Age and growth of franciscana dolphin (Pontoporia blainvillei) and Guiana dolphin (Sotalia guianensis) from coastal waters of southern São Paulo and northern Paraná

Estimating the age of individuals in a population is one of the most important tasks when investigating aspects related to life history. The present study goal was to estimate the age, as well to obtain the growth parameters of franciscana dolphins (Pontoporia blainvillei) and Guiana dolphins (Sotalia guianensis) incidentally caught in gillnets or found stranded at the south coast of São Paulo and northern Paraná states, Brazil, from 1995 to 2016. Age was estimated by counting the number of growth layer groups present in the dentine and cementum of teeth. Growth parameters were estimated by fitting the von Bertalanffy, Gompertz, Logistic and Richards models to length-at-age data. Growth curves were separately constructed for males and females of both species, however, as S. guianensis showed no sexual dimorphism in growth, results were presented for all individuals pooled together. Asymptotic lengths estimated for franciscana dolphins were 116.7 cm for males and 135.7 cm for females, while for Guiana dolphins the estimate was 183.9 cm for both sexes. Growth rate of male and female of franciscana dolphins was 1.13 and 0.64, respectively, and for Guiana dolphins was 0.41. Estimated size at birth of franciscana dolphins was 85.9 cm for males and 88.5 cm for females, while for Guiana dolphins the estimate was 95.7 cm. (AU)