Report of the Working Group on Biology and Ecology

Abstract

Growth The asymptotic lengths of individuals of the southern form of P. blainvillei (distributed south of 32oS) vary between 129.8cm and 136.4cm for males, and between 146.4cm and 161.9cm for females (Kasuya and Brownell, 1979; Walter, 1997; Barreto et al., 2000). The northern form of the species (distributed north of 27oS), has asymptotic lengths that vary between 113.3cm and 117.1cm for males, and between 128.9cm and 144.7cm for females (Rosas, 2000; Ramos et al., 2000a; Ramos et al., 2000b). These results corroborate the populational differences in body size between the northern (smaller individuals) and southern forms (larger individuals) based on osteological data (Pinedo, 1991) and those from genetic studies (Secchi et al., 1998). These data also suggest populational differences within each of the geographic forms. The asymptotic lengths obtained by Rosas (2000) for franciscanas in an intermediate area (Sao Paulo and Parana) of the species’ distribution were smaller than those close to the northern limit of its distribution (Ramos et al., 2000a). Additionally, the asymptotic lengths presented by Ramos et al. (2000b) from Sao Paulo were also smaller than those for the more northern Rio de Janeiro coast. The different body sizes observed among the individuals within the northern form might also be due to populational differences, as result of an isolation of the individuals in the northern region of Rio de Janeiro and Espirito Santo (Siciliano et al., 2000).