Artificial fertilization of tambaqui oocytes (Colossoma macropomum, Cuvier, 1818) at different waiting times and cooled semen without the use of cryoprotectants

Abstract

Artificial propagation of tambaqui (Colossoma macropomum) is fundamental for aquaculture, but the optimization of fertilization timing, especially oocyte viability time post-extrusion, still presents challenges. Therefore, the objective of this study was to evaluate the effects of different waiting times (15, 30, 45, 60, and 80 minutes) on the fertilization of tambaqui oocytes, using chilled semen (4 °C) without cryoprotectants. The study was conducted on a commercial scale, where male and female broodstock were hormonally induced. After extrusion, the oocytes were held and fertilized at the different sampling times with chilled semen. Fertilization rates were evaluated 6 hours post-insemination, under monitored water quality conditions, which remained adequate (average temperature of 28 °C). The highest fertilization rates were observed at 15 min (87.02%) and 30 min (86.80%). After 30 minutes, a progressive and significant decrease in fertilization efficiency was observed for the remaining times. It is concluded that, although tambaqui oocytes can withstand a waiting period of up to 80 minutes, the fertilization rate decreases after 60 minutes. The study defines an optimal time window, up to 30 mins for fertilization with chilled semen; after 45-60 min, the fertilization rate begins to drop. This information is crucial for optimizing or maximizing reproductive success in tambaqui larviculture.