Contrasting migratory strategies of marine and freshwater eels

Abstract

Eels of the order Anguilliformes are very diverse in their behavior and in the habitats they use, but all species spawn in the ocean and have a leptocephalus larva, The catadromous eels of the Anguillidae are famous for making long spawing migrations from freshwater to the open ocean. In contrast, recent studies of tropical anguillids indicate that they appear to have much shorter spawning migrations and potentially year-round spawning. However, the most widespread tropical eel, Anguilla marmorata, appears to have a northern subpopulation that has a spawning migration similar to the temperate species Anguilla japonica and recruits as far north as southern temperate areas of Japan. A similar pattern is emerging for marine eels that live in coastal or coral reef areas, with evidence that some species of congrid eels in temperate regions make relatively long spawning migrations, but tropical/subtropical species appear to spawn in shallow water or make shorter spawning migrations to the shelf break or deep water, Thus, the latitudinal range and presumably the environmental conditions in the coastal waters surrounding the growth habitats of eel species may be important factors determining the distance of the spawning migrations of eel species, as a result of the unique ecology of their leptocephalus larvae.