Sharks are the ultimate blend of power, efficiency and predation. No other group of fish in the oceans is more feared or more misunderstood.
An estimated 525 species of sharks occupy the waters of our planet. Here at the Newport Aquarium, you will see more than a dozen species, including sand tiger, sand bar, black tip, nurse and others.
All the species you will see at the Newport Aquarium live in saltwater, but some species are able to live in freshwater too. Eighty percent of sharks are smaller than the average human, and only a dozen species have been known to attack humans.
Our sharks are fed one to three times per week, depending on the species. They have very efficient digestive system, so they can go for months without food in the wild.
Although sharks existed before dinosaurs, they now face an uncertain future. Low reproduction rates and the killing of sharks for such things as shark fin soup have led to a dangerous decline in the number of sharks worldwide.
Sharks are critical to the health of the oceans. For example, they keep populations of fish, especially around reefs, in proper balance. Just like other predators, sharks will cull out fish that may be diseased or injured, and this helps keep fish populations healthy. Sharks also keep down the population of intermediate predators, such as groupers and jacks. If those fish become too numerous, smaller fish populations will collapse.
A shark’s body is unique. Unlike most fish, its skeleton is made of cartilage instead of bone. Sharks also do not have swim bladders to provide buoyancy, as bony fish do. A large and oily liver provides a shark with buoyancy. Instead of having scales like other fish, a shark’s skin is covered with dermal denticles – tiny teeth-like points -- that give it a very rough feel but allow the shark to swim efficiently through the water. Every part of a shark’s body is highly efficient and able to function without burning up much energy.
Sharks are highly aware of their surroundings. They use six senses -- vision, smell, hearing, taste, touch and electroreception. Electroreception occurs through special sensors (Ampullae of Lorenzini) on the shark’s head. These sensors allow the shark to detect weak electrical signals given off by other aquatic animals.
Teeth are plentiful in sharks. When they lose a tooth, a replacement is ready to take its place. The shape and size of the teeth are specific to each species and can help identify an animal. Some teeth are good for tearing apart large chunks of flesh (for example, our sandbar sharks); others are best for holding onto smaller slippery foods (like our nurse sharks); others are made for crushing shells (such as the Port Jackson shark).
Our volunteer divers routinely find shark teeth, especially under the feeding stations. You may be lucky enough to see a diver show off some shark teeth through our display windows.
Sharks use a variety of reproduction methods, depending on species:
- Oviparity: Some species lay eggs containing a developing shark embryo that is fed by a yolk. Once the yolk is consumed and the shark “pup” fully developed, it will hatch from the egg case, just as chickens do.
- Ovoviviparity: Some species retain the embryo and yolk inside the mother shark until the shark pups are ready to be born.
- Viviparity: Finally, some species of shark have embryos that receive nutrition from the female via a placenta, like a mammal. Eventually the female gives birth to live pups. Once born, all shark pups are at risk of being eaten by larger fish or other sharks.
The Sharks of Newport Aquarium
Sand Tiger Shark (Carcharias taurus)
The Sand Tiger shark has a menacing look due to its protruding teeth. These needle-like teeth are perfect for grabbing slippery fish but not for tearing flesh, so these sharks will swallow whole any fish they catch.
Sand Tiger sharks are found in all tropical waters except for the eastern Pacific.
It is the only species of shark known to gulp and store air in its stomach in order to achieve neutral buoyancy – that is, to maintain a steady position without sinking or bobbing up as it swims.
Sand Tiger sharks are ovoviviparous and give birth to two pups after a gestation period of nine to 12 months.
Among all the shark species at Newport Aquarium, the Sand Tiger is the closest genetic relative to the famous Great White shark. Although the slow-moving Sand Tigers look fierce, they are considered non-aggressive.
Blacktip Reef Shark (Carcharhinus melanopterus)
As its name implies, a Blacktip Reef Shark is easily identified by the dark edging on all of its fins. These sharks are very sleek looking with a counter-shading pattern -- a dark back and light underside.
Blacktip Reef sharks are found near reefs and sand flats of the Indo-Pacific region. They prefer to feed on fish, but will also eat cephalopods and crustaceans.
They are viviparous and only give birth to two to four pups at a time. Gestation for Blacktip Reef Sharks is around nine months in warmer waters, but up to 12 months in cooler waters.
California Leopard Shark (Triakis semifasciata)
These striking fish, with thick, saddle-like markings on their backs, can grow up to seven feet long and swim in schools, unlike most sharks. They are native to the kelp forests off the coast of California. Because they are adapted to rubbing up against aquatic plants, they are comfortable being touched by humans.
Port Jackson Shark (Heterodontus portusjacksoni)
The head of this species is bull-shaped, and its back has distinctive black harness-like markings. This shark spends most of its time sitting on the bottom. (Contrary to popular belief, most sharks, do not need to swim all the time.) Native to the waters off Southern Australia, they also grow among kelp forests. They are part of a family called Bullhead or Hornsharks.