Patterns and drivers of the diving behavior of large pelagic predators

Abstract

Many large pelagic predators, including shark, tuna, and billfish, periodically dive to deep oceanic layers, connecting the surface and mesopelagic ecosystems. However, the patterns and drivers of deep dives across species remain poorly understood. To close this gap, we conduct a meta-analysis of the diving behavior of 24 pelagic predator species from the global ocean, resulting in 671 independent diving depth estimates from 87 tagging studies. Our analysis reveals consistent large-scale patterns in diving depths, with predators diving deeper offshore and during the day, and shallower closer to the coast and during the night. Deep diving species show similar diving depths during the night, with deeper dives for sharks, and shallower dives for tuna and swordfish. These patterns are reversed during the day, widening the gap between day and night vertical ranges for these groups. In contrast, shallow diving species show smaller variations between day and night dives, with sharks diving slightly deeper on average, followed by tuna and billfish. Correlations with co-located environmental variables suggest an important predictive role for proxies of prey abundance and light availability, as well as variables that influence physiology, such as oxygen and temperature. These relationships are more robust for deep divers during the day, and shallow divers at night. Our analysis highlights the value of tagging observations for the development of a mechanistic, quantitative characterization of vertical habitat use of large marine predators and its environmental constraints.