Expanded vertical niche for two species of pelagic sharks: depth range extension for the dusky shark Carcharhinus obscurus and novel twilight zone occurrence by the silky shark Carcharhinus falciformis

Abstract

Studying the behavior of pelagic sharks can be challenging due to the logistical difficulties of locating migratory individuals in the open ocean. This is further compounded by their rarity in certain ocean regions due to overfishing. The accessibility of deep-water basins in The Bahamas provides a unique model system for describing how pelagic sharks connect surface and deep ocean habitats through vertical behavior. Using custom deep-sea landers in The Bahamas, we provide novel depth data for two species of pelagic sharks: a depth range extension for the dusky shark at 767 m and novel occurrence at twilight zone depth for the silky shark at 470 m. These observations expand the vertical niche for these two species, suggesting that deep diving behavior is likely more common than previously thought and likely important for ecosystem connectivity.