Meandering swims mean some fish may start journey one breeding season, spawn the next, tracking data suggest
Storied spawning runs of European eels may not be an en masse push to a mating site. Roundabout routes may delay many eels so much that they miss the big event and have to wait to mate until next season.
The most extensive reconstructions of individual eel journeys challenge an assumption that Europe’s freshwater eels (Anguilla anguilla) migrate and spawn as a group, says behavioral ecologist David Righton of the Centre for Environment, Fisheries and Aquaculture Science in Lowestoft, England. Eels tagged for the study took so long on their various journeys that tags scheduled to pop off on April 1 — the expected peak of the spawning — found that none of 33 ocean-going eels had yet made it all the way to the Sargasso Sea mating grounds.
Calculating routes and speeds indicates that many eels were already too far off-track to reach the mass gathering that season without unrealistic