Abstract
AbstractThe franciscana dolphin, Pontoporia blainvillei, is one of the most threatened cetaceans in the Southwestern Atlantic. Within their limited coastal range off Argentina, Uruguay, and Brazil, franciscanas face human activities, including artisanal gillnet fishing and coastal development. A lack of information on ranging patterns, population structure, and behavior for informing management led to efforts to develop and apply approaches to tag franciscanas in Argentina (Bahía Samborombón [BS], Bahía San Blas [BSB]) and Brazil (Baía Babitonga [BB]) during 2005–2013. Findings from VHF tags deployed in BS in 2005 during feasibility tests for catching and handling franciscanas for tagging suggested residency over periods of weeks. Subsequently, satellite‐linked tags confirmed patterns of residency at each site. Home range size varied, with ranges of 5–7 km2 for BB, 51–312 km2 for BS, and 49–1,014 km2 for BSB. Diving patterns varied across sites, with the animals using the entire water column, exposing them to fishing nets regardless of the depth at which the nets were set. Tracking durations and follow‐up observations indicated that this research approach is useful for studies of franciscanas. Small, definable ranges facilitate relating specific geographically based threats to appropriate population units, increasing the potential for effective conservation.
Highlights
Small cetaceans around the world are subject to a variety of threats, many of them from human activities
We describe how we adapted a catch-and-release approach and tagging techniques developed for common bottlenose dolphins, Tursiops truncatus, to be able to obtain the first data of their kind on the movements and behavior of franciscana dolphins, Pontoporia blainvillei, in three bays in Argentina and Brazil, where they face anthropogenic threats
In order to better understand the behavior of franciscanas relative to exposure to specific anthropogenic threats, research was conducted in the waters of Argentina (Bahía Samborombon and Bahía San Blas) and Brazil (Baía Babitonga) during 2005–2013 with the objectives of: (1) determining the feasibility of capture-release for tagging; (2) exploring the feasibility of tagging and tracking franciscanas; (3) describing franciscana movement, home range patterns, and home range size; and (4) investigating franciscana use of the water column through examination of dive behavior
Summary
Small cetaceans around the world are subject to a variety of threats, many of them from human activities. Franciscana dolphins are found in waters up to 30 m deep (Gomez & Cassini, 2015), extending up to 50 m in some areas (Amaral et al, 2018; Danilewicz et al, 2009) This limited range overlaps the main areas used for fishing activities, and is the zone where many human activities related to coastal development, and that potentially affect the species, occur (Cremer et al, 2018; Secchi, 2010). In order to better understand the behavior of franciscanas relative to exposure to specific anthropogenic threats, research was conducted in the waters of Argentina (Bahía Samborombon and Bahía San Blas) and Brazil (Baía Babitonga) during 2005–2013 with the objectives of: (1) determining the feasibility of capture-release for tagging; (2) exploring the feasibility of tagging and tracking franciscanas; (3) describing franciscana movement, home range patterns, and home range size; and (4) investigating franciscana use of the water column through examination of dive behavior
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