Year-round spawning by a tropical catadromous eel Anguilla bicolor bicolor

Abstract

Remarkably little is known regarding the spawning area, spawning ecology or life history after recruitment of tropical eels to coastal areas across the Indo-Pacific region. In contrast, eel species in temperate areas, including the American, Australasian, European and Japanese eels, are known to have well-defined spawning and recruitment seasons, and spawning migrations generally take place during autumn months. Using monthly collections and analyses of both gonadosomatic index and gonad histology, we determined that the final stage of maturation for seaward spawning migration occurred throughout the year and year-round spawning and recruitment were evident in the tropical coastal areas from the open ocean. This non-seasonal spawning ecology is notably different from that of temperate catadromous eels. The unique year-round spawning ecology of Anguilla bicolor bicolor may facilitate mating between adult eels from different year classes (cohorts) or from different habitats