Environmental manipulation on Astyanax altiparanae out-of-season spawning

ABSTRACT This study aimed to evaluate the effect of manipulating hours of light and water temperature in some important reproductive parameters for Astyanax altiparanae fish farming during winter. The experiment was conducted from July 3rd to August 28th 2013 (57 days), and two groups of 32 couples of fish (G1 and G2) were used. On G1, hours of light and water temperature were not controlled; on G2, otherwise, these variables were manipulated in order to achieve similar conditions to those observed in spring. Every 14 days, eight couples of each group were hormonally induced with carp pituitary gland extract, and eggs were collected after semi-natural spawning. The percentage of females from G2 that spawned was higher than G1 (81.25 vs. 9.38%), the same trend was observed for a number of eggs produced per female (G1: 2,976.57 ± 1,085.71; G2: 8,471.14 ± 860.08). The G2 ovaries presented a higher incidence of primary growth oocytes and post-ovulatory follicles whereas G1 ovaries had more atretic follicles. Economic analysis showed that operational profit from eggs and larvae production on G2 was higher than on G1, as well as the gross margin. In conclusion, the results showed that environmental manipulation might improve reproduction management practices extending eggs and larvae production during the natural non-breeding season. Further studies are necessary to determine more appropriate facilities to be used by farmers in large scale, as well as management protocols to ensure the survival of post-larvae.