Growth patterns in otoliths as an indication of daily growth variations of larval herring (Clupea harengus) from an experimental ecosystem
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Larval herring were released in a large outdoor basin four days after hatching and the mean growth in length and weight of the herring larvae and fry was monitored for 100 days. The food supply was estimated from weekly sampling of zooplankton. At termination of the experiment herring fry were collected and the width of the daily growth zones were measured in the otoliths of some of the herring fry. The mean zone width on a day to day basis mimiced the mean larval growth rate. As the variation in food supply determined the growth rate, there was also a close relation between mean zone width and the food supply. A method for measuring the zone widths by means of a digitazing board is described.