Length-weight relationship of two fish species from a dryland intermittent river in northeastern Brazil

Elmo Pereira da Silva, Maria Rita Nascimento Duarte, Elvio Sergio Figueredo Medeiros

Abstract


Given the context of high hydrological uncertainties and stress in dryland streams, the evaluation of length-weight relationships and condition factors of fish becomes of chief concern for the understanding of these systems. Length-weight relationships were estimated for two fish species, Astyanax fasciatus (Cuvier 1819) and Astyanax bimaculatus (Linnaeus 1758), from temporary pools in a dry river bed. Length-weight relationship information was compared between dry and rainy seasons. Sampling was performed using gillnets, manual trawls and cast nets at different reaches of the river. Estimates for the values of b of the length-weight relationship were 2.63 for A. fasciatus, and 2.78 for A. bimaculatus, indicating a negative allometric growth. The condition factor ranged between 0.0180 and 0.0187 for both species, without significant difference between seasons, and meaning a greater investment in growth rather than weight gain. Results indicated that fishes tended to be larger during the rainy season, likely representing the result of a higher frequency of immature and smaller individuals during the previous dry season as a consequence of reproductive activity of adults.

Keywords: Astyanax fasciatus, Astyanax bimaculatus, temporary pools, condition factor.


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