-900, Brazil
2Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul, Torres, RS 95560-000, Brazil
3Instituto Aqualie, Juiz de Fora, MG 36036-330, Brazil
4Programa de Pós-graduação em Zoologia, Universidade Estadual de Santa Cruz, Ilhéus, BA 45662-900, Brazil
5Universidade Estadual do Rio Grande do Sul, Osório, RS 90010-460, Brazil
6Laboratório de Mamíferos Aquáticos e Bioindicadores, Programa de Pós-graduação em Oceanografia, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ 20550-013, Brazil
7Laboratório de Genética e Conservação de Cetáceos, Universidade Federal do Espírito Santo, São Mateus, ES 29932-540, Brazil
8Laboratório de Nectologia, Depto. Oceanografia e Ecologia, Universidade Federal do Espírito Santo, Vitória, ES 29075-910, Brazil
9Cooperative Institute for Climate, Ocean and Ecosystem Studies, University of Washington and Marine Mammal Laboratory, Alaska Fisheries Science Center, Seattle, WA 98115, USA
10Marine Ecology and Telemetry Research, Seabeck, WA 98380, USA
*Corresponding author:

ABSTRACT: The franciscana Pontoporia blainvillei is the only extant member of the family Pontoporiidae, and its occurrence is restricted to coastal waters from Brazil to Argentina. The species is one of the most threatened cetaceans in the southwestern Atlantic Ocean, due to unsustainable bycatch levels. A total of 11 Franciscana Management Areas (FMAs) have been defined throughout the species’ range. FMA Ia represents the northernmost franciscana population, demographically isolated on the north coast of Espírito Santo State, Brazil. In March 2018, aerial surveys were conducted to assess the distribution and estimate the abundance of franciscanas in FMA Ia. A total of 2986 km of survey effort was conducted, and 27 groups were seen (average group size: 2.52 ind., coefficient of variation [CV] = 0.50) in coastal habitats (average distance from the shore: 3.3 km, CV = 0.70). Abundance, corrected for visibility bias and group size bias, was estimated at 1183 (CV = 0.76) individuals, and the potential biological removal was computed at 1. Results suggest that at least during the summer, franciscanas in ES are distributed in coastal habitats between Conceição da Barra and Santa Cruz, with a high-density area observed near the estuary mouth of the Doce River. This is one of the smallest of all franciscana populations and one with a restricted range. The estimated abundance indicates that the ES population qualifies for listing as Endangered under IUCN Red List criterion C2a(ii). In order to reduce threats to this population, management actions are urgently needed.


KEY WORDS: Distribution · Abundance · Aerial surveys · Franciscana · Threatened species · Potential biological removal


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Cite this article as: Sucunza F, Danilewicz D, Ott PH, Neves M, Farro AC, Martins AS, Zerbini AN (2023) Distribution, population size and IUCN Red Listing of an isolated population of the threatened franciscana. Endang Species Res 52:17-26. https://doi.org/10.3354/esr01262

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Published in ESR Vol. 52. Online publication date: September 14, 2023
Print ISSN: 1863-5407; Online ISSN: 1613-4796
Copyright © 2023 Inter-Research.
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