Scientia Marina, Vol 62, No 3 (1998)

Approaches to otolith age determination: image signal treatment and age attribution


https://doi.org/10.3989/scimar.1998.62n3247

Beatriz Morales-Nin
Institut Mediterrani d´Estudis Avançats, CSIC/UIB, Spain

Antoni Lombarte
Institut Mediterrani d´Estudis Avançats - Institut de Ciències del Mar (CSIC), Spain

Beatriz Japón
Institut de Ciències del Mar (CSIC), Spain

Abstract


Population studies of fish depend upon correct age estimates. However ageing from otoliths is often a subjective activity, based on experience. To produce more objective and reproducible results, image analysis systems for semi-automatic otolith reading are being developed. We propose determinig the daily growth and annual structures in each otolith by means of Fourier analysis of the luminous signal, after filtering the high frequencies by means of a moving threshold. A new approach using 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 increment widths.

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