Will Killing Sharks Finally Stop Hawai‘i’s Epidemic of Attacks?
Shark attacks spiked 56 percent over the past four years. Folks on O‘ahu and the Neighbor Islands are nervously asking why. HONOLULU dives deep to find out what’s going on, and what’s different, this time around.
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Where Are the Attacks?
Source: DLNR, ISAF, GSAF
Over time, people have tried an impressive range of tactics to repel sharks. But do they work? Not well enough ...
YE OLDE STYLE: A 1980 patent for a suit of shark-proof armor was never produced, but it led to Neptunic’s chain mail, used by professional divers to ward off bites. Too heavy for hanging 10!
WATCH OUT!: Colorful wristbands send out magnetic waves that allegedly disturb sharks’ electromagnetic sensors. Said to work best if a whole group wears them. sharkbanz.com/technology
GOOD VIBRATIONS: An electronic device attached to a surfboard and ankle via a surf leash, Shark Shield is used in Australia, where tests show great whites stop at nothing. sharkshield.com/technology
STINKY SPRAY-ON: An aerosol of putrified shark tissues. Yeah, that would keep us away if we were a shark. sharktecdefense.com
BLUE MAN SUIT: If sharks really are colorblind, surely they won’t see you in a blue bodysuit. No, really, you go first. radiator.net
SSSSSNAKE: The venomous, striped sea snake strikes such fear in sharks that stripes will keep them at bay. That’s the theory, anyway.
Getting to Know You
CLICK ON THE IMAGE TO ENLARGE.
Sharks sense us way before we see them—unless the water’s murky.
Illustration: Kelsey Ige
How a shark “reads” you; how you can “read” a shark
Shark scientists say a shark can hear you from 1,000 to 10,000 meters away; smell, see and sense you at from 10 to 100 meters; and perceive you electromagnetically via sensors called ampules de lorenzini at half a meter (50 cm), before switching to direct contact.
Researchers and dive-tour operators can, like any animal trainer or wrangler, “read” sharks from their posture. The tiger above is already showing multiple “agonistic” signs of impending aggression toward another shark or prey: (A) an elevated snout, (B) a gaping jaw, (C) both fin and tail down, (D) an arched back and, overall, a torso that’s shivering or making stiff, jerky movements. A shark in this flank display mode will circle back (E) and engage in various challenges: charges, gill pouch billowing, head shaking, jaw snapping, corkscrewing and ramming. But almost every shark is also ready to make a rapid withdrawal in submission to a dominant shark or rival predator (which could be a swimmer who maintains eye contact and, if necessary, strikes the underside of the snout, preferably with an object, not a hand).
sources: sharkshield.com; “a review of shark agonistic displays,” marine and freshwater behavior physiology, vol. 40, issue 1, 2007.
Tiger Shark, HI Risk
“Niuhi” runs to 16 feet, is called “garbage can of the sea” for its wide variety of diet, and is responsible for most serious attacks and almost all fatalities in Hawai‘i.
galapagos shark, Low Risk
No man-eater except in WWII shipwrecks far offshore, this bottom-feeder snatched seal pups in French Frigate Shoals when lobsters grew scarce—and may bite.
Sandbar Shark, Low Risk
Frequently seen near shore due to its diet of octopus, squid, mollusks and small reef fishes, the sandbar shark may take a rare bite in murky or low-light water.
Blacktip Shark, Low Risk
“Manō Pō‘ele” is common near shore, including a heiau sacred to sharks at Pu‘ukoholā on the Big Island. A biter only in poor visibility or if provoked.
Hammerhead Shark, Rare Risk
“Manō kihikihi” live offshore but give birth to pups in such shallow bays as Kāne‘ohe, Waimea and Hilo. Our scalloped hammerhead nips, not bites.
Great White Shark, Some Risk
“Niuhi” is a name reserved for man-eaters, “with fiery eyes,” says a chant; a small number of great whites do make rare visits at long cycles.
Illustrations: Kelsey Ige
How a Tiger Feeds
Hunting in a yo-yo pattern, tigers rarely cross paths with people.
Nervous about sharks? Just envision a yo-yo. “Tiger sharks are vertically dynamic swimmers, constantly yo-yo diving between the surface and the seabed,” say Kim Holland and Carl Meyer, who’ve partnered for decades on shark research. Why is this important? Because that up-and-down foraging pattern takes them down to the seabed, and depths up to 1,800 feet, eating all the way. That means they’re not spending much time on the surface and near offshore, where we do our swimming, surfing and diving and so forth. Now add to your mental yo-yo the lateral range—a tiger can cruise 60 miles in a day, and may range several thousands of miles in a month or two—and watch the odds of one popping up next to you go way down.
42% Sharks and Rays
35% Lobster and Crabs
sources: percentages of contents of 554 large (>10 ft.) tiger shark stomachs culled 1959-’76 from “a review of shark control in hawai‘i with recommendations for future research,” pacific science, vol. 48, no. 2, 1994. due to wide variety of food in stomachs, percentages add up to more than 100 percent.
Follow That Shark!
scientists lead the way by tagging tigers, whose tracks hint of close encounters—and journeys as far off as Mexico.
Click on the image to enlarge.
Thanks to recent attacks, shark science has entered a golden age. You can see how tagged tigers roam Island waters (and far offshore), due to ongoing efforts by Carl Meyer and Kim Holland (pictured at right) and teams at the Hawai‘i Institute of Marine Biology. Over 450 sharks, including 174 tigers, are monitored by various sensors. Tagging revealed that
tiger shark growth and reproduction rates here are double the norm elsewhere and that our tigers “have large home ranges that typically include several islands, but each individual shark is most frequently found around a ‘core’ island.”
But a killer app is the Pacific Islands Ocean Observing System (oos.soest.hawaii.edu/pacioos/projects/sharks). It shows the date, time and location whenever one of 28 tagged tigers’ dorsal fins broke the surface from late 2013 to July 2015. The tagging was in response to a “higher number of unprovoked shark attacks than in previous years” in Maui waters, including reports from “local spear fishers … of increasing boldness in large sharks encountered.” We clicked on Tiger 137070, a 12.1-foot male, whose home turf is between Ka‘ena and Kahuku points, with hang time in the Kaiwi Channel between O‘ahu and Maui. On Nov. 4, 2014, he shows up right off Pipeline; visits Mokulē‘ia on Nov. 5; and on Dec. 11 travels from far out in the Kaua‘i Channel to Waikīkī, where by 4:45 p.m. on Dec. 19 he’s hovering near the Waikīkī Aquarium outfall (locations are accurate up to a mile). Then it’s off to Kea‘au Beach Park and the Kaua‘i Channel before spending New Year’s far off Kāne‘ohe.
In Western Australia, where great-white attacks are also on the rise and fatalities are far more common, tagged sharks and sightings are logged immediately via Twitter in the government’s SharkSmart app. Sign us up!
In October begins Makahiki, the Hawaiian harvest festival, dedicated to Lono, god of fertility, when gravid tiger sharks come to the warm, shallow waters between Maui and Kaho‘olawe to feed and give birth, when Captain Cook arrived, the time in which, as a traditional Hawaiian poem says, “the wiliwili tree blooms, and the shark bites.” Pre-contact Native Hawaiians mostly stayed out of the water, taking part in games and rituals on land.