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Growth and mortality of post-metamorphosed plaice were studied by means of daily increments in the sagittal otoliths. The Gompertz model was the best fit to length-at-age data and there were no significant differences between length-at-age and back-calculated lengths. The microstructure pattern of the otoliths at metamorphosis was also used to estimate hatching and settlement distributions. Differential growth and mortality occurred among sub-cohorts; growth rates and mortality were higher in fish that settled earlier. In 1986, the best survival was for a sub-cohort settling in late May to early June. In contrast, in the warmer season of 1987, survival was highest for the second and third sub-cohorts settling in late April and mid May.

A new approach to break down fisheries length-frequency data into age groups, using information on relative growth rate with age, is introduced. The method was verified with data used to test previously published methods. Good starting values for the mean lengths of the fish with age in the statistical analysis of distribution mixtures are often critical. Incorporation of relative growth rate information significantly improves the precision of the ageing procedure even when starting values are less accurate.