Student information

Hooi Ling did her thesis on fish welfare

Hooi Ling Khaw from Malaysia finished her EMABG thesis in summer 2009 at AgroParisTech in France.

Thesis title

Adaptation of fish to their environment: link between phenotypic plasticity and classical welfare measurement


Fish welfare for aquaculture species is still far from being achieved, especially in finding efficient welfare indicators.  Phenotypic plasticity is sensitivity of a genotype to environmental changes and it is a global trait that expects to be well integrative with all aspect of life conditions.

The objectives of this study were to determine genetic basis of phenotypic plasticity, and its relationship with cortisol. Phenotypic plasticity was measured through coefficient of variation and environmental variance of body weight for rainbow trout clones. The plasma cortisol levels were obtained from blood sample of fish exposed to acute stress.  The plasticity results showed that B45 and B61 were clones with high sensitivity to environmental changes, and AP2 was clone with less sensitivity.

The significant clone effect obtained from ANOVA based on coefficient of variation indicated that phenotypic plasticity had genetic basis.  Based on result, cortisol had positive correlation with coefficient of variation and environmental variance, 0.70 and 0.61.

As a conclusion, with the genetic basis found in phenotypic plasticity, it is possible to select for plasticity and at the same time improve fish welfare. However, all the estimates in this study were obtained from clone population, which may not truly represent the original population.


Phenotypic plasticity, fish welfare, cortisol, clone, rainbow trout.