Note on otolith growth in elvers, Anguilla anguilla (L.), and the relative otolith size during somatic growth

Newly pigmented glass-eels were kept in a cold water quarantine, before being exposed to increased water temperature and weaned with cod roe and commercial dry feed. The otoliths started to grow before fish growth was observed. As a consequence, the relative otolith size increased. This increase was higher at higher temperature. During the first period with significant eel growth, no further change in the otolith/fish size ratio was observed. Initially, the otolith size was not correlated to fish size, but a positive correlation occurred in growing elvers. The results are discussed with reference to variation in relative otolith size of larger eels. As otoliths have frequently been used in back-calculation of previous eel size, further studies on factors determining otolith growth are suggested.