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

Abstract

Age estimation of individuals in a population is one of the most important tasks on investigating the life cycle aspects. The counting of growth layers groups (GLGs) technique has been deployed to estimate the age of cetacean odontocetes. These layers groups are regularly deposited on dentin and cementum layers of the teeth. In this context, this study aims to estimate the age and to obtain the growth parameters of the most accessible species of odontocetes on the Brazilian coast, the franciscana and the guiana dolphins. The specimens were found dead on the southern coast of São Paulo and northern coast of Paraná between 1995 and 2016. Teeth collected from 155 individuals of franciscana dolphin (86 males; 69 females) and 83 of guiana dolphin (37 males; 26 females; 20 undefined sex) will be analyzed. The method used to obtain the teeth's histological sections will follow an internationally standardized protocol and the both species' ages will be estimated by counting the number of GLGs. The growth parameters will be evaluated by means of mathematical functions and the growth curves will be adjusted for both males and females. These results will complement the database of the life history of both species population stocks which are still poorly known. (AU)