Improving the precision of ageing assessment for long rough dab by using digitised pictures and otolith measurements
Journal : Fisheries Research , vol. 60 , p. 53–64 , 2003
Publisher : Elsevier
International Standard Numbers
Printed : 0165-7836
Electronic : 1872-6763
Publication type : Academic article
Issue : 1
DOI : doi.org/10.1016/S0165-7836(02)...
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Otoliths of long rough dab (Hippoglossoides platessoides) were analysed using both stereomicroscope and digitised pictures. Approximately 400 fish were aged twice by each technique. The use of digitised pictures gave consistently higher precision of age-determinations. This was shown both graphically and by use of the coefficient of variation. Age determined from digitised pictures was generally higher than that determined by using a stereomicroscope. This was particularly true for older specimens. For some individuals a change in the zoning pattern in the otoliths was observed. The occurrence of these changes was not closely correlated with the visually determined maturation index. For fish of similar size otolith radius was correlated with age. The growth rate also influenced otolith morphology. This additional information is incorporated in the outline of an objective age-determination suggested by this study.