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AD 2016 Q1

LIFE AQUATIC SAND TIGERS

LIFE AQUATIC SAND TIGERS are around 3 feet long at birth; the average length for adult males is 8 feet, while females max out at around 10 feet and 350 pounds. Sand tigers tend to mate in late winter to early spring. The male shark will bite the female on the pectoral fin to latch on during the mating process. Each year in May, at the beginning of the dive season in North Carolina, many females are seen sporting grizzly wounds. But the sharks are fast healers. Come July the wounds are mostly healed with only faint scars remaining. Every two or three years, after a gestation period of eight to 12 months, females typically give birth to one or two pups, typically one from each of her two uteri. These young sharks are frequently seen on the wrecks and are easy to approach. This small number of births is due to the fascinating but macabre phenomenon of intrauterine cannibalism, in which the larger and stronger fetuses consume the lesser ones. A pregnant female may start off with as many as 40 embryos but give birth to just the one or two pups. Hence, sand tiger sharks obtain their hunting instincts even before birth. The disadvantage of this is that sand tigers have one of the slowest rates of reproduction of any shark species. When their numbers are down it takes longer for them to rebound. Overfishing of sand tigers has caused their numbers to plummet worldwide. In the 1970s and ’80s in Australia, divers purportedly used explosive powerheads to kill sharks for sport. Because of how easy it is to approach sand tigers, little skill was involved in this style of fishing, and the results were devastating. In the United States, recreational fishermen as well as commercial longliners and purse seiners often caught sand tigers unintentionally. Considered a “trash fish,” sand tigers caught as bycatch usually died. These and other unchecked and destructive fishing practices took a toll on sand tiger shark numbers to the point that they became a protected species in Australia, South Africa and the United States in 1997. Today they are listed as vulnerable on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List of Threatened Species. The answer to whether sand tiger numbers are increasing depends on who you ask. “I do not have any scientific evidence, but I do believe sand tiger shark populations might be on an upward trend,” said Chris Paparo, manager of the Marine Sciences Center at the Southampton campus of Stony Brook University. “In recent years, anglers targeting fluke or striped bass have been catching both adult and juvenile sand tiger sharks with greater frequency.” Recreational divers who have been diving North Carolina’s wrecks for more than 25 years also report The Atlas tanker’s mazelike remains are a perfect backdrop for photographing sand tiger sharks. seeing more sand tiger sharks now then ever before. “Shark numbers may be stabilizing, but to say they are increasing may be a stretch,” Fessler countered. “There are more eyes in the water today looking for sharks than there were 25 years ago; in turn more sharks are being seen.” Based on what I have witnessed over the past 15 years, I believe shark numbers are slowly on the rise. I’m seeing sharks on wrecks where they were rarely seen before and with more regularity. Regardless of whether their numbers are increasing or not, sand tiger sharks, like all marine apex predators, require continued protection. The health of the ocean ecosystem, on which we are dependent for fish stocks, starts at the top of the food chain. Abundant sharks equates to abundant marine life. It’s no coincidence that when we see the greatest numbers of sharks on wrecks we also see large gatherings of other fish such as Atlantic spadefish, grouper, jacks and flounder. When I was a dive boat captain in North Carolina, each morning before departure I would ask the divers where they wanted to go. Most would say without hesitation, “We want sharks!” There was no need to twist my arm; a few minutes later we would be under way to wherever the hot spot for sand tigers was at the time. The wrecks of the Caribsea, Proteus, Atlas, Aeolus, USCGC Spar and W.E. Hutton (also known as the Papoose) are some of the famous sand tiger haunts that were often at the top of the hit list. As long as Mother Nature cooperated enough to allow us to venture offshore, we could pretty much count on outstanding shark diving. As divers walked down the dock at the end of a successful day of shark encounters, I could tell I was going to see many of them again soon. It was apparent these divers had been bitten — not by a shark but by a bug: Sand tiger shark diving is highly contagious. AD 42 | WINTER 2016

RESEARCH EDUCATION MEDICINE The Duane is a former U.S. Coast Guard cutter sunk off the coast of Key Largo, Fla., in 1987. It is now lavishly decorated with sponge and orange cup corals and is home to abundant marine life. STEPHEN FRINK 44 DAN WAS THERE FOR ME / 46 ADVANCED DIVING / 50 EXPERT OPINIONS 56 SAFETY 101 / 58 FROM THE MEDICAL LINE 62 SKILLS IN ACTION / 64 INCIDENT INSIGHT ALERTDIVER.COM | 43

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