581 



Abstract — The reproductive biology 

 of male franciseanas iPontoporia 

 blainvillei), based on 121 individu- 

 als collected in Rio Grande do Sul 

 State, southern Brazil, was studied. 

 Estimates on age, length, and weight 

 at attainment of sexual maturity are 

 presented. Data on the reproductive 

 seasonality and on the relationship 

 between some testicular characteris- 

 tics and age. size, and maturity status 

 are provided. Sexual maturity was 

 assessed by histological examina- 

 tion of the testes. Seasonality was 

 determined by changes in relative and 

 total testis weight, and in seminifer- 

 ous tubule diameters. Testis weight, 

 testicular index of maturity, and 

 seminiferous tubule diameters were 

 reliable indicators of sexual maturity, 

 whereas testis length, age, length, 

 and weight of the dolphin were not. 

 Sexual maturity was estimated to be 

 attained at 3.6 years (CI 957c = 2.7- 

 4.5) with the DeMaster method and 

 3.0 years with the logistic equation. 

 Length and weight at attainment of 

 sexual maturity were 128.2 cm (CI 

 95<£ = 125.3-131.1 cm) and 26.4 kg (CI 

 95^=24.7-28.1 kg), respectively. It 

 could not be verified that there was 

 any seasonal change in the testis 

 weight and in the seminiferous tubule 

 diameters in mature males. It is sug- 

 gested that at least some mature males 

 may remain reproductively active 

 throughout the year. The extremely 

 low relative testis weight indicates 

 that sperm competition does not occur 

 in the species. On the other hand, 

 the absence of secondary sexual char- 

 acteristics, the reversed sexual size 

 dimorphism, and the small number 

 of scars from intrassexual combats in 

 males reinforce the hypothesis that 

 male combats for female reproductive 

 access may be rare for franciscana. 

 It is hypothesized that P. blainvillei 

 form temporary pairs (one male copu- 

 lating with only one female) during 

 the reproductive period. 



Reproductive biology of male franciseanas 

 (Pontoporio blainvillei) (Mammalia: Cetacea) 

 from Rio Grande do Sul, southern Brazil* 



Daniel Daniiewicz 



Grupo de Estudos de Mamiferos Aquaticos do Rio Grande do Sul (GEMARS) 



Rua Felipe Nen, 382/203 



Porto Alegre 90440-150, Brazil 



Present address: Laboratono de Dinamica Populacional-Pontilicia Universidade Catolica do 



Rio Grande do Sul (PUCRS) 



Av. Ipiranga, 6681 



Porto Alegre 90619-900, Brazil 

 Email address (for D Daniiewicz): Daniel. Danilewicza 1 terra com br 



Juan A. Claver 



Alejo L. Perez Camera 



Area Histologia y Embnologia Facultad de Ciencias Vetermarias 

 Universidad de Buenos Aires 

 Ar Chorroarin 280 C1427CWO 

 Buenos Aires, Argentina 



Eduardo R. Secchi 



Laboratono de Mamiferos Mannhos, Museu Oceanografico "Prof. Eliezer C. Rios" 

 Fundacao Universidade Federal do Rio Grande, Cx P. 379 

 Rio Grande 96200, Brazil 



Nelson F. Fontoura 



Laboratono de Dinamica Populacional-Pontificia Universidade Catolica do 



Rio Grande do Sul (PUCRS) 



Av. Ipiranga, 6681 



Porto Alegre 90619-900, Brazil 



Manuscript submitted 4 October 2002 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 18 May 2004 by the Scientific Editor. 



Fish. Bull. 102:581-592 (2004). 



The franciscana (Pontoporia blainvil- 

 lei) is a small dolphin endemic to the 

 coastal waters of the southwestern 

 Atlantic Ocean. The distribution of 

 this species ranges from Golfo Nuevo 

 (42°35'S; 64°48'W), Chubut Province, 

 Argentina (Crespo et al., 1998) to 

 Itaunas (18°25'S; 30°42'W), Espirito 

 Santo, southeastern Brazil (Moreira 

 and Siciliano, 1991) (Fig. 1). 



The franciseanas coastal habitat 

 makes it vulnerable to being caught 

 as incidental catch in gill nets and 

 trammel nets throughout most of the 

 species range (e.g., Praderi et al., 

 1989; Corcuera et al., 1994; Secchi et 

 al., 2003). Because of its vulnerability 

 as bycatch, the franciscana has been 

 considered the most impacted small 



cetacean in the southwestern Atlantic 

 Ocean (Secchi et al., 2002). In the 

 Rio Grande do Sul coast, southern 

 Brazil, this species has been subject 

 to an intense bycatch in gill nets for 

 at least three decades (Moreno et al., 

 1997; Secchi et al., 1997; Ott, 1998; 

 Ott et al., 2002). The annual mor- 

 tality of franciseanas in this region 

 was estimated to range from several 

 hundred up to about a thousand indi- 

 viduals (Ott et al., 2002). Simulations 



^Contribution 012 from the Grupo de 

 Estudos de Mamiferos Aquaticos do Rio 

 Grande do Sul (GEMARS), Rua Felipe 

 Neri, 382/203, Porto Alegre 90440-150, 

 Brazil. 



