Early post-larval growth and otolith patterns in the eel Anguilla anguilla

The length, weight, development and otolith growth of glass eel and elver were examined from their first arrival in the estuary through the summer during their upstream migration into freshwater. The level of pigmentation developed significantly from November to August, while there were significant decreases in both length and weight from February to July. No relationship could be found between radius of otolith and date of sampling, pigment stage, eel length or weight in the early months of the year indicating that sea growth of the larva and otolith growth were not directly linked. From May to August, otolith growth was significantly related to the developing pigmentation and to date of sampling, but not to either length or weight of the migrating elver, suggesting that over this time period otolith growth continued independently of somatic growth. Growth outside the first winter ring of the otolith, therefore, is not equivalent to somatic growth. Back-calculation based on an assumption that there is no somatic growth in the first freshwater summer would give a more accurate estimate of the growth curve although the differences are probably not significant for eel management. (C) 2003 Elsevier Science B.V. All rights reserved.