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Tank Snatches Sharks From Jaws of Myth

March 14, 1985|JOHN DREYFUSS | Times Staff Writer

Bob Johnson stood in front of his new fishbowl the other day and declared that the reputation sharks have for devouring humans is greatly exaggerated.

Johnson's fishbowl is 14 feet long, holds 1,500 gallons of water and is full of sharks. It is the newest attraction at Cabrillo Marine Museum in San Pedro.

The shark tank will open for public viewing Saturday.

"Most Southern California sharks that people might run into are small, shy, retiring animals," Johnson said, watching a 2-foot leopard shark bump his nose against the side of the tank.

"The reputation of sharks being killers is true for some sharks," continued the aquarium curator. "But fewer than 20% of the 350 species have been known to make contact with man, let alone bite him.

"I don't recommend anyone swimming with sharks, or playing games with them, but they are not an animal man has much to fear from."

Certainly the sharks in the museum's new tank are no threat to anyone's safety.

The most striking fish in the tank are three leopard sharks--graceful, spotted animals about two feet long who either slide through the water without apparent effort, making frequent stops to peer out of the tank, or lie on the bottom watching the world go by.

Perhaps the least striking species in the tank are three shovel-nosed guitar fish, a ho-hum variety of shark that partially buries itself in the sand, where it lounges and feeds on crab and shrimp.

The tank's shark population also includes two angel sharks--inelegant-looking creatures who flop around on the aquarium's sandy bottom. Johnson knows of only two other angel sharks in captivity.

If visitors are lucky, and the creatures aren't hiding behind a rock, viewers also will see a couple of nocturnal horn sharks, members of a species that hasn't changed in 150 million years.

Other sharks in the 58-degree sea-water exhibition include a swell shark that can blow itself up

'This tank provides the ability to study shark behavior in small specimens . . . '

to twice its normal width in order to appear more ominous and to lock itself in among rocks so other fish can't get a good grip on it, and two undistinguished gray smoothhounds, among the most common of sharks.

The fact that the biggest shark in the new display is only two feet long has its advantages, said Susanne Lawrenz-Miller, co-director of the museum.

"The tank is our largest tank, but it's still small enough so you can always see the animals very close up and in their entirety," she said. "You can pick out some of the highly detailed, interesting structural aspects of the animals, and it is easier to see the fish as a part of their various microhabitats than it would be in a large tank.

"Also, you can see some shark relatives in the tank, especially various types of rays."

Those types include thorn-back rays, stingrays and bat rays. And there are starfish, sea anemones, seaweeds, coral, rock scallops, sea snails and barnacles, all living in apparent comfort, side by side.

It is the sharks, however, that are the heroes of the tank. The aquarium was built for them, and museum officials say they are the main attraction.

Certainly, they are the oldest attraction. Sharks have been evolving for 350 million years, about 346 million years longer than humans, according to Jeff Landesman, aquarist at the Cabrillo Marine Museum.

Sharks, skates and rays are all cousins. They are distinct from other fish because they have no bones. Their skeletons are made of cartilage.

Johnson, whose major interest is sharks, noted that sharks have some unusual and highly refined senses. A shark, for example, can sense magnetic fields of the Earth and use that sense to travel hundreds of miles through the ocean and then return to its exact starting point.

Sharks are so sensitive to changes of pressure in the water that they can "feel" a fish moving its tail up to 100 yards away. They can hear an injured fish thrashing in the ocean two-thirds of a mile away, and can see at night better than cats, Johnson said.

Sometimes having so many senses at work gets sharks in trouble. Johnson has seen sharks trying to reach food that one sense tells them is right in front of them, despite the input from another sense that there is chicken wire between them and the food. In such a situation, the sharks are likely to swim repeatedly into the wire. "They are using one sense, say their sense of smell, and they don't use their sense of vision to find the food," Johnson said. "It's difficult for them to change quickly from one mode of sensing to another. They can do it, but it's hard."

Exhibits near the new shark tank illustrate qualities like those mentioned above, plus providing information on other aspects of sharks and how they live, such as their ability to use their sense of smell to tell if they are getting closer to an injured fish (a trait confined among fish to sharks, Johnson said), their different types of teeth (serrated for ripping, pointed for holding and flat for grinding), how they take advantage of their rigid fins (by using them like airplane wings) and how they detect electrical fields produced by the muscles of other sea life.

"The uniqueness of this tank provides us the ability to study shark behavior in small specimens, which can be directly related to many of their larger counterparts at sea." Johnson said. "And, on top of that, our visitors can share in this unique view of these beautiful creatures."

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