Here's How to Save Swimmers Without Killing Sharks
It’s that time of year when you’ll be inundated with all things shark, what with Sharknado 2 and "Shark Week" on the Discovery Channel. And so scientists want to remind you that we can coexist with the landlord, as surfers refer to the ocean’s top predator.
“More humans are killed by toasters, cows, or vending machines than are killed by sharks, and heart disease kills about a million times as many people as sharks do,” David Shiffman, a shark scientist at the University of Miami, wrote in a commentary published Monday in the journal Animal Conservation. “Many commonly used ‘shark control’ strategies involve killing sharks with the goal of reducing the probability of a swimmer encountering a shark.”
Amid shark culls, such as the one in Western Australia, scientists in Brazil found that a strategy of catching sharks and relocating them resulted in a 97 percent drop in attacks off the coastal city of Recife between 2004 and 2011. Shark attacks on humans were unknown until 1992, when construction of a commercial port began. Suddenly there was an outbreak of shark bites, with 36 percent of the attacks proving fatal, according to the scientists’ study. They suspected the building of the port disturbed the sharks’ territory, sending them into areas frequented by swimmers.
But instead of killing the sharks, the local government started a program to lay baited hook lines to catch sharks associated with the attacks and then transport them elsewhere for release. Other countries have deployed nets near beaches to catch sharks, but the nets also resulted in the deaths of hosts of harmless fish, turtles, and other marine life. The scientists found that the Brazilians' use of fishing lines, on the other hand, significantly reduced such bycatch as well as shark death rates. No protected species were killed during the program.
"Shark bites are not a terribly likely occurrence," Shiffman said in an email. "I recently calculated that Jack Bauer has killed more people onscreen in 24 than every shark attack worldwide since 1580, when the species of shark was identified."
Still, catch-and-release is not a perfect solution, according to Shiffman.
“A single boat and crew could manage a relatively small area such as that used in this study, but this expense will rapidly increase as this method is scaled up to larger geographic areas,” he wrote. “Additionally, if the area we are removing sharks from represents an important habitat for them (a migration corridor, mating aggregation area or nursery), they will likely keep coming back.”
Still, given that the International Union for the Conservation of Nature Red List has identified 25 percent of shark species as threatened by extinction, catch-and-release “has the potential to be a revolution in shark control,” Shiffman noted.