Transequatorial migrations by basking sharks in the western Atlantic Ocean

Area of Science:

• Marine Biology
• Ichthyology
• Conservation Science

Background:

• Basking sharks (Cetorhinus maximus) inhabit temperate oceans, with seasonal movements and mesopelagic dives previously observed.
• Their distribution was thought to be limited to temperate latitudes, with deep-water habitat use remaining unclear.

Purpose of the Study:

• To investigate the migratory patterns and habitat utilization of basking sharks beyond temperate regions.
• To determine if basking sharks exploit deeper, tropical waters and assess migratory connectivity.

Main Methods:

• Satellite archival tagging of basking sharks.
• Application of a novel geolocation technique to track movements.
• Analysis of dive profiles and habitat depths.

Main Results:

• Basking sharks undertake seasonal migrations from temperate feeding grounds to mesopelagic tropical waters.
• Tagged sharks traveled from New England to the Caribbean and South America, reaching the Southern Hemisphere.
• Sharks remained at mesopelagic depths for extended periods (weeks to months) in tropical areas.

Conclusions:

• Tropical waters do not impede migratory connectivity for basking shark populations.
• The findings necessitate global conservation strategies for basking sharks throughout their extensive migratory range.