Heritable variation in swimming performance in Nile tilapia (Oreochromis niloticus) and negative genetic correlations with growth and harvest weight

Abstract

Nile tilapia is predominantly produced in smallholder ponds without aeration. We hypothesize that Nile tilapia with high oxygen uptake efficiency (O₂UE) may perform better under these conditions than Nile tilapia with low O₂UE. Critical swimming speed (U_crit, in cm s⁻¹) is a potential indicator for O₂UE. Our objectives were to estimate variance components for U_crit and fish size at swim testing early in life, and genetic correlations (r_g) between U_crit with harvest weight (HW) and daily growth coefficient (DGC) later after grow-out in a non-aerated pond. Substantial heritability was found for absolute U_crit (0.48). The estimated r_g between absolute U_crit and fish size at testing were all strong and positive (range 0.72–0.83). The estimated r_g between absolute U_crit and HW, and absolute U_crit and DGC were − 0.21 and − 0.63 respectively, indicating that fish with higher absolute U_crit had lower growth in the non-aerated pond as compared to fish with lower absolute U_crit. These results suggest a juvenile trade-off between swimming and growth performance where fish with high U_crit early in life show slower growth later under conditions of limited oxygen availability. We conclude that U_crit in Nile tilapia is heritable and can be used to predict growth performance.