Comparison of different models to predict the in situ embryonic developmental rate of fish, with special reference to white sucker (Catostomus commersoni)

We performed laboratory incubations of white sucker (Catostomus commersoni) eggs to determine (i) the incubation time to organogenesis, eyed egg, hatching, and swim-up phases at eight different temperatures (8.5-21.2 degrees C), and (ii) the best model to describe the relationship between these incubation times and temperature. Seven models (degree-day, power-law, Belehradek's equation, quadratic equation, first- and second-order exponentials, and a thermodynamic model) all gave comparable and highly significant fits to our data (R-2 > 0.90). We thus compared the in situ and predicted incubation times by (i) the degree-day model, because of its simplicity, and (ii) the thermodynamic model, because of its theoretical foundation. The degree-day model was at least as accurate as the thermodynamic model (overall mean difference between predicted and observed incubation times of 1.4 +/- 1.0 and 1.2 +/- 1.2 days for the thermodynamic and degree-day models, respectively). Given its high accuracy and simplicity of use, we conclude that the degree-day model should be used to predict the incubation times of white sucker. We also observed a synchronization of hatching in situ that suggested an influence of photoperiod in addition to that of water temperature.