The effects of temperature, river flow, and tidal cycles on the onset of glass eel and elver migration into fresh water in the American eel

Abstract

Anguilla rostrata elvers were collected in the Annaquatucket R., Rhode Island, and their otoliths extracted. Daily increments beyond the check mark formed upon entry into fresh water were counted and the date of freshwater entry was estimated. The effects of river temperature, difference between seawater and freshwater temperature, river flow and tidal stage on the number of elvers arriving on each date were estimated for six collection dates. At the earliest collection date (23 March), increasing river temperatures and reduced flow increased elver migration. At later dates (16 May‐12 June), tidal stage was the most important factor in determining the magnitude of elver migration.