Deep-Sea Predator-Prey Dynamics Revealed by Biologging and eDNA Analysis

Abstract

At depths below 200 m, the pelagic deep sea comprises the largest, but least explored, part of the ocean. In this vast environment, animals are hard to find, and interactions among them are even harder to investigate (Robison, 2009). Climate change and industrial exploitation simultaneously impose increasing pressure on deep-sea ecosystems, leading to reduced ecosystem health and services at a global scale. Many of these changes occur outside of the range of human observation and are unrecognized so that effective conservation is limited. Such changes can include interactions between elusive and sometimes giant deep-sea predators such as cetaceans and their prey. The use of on-animal recorders has revealed that multiple species of cetaceans make extensive use of the deep sea, specifically the meso- (200–1,000 m depth) and bathypelagic (1,000–4,000 m depth) zones, to hunt for diverse, often cephalopod-dominated prey populations (Tyack et al., 2006). Because their dives to remote depths are energy consuming, the prey reward needs to be substantial to make the dives profitable. Thus, we expect that deep-diving cetaceans selectively target distinct foraging zones that hold specific prey communities to optimize their foraging performance.