Predatory animals inspire a sense of awe, respect and fear among humans. On land, big cats, wolves, and bears are some of the quintessential predators. Dip beneath the waves, however, and sharks take the stage, alongside orcas, sperm whales, and large squids and fishes. Although there are many marine predators, it is the sharks that have been most stereotyped as the "killers from the deep".
There's no denying the fact that sharks are carnivorous and predatory. Generally, however, sharks have a more diverse diet than usually credited by the general public. The giant filter-feeding basking shark (Cetorhinus maximus) is inclined to consume copepods of the genus Calanus. The whale shark (Rhincodon typus), another very large filter-feeder (see link on this species below), also feeds on zooplankton, although it is not averse to taking small- to medium-sized fishes swept up in its enormous maw. Some sharks concentrate mainly on certain types of prey, such as cephalopods (squids and octopuses); crustaceans (lobsters, shrimps, etc.); shellfish, or small fishes, whereas others will take prey from any of these groups. Many sharks are oppurtunistic, meaning they will feed on most edible items they encounter.
Whatever their dietary preference, sharks are well-adapted to deal with their prey type. Many bottom-dwelling sharks, such as the orectolobiformes (including the nurse sharks) and heterodontiformes (such as the Port Jackson shark [Heterodontus portjacksoni]) have flattened molar-like teeth and strong jaw muscles, all the better to crush the shells of their common prey, molluscs and crustaceans. Another, better known, example of dietary adaptation is the infamous white shark...
Giant Nurse Shark!
The picture shows a diver posing beside a truly monstrous tawny nurse shark (Nebrius ferrugineus) at Marion Reef in Australia, an oceanic atoll 500 km (310 miles) off Townsville, Queensland. The maximum size for the tawny nurse shark is 14 ft. The shark in the above photo appears to be much longer than that, but this is an optical illusion caused by the diver being further away from the camera than the shark. The shark is actually about 13-14 ft long: still a monster by anyone's book!
Megamouth shark.
ON THE NIGHT OF FEBRUARY 20, 1998, three fishermen in Macajalar Bay, Cagayan de Oro caught a fish they couldn't identify. A local radio station reported the find the following morning. The fish was later hacked into pieces and consumed that day. Subsequent reports, quoting government sources, said the strange fish was a whale shark. But research conducted by this writer using the Internet revealed that it was a megamouth, an extremely rare species with previously only 10 sightings worldwide.
