# Log-transformed variance from individual growth curves as a potential indicator of resilience in Nile tilapia Oreochromis niloticus

## TL;DR

This study explores how log-transformed variance in growth can indicate resilience in Nile tilapia under different pond conditions.

## Contribution

The study introduces LnVarind as a novel indicator of resilience in Nile tilapia for breeding programs.

## Key findings

- Heritability for LnVarind was higher in non-aerated ponds (0.28) than in aerated ponds (0.06).
- Genetic correlations between LnVarind and growth traits were negative in both pond types.
- A moderate genetic correlation (0.50) between LnVarind in aerated and non-aerated ponds suggests shared genetic basis.

## Abstract

The ability of the animal to cope with environmental changes may be measured by log-transformed variance of deviations from expected weights (LnVar). We calculate LnVar by fitting the expected individual growth curve based on longitudinal weights (LnVarind) of Nile tilapia that were grown in either an aerated or a non-aerated freshwater pond. We estimated genetic parameters for LnVarind in Nile tilapia, the genetic correlation between LnVarind and growth and the genetic correlation for LnVarind between aerated and non-aerated pond. The heritability estimate for LnVarind (0.28) in the non-aerated pond was higher than in aerated pond (0.06). In the aerated pond, genetic correlations of LnVarind were − 0.44 ± 0.23 with daily growth coefficient (DGC) and − 0.45 ± 0.24 with harvest weight (W5). In the non-aerated pond, genetic correlations with DGC and W5 were − 0.68 ± 0.12 and − 0.52 ± 0.17, respectively. These values suggest that selection for fish with high growth rate will reduce LnVarind. However, genetic correlation of LnVarind between aerated and non-aerated pond was 0.50, suggesting that genetic improvement in the aerated environment will reduce LnVarind in the non-aerated environment. Therefore, incorporating records from relatives in non-aerated pond is beneficial for breeding programs targeting this environment.