Why do some fish stay directly under a shark, almost as if stuck by a magnet?

Question

So i'm watching MythBusters Shark Week Special 2 right now, and a few days ago when I watched it as well, I noticed these long fish that were swimming in the exact pattern and path beneath the shark, not 7 inches from it's belly. What are these fish? Why do they stick so close?

Answer 1

These fish aren't scared. How big are the fish? The small ones will get scared.

Answer 2

The fish were most likely Remora's  (http://en.wikipedia.org/wiki/Remora). Remora's are usually found with other fish in a commensalist relationship (though the remora benefits more than the host).

Answer 3

they keep the shark clean from small organic animals and they also clean by eating bacteria or organisms from its gills and skin.

Answer 4

Actually, they are cleaning the shark, and the shark lets them.

They also clean his teeth.  Seen a special on it once.

Answer 5

Most often when smaller fish are under or near a larger fish or predator, it may be using the larger fish for protection from other fish that might want to eat or attack those smaller fish. So that the larger fish will ignore the smaller fish,  they usually preform a role in cleaning the host fish, or hang on the host fish so that they cant be shaken off, or attacked by the larger fish.

Answer 6

There are two main species of fish that can often be found swimming in close relationship with sharks (as well as other large fish or marine mammals), namely the Remoras and the Pilot fish.

Both of these fish form a symbiotic relationship with the shark, the Remora (as already mentioned by Stef D) is a Commensalism relationship where the Remora gains basically all of the benefits such as protection from other predators and free transport as the Remora attaches itself directly to the shark by means of a sucker on the top of it's head. The shark gains no real benefit from this relationship as they tend not to feed on ectoparasites on the shark etc, but neither is the shark directly harmed, as the Remora's sucker does not cut into the flesh or damage the skin to any noticeable extent.

The Pilot fish on the other hand, shares a Mutualism relationship where the benefits are to both the Pilot fish and the shark. Pilot fish do not attach themselves to the shark but instead swim in an almost perfect harmony and favour such species as the Oceanic Whitetip Shark. They again gain a great source of protection from other predators and also a regular food supply from left over scraps from the sharks meals, but also more importantly feed on the ectoparasites on the sharks skin. It is this last part that makes this relationship mutualist, as the sharks can enjoy a virtually ectoparasite free life. Small juvenile Pilot fish also serve as good dentists, and will happily swim into the obliging shark's open mouth to clean food particles from between the teeth with virtually no fear of becoming a meal themselves.