High-speed chases along the seafloor put Bryde's whales at risk of entanglement

Abstract

Recent changes in the South African marine ecosystem and the introduction of an experimental octopus fishery have resulted in an unsustainably high rate of fatal Bryde's whale entanglements. Using suction-cup attached bio-loggers, we identified a previously undescribed feeding behavior used by Bryde's whales to catch prey, and this behavior may make them susceptible to entanglement and mortality in bottom-mounted fishing gear. As they chase down their prey, inshore Bryde's whales sprint and maneuver along the seafloor for extended periods of time, making multiple direction changes, and reaching extraordinarily high swimming speeds. These findings assisted in the implementation of mandatory changes to octopus fishing gear that have drastically reduced the number of entanglements. The novel finding that Bryde's whales use high-speed chases near the seafloor to catch their prey highlights the value of using species-specific, behavioral information for making conservation recommendations.