Discrepancies between otoliths of larvae and juveniles of the American eel: is something fishy happening at metamorphosis?

The use of otoliths to interpret early life history in fishes depends upon the assumptions that otoliths record past events accurately and consistentl y and that records of events in otoliths are continuous. Both the number of growth microincrements (I) and the radii (R, mum) of otoliths of American eel Anguilla rostrata leptocephali increased linearly and highly significan tly with leptocephalus body length (L, mm), as expected on the above assump tions (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 leptocephal us growth zones of otoliths of glass-phase American eels were not related t o body length, and they were lower than predicted by the relationships deve loped for leptocephali. Thus, otoliths of American eels apparently violate one or both assumptions. Possibly, the margin pf the otolith is resorbed du ring metamorphosis from leptocephalus to glass eel, perhaps as part of calc ium metabolism as skeletal elements are being formed. (C) 2000 The Fisherie s Society of the British Isles.