[MARMAM] New paper on abundance estimates of Guiana dolphins in the Cananeia estuary, Brazil

Marcos Santos sotalia at gmail.com
Sat Mar 23 11:40:51 PDT 2019

Dear Marmamers, just sharing that a new paper on abundance estimates of
Guiana dolphins (*Sotalia guianensis*) in the Cananeia estuary,
southeastern Brazil, is now available.


Prof. Marcos Cesar de Oliveira Santos
Laboratorio de Biologia da Conservacao de Mamiferos Aquaticos (LABCMA)
Instituto Oceanografico, Universidade de Sao Paulo

Mello, AB; Molina, JMB; Kajin, M & Santos, MCO 2019. Abundance estimates of
Guiana dolphins (*Sotalia guianensis*; Van Bénéden, 1864) inhabiting an
estuarine system in southeastern Brazil. *Aquatic Mammals* 45(1): 56-65.

ABSTRACT: Baseline demographic information is essential for effective
conservation and management strategies for most living species. The
abundance of Guiana dolphins (Sotalia guianensis) is poorly known, yet
species conservation is considered a high priority in areas where human
activities may induce population declines. This study estimated abundance
for Guiana dolphins in the Cananeia estuary (25o03' S, 47o55' W) in
southeastern Brazil using mark-recapture data and Pollock’s Robust Design
Model. Systematic boat-based photo-identification surveys were based on
data collected in the summer and winter of 2015 and in the summer of 2016.
A total of 55 capture events allowed identification of 133 different
individuals. The best model indicated a popula- tion with random temporary
emigration, a time-constant survival rate, and heterogeneous time-varying
capture probabilities among primary periods. The temporary emigration rate
(γ’’= γ’) was 0.05 (± 0.03). Estimated population sizes were 430 (95% CI:
410 to 451) individuals in the summer of 2015, 384 (95% CI: 366 to 403)
individuals in the winter of 2015, and 414 (95% CI: 392 to 438) individuals
in the summer of 2016, indicating that environmental variables among
seasons may have a mild effect on the estimated size of this surveyed
population. These estimates should stand as an important baseline for
future comparisons. Systematic, long-term monitoring of this population is
recommended, and is required to accurately assess population trends.
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