Effects of growth rates on the otolith increments deposition rate in capelin larvae (Mallotus villosus)

Otolith microstructure analysis was applied to known age capelin larvae (Mallotus villosus) in order to examine the formation of daily increments. In two validation experiments, newly hatched yolk sac larvae were stocked into eight 10 m3 plastic bags where environmental conditions were kept as natural as possible. The bags were terminated after 35-79 days, the surviving larvae were collected and the otoliths were analysed. Survival in the bags varied between 39 - 71% with average individual length growth rates of 0.25 mm day-1. The ages of most larvae were underestimated and the accuracy in age estimation was generally low. Highest accuracy was found for fast growing larvae. On average, the larvae started to form increments about 12 days after hatching, and the increment width increased with age and/or length of the larvae. Larvae showing low body growth rates had fast otolith growth relative to body length.