Does reservoir age influence reproductive tactics in opportunistic fishes? An analysis of Astyanax minor reproduction in water supply reservoirs of southern Brazil.

Autor: Oliveira, Elton C., Muelbert, Adriane E., Silva, Juliano P. A., Ghisi, Nédia C., Fávaro, Luís F.
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Zdroj: Lakes & Reservoirs: Research & Management; Sep2013, Vol. 18 Issue 3, p247-258, 12p, 3 Charts, 6 Graphs, 1 Map
Abstrakt: The goal of this study was to assess the reproductive tactics of the 'lambari tetra' (Astyanax minor) in two reservoirs of different age (Irai Reservoir = 5-6 years old; Passaúna Reservoir = 17-18 years old), both being located in the same geographical region in southern Brazil. Sampling took place monthly from July 2006 to June 2007 in both reservoirs. Collected specimens were identified and their morphometric data measured. The gonads were macroscopically and microscopically analysed. Gonadosomatic Index (GSI) and condition factor results indicate there was a higher reproductive investment in Passaúna Reservoir for both sexes, although with lower total condition. The occurrence of partially spawned ovaries allowed the characterization of partial spawning in both reservoirs. Higher growth rates and the largest individuals were found in Passaúna Reservoir for both sexes, according to length-weight relationships and length class distributions. Significant seasonal sexual rate differences were only detected in Passaúna Reservoir, with male predominance. Total length explained just a small fraction of GSI variability of mature females and males, supporting the hypothesis of local factor influence. It was concluded that this species uses distinct reproductive tactics in each of the two studied reservoirs and that these tactics seem to be reflective of environmental stability. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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