Tracking Eels Across the Oceans
Tagging
Over the past few years, scientists from NIWA and the University of Tokyo have tried tracking New Zealand longfin eels to their spawning grounds, using a system of electronic tags. The tags record and store environmental information along the journey. Data recorded includes water temperature and day-length figures, and the times of sunrise and sunset; the latter can be used to calculate the latitude and longitude of an eel each day and map the track of the migrating fish.
Tags are attached to the eels using a tether. At a specified date and time, the tag actively corrodes the pin to which the tether is attached, releasing the tag from the animal. The tag then floats to the surface and transmits summarised information to an Argos satellite.
