Use of deformable template for two-dimensional growth ring detection of otoliths by digital image processing: Application to plaice (Pleuronectes platessa) otoliths

Today, most computer-assisted age reading software is limited to one-dimens ional processing. Automated two-dimensional growth ring detection is closel y linked to the ability of image processing algorithms to perceive structur e continuity. By using deformable models, based on closed B-splines, it is possible to fit a shape to the image features using maximum or minimum crit eria according to the nature of translucent or opaque zones. Otolith edge c ontours were used as templates that were inflated from the core toward the edge in order to detect the growth zones. Template step sizes were modulate d by an a priori growth pattern in order to take into account the decrease in ring size. A reference test image set (n=102) of plaice otoliths, previously aged by o ne reader, was processed. For the first age groups, there was a total agree ment with reader estimates. Mean agreement with reader estimates for age gr oups 1-5 averaged 80% but decreased for age groups 6-8. Overall, age was si gnificantly underestimated by an average of -0.89 year. (C) 2000 Elsevier S cience B.V. All rights reserved.