Development of a pressure-induced triploidy protocol and its effects on growth performance and fertility in tambaqui Colossoma macropomum (Cuvier, 1816)

We evaluated combinations of post-fertilization timing and shock duration using 8000 psi hydrostatic pressure to develop an efficient protocol for inducing triploidy in tambaqui Colossoma macropomum (Cuvier, 1816). Two trials were conducted. In the first (T1), newly fertilized eggs were exposed to 8000 psi for 120 s, initiated at 65 (T1.1), 95 (T1.2), 125 (T1.3), 155 (T1.4), 185 (T1.5), and 312 (T1.6) seconds post-fertilization (spf), with untreated eggs serving as control. All treatments produced high triploidization rates (>93%), but shocks applied at 65 and 95 spf (T1.1 and T1.2) resulted in higher fertilization (FGS >90%) and embryo survival indexes (ES >87%) than later treatments. Based on these results, a second trial (T2) optimized shock duration at 8000 psi: 65 spf for 60 s (T2.1) and 90 s (T2.2), and 95 spf for 60 s (T2.3) and 90 s (T2.4), with a control group. Triploidy rates were 56% in T2.1 and > 94% in T2.2–T2.4. FGS and ES were highest in T2.3 and T2.4. Growth evaluation of diploid (control; two ponds) and treated (combined T2 groups; two ponds) progenies reared in earthen ponds showed that triploids exhibited significantly greater body weight, height, and total and standard lengths during the first six months. Histological examination of 20-month-old progenies confirmed that triploids were infertile, whereas diploids reached sexual maturation. This study establishes a reliable 8000 psi pressure-shock protocol for producing sterile triploid C. macropomum , supporting its application in sustainable large-scale aquaculture.