Analysis of Otolith Microstructure to Determine Growth Histories in Larval Cohorts of a Tropical Herring (Herklotsichthys castelnaui)

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Abstract
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 temperatures series were modelled for each cohort using time series analyis. 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.