You can’t tell a 1,000-pound leatherback sea turtle what to eat or where to nest.
He – or she – will eat the same thing nearly every day of the year: plump, tentacle-streaming jellyfish.
And a female will usually return to the area where she’s always nested, during a life that may extend up to 50 years.
“It was successful for her mother,” explained John Roe, UNC Pembroke biology professor. Even if those beaches are overrun by development or washed away by a hurricane, he says, she will keep on trying.
Nesting beaches are often a continent away from the turtles’ feeding grounds, and they spend several months crossing thousands of miles of ocean to get from one to the other. They’ve been clocked at what for turtles is lightning speed – 22 mph.
The leatherback has a lineage stretching back more than 100 million years. It’s the largest sea turtle, at up to 6 1/2-feet long, and sometimes weighs more than a ton. Its size and the blue-black rubbery skin that serves as a shell make it distinctive.
“If you ever saw a leatherback, you’d never mistake it,” said the Ocean Foundation’s Kelly Stewart, who studies leatherbacks off the Carolinas coasts.
But its instincts, particularly for long-distance travel, are bringing it increasingly in conflict with one of humankind’s ancient activities: fishing.
The same algae blooms that attract jellyfish also attract small fish that are eaten by larger fish. Those larger fish are in turn devoured by the tuna, swordfish and marlin that attract fishing boats, hooks at the ready.
Longline fishing fleets don’t set out to harm turtles, said Roe, who is lead author of one of two recent reports on the locations – and possible collision spots – of leatherbacks and fishing fleets.
But accidental hooking or being tangled in long lines leads to drowning, and this bycatch is considered one major reason that leatherbacks’ numbers in the Pacific have plummeted drastically, as much as 90 percent in the last 25 years, Roe said.
Tracking turtles and boats
In Costa Rica, one of the main Pacific nesting areas, leatherback numbers have dwindled from 1,500 in the late 1980s to a few dozen, he said.
In a 16-year effort, Roe and 13 other U.S. and Costa Rican scientists pooled data from their satellite tracking of 135 turtles migrating across the Pacific. They analyzed data on catches of billfish and tuna, then pinpointed “hotspots” of dual turtle/fishing activity.
Another group of 27 scientists from 13 nations did the same in the Atlantic, tracking 106 turtles. Lead co-authors of that report are Sabrina Fossette, now at the Southwest Fisheries Science Center in California, and M.J. Witt, lecturer at the University of Exeter in the United Kingdom.
The idea, said Roe, is to provide broad, general data that hopefully will lead to more specific, localized studies, which in turn will persuade governments and coalitions of governments to provide protection.
For an unknown reason, “the Atlantic populations are doing pretty well,” Fossette said. “Some are stable, and some are increasing.”
But more study and more protection are needed, she said. Though some countries ringing the Atlantic have protections in place, others do not.
A rare sight
A nesting leatherback is a rare sight on Carolinas beaches; there have been eight recorded in North Carolina and 11 in South Carolina in the last five years.
South Florida and the Caribbean are popular nesting spots, and turtles leaving those areas to forage northward make the waters off the Carolinas coast one of the potential hotspots for conflict mentioned in the report.
Protections in place here include turtle excluder devices on shrimp trawlers that are large enough to let leatherbacks escape, and the use of circle hooks, rather than older “J”-shaped hooks, by Longline fleets.
Circle hooks, National Oceanic and Atmospheric Administration biologist Robert Hoffman said, are harder for the turtles to swallow.
When Hawaiian fisheries first substituted fish for squid as bait and started using circle hooks, bycatch of leatherbacks dropped 80 percent, Roe said. For loggerheads, it was 90 percent, and the swordfish catch increased.
Other measures in use elsewhere include closing certain waters to fishing at certain times and the creation of marine protected areas that function like wildlife-friendly national parks.
Roe said the most advanced effort currently is in Hawaii, where a NOAA agency issues electronic advisories to boats, based on satellite information.
It checks currents, algae blooms and weather and tells fleets, “On this date, these are the regions of the ocean where we advise against fishing because there are going to be a lot of turtles out there,” Roe said.
A basis for action
Roe hopes that the information in the recently published reports, when spread by conservationists, will become a springboard for cooperation between governments in affected areas.
Costa Rica and its neighbors already have cooperatively designated their mutual waters as a critical marine habitat, he said.
And in the area of greatest Pacific nesting – Papua, New Guinea, and nearby Indonesian provinces – nations are talking to one another but have no protections in place yet, Roe said. That area and the open ocean southwest of the Galapagos Islands are perceived to offer the greatest risk.
The ultimate goal, Roe said, is to find mechanisms to maintain a balance between an ancient creature’s right to exist and an important human activity.
“Our study is a step in that direction,” he said.