Triennial migration and philopatry in the critically endangered soupfin shark (Galeorhinus galeus)

Globally, one-quarter of shark and ray species is threatened with extinction due to overfishing. Effective conservation and management can facilitate population recoveries; however, these efforts depend on robust data on movement patterns and stock structure, which are lacking for many threatened species, including the Critically Endangered soupfin shark (Galeorhinus galeus), a circumglobal coastal-pelagic species.

Using passive acoustic telemetry, we continuously tracked 34 mature female soupfin sharks, surgically implanted with coded acoustic transmitters, for seven years via 337 underwater acoustic receivers stationed along the west coast of North America. These sharks and an additional six were also externally fitted with spaghetti identification tags. Our tagging site was a shallow rocky reef off La Jolla (San Diego County), California, USA, where adult females were observed to aggregate every summer.

Tagged soupfin sharks were highly migratory along the west coast of North A...