INTERPRETATION OF GEOGRAPHIC-VARIATION IN SIZE OF AMERICAN EEL ANGUILLA-ROSTRATA ELVERS ON THE ATLANTIC COAST OF NORTH-AMERICA USING THEIR LIFE-HISTORY AND OTOLITH AGING

Elvers of the American eel Anguilla rostrata (LeSueur) were collected from 6 estuaries ranging in location from Haiti to the U.S. Atlantic c oast and north to Canada during the fishing season in 1995. Time of me tamorphosis from leptocephalus to glass eel was determined from otolit h daily growth increments, in which the increment width and strontium/ calcium ratios changed drastically. Mean age of the leptocephalus at m etamorphosis (T-m) was 189 to 214 d, while age upon arrival at the est uaries (T-t) was 220 to 284 d. Time from metamorphosis to arrival at t he estuaries (Tt-m) was 32 to 80 d. Faster-growing and earlier-metamor phosing leptocephali migrate to the mid-point of the sampling range, b ut slower-growing and delayed-metamorphosis leptocephali occur in both the southern and northern ranges. Duration of the glass eel phase was longer in the north than in the south, while glass eels grew faster i n the south than in the north. Mean total length of elvers at entry to the estuaries increased significantly from 48 mm in the south to 60 m m in the north. Geographic variation in elver length was due to durati on of the glass eel phase rather than timing of metamorphosis from lep tocephalus to glass eel, because elver length was significantly positi vely correlated with Tt-m (r = 0.79, p < 0.01) but not significantly c orrelated with T-m (p > 0.05). Duration of the glass eel phase was inf luenced by the coastal oceanographic conditions.