Physical and behavioural controls on the oceanic distribution and migration of leptocephali

• Published in: Journal of Fish Biology
• Main Author: McCleave, J. D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1993
• Subjects: North Atlantic
• Online Access: http://dx.doi.org/10.1111/j.1095-8649.1993.tb01191.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1095-8649.1993.tb01191.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1095-8649.1993.tb01191.x

A pelagic, long‐lived leptocephalus is common to families of eels, whether the juveniles inhabit the open ocean, shelf waters, or estuarine and fresh waters. Successful leptocephali of continental species must leave the open ocean, while those of oceanic species must avoid advection from the open ocean. The movements of leptocephali of migratory species should be considered conceptually as a dispersal‐mortality problem. On the basis of the distribution of small (recently hatched) leptocephali, the Sargasso Sea in the western North Atlantic Ocean is identified as a spawning area for the catadromous American and European (angui llid) eels, western Atlantic shelf‐dwelling Conger eels, and numerous oceanic species, e.g. Nemichthys scolopaceus, Serri voiner beanii, Derichthys serpentinus and Nessorhamplms ingolfianus . Within the Sargasso Sea, the Subtropical Convergence Zone is a narrow latitudinal zone where northern and southern bands of thermal density fronts occur, especially in winter. Spawning of the two catadromous eels and the two western conger eels seems to be limited to areas in or south of the southern band of fronts, where southern Sargasso Sea water occurs. Spawning of most of the oceanic species occurs on both sides of these fronts. Some feature of the frontal zone or the southern waters, such as odour, may serve as a signal to trigger cessation of migration and initiation of spawning in catadromous eels. Thus the source of leptocephali of the two species of Anguilla may be zotially restricted. Because of confluence of water into fronts and resulting eastward jet‐like currents, fronts may be sinks for a portion of the leptocephali of numerous shelf‐dwelling species, which may be advected away from suitable juvenile habitat. The size distributions of leptocephali suggest that gyres in the southwestern Sargasso Sea, an Antilles Current, and the Florida Current north of the Bahamas are routes of exit for anguillid and congrid eels. Shorter larval duration and more northerly spawning facilitates retention ...