Biogeophysical and physiological processes drive movement patterns in a marine predator.

Area of Science:

• Marine Biology
• Oceanography
• Fisheries Science

Background:

• Blue sharks (Prionace glauca) are abundant, widely distributed oceanic sharks heavily impacted by fisheries.
• Current understanding of Atlantic blue shark movement and vertical behavior is limited, hindering effective management.
• This study addresses knowledge gaps in blue shark ecology and movement patterns.

Purpose of the Study:

• To describe behavioral and ecological patterns of aggregating and migrating blue sharks.
• To compare observed patterns with existing Atlantic movement models.
• To inform sustainable management and stock assessment of blue sharks.

Main Methods:

• Utilized pop-up satellite archival tags on 23 blue sharks in the Northwest Atlantic.
• Employed statistical predictive regression models to analyze habitat use and environmental influences.
• Tracked movements exceeding 3700 km and analyzed depth use in relation to bathymetry, latitude, and oceanographic features.

Main Results:

• Blue sharks exhibited distinct depth use patterns during aggregation versus dispersal.
• Depth use off the continental shelf was significantly deeper with more frequent deep-diving.
• Sexual segregation was observed, with mature females undertaking long-distance migrations.

Conclusions:

• Vertical behavior and habitat use of blue sharks vary significantly by location and life stage.
• Sexual segregation during aggregation periods may increase vulnerability to exploitation.
• Findings augment Atlantic migration models and underscore the need for cooperative North Atlantic management.