Manejo e parâmetros genéticos de características reprodutivas de fêmeas de tilápia do nilo

Abstract

Although Nile tilapia is widely produced, the reproductive nature is characterized by asynchronous spawning becomes an obstacle to the constant supply of fingerling demand and the greater efficiency of the specie genetic improvement programs. Therefore, strategies that aim to reduce the consequences of this reproductive behavior must be verified. Thus, a better understanding of the genetic inheritance of reproductive traits, as well as alternatives aimed at the phenotypic selection of females that are able to spawn, can benefit genetic improvement programs that need a shorter interval between spawns to obtain a large number of families in short order space of time, as well as hatcheries that seek constancy and uniformity in the production of fingerlings. For this, the influence of two forms of phenotypic selection in 284 females of Nile tilapia of the varieties UFLA VERMELHA and UFLA CINZA were evaluated. Half were chosen to mate by visually checking the urogenital papilla and the other half after receiving massage on the urogenital papilla in the craniocaudal direction, to remove a sample of oocytes in order to visually determine their degree of maturation. These were classified as mature, maturing or atresia stage. The couples were evaluated weekly for the presence of spawning, when verified that, the following characteristics were evaluated: spawning success, female weight to spawn (PFD), days to spawn (DPD), spawning weight (PDD), number of eggs in 1gram of spawn (NEW), absolute fecundity (FA) and relative fecundity (FR). In addition, it was verified whether the visual evaluation method had an influence on the days for the female to spawn. The oocyte sampling process increased the days the females spawned. However, when only females that had their oocytes classified as mature were considered, the days to spawn between selection methods were similar. There was no significant difference between the different managements regarding the reproductive performance of females. In a second moment, the genetic parameters for PFD, DPD, PDD, NOVOS, FA and FR from the spawning of 172 tilapia females were estimated. The heritability estimates obtained were 0.21, 0.03, 0.36, 0.14, 0.02 and 0.26, respectively, indicating that selection was carried out using some of the reproductive performance characteristics as selection criteria, one can obtain genetic gain and improve the reproductive efficiency of the herd.