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Intrapopulation variation in the diet of franciscana dolphin (Pontoporia blainvillei) off southern Brazil

Published online by Cambridge University Press:  25 June 2021

Manuela Bassoi Open the ORCID record for Manuela Bassoi [Opens in a new window] ,
Eduardo R. Secchi ,
Daniel Danilewicz ,
Ignacio B. Moreno ,
Roberta A. Santos  and
John G. Shepherd
Manuela Bassoi*
Affiliation:
Laboratório de Ecologia e Conservação da Megafauna Marinha (EcoMega), Universidade Federal do Rio Grande-FURG, Avenida Italia km8 s/n, 96203-900, Rio Grande, RS, Brazil
Eduardo R. Secchi
Affiliation:
Laboratório de Ecologia e Conservação da Megafauna Marinha (EcoMega), Universidade Federal do Rio Grande-FURG, Avenida Italia km8 s/n, 96203-900, Rio Grande, RS, Brazil
Daniel Danilewicz
Affiliation:
Grupo de Estudos de Mamíferos Aquáticos (GEMARS), Rua Felipe Neri 382/203, 90440-150, Porto Alegre, RS, Brazil
Ignacio B. Moreno
Affiliation:
Centro de Estudos Costeiros, Limnológicos e Marinhos (CECLIMAR/UFRGS), Campus Litoral Norte, Universidade Federal do Rio Grande do Sul, Avenida Tramandaí, 976, 95625-000, Imbé, RS, Brazil Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, 91540-000, Porto Alegre, Brazil
Roberta A. Santos
Affiliation:
Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio), Centro Nacional de Pesquisa e Conservação da Biodiversidade Marinha do Sudeste e Sul (CEPSUL), 88301-445, Itajaí, SC, Brazil
John G. Shepherd
Affiliation:
School of Ocean and Earth Science, National Oceanography Centre, Southampton SO14 3ZH, UK
*
Author for correspondence: Manuela Bassoi, E-mail: manu.bassoi@gmail.com
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Abstract

The franciscana dolphin (Pontoporia blainvillei) is a coastal dolphin endemic to the western South Atlantic Ocean. The dolphin is listed as vulnerable in the IUCN Red List, with incidental catches in gillnet fisheries the greatest conservation concern for this species. Insights into the feeding habits of this dolphin are essential to understand its distribution, movements and use of habitat, which are fundamental for effective management of the species. The feeding habits of franciscana dolphins were investigated from analyses of stomach contents of animals incidentally caught by two fishing operations from southern and northern regions of the southern Brazilian coast. In this study we investigate the existence of intrapopulation (sexual maturity and sex-related) variation in the diet of the franciscana dolphin, evaluating the spatial (northern and southern geographic areas) and seasonal influences. The analyses were based on Linear and Generalized Linear Models (LM and GLM). The majority of identified prey species were bottom-dwelling teleosts and the squid Doryteuthis sanpaulensis. The most important prey differed spatially and seasonally between northern and southern regions of the study area, and our results revealed significant differences between sexes and sexual maturity stages, mainly related to prey species sizes. This variation might indicate differences in prey selection, availability or habitat use patterns among these groups. In any case, these dietary differences are likely to minimize intraspecific competition for food resources, and/or indicate spatio-temporal variation in prey availability.

Keywords

Feeding ecologyLa Plata river dolphinstomach contentsWestern South Atlantic
Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 101 , Issue 3 , May 2021 , pp. 621 - 637
Copyright
Copyright © The Author(s), 2021. Published by Cambridge University Press on behalf of Marine Biological Association of the United Kingdom

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