Briefly, the fish were placed in a600-l tank connected to a controlled cooling water system and acclimated to 16 jC.
The temperature was lowered at a rate of 0.5 jC every 2 days, until it reached 8 jC and kept at that level until all fish died. Dead fish were collected once a day and a parameter termed ‘‘Cooling-Degree Days’’ (CDD) was calculated to quantify the empirical estimation of cold tolerance.
This parameter represents the sum of the days the fish survived multiplied by the differences between the daily temperature and the initial temperature (16 jC) foreach fish.