Sharks surf the slope: current updrafts reduce energy expenditure for aggregating marine predators

An animal’s energy landscape considers the power requirements associated with residing or moving through habitats. Within marine environments, these landscapes can be dynamic, as water currents will influence animal power requirements and can change rapidly over diel and tidal cycles.

In channels and along slopes with strong currents, updraft zones may reduce energy expenditure of negatively buoyant fishes that are also obligate swimmers. Despite marine predators often residing within high-current area, no study has investigated the potential role of the energetic landscape in driving such habitat selectivity.

Over 500 grey reef sharks (Carcharhinus amblyrhinchos) reside in the southern channel of Fakarava Atoll, French Polynesia. We used diver observations, acoustic telemetry, and biologging to show that sharks use regions of predicted updrafts and switch their core area of space use based on tidal state (incoming vs outgoing).

During incoming tides, sharks form tight groups a...