Basking Shark
The basking shark is the second-largest shark species, and can reach lengths up to 30-40 feet. Weights for the basking shark have been estimated at 4-7 tons (about 8,000-15,000 pounds). They are filter-feeders who are often seen feeding near the surface with their huge mouths agape.
Basking sharks got their name because they are often seen “basking” on the surface of the water. It may appear the shark is sunning itself, but in fact it is often feeding on tiny plankton and crustaceans.
While it is at the surface, its prominent dorsal fin, and often the tip of its tail, can be seen, which may cause confusion with the Great White or other more threatening shark species when a basking shark is seen from land.
Basking sharks have been reported in all oceans of the world. They are found mainly in temperate waters but have also been seen in tropical areas. During the summer, they feed near on plankton near the surface in more coastal waters. It was once thought that basking sharks hibernated on the ocean bottom in the winter, but some research shows that they migrate to deeper waters offshore and also shed and re-grow their gill rakers, and a study published in 2009 showed that basking sharks traveled from Cape Cod, Massachusetts, all the way to South America in the winter.
Each basking shark has 5 pairs of gill arches, each with thousands of bristle-like gill rakers that are up to 3 inches long. Basking sharks feed by swimming through the water with their mouths wide open. As they swim, water enters their mouth and passes through the gills, where the gill rakers separate out plankton. The shark periodically closes its mouth to swallow. Basking sharks can strain up to 2,000 tons of salt water per hour.
Basking sharks have teeth, but they are tiny (about ¼-inch long). They have 6 rows of teeth on their upper jaw and 9 on their lower jaw, totaling about 1,500 teeth.
Basking sharks are ovoviviparous and give birth to 1-5 live young at a time.
Not much is known about the basking shark's mating behavior, but it is thought that basking sharks exhibit courtship behavior such as swimming parallel to each other and gathering in large groups. During mating, they use their teeth to hold on to their partner. The gestation period for the female is thought to be about 3 ½ years. The basking shark pups are about 4-5 feet long at birth, and they immediately swim away from their mother at birth.
How Fast Can a Shark Swim
In a race among the sharks, the shortfin mako shark (Isurus oxyrinchus) would be the winner.
The robust, streamlined shortfin mako shark is reported to have been clocked at 22 mph, although some sources say it can reach up to 60 mph. This may be because it is capable of chasing even quicker fish, the sailfish and swordfish, which can reach speeds over 60 mph (when leaping). The mako can also perform giant leaps of up to 20 feet out of the water.
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Whale Shark
While its name may be deceiving, the whale shark is actually a shark, and the largest fish in the world. Whale sharks can grow to 65 feet in length and up to about 75,000 pounds in weight. Females are generally larger than males.
They are huge and streamlined, and have a beautiful coloration pattern on their back and sides that is made up of light spots and stripes over a dark gray, blue or brown background. They have a white underside.
Like the basking shark, whale sharks feed by filtering small organisms, such as plankton, crustaceans, tiny fish, and occasionally larger fish and squid. Unlike the basking shark, which moves water through its mouth by slowly swimming forward, the whale shark feeds by opening its mouth and sucking in water, which then passes through the gills. Along the way, organisms get trapped in the shark's dermal denticles (small, tooth-like structures) and the pharynx, which is a rake-like structure. A whale shark can filter over 1,500 gallons of water an hour.
Whale sharks are ovoviviparous and females give birth to live young that are about 2 feet long. Their age at sexual maturity and length of gestation is unknown. Not much is known about breeding or birthing grounds either, although in March 2009, a 15-inch long baby whale shark was rescued from a coastal area in the Philippines, where it had been caught in a rope. This may mean that the Philippines is a birthing ground for the species.
Whale sharks appear to be a long-lived animal. Estimates for longevity of whale sharks are in the range of 60-150 years.
The whale shark is listed as vulnerable on the IUCN Red List, because of hunting, its highly migratory nature, impacts of diving tourism and overall low abundance, which make it "vulnerable to exploitation."
Shark Week is Here
Image: Great white shark, Stephen Frink / Getty Images
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Shark Attack Tips
Even though you're more likely to die from a lightning strike, alligator attack or on a bicycle than from a shark attack, sharks do sometimes bite humans. According to the International Shark Attack File there were 59 cases of unprovoked shark attacks worldwide in 2008. Forty-one of these unprovoked attacks were in U.S. waters, and 32 of these were in Florida.
There are many ways (most of them common-sense) that you can avoid a shark attack. Below is a list of what not to do if you'll be swimming in waters where sharks might be present, and techniques for getting away alive if a shark attack really does happen.
Don't swim alone.Don't swim during dark or twilight hours.Don't swim with shiny jewelry.Don't swim if you have an open wound.Don't swim too far offshore.Ladies: don't swim if you're menstuating.Don't splash excessively or make erratic movements.Keep pets out of the water.Don't swim in areas where there are sewage (for other obvious reasons!) or pinnipeds that are hauled-out. Both areas can attract sharks.Don't swim in areas being used by fishermen, as their bait could attract sharks.Don't push your luck - never harass a shark. Get out of the water if one is spotted.