Reproductive performance of lambari (Astyanax altiparanae) in a seminatural system using different protocols

We evaluated lambari (Astyanax altiparanae) reproductive performance by administration of gradually increasing doses of analogue of salmon gonadotropin‐releasing hormone (sGnRHa). We performed two consecutive experiments applying six sGnRHa single doses in three replicates (ranging from 1 to 160 µg/kg) (Exp. 1) and three sGnRHa‐fractioned doses in four replicates (10% + 90% – 12 hr interval) (10, 100 and 1,000 µg/kg) (Exp. 2) in 6 months old breeders. In both experiments, 6 mg of Carp pituitary extract (CPE)/kg and saline solution (without hormonal therapy) were used as positive and negative controls, respectively. Reproductive performance was recorded for both experiments; and quantification of 17α‐20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) and prostaglandin F2α plasma levels and ovarian histological evaluations were introduced in Exp. 2. Using a single dose, the spawning rate was low and similar between all groups (from 0% to 20%). Using fractioned doses, the spawning rate of CPE (60%) was higher than other groups (from 10% to 25%), but similar to 1,000 µg of sGnRHa/kg (40%). 17,20β‐P increased at the final sampling regardless of treatment (including controls) or successful spawning, suggesting that the simple grouping of fish caused this increase. 17,20β‐P and PGF2α plasma levels did not explain ovulation failures in this species. CPE‐fractioned doses improved lambari ovulation and provided final maturation in all evaluated females; however, hormonal induction was not conditional for obtaining ovulation since spawning was registered in negative control. Concluding, CPE‐fractioned doses protocol can be applied to increase reproductive performance of this species.