Résumé
The spawning areas of the Atlantic freshwater eels were discovered about a century ago by the Danish scientistJohannes Schmidt who after years of searching found newly hatched larvae of the European eel, Anguillaanguilla, and the American eel, Anguilla rostrata, in the southern Sargasso Sea. The discovery showed thatanguillid eels migrate thousands of kilometers to offshore spawning areas for reproduction, and that theirlarvae, called leptocephali, are transported equally long distances by ocean currents to their continentalrecruitment areas. The spawning sites were found to be related to oceanographic conditions several decadeslater by German and American surveys from 1979 to 1989 and by a Danish survey in 2007 and a Germansurvey in 2011. All these later surveys showed that spawning occurred within a restricted latitudinal range,between temperature fronts within the Subtropical Convergence Zone of the Sargasso Sea. New data andre-examinations of Schmidt’s data confirmed his original conclusions about the two species having someoverlap in spawning areas. Although there have been additional collections of leptocephali in various parts ofthe North Atlantic, and both otolith research and transport modelling studies have subsequently been carriedout, there is still a range of unresolved questions about the routes of larval transport and durations of migration.This paper reviews the history and basic findings of surveys for anguillid leptocephali in the North Atlantic andanalyses a new comprehensive database that includes 22612 A. anguilla and 9634 A. rostrata leptocephali, whichprovides a detailed view of the spatial and temporal distributions and size of the larvae across the Atlantic basinand in the Mediterranean Sea. The differences in distributions, maximum sizes, and growth rates of the twospecies of larvae are likely linked to the contrasting migration distances to their recruitment areas on eachside of the basin. Anguilla rostrata leptocephali originate from a more western spawning area, grow faster, andmetamorphose at smaller sizes of <70mm than the larvae of A. anguilla, which mostly are spawned further eastand can reach sizes of almost 90 mm. The larvae of A. rostrata spread west and northwest from the spawningarea as they grow larger, with some being present in the western Caribbean and eastern Gulf of Mexico. Larvaeof A. anguilla appear to be able to reach Europe by entering the Gulf Stream system or by being entrainedinto frontal countercurrents that transport them directly northeastward. The larval duration of A. anguillais suggested to be quite variable, but gaps in sampling effort prevent firm conclusions. Although knowledgeabout larval behaviour is lacking, some influences of directional swimming are implicated by the temporaldistributions of the largest larvae. Ocean–atmosphere changes have been hypothesized to affect the survivalof the larvae and cause reduced recruitment, so even after about a century following the discovery of theirspawning areas, mysteries still remain about the marine life histories of the Atlantic eels.