Abstract
Reproductive activity of ‘piau gordura’ Leporinus piau was studied using biometric, macroscopic and microscopic analysis. A total of 74 specimens of L. piau were collected quarterly from January to December 2005 in a small deactivated hydropower plant located at Jorge Pequeno Stream and preserved in a fixative solution until analysis. The alterations after fixation were evaluated. The stages of gonadal maturation were determined by histology and gonadosomatic index (GSI). The females and males in the spawning capable and regressing stage were registered from October to December. L. piau is total spawning and the HSI (hepatossomatic index), SRI (stomach repletion index) and CFI (coelomic fat index) of females and males did not showed a statistical difference. However they were numerically different between the stages of maturation. For both sexes, the smallest specimens captured during the reproductive activity have measured around 8.3 cm in total standard. The length-weight relationship observed for the parameter ‘b’ was 3.01 and the parameter ‘a’ was 0.02. This study demonstrates the importance of Jorge Pequeno Stream in the reproductive activity of migratory fish in the upper São Francisco river.
Highlights
Reproductive behavior varies greatly in teleost fishes depending on the environmental conditions and on reproductive strategies
In iteroparous species, spawning pattern will depend on the rhythm of ovulation: (a) total spawning which the oocytes are released during a short period of time, and (b) multiple spawning where oocytes are released in several batches throughout the spawning season (JALABERT, 2005; LUBZENS et al, 2010)
Specimens were fixed in 10% formaldehyde solution and after dissection the following parameters were recorded: standard length (SL), body weight (BW), sex, gonad weight (GW), liver weight (LW), stomach weight (SW) and coelomic fat weight (CFW)
Summary
Reproductive behavior varies greatly in teleost fishes depending on the environmental conditions and on reproductive strategies. In iteroparous species, spawning pattern will depend on the rhythm of ovulation: (a) total spawning which the oocytes are released during a short period of time, and (b) multiple spawning where oocytes are released in several batches throughout the spawning season (JALABERT, 2005; LUBZENS et al, 2010). The variation of biological indexes during the reproductive cycle represents the way the species uses the energetic resource from the environment, defining its life history strategies (VAZZOLER, 1996). Life history parameters such as sex ratio may vary between populations of a species and temporally within population (MORGAN, 2008). Length-weight relationships are useful in determining weight and biomass when only length measurements
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