LAUSR

Abstract Animal individuality is proposed to describe individual differences in behavior. Individuals may exhibit consistent differences in behavioral traits within a population, and these traits are heritable. It has also been known that animal individuality can be attributed to both genetic and environmental effects. We previously observed the presence of bold individuals (BI) and shy individuals (SI) in olive flounder (Paralichthys olivaceus). However, the individuality distribution and the behavioral phenotype of offspring with different individualities remain unclear. In this study, the temperature and acidity challenges of larvae at 25 days-post-hatch (DPH) and juvenile (50 DPH) of bold and shy flounder offspring were investigated at pH = 7.3, 7.7, 8.1 and temperature at 4, 18, 28 °C. On 25 DPH, bold offspring (BO) showed higher survival rates with acidity at pH = 7.3 and 4 °C challenge. Three behavioral phenotypes (bold, middle and shy individuals, BI, MI and SI) were observed in both juvenile (8 MPH) bold and shy flounder offspring. The percentage of SI offspring from the shy maternal line (SS) was higher than BI offspring from the bold maternal line (BB) (0.75 vs. 0.58). BI from both BO (BB) and SO (SB) were more motivated to feed and active during net confinement than SI (BS and SS). Furthermore, BB and SB exhibited higher metabolic rates and actively responded to predator stressor, while BS and SS showed a divergent tendency. However, the metabolism of the offspring seemed to be partially affected by their maternal line. Taken together, our study indicates that screening of animal individuality in population would improve animal welfare and increase the output efficiency of flounder in aquaculture.