Studying the sea dogs
KEKAHA — Mix three parts muddy water with two parts dead fish, add in a sprinkle of fresh blood, and you’ve got shark soup — not the kind you take a bite of, the kind that could take a bite out of you.
Those are the kinds of elements that attract sharks, according to the Department of Land and Natural Resources’ Kauai district aquatic biologist, Don Heacock and Hanalei-based biologist Terry Lilley.
And those were the conditions in the Westside waters surrounding Kekaha and the Kinikini Ditch mouth this past week, as a result of a fish kill at Kauai Shrimp on Monday.
“I wouldn’t recommend anyone swimming in dirty water, especially with dead fish in it that’s been discharged into the ocean, that’d be foolhardy,” Heacock said.
Lilley said he was positive that the fish kill incident attracted sharks, at least for a while.
“Any time you have a fish kill like that, or heavy rain that washes dead animals down the river, it attracts sharks,” Lilley said.
Conditions, however, are clearing fast.
Derek Pellin, South Shore resident, who checked the Kekaha waters on Friday, said the recent big swell “cleaned up the beach quite a bit.”
Experts at The Florida Museum of Natural History said in early February that 2015 saw a record-setting 98 unprovoked shark attacks worldwide. Of those, six people died.
In early January, there were two people on Kauai who reported shark encounters with one sustaining injuries. The prior shark incident on Kauai occurred in 2013 on Pila’a Beach. There were no injuries in that encounter.
In Hawaii, there were 10 shark incidents reported to DLNR’s department of aquatic resources in 2015. In 2014, there were six incidents reported. In 2013 there were 14, and there were 11 incidents reported in 2012.
Lilley said the reason for the increase in shark encounters is simple — humans are protecting the sharks more than they have in the past, and the populations have returned. In addition, there has been an increase in human population and in the amount of humans that are in the water.
“We have an increase in the shark population and an increase of people in the water, there’s going to be an increase of accidental shark bites,” Lilley said. “But statistically, it’s still a very rare event.”
Sharks are the wolves of the sea, and wolves are the janitors of the terrestrial animal kingdom, Heacock said.
“Like wolves, sharks primarily feed off on the sick, dead and dying,” Heacock said. “They aren’t territorial, they have a forage range of hundreds of miles and they’re essential to the ecosystem.”
Though sharks are known to eat other sharks, fish and turtles, the smell of dinner is decay and blood, and they can lock onto that scent from miles away, Heacock said.
“If I drop a drop of blood in the water, a shark 10 miles away can’t smell that, but if it is diluted and the current carries it 10 miles away, that shark will follow it back to where it was spilled,” Heacock said.
Sharks have another extraordinary sensory skill — they can detect electrical pulses in the water.
All animals give off bioelectrical impulses through muscle movements, and sharks detect those impulses with their Lorenzini ampoules, or electroreceptors that line the shark’s nose and head.
According to Lilley, most sharks swimming at 40 mph can come within a quarter of an inch of their mark every time using their electroreceptors in clear water, and that margin of error only increases to a foot in muddy water.
“Humans aren’t food, so even if there’s dead fish everywhere and the sharks are zooming around, if the conditions are clear they won’t eat the human,” Lilley said. “If the water is muddy at the same time, that’s not a good scenario.”
Of the nearly 40 shark species that can be found in Hawaiian waters, the tiger shark is the leader in unprovoked fatal attacks.
The species is second only to the great white shark in worldwide, unprovoked fatal attacks, according to the Florida Museum of Natural History. Heacock said Hawaiian waters are too warm for great whites in general.
“The average movement of a tiger shark in a 24-hour period is about 75-150 miles,” Heacock said. “They don’t stay put, especially the bigger ones. There isn’t enough food in one spot to maintain the biomass of a really big shark.”
Lilley said the scientific community has long pondered why humans “just aren’t on the mental menu” for sharks, and he compared it to trying to take a bite out of a chair.
“You wouldn’t eat a chair because it’s not food,” Lilley said. “All of the shark bites are accidental, usually when they’re chasing their food.”
Lilley explained that in shark attack cases, the shark doesn’t come back and try to eat the person, which is another huge indicator that sharks don’t eat people.
“No predator like a shark is going to make a mortal bite on prey and turn around and leave it,” Lilley said. “If they’re chasing prey and expending that energy to make the killing bite, they’re going to hang around and eat the prey.”
Heacock said the key to getting a shark to back off during a confrontation is to give it a good reason to give up on what it thinks is dinner.
“Punch them. Poke them. Hurt the shark back,” Heacock said. “When you’re being attacked by a shark, sitting there quietly waiting for help isn’t the best thing to do.”