Statistical analyses were carried out using the SAS Release 9.4
software Survival and the cumulative
survival probability in experiment 1 were determined by the Kaplan–
Meier method. A log-rank test was performed to compare the difference
in survival time between groups. A Cox proportional hazard model was
used, with the water tanks as a covariate factor, to test for the possible
influence of the different water tanks on the survival rates.