Can the regression model for trout from the tributaries predict future migratory behaviour of trout from the mainstream?
The ability of the highly significant logistic regression model obtained from the tributary-collected trout sampled in mid-April to predict future migratory behaviour in the independent group of trout caught in early April in the mainstream (River Lille Aa) was explored. The regression curve for the tributaries is included for comparison in Fig. 2. A threshold probability of migration was used to predict the behaviour of the mainstream individuals as either future migrants, comprising fish with probabilities of migration higher than or equal to the threshold, or future residents, consisting of fish with probabilities of migration lower than the threshold. Predicting migration The effect of changing the threshold probability of migration on the ability of the logistic regression model to predict future migration is illustrated in Fig. 4. Setting the threshold probability at 0, i.e. predicting all individuals as future migrants, resulted in a predicted number of migrants equal to 104. Th
