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

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 < 0.01). The linear effect of light intensity was not significant (P > 0.05) but the quadratic effect had a significant effect on the fry survival rate (P < 0.01). The interactions between temperature and light intensity on fry viability were not significant (P > 0.05). A model equation of the survival activity index (SAI) of temperature and light intensity was established, with r(2), Adjusted r(2) and Predictive r(2) values as high as 0.9832, 0.9665 and 0.898, respectively. By applying the optimisation technique, the optimum conditions for viability were 26 degrees C and a light intensity of 10001x, at which the SAI was 9.53 and the desirability value was as high as 0.948.