Tagging, ranging patterns, and behavior of franciscana dolphins (Pontoporia blainvillei) off Argentina and Brazil: Considerations for conservation

摘要

Abstract The 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.