A total of 152 shark specimens of the genus Etmopterus were collected in southern Brazil between Chuí (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.

Taxonomic distinction to species level of deep water sharks is complex and often impossible to achieve during fisheries-related studies. The species of the genus Etmopterus are particularly difficult to identify, so they often appear without species assignation as Etmopetrus sp. or spp. in studies, even those focusing on elasmobranchs. During this work, the morphometric traits of two species of Etmopterus, E. spinax and E. pusillus were studied using 27 different morphological measurements, relatively easy to obtain even in the field. These measurements were processed with multivariate analysis in order to find out the most important ones likely to separate the two species. Sexual dimorphism was also assessed using the same techniques, and it was found that it does not occur in these species. The two Etmopterus species presented in this study share the same habitats in the overlapping ranges of distribution and are caught together on the outer shelves and slopes of the north-eastern Atlantic.