Spawning migration and larval dispersal of tropical Pacific eels (Anguilla spp.) in the centre of their distribution ranges

Abstract

It is unknown how many spawning areas exist for tropical South Pacific eels (Anguilla marmorata, A. megastoma, A. obscura) populating island archipelagos between Papua New Guinea and French Polynesia. They could spawn at single centralised eastern and western locations, implying long-distance migrations by some eels, or at several local spawning areas. Larval catches, morphological and genetic investigations, and tagging experiments have provided no unequivocal answer. In this study, A. marmorata and A. megastoma were tagged with pop-up satellite archival transmitters at Samoa, in the centre of their distribution ranges. Tags surfaced prematurely after 11 to 25 d, 91 to 345 km from the point of release. One A. marmorata and one A. megastoma came within 180 and 230 km, respectively, from where a small A. marmorata leptocephalus was caught north of American Samoa during a recent research cruise, suggesting that eels may spawn near the archipelago. Silver eels exhibited diel vertical migrations between 180 m during the night and more than 700 m during the day. At their upper migration depths, eels migrated towards increasing salinity and towards local eddies, raising the question of whether they may actively search for these oceanographic features. Up to 15% of virtual larvae released near Samoa were retained within local eddies and could have recruited back to the archipelago. The remaining larvae drifted as far as Fiji and the Cook Islands to the west and east, respectively. The exchange of leptocephali probably connects several local spawning areas throughout the South Pacific Ocean, causing genetic exchange among areas.