Antarctic krill (Euphausia superba) distributions, aggregation structures, and predator interactions in Bransfield Strait

The Antarctic krill, Euphausia superba, is a major component of the Southern Ocean’s ecosystem. Limited high-resolution data on relative importance oceanographic processes behavioral responses krill at traditional predator foraging grounds constitutes obstacle in understanding krill-environment coupling and ecosystem-based management this resource. Aggregation structures interactions were investigated using active acoustic collected by WBAT echosounders deployed moorings two hydrographically different sites Bransfield Strait. Near Nelson Island, water flows from northwest to southeast while Deception Island influenced stronger net current velocities southwest northeast. Krill aggregations identified then classified three clusters swarm-identification algorithm hierarchical clustering aggregation morphological characteristics: density, mean depth, center mass, inertia, equivalent area, index, proportion occupied. A total 693 736 detected mooring close Islands. categories ranged high low densities, evenness, dispersion distributed throughout column. density distribution thickness are direction. majority observed dive profiles occurred over type with highest densities both Islands, within first 25 m heterogeneity potentially impacts strategies predator–krill hydrodynamically