Evidence for spatial and temporal resource partitioning of sharks at Roca Partida, an isolated pinnacle in the eastern Pacific

In the open ocean, cycles in vertical movement of predators in response to physical environments and distributions of prey are fundamental to the behavior of predatory species. Multi-species assemblages of sharks provide an ideal venue to study habitat partitioning by upper-level predators in the marine environment. We conducted a pilot study, using acoustic telemetry, to examine the vertical habitat use of four species of sharks at Roca Partida, a small island within the Revillagigedo Archipelago. Roca Partida is a very small (length 100 m) but highly productive pinnacle in the open ocean and may represent an “oasis” for large marine predators. Individuals of four species, the dusky, Galapagos, silvertip, and whitetip reef shark, were detected at Roca Partida for varying periods over two and a half years, exhibiting high levels of residency. Some sharks stayed on only one side of Roca Partida over this entire period of time. We found evidence for vertical habitat partitioning between species which may represent resource partitioning, although there was some intraspecific variability. Our preliminary data suggests that Roca Partida may be an ideal location to study niche partitioning amongs sharks due to limited habitat availability but high productivity.