Timing of metamorphosis and larval segregation of the Atlantic eels Anguilla rostrata and A-anguilla, as revealed by otolith microstructure and microchemistry

Otolith microstructure and microchemistry were examined in juveniles of Ame rican (Anguilla rostrata) and European (A. anguilla) eels. Otolith incremen t width markedly increased from age 132 to 191 d (156 +/- 18.9 d; mean +/- SD) in A. rostrata and 163 to 235 d (198 +/- 27.4 d; mean +/- SD) in A. ang uilla, both of which were coincident with drastic decreases in otolith Sr:C a ratios, suggesting that metamorphosis from leptocephalus to glass eel beg an at those ages in each species. The duration of metamorphosis was estimat ed to be 18 to 52 d from otolith microstructure, for both species studied. Ages at recruitment were 171 to 252 d (206 +/- 22.3 d; mean +/- SD) in A. r ostrata and 220 to 281 d (249 +/- 22.6 d; mean +/- SD) in A. anguilla. In t hese two species, positive linear relationships were found in ages between the beginning of metamorphosis and recruitment, suggesting that early metam orphosing larvae recruited at younger ages. Duration of the leptocephalus s tage to recruitment in A. anguilla was about 40 d longer than that in A. ro strata. The geographical segregation between the two species in the Atlanti c Ocean seems to be involved in the differences in the duration of the lept ocephalus stage (age at metamorphosis).