Abstract
The reproductive process promotes morphophysiological and behavioral changes in fish species throughout their life cycle. Its success is vital to define their resilience in the environment. This study aimed to evaluate the reproductive biology of the endemic fish species Astyanax bifasciatus in a tributary of the Lower Iguaçu River Basin, Paraná, Brazil. Fish were collected monthly at four sites along the Jirau Alto River in the city of Dois Vizinhos from October 2015 to September 2016. A standardized catch effort with gill nets and fish traps was used. In the laboratory, standard length and total weight were recorded. After anesthesia, the animals were sectioned to macroscopically determine the sex, sexual maturity stage, and presence of celomatic fat. The gonads and liver were removed to determine the gonadosomatic and hepatosomatic indexes, respectively. A total of 160 individuals (104 females and 56 males) were used. The gonadosomatic index, frequency of the gonadal maturation stages, and condition factor showed a long reproductive period with two investment cycles for both sex. Length at first sexual maturity was 4.57 cm for females and 3.56 cm for males. The reproductive data corroborate the generalist profile of the species and demonstrate a high degree of adaptive capacity, even in smaller tributaries.
Highlights
The population viability of a fish species is entirely dependent on its capacity to adapt its reproductive tactics to the primary environmental conditions or the new conditions brought about by anthropic activities
The reproductive tactics of fish are evaluated through multiple indicators, which are obtained from the morphophysiological and behavioral changes that occur in the populations, due to local and seasonal environmental conditions (Winemiller, 1989)
The reproductive indicators used in this study were sensitive and responsive, and showed morphophysiological changes that occurred in A. bifasciatus individuals collected for one year in the Jirau Alto River, a tributary of the Lower Iguaçu River Basin
Summary
The population viability of a fish species is entirely dependent on its capacity to adapt its reproductive tactics to the primary environmental conditions or the new conditions brought about by anthropic activities. Given the current scenario of multiple environmental impacts, many anthropic variables interfere with the homeostasis of the systems and, species fitness (Louiz, Ben-Attia, & Ben-Hassine, 2009), imposing an adaptive pressure on the reproductive tactics in order to ensure population viability. In this context, pollution is one of the many impacts faced by native species (Yamamoto et al, 2016), in addition to the changes in watercourses that generally occur as a result of dams (Weber et al, 2013; De Fries, Rosa, Silva, Vilella, & Becker, 2018)
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