Why do basking sharks swim with their mouths open?
The basking shark is usually seen swimming with its mouth wide open, taking in a continuous flow of water. Food is strained from the water by gill rakers located in the gill slits. The 1000-1300 gill rakers in the basking shark’s mouth can strain up to 2000 tons of water per hour. Occasionally the basking shark closes its mouth to swallow its prey. These sharks feed along areas that contain high densities of large zooplankton (i.e., small crustaceans, invertebrate larvae, and fish eggs and larvae). There is a theory that the basking shark feeds on the surface when plankton is abundant, then sheds its gill rakers and hibernates in deeper water during winter. Alternatively, it has been suggested that the basking shark turns to benthic (near bottom) feeding when it loses its gill rakers. It is not known how often it sheds these gill rakers or how rapidly they are replaced. For more information on the basking shark, click HERE..
