Combined effects of temperature and light intensity on the fry viability of Ussuri catfish Pseudobagrus ussuriensis

•The linear and quadratic effects of temperature had a significant effect on viability.•The linear effect of light intensity was not significant but the quadratic effect had a significant effect on survival rate.•The optimum conditions for viability were 26°C and 1000 lx were determined by applying the optimisation technique. The combined effects of temperature and light intensity on the viability of Ussuri catfish, Pseudobagrus ussuriensis, were evaluated using a central composite orthogonal quadratic design and the response surface methodology. The optimum experimental combination was also determined. The linear and quadratic effects of temperature had a significant effect on viability (P 0.05) but the quadratic effect had a significant effect on the fry survival rate (P 0.05). A model equation of the survival activity index (SAI) of temperature and light intensity was established, with r2, Adjusted r2 and Predictive r2 values as high as 0.9832, 0.9665 and 0.898, respectively. By applying the optimisation technique, the optimum conditions for viability were 26 ℃ and a light intensity of 1000 lx, at which the SAI was 9.53 and the desirability value was as high as 0.948.