Aspects of the population structure and reproductive biology of sharks of the genus Etmopterus on the upper continental slope of southern Brazil

A total of 152 shark specimens of the genus Etmopterus were collected in southern Brazil between Chui (34°20′S) and the Santa Marta Grande Cape (28°30′S). The specimens were caught by bottom-trawl cruises at depths ranging between 100 and 600 m from August to September 2001 and March to April 2002. The species, identified as Etmopterus gracilispinis, E. lucifer and E. bigelowi, occurred only in the south of 31°S at different depth layers. Etmopterus bigelowi occurred in the deep strata from 400–599 m, whereas E. gracilispinis occurred from 300–599 m. Moreover, two sampled E. lucifer males occurred at a depth of 540 m. The hydrographic conditions of temperature and salinity revealed no seasonal differences. The fact that most of the collected specimens were immature is strong evidence of size segregation, suggesting that the adults of these species occur at depths greater than 600 m. Sexual maturity in E. bigelowi occurred at 63–65 cm total length (TL) in females and 60 cm TL in males. All E. gracilispinis specimens were immature. One E. bigelowi female caught in August was pregnant. Birth was confirmed only in March for E. bigelowi and E. gracilispinis with TL at birth of about 17 and 13 cm, respectively.