Abstract
The troglobitic electric fish Eigenmannia vicentespelaea, endemic to a single cave-system and included in the Brazilian Red List of Threatened Fauna, was studied in relation to population densities and habitat. For comparison, we used the epigean species, E. trilineata. We verify if the population densities recorded for E. vicentespelaea follow the pattern observed for other subterranean fishes; if there are seasonal fluctuations in these densities and which environmental variables explain the densities variation. We estimated abundances and population densities during three consecutive dry seasons concomitant with habitat description and physicochemical variables measurements. For E. vicentespelaea: in six stream reaches in the São Vicente II cave. For E. trilineata: from counts of active fish in rio da Lapa. The mean population density recorded for E. vicentespelaea is considered low (0.17 ind.m-2), similar to those of E. trilineata (0.13 ind.m-2), without significant differences between the years, but with marked fluctuations during dry seasons within each year, suggesting seasonality. Estimated population size of E. vicentespelaea is considered low (270 individuals in average). Depth, water current and substrate, allied to plant debris explain better the variation of densities. Urgent actions for E. vicentespelaea conservation include protection of headsprings in Terra Ronca State Park.
Highlights
Communities established in subterranean habitats, which are highly fragmented and completely dark in deep zones, tend to contain scarce food (Poulson & White, 1969)
In this study we established three central questions relative to population parameters of E. vicentespelaea: 1) Do population densities of E. vicentespelaea follow the pattern observed for other subterranean fishes, and are they comparable with those recorded for a related epigean species, E. trilineata? 2) Are there seasonal fluctuations in the population densities of E. vicentespelaea? 3) Which environmental variables explain the variation in population densities of E. vicentespelaea? To answer these questions we investigated, during three consecutive dry seasons, aspects of population biology and habitat characteristics of E. vicentespelaea
Our morphological study (Bichuette & Trajano, 2006) showed prominent variability of pigmentation and eye condition and a maximum length of 164.5 mm. Because such variation is not observed in epigean Eigenmannia species, it supports the troglobitic status for E. vicentespelaea, indicating isolation determined by morphological differentiation, consistent with geographic isolation in the São Vicente cave system
Summary
Communities established in subterranean habitats, which are highly fragmented and completely dark in deep (aphotic) zones, tend to contain scarce food (Poulson & White, 1969). These communities are under strong selective pressures and are naturally isolated, favoring the survival of relict species (Gibert & Deharveng, 2002). Due to their intrinsic fragility and vulnerability to disturbance, this environment is among the most threatened in the world (Sket, 1999). Fish are among the most conspicuous components of cave aquatic communities, with more than 170 troglobitic species around the world primarily in China and the Neotropical region (Proudlove, 2010).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
