a) Standard length of analysed O. korogwe, O. niloticus and O. korogwe × O. niloticus hybrids; b) Growth increment as a function of mean scale diameter, separated by species group; c) Growth increment as a function of standard length, separated by species group; d) Mean scale diameter as a function of standard length, separated by species group. In b–d, individual data points represent the predicted values from the linear model, fitted lines are calculated from fixed effect estimates and shaded areas represent 95% confidence intervals.