Understanding Silver Eel Migration Behaviour at Sea: Insights from Field and Virtual Tracking

Anguillid eels are notorious for the remarkable migrations they undertake to oceanic spawning grounds after the onset of reproductive maturation in continental waters. Yet after over a century of research, most information surrounding their migration remains a complete mystery. Neither the exact location of the spawning ground nor the migration routes are known. In this study, two approaches were developed to try to elucidate the mystery of the oceanic migration of the American eel. The first one is actual tracking using miniaturized pop-up satellite archival tags fitted on 33 American eels released in coastal waters. It provided significant pieces of information regarding the behaviour of migrating eels such as diel vertical migrations and trajectories. The second and complementary approach is the development of a coupled biophysical particle-tracking model. Thousands of particles with various horizontal and vertical behaviors were tracked from coastal waters to the pop-up locations and their trajectories were compared to those revealed by the field experiments. It provided interesting insights into eels’ behaviours during the early phase of their marine migration.