Friday, August 5, 2011

Basking Sharks - The Lazy Predators

As we close out this week, we’d like to focus on a shark that just doesn’t get any respect; the basking shark. Although it’s one of the largest species of fish in the world, the whale shark is larger, so it won’t set any records there. It isn’t a vicious predator either, and despite being as long as a city bus poses absolutely no danger to humans or any large creature of the sea.

The basking shark gets its name from its appearance of relaxing (i.e. basking) in warmer waters near the surface while it feeds; and due to their massive size they are quite hard to miss. Basking sharks are usually 20-35 feet in length and weigh about 4 tons. The largest specimen ever confirmed was over 40 feet long and weighed an estimated 34,000lbs!
Basking shark filter feeding
Although basking sharks are sometimes mistaken for great white sharks, the two could not be more different. Whereas great whites are active hunters, the basking shark is a passive filter feeder. It feeds on zooplankton and small fish simply by swimming around very slowly with its enormous mouth wide open. Prey is snagged by the basking shark’s many sets of gill rakers. During this process, the shark naturally takes in a massive amount of water. However, unlike other filter feeding sharks that can close their mouths and pump this water out manually, the basking shark can only expel water by continuing to swim at its lumbering 3mph pace.
Basking shark head
Basking sharks do migrate throughout the year and can travel thousands of miles in a season. It is assumed that this travel is related to reproduction or following plankton blooms. Due to this migration, at certain times of the year basking sharks may be found in nearly every ocean of the world.

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