The filtering surfaces are gill rakers, horn-like structures lining the gill arches that comb plankton from the passing flow. Water enters the open mouth, exits through gill slits that nearly circle the head, and leaves its cargo of copepods behind. The shark cannot generate suction, so feeding rate is tied directly to swimming speed and prey density.
Basking sharks shed and regrow their gill rakers, and animals have been found in winter without a full set. This once supported the idea that the species hibernates on the seabed through the cold months.
Satellite tagging has largely dismantled that picture. Tagged basking sharks continue to travel through winter, often at depth and sometimes across ocean basins, including transatlantic movements and crossings of the equator. The species remains Endangered globally, and its very slow reproduction means that populations depleted by twentieth-century fisheries recover over decades rather than years.