Genotype by environment interaction across time for Nile tilapia, from juvenile to finishing stages, reared in different production systems

Abstract

Nile tilapia is one of the most important fish for aquaculture worldwide and it is produced under many different environmental and system conditions. Even though genotype by environment interaction (GEI) can arise due to many factors, most studies with Nile tilapia have focused more on the effects of water quality parameters and pound or cage systems. There is also lack of knowledge on GEI between fish at different ages, as before and after reaching sexual maturity. Therefore, the objective of the current work was to evaluate the magnitude of GEI on body weight in Nile tilapia raised in biofloc technology (BFT), cage and recirculation aquaculture systems (RAS) from 100 to 350 days of age. To evaluate the temporal trend of GEI a multi-trait random regression model (MTRRM) with age as random regression covariable was employed. Higher values of heritability estimates were found around 225 days, with a maximum of 0.4 for BW at RAS. Estimated genetic correlations between BFT and RAS were above 0.7 for almost any combination of ages evaluated. On the other hand, genetic correlations between Cage at ages below 150 days and either BFT or RAS at any other age were positive but lower than 0.6. Results for the estimated ratio of the indirect by direct response to selection were lower for selection performed at very younger ages whereas the desired response is for older ages. However, if the selection is performed around 225 days for either BTF or RAS this ratio is above 0.8 for most of the situations considered. In conclusion, MTRRM is shown to be a powerful statistical tool to assess changes across the time for genetic parameters of interest, such as covariance, correlations, and heritability. Also, the GEI across the three production systems considered was found to be dynamic across the ages evaluated, with stronger effects between Cage and both BFT and RAS if the selection is performed prior to 150 days of age.