Sharks and I go back a long way. As a child, growing up in Cape Town, South Africa, I would vacation with my family at a small fishing village called Langebaan on the shores of Langebaan Lagoon, a long, narrow coastal lagoon about 80 miles north of Cape Town. Sand sharks, which are a type of shovelnose ray, would come into the shallows of the lagoon to warm themselves in the sun. Since they blended so well with the sand and liked to burrow slightly under it, it was hard to see them, which would occasionally result in someone stepping on one, causing said person to emit a bloodcurling shriek and to leap several feet into the air, only to come down on another one, after which the process would be repeated. This was always hugely entertaining to observers (the sand sharks were harmless.)
This is what they look like:
Langebaan Sand Shark (Rhinobatos annulatus)
Looking through the Jorgensen book, this looks very much like a squatiniform or angel shark, but apparently the order is not squatiniformes but rhinopristiformes, both of which fall under the class Elasmobrachii, which includes all cartilaginous fish, such as sharks, skates, and rays. Then I got really confused by reading a Wikipedia article that said the class was actually Chondrichthyes and that Elasmobranchii and Holocephali are subclasses. The confusion was cleared up by an article that describes Chondrichthyes as an older classification. Apparently the word elasmobranch comes from elasmos, which is Greek for "metal plate", and branchus, which is Latin for "gill." Sand sharks are also known as lesser sand sharks and lesser guitarfish and have the scientific name Rhinobatos annulatus. Thankfully, both rhinopristiformes and squatiniformes are listed among the 13 orders of sharks and rays, so perhaps the sand shark is a real shark. On the other hand, the classification of elasmobranchs is regularly revised, and some studies suggest that there is molecular evidence that skates and rays (batoids) are not derived sharks and should have their own group. I hope sand sharks are real sharks. I'd like to say I've jumped on a real shark.
When I was about seven years old, my family drove up to Durban to visit my grandparents, during which time we visited an aquarium on the Durban beach front (I think this is now the uShaka Sea World Aquarium.) One of the tanks was absolutely packed and overcrowded with fish. I suspect a new batch of fish had recently been brought in from the Indian Ocean and had been placed in that tank to be processed. About seven feet away from me was a stocky, cigar-shaped shark, perhaps five or six feet long. It had a pinkish-purplish hue, but perhaps that was because of the lighting. We made eye contact and gazed at one another for several spellbinding seconds before it charged me. It rammed its snout against the glass, and then withdrew a few feet in disgust, continuing to glower at me in a singularly aggrieved and hostile manner. I am sure it wasn't happy to be confined. From its size and "bump and bite" behavior, I wonder if it may have been a juvenile bull shark. These were sometimes called "Zambezi sharks" in South Africa and appear to be responsible for several attacks off the Natal (now Kwazulu) coast.
Bull sharks are amazingly adaptive and can live in fresh water, meaning they have made their way inland via the Amazon, the Ganges, the Mississippi, and the Zambezi. They even thrive in Lake Nicaragua. Apparently they originally got there by traversing the 112 mile San Juan River, which flows from the lake into the Caribbean. They were able to leap up rapids like salmon to get there. Half (three of six) of all recorded shark attacks in Nicaragua occured in Lake Nicaragua.
Other freshwater sharks include those of genus Glyphis, of which only six species are known. Apparently they are rare, little is known about them, they are critically endangered, and they are mostly found in the Indo-Pacific region. Animal Planet covered Glyphis sharks in it's series on River Monsters.
Craig and I scuba dived knowingly with (harmless) black-tipped reef sharks on our honeymoon in the Maldives and unknowingly with a tiger shark (our dive instructor informed us of that once we were out of the water -- I'd been wondering why he seemed a bit nervous.) Later we unknowingly dived with two tiger sharks in the Seychelles (one of the workers on the boat was kind enough to tell us that as we surfaced from our dive; we proceeded to scale the boat fairly rapidly.) My children have dived with reef sharks in Hawaii. I suppose sharks are always around when people dive, but thankfully they are not usually interested in a human snack.
Jorgensen's book has some wonderful photographs. I hope to get some good videos of marine life to watch with the kids. A vacation in the Caribbean is a very appealing prospect and would allow the family to get in some more scuba diving and to explore the oceans. Laura and Emma still need to get their PADI certifications updated.
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