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.
Highlights
Dado o contexto de stress hídrico e alta variabilidade temporal em rios de regiões secas, o entendimento da relação peso-comprimento e fator de condição de peixes se apresenta como importante mecanismo para a compreensão desses sistemas
Since fish nutritional status and/or spending reserves are a reflection of their relationship with the environment, length-weight relationships and condition factors of populations constrained in harsh habitats, such as temporary pools in dryland river beds, are of great importance (Medeiros and Maltchik, 2001)
Given the context of high hydrological uncertainties and stress presented by dryland intermittent streams, the evaluation of length-weight relationships and condition factors of fishes becomes of chief concern for the understanding of these systems, and the knowledge on fish population dynamics in intermittent streams
Summary
Dado o contexto de stress hídrico e alta variabilidade temporal em rios de regiões secas, o entendimento da relação peso-comprimento e fator de condição de peixes se apresenta como importante mecanismo para a compreensão desses sistemas. The study of the length-weight relationship of fishes provides a measure of the expected weight change for the length of an individual or group of individuals and an indication of the welfare or overall condition of an individual or population (Le Cren, 1951). Since fish nutritional status and/or spending reserves are a reflection of their relationship with the environment, length-weight relationships and condition factors of populations constrained in harsh habitats, such as temporary pools in dryland river beds, are of great importance (Medeiros and Maltchik, 2001).
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