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Fishery Bulletin 102(4) 



Figure 1 



Map of the study area showing the locations along the southern coast of Brazil 

 where franciscanas were caught as bycatch between 1992 and 1998. 



studies on the effects of incidental captures on francis- 

 canas in Rio Grande do Sul were carried out by using 

 available data on vital rates, stock size, and bycatch 

 estimates (e.g., Secchi, 1999; Kinas, 2002). All these 

 studies showed that there is a decline in franciscana 

 abundance in this region. 



Although the reproductive biology of the female fran- 

 ciscanas have been studied in detail in Uruguay (Ka- 

 suya and Brownell, 1979; Harrison et al., 1981), Rio 

 Grande do Sul (Danilewicz et al., 2000; Danilewicz, 

 2003), and Rio de Janeiro (Ramos, 1997), there are few 

 data about male reproduction. Kasuya and Brownell 

 (1979) presented information on male reproduction for 

 Uruguay, although their small sample size precluded 

 them from estimating age and size at attainment of 

 sexual maturity. 



In the Rio Grande do Sul coast, franciscanas are 

 known to reproduce seasonally; births occur from Oc- 

 tober to early February (about 75"7r from October to De- 

 cember). Because the gestation period was estimated to 

 last about 11.2 months, mating and conception may take 

 place between November and early March I Danilewicz, 

 2003). Seasonal changes in testicular size and activity 

 have been used to infer or corroborate mating seasons 

 in some cetacean species (e.g., Neimanis et al., 2000 I. 

 Nevertheless, it is not known if male franciscanas also 

 undergo seasonal changes in the testicular activity. 



In this study, we describe the reproductive biology of 

 male franciscanas from Rio Grande do Sul and present 

 evidences for the species' mating system. 



Materials and methods 



Sampling procedures 



Data and samples collected from 121 specimens inci- 

 dentally caught (889c) or beached (12%) along the Rio 

 Grande do Sul coast between 1992 and 1998 were used 

 for the analysis on reproduction of male franciscanas. 

 The sampling of the incidentally caught animals was 

 carried out through the monitoring of the commercial 

 fishery fleet from Rio Grande (32°08'S; 52°05'W) and 

 Tramandai/Imbe (29°58'S, 50°07'W). Stranded dolphins 

 were sampled from systematic beach surveys conducted 

 in an area with an extension of 270 km of sandy beaches, 

 between Torres (29°19'S, 49°43'W) and Lagoa do Peixe 

 (31°15'S, 50°54'W). 



Not all information could be collected from each car- 

 cass; therefore sample sizes varied among parameters. 

 Standard length (SL, n = 118) was measured by following 

 the guidelines established by the American Society of 

 Mammalogy (1961). The animals were weighed (rc = 97) 

 and teeth were extracted and preserved dried or in a 

 1:1 mix of glycerin and alcohol (70%). Testes and epi- 

 didymis were removed and fixed in 10'> formalin. 



Age determination 



Age was estimated by counting the growth layer groups 

 (GLGs) in thin, longitudinal sections of teeth (ra=47). 

 The teeth were decalcified in nitric acid or in RDO 



