The top predators of the ocean, sharks have been making headlines in recent years. Find out more about these notorious fish (yes, they are fish!).
Shark meat is tasty and nutritious if properly prepared. In some countries shark meat is marketed under its common name; in others it is called something else. The fish in England's "fish & chips" is sometimes dogfish or school shark, although this would be considered low quality fish & chips. True fish & chips consists of cod or haddock (the two most popular) and also plaice. The prejudice against shark meat arises from a distaste for the scavenging habits people attribute to sharks, and to the fact that the meat spoils quickly. The meat of certain species can have a strong flavor. This can be reduced by icing for 24 hours, then soaking for two hours in brine. Dry salted shark has become a staple food in some countries where salt cod was formerly popular. But you should never eat shark liver; its high concentrations of vitamins can cause illness in humans.
It is only a rumor that the hammerhead is poisonous.
In life the blue shark displays a brilliant blue color on the upper portion of its body and is normally snowy white beneath. The blue quickly fades to dull grey after the shark is killed. The mako and porbeagle sharks also appear blue, but are not nearly as brilliant as blue sharks. In life most sharks are brown, olive, or grayish.
Considerable research has been devoted to finding out what attracts sharks and causes them to attack. Results are mostly inconclusive, but some general principles have been advanced:
The most dangerous species in order of documented attack records are:
Some species such as the nurse shark are extremely sluggish and have poorly developed teeth, but even these have been known to attack people when excited or disturbed.
The barracuda (though divers claim its ferocious reputation is undeserved), moray eels, octopuses, and sharp-spined sea urchins can be dangerous to swimmers. The Portuguese man-of-war has tentacles up to 50 feet long with specialized cells that produce painful stings and welts on contact by swimmers.
Sting rays, toadfish, catfish, and jellyfish can injure swimmers and waders. Divers should also avoid certain coral-reef organisms.
Sharks do not have bones—they are made up of cartilage. They are called Elasmobranchs, which translates into fish made of cartilaginous tissues. Even though they don't have bones, they still can fossilize.
Shark skeletal systems are composed of cartilage, the clear gristly stuff that your ears and nose tip are made of. And in its pure form, cartilage doesn't fossilize. However, as most sharks age, they deposit calcium salts in their skeletal cartilage to strengthen it. The dried jaws of a shark appear and feel heavy and solid, much like bone. These same minerals allow most shark skeletal systems to fossilize quite nicely. The teeth have enamel so they show up in the fossil record too.
Sharks have very good eyesight. In fact, sharks can see extremely well in dark lighted areas, have fantastic night vision, and can see colors. Avoid wearing bright colors, such as oranges and yellows, in the water, as sharks can indeed see them.
Sharks have eight unique senses. They are hearing, smell, lateral line, pit organs, vision, Lorenzini, touch, and taste. The shark shares many sense that humans do such as taste and smell, but it has three senses that we do not have. The lateral line, pit organs and Lorenzini are senses that have been discovered over the past 10 to 20 years, and play an important role in how the shark functions when swimming around.
It has been observed that sharks can go up to approximately 6 weeks without feeding. The record for a shark fasting was observed with a Swell Shark, which did not eat for 15 months. Sharks can enter what is called an "eating phase" which perhaps might constitute hunger, but on the grand scale of things, a shark is not always hungry.
Sharks are fish. They live in water, and use their gills to filter oxygen from the water. Sharks are a special type of fish known because their body is made out of cartilage instead of bones like other fish. The classification of this type of fish is "elasmobranch." This category also includes rays, sawfish, and skates.
Sharks will eat anything. In fact, things like tires, license plates, a fur coat, a chicken coop, and even a full suit of armor have been found in their stomachs! But generally, sharks are omnivorous, which means usually they just eat meat and plants. If there is not an abundant supply of meat in the area, they will resort to eating sea vegetation. The largest shark of all, the whale shark, is mainly a plankton feeder.
Veteran intern Antonio Jones at an oyster farm in Drayton Harbor, Washington, checking traps for European Invasive Green Crab. Credit: Northwest Straits Commission
The Fishadelphia team. Credit: Dr. Talia Young.
