Abstract
The use of otoliths to interpret early life history in fishes depends upon the assumptions that otoliths record past events accurately and consistently and that records of events in otoliths are continuous. Both the number of growth microincrements ( I ), and the radii ( R ,μm) of otoliths of American eel Anguilla rostrata , leptocephali increased linearly and highly significantly with leptocephalus body length ( L , mm), as expected on the above assumptions ( I , =2·29 L , − 5·75 and R , =1·05 L , + 12·02, r 2 ,=0·938 and 0·931, n , =20). In contrast, the number of increments and the radii of the leptocephalus growth zones of otoliths of glass‐phase American eels were not related to body length, and they were lower than predicted by the relationships developed for leptocephali. Thus, otoliths of American eels apparently violate one or both assumptions. Possibly, the margin of the otolith is resorbed during metamorphosis from leptocephalus to glass eel, perhaps as part of calcium metabolism as skeletal elements are being formed.