Assessing the growth rate of endangered Franciscana dolphin (Pontoporia blainvillei) by using Leslie's approach

CÁCERES, M.O.; CÁCERES SAEZ, I.; SECCHI, E.R.; NEGRI, M.F. ; PANEBIANCO, M.V.; CAPPOZZO, L.

Buenos Aires, Argentina

Conferencia; Latin American Conference on Mathematical Modeling of Biological Systems; 2015

Universidad de Buenos Aires, CONICET

Several cetaceans species are subjected to anthropogenic threats and posses life history traits that make them vulnerable to population declination. The Franciscana dolphin is a small dolphin in the Southwestern Atlantic Ocean, critically affected by incidental fishery mortality (or bycatch) along their coastal distribution from Argentina to Brazil1. The International Union for Conservation of Nature (IUCN)2 has classified this species as Vulnerable throughout its geographical range, due to the population decline of more than 30% over three generations, with approximately 2000-3000 dolphins incidentally captured in fishing nets each year.In this study a method is presented for assess the growth rate of the Franciscana dolphins. The mathematical approach is based on vital parameters information (reproductive rates and survival probabilities). Population models could be improved considering the situation where vital parameters may make random incidental contributions3. Here we apply a Leslie analysis to calculate the growth rate for the time-dependent population vector state, through an algorithm for a 14 x14 matrix model. Thus the growth rate can be characterized by studying the time evolution of the population vector. Our analysis shows that this population cannot sustain such levels of incidental mortality. Therefore we agree with other authors conclusions, and in fact our results are also critical in the sense that the dynamics of the vector state indicates that only a dramatic decline in mortality would allow the population to withstand the present incidental mortality values.