377 



Abstract-Teeth of 71 estuarine dol- 

 phins iSotalia guianensis) inciden- 

 tally caught on the coast of Parana 

 State, southern Brazil, were used to 

 estimate age. The oldest male and 

 female dolphins were 29 and 30 years, 

 respectively. The mean distance from 

 the neonatal line to the end of the first 

 growth layer group (GLG) was 622.4 

 ±19.1 pm (n=48). One or two accessory 

 layers were observed between the neo- 

 natal line and the end of the first GLG. 

 One of the accessory layers, which was 

 not always present, was located at a 

 mean of 248.9 ±32.6 pm (^=25) from 

 the neonatal line, and its interpreta- 

 tion remains uncertain. The other layer, 

 located at a mean of 419.6 ±44.6 pm 

 (n=54) from the neonatal line, was 

 always present and was first observed 

 between 6.7 and 10.3 months of age. 

 This accessory layer could be a record 

 of weaning in this dolphin. Although 

 no differences in age estimates were 

 observed between teeth sectioned in 

 the anterior-posterior and buccal-lin- 

 gual planes, we recommend sectioning 

 the teeth in the buccal-Ungual plane 

 in order to obtain on-center sections 

 more easily. We also recommend not 

 using teeth from the most anterior 

 part of the mandibles for age estima- 

 tion. The number of GLGs counted 

 in those teeth was 50% less than the 

 number of GLGs counted in the teeth 

 from the median part of the mandible 

 of the same animal. Although no sig- 

 nificant difference (P>0.05) was found 

 between the total lengths of adult male 

 and female estuarine dolphins, we 

 observed that males exhibited a second 

 growth spurt around five years of age. 

 This growth spurt would require that 

 separate growth curves be calculated 

 for the sexes. The asymptotic length 

 (TL^), k, and ^,j obtained by the von Ber- 

 talanffy growth model were 177.3 cm, 

 0.66, and -1.23, respectively, for fe- 

 males and 159.6 cm, 2.02, and -0.38, 

 respectively, for males up to five years, 

 and 186.4 cm, 0.53 and -1.40, respec- 

 tively, for males older than five years. 

 The total weight (TW)/total length (TL) 

 equations obtained for male and female 

 estuarine dolphins were TW = 3.156 x 

 10-6 X TL 3 2836 (r=0.96), and rW = 8.974 x 

 10-5 X XL 2 '5182 (r=0.95), respectively. 



Manuscript accepted 28 October 2002. 



Manuscript received 31 December 2002 

 at NMFS Scientific Publicaitions Office. 



Fish. Bull. 101:377-383 (2003). 



Age and growth of the estuarine dolphin 

 (Sotalia guianensis) (Cetacea^ Delphinidae) 

 on the Parana coast, southern Brazil 



Fernando Cesar Weber Rosas 



Institute Nacional de Pesquisas da Amazonia (INPA) 



Laboratono de Mamileros Aquaticos 



Caixa Postal 478 



Manaus, AM, 69011 970, Brazil 



E-mail address; frosas@inpa gov br 



Andre Silva Barreto 



Universidade do Vale do Itaiai (UNIVALI) 

 CTTMar, Caixa Postal 360 

 Itaiai, SC, 88302 202, Brazil 



Emygdio Leite de Araujo Monteiro-Filho 



Universidade Federal do Parana (UFPR) 



Departamento de Zoologia 



Caixa Postal 19020 



Curitiba, PR, 81531-970, Brazil 



and 



Institute de Pesquisas Cananeia (IPeO 

 Rua Joao Salim, Lote 26-Quadra Y 

 Parque Xangrila 

 13098-106, Campinas, Sao Paulo, Brazil 



Until recently the genus Sotalia was 

 monospecific (S. fluviatilis) and had a 

 marine and a riverine ecotype (da Silva 

 and Best, 1996). Using tridimensional 

 morphometric analyses, Monteiro-Filho 

 et al. (2002) were able to separate it into 

 two distinct species: Sotalia fluviatilis, 

 which lives in freshwater, and Sotalia 

 guianensis. which lives in the marine 

 environment. Because tucuxi is the 

 vernacular name used for the freshwa- 

 ter species, Rosas and Monteiro-Filho 

 (2002) suggested "estuarine dolphin" 

 as the vernacular name for S. guianen- 

 sis, as previously mentioned by Watson 

 (1988). 



Age is important in characterizing 

 population dynamics of mammals. 

 Growth layer groups (GLGs) observed 

 in teeth of mammals have been used 

 to estimate ages, and the greatest 

 progress in this area has occurred with 

 studies carried out on marine mammals 

 (Klevezal, 1980; Hohn et al., 1989). The 

 method consists of counting GLGs found 



in the dentine and cement of the ani- 

 mals' teeth, which are deposited every 

 year in most species (Klevezal, 1996). 

 Calibrating age estimates and identify- 

 ing accessory layers (not annual) are 

 essential for reliable age determination 

 (Hohn, 1990). Some population param- 

 eters are extremely sensitive to errors 

 and age estimate deviations, and the 

 absence of or an inadequate calibration, 

 could lead to incorrect interpretations 

 (Hohnetal., 1989). 



Because there is no sexual dimorphism 

 in the body proportions of adult Sotalia 

 guianensis, all previous growth studies 

 analyzed both sexes together (Borobia, 

 1989; Schmiegelow, 1990; Ramos et al., 

 2000). However, there is evidence of dif- 

 ferentiated growth between male and 

 female estuarine dolphins around pu- 

 berty (Rosas and Monteiro-Filho, 2002), 

 thereby making it necessary to analyze 

 growth separately for the sexes. 



The objectives of this paper were 1) 

 to estimate the ages of S. guianensis 



