APPROACHES TO OTOLITH AGE-DETERMINATION - IMAGE SIGNAL TREATMENT AND AGE ATTRIBUTION

Population studies of fish depend upon correct age estimates. However ageing from otoliths is often a subjective activity, based on experien ce. To produce more objective and reproducible results, image analysis systems for semi-automatic otolith reading are being developed. We pr opose determinig the daily growth and annual structures in each otolit h by means of Fourier analysis of the luminous signal, after filtering the high frequencies by means of a moving threshold. A new approach u sing spatio-frequential wavelet analysis is discussed for otolith age determination. The different readings of each otolith are standardised and weighted to obtain a combined age determination and vector of inc rement widths.