Spatial and temporal habitat use of bottlenose dolphin, Tursiops truncatus, inhabiting
the Patos Lagoon estuary, southern Brazil.
Di Tullio, Juliana1, 2,3; Fruet, Pedro1, 3, 4; Dalla Rosa, Luciano 1,5 , Möller, Luciana 6; Secchi, Eduardo1, 2
(1) Laboratório de Mamíferos Marinhos, Museu Oceanográfico “Prof. E.C. Rios”, FURG. 96200-970,
Cx.P. 379, Rio Grande, RS, Brazil.
(2) Laboratório de Tartarugas e Mamíferos Marinhos, Departamento de Oceanografia, FURG. 96200970, Cx.Postal 474, Rio Grande, RS, Brazil.
(3) KAOSA. Maria Araújo, 221. 96207480, Rio Grande, RS, Brazil.
(4)Laboratório de Estatística/Departamento de Matemática, Fundação Universidade Federal do Rio
Grande, Cx.P. 474, Rio Grande-RS, Brazil, 96200-970
(5) Marine Mammal Research Unit, University of British Columbia, Vancouver, BC, Canada.
(6) Marine Mammal Research Group, Graduate School of the Environment, Macquarie University,
Sydney, NSW 2109, Austrália.
[email protected]
Studies of the small population of bottlenose dolphins (Tursiops truncatus) inhabiting the Patos
Lagoon estuary using photo-identification were conducted in 1976/77, 1993/94, 1998 and 2005/06.
Photographs of individuals with long-lasting marks were catalogued in all studies and were compared
to assess the resighting rates among years. Of 14 dolphins catalogued in 1977, 42.86% were resighted
in 1994, 57.14% in 1998 and 35.71% in 2005 and 2006. Of 27 dolphins catalogued in 1994, 70.37%
were resighted in the 1998 catalogue, composed of 43 animals, 48.14% were also present in the 2005
catalogue of 54 individuals and 44.44% were seen in the 2006 catalogue of 64 individuals. From the
1998 catalogue, 51.2% and 46.51% of the dolphins were resighted in 2005 and 2006, respectively.
Almost all dolphins (94.44%) catalogued in 2005 were resighted in 2006.
Information on spatial distribution was investigated based on 21 systematical boat-based surveys
conducted from September 2006 to June 2007, inside (approximately 24 km from the mouth inwards)
the Patos Lagoon estuary (361.2 km surveyed on effort) and on the adjacent coastal areas up to 20km
northward (282.5 km surveyed) and southward (290.3 km surveyed) of the estuary. Sighting (number
of dolphins) per effort (in kilometers surveyed) was used as an index of density. The mean density was
higher inside (mean=0.40; sd=0.21) than outside (mean=0.14; sd=0.12) the estuary (H=4.5; p=0.034).
The mean density was also higher in areas close (mean=0.62; sd=0.84) than distant (mean=0.09;
sd=0.15) to the estuary mouth (H=9.8; p =0.002). These long-term and relatively high resighting rates,
the higher density in the mouth of the estuary as well as the decrease in density as the distance to the
estuary mouth increases indicate that this population is highly resident and dependent on the estuary.