Otolith microstructure was used to characterize growth in five cohorts of larval Herklotsichthys castelnaui from Townsville, north eastern tropical Australia in spring/summer of 1987. Ontogenetic development of larval H. castelnaui is described, and is correlated with changes in otolith microstructure. Development of fin rays coincided with a period of rapid otolith and somatic growth. Otolith increment width and water temperature series were modelled for each cohort using time series analysis. Cross-correlation functions showed no detectable dependencies between increment widths and temperature. Length-at-age relationships were significantly different among cohorts. Repeated-measures analysis of variance was used to establish differences in increment spacing among cohorts. Measurement of otolith radii allowed back-calculation of absolute growth rates of cohorts over the first 30?d of larval life. Significant differences in growth trajectories were detected among cohorts. Data presented here suggest that growth may vary among cohorts separated by as little as 2?wk, and that these differences are detectable by otolith increment analysis.