Fundamentals of Statistics contains material of various lectures and courses of H. Lohninger on statistics, data analysis and here for more.

Exercise - Estimation of fish weight from size

The following  interactive example  shows how to apply simple regression to estimate the weight of a fish from its dimensions. The data set FISHCATCH used in this example has been extracted from a publication about the Finnish fishing industry . Data concerning several species of perch has been collected.

Note: the interactive example above gives you a quick introduction. For more extensive calculations with the fish data, you may want to start up the  DataLab  . You should pay attention to setting up a regression model with more than one species envolved (hint: use an indicator variable for the various kinds of fish).