A study that points causes to the decline of the Franciscanas

Although it has been, and remains, a major challenge to obtain quantitative data for proper population assessment, there is reason to believe that the Franciscana is threatened throughout its range, and particularly in areas of intensive gillnet fishing. As stated in the IUCN cetacean action plan, the Franciscana "may be at greater risk of extinction than any other cetacean species in the western South Atlantic," and "the greatest immediate requirement" for its conservation is "to reduce levels of incidental mortality in gillnets" (Reeves et al. 2003). Simulations of the Rio Grande do Sul/Uruguay (hereafter RS/URU) subpopulation using a plausible range of assumed rates of increase and an estimated removal rate based on available abundance and bycatch data suggest a decline over three generations of close to 50%, which would meet the decline threshold for EN under criterion A. The suspected reduction in population size and its causes may not have ceased (subcriterion A2), based on actual or potential levels of exploitation (in the form of bycatch) (subcriterion d under A1). Two other lines of evidence (indices) can be interpreted as corroborative of a marked decline in abundance of this subpopulation: (1) a decline of approximately 71% in the bycatch of franciscanas per unit of fishing effort was reported in Uruguay from the 1960s to 1980s; and (2) stranding rates of franciscanas in southern Brazil decreased by nearly 70% between the 1970s and 1990s. The Cetacean Specialist Group, having reviewed the data and analyses presented by the assessors (and see Secchi and Wang 2002), was reluctant to recommend EN status at this time (May 2003). Instead, it was agreed to recommend VU status, on the understanding that a reassessment and re-evaluation would be conducted in the near future, taking into account newly obtained data on abundance and bycatch, and perhaps treating the existing evidence with somewhat more elaborate statistical methods. Consultation and Peer Review: Information included as supporting documentation for this assessment was discussed with participants at the 4th Workshop for the Coordination of Research and Conservation of Franciscana in the Western South Atlantic (held in Porto Alegre, Brazil, in 2000). That group discussed progress on Franciscana research and expressed support for the need to change the IUCN Red List status of this species. This documentation was drafted principally by Eduardo Secchi and John Wang, and their work was edited and revised by Randall Reeves following extensive review by the membership of the Cetacean Specialist Group prior to submission to IUCN. For further details, see Secchi and Wang (2002).



http://www.iucnredlist.org/details/full/41761/0