1. Following fantastic
2. Turning turtle
3. To track, to conserve
The tracks of two loggerhead sea turtles,
released in September, 2002, against a map of sea surface temperature
for February, 2003. Both turtles traveled along the edge of the
Gulf Stream before spending months in eddies (large whirlpools).
Turtle researchers are still getting data from #37200 as she heads
back toward North Carolina, more than 500 days later. Graph:
Catherine McClellan and Andrew Read, Duke University.
these rich fishing grounds, American swordfishing boats face restrictions
designed to prevent bycatch of sea turtles. Boats from other nations,
however, fish here without restriction.
Original map: NASA
with many large sea critters, the study of sea turtles suffers from
the now-you-see-them, now-you-don't problem. After a turtle hatches
on a beach, it may not be seen by humans until it returns 10 to 30 years later
to lay its own eggs. A male turtle may never reappear, even if it
survives what some researchers call the "gauntlet of hooks" in the
An admiring diver ogles a loggerhead sea
turtle. Loggerheads have a suicidal tendency to swallow hooks set
for tuna and swordfish. As new electronic tagging projects answer
questions about the movement of loggerheads and other long-distance
swimmers, could they help preserve vanishing marine creatures? Photo:
In the meantime, a sea turtle may migrate half-way across the ocean, or get hooked or netted.
Those lines and nets cause a lot of death.
Larry Crowder, professor of marine biology at Duke University, estimates
that 250,000 loggerheads get caught in fishing gear each year, and
30 percent to 50 percent die. Number-crunching, he says, suggests
"the Pacific loggerhead has a 50 percent chance of extinction in
two generations," and that a similar fate awaits Pacific leatherbacks,
about 60,000 of which get snagged each year.
So what if these turtles go extinct? Consider that the leatherback:
out with dinosaurs (the turtle's evolutionary history stretches
back 100-million years).
holds the sea-turtle deep diving record, more than one-half mile.
is the only sea turtle without a hard shell.
is warmer than the average reptile. "They aren't cold blooded in
the sense that most reptiles are," Crowder says. "Because of their
activity level and size, the temperature runs higher than background."
As marine biologists learn more about the movement of endangered and threatened ocean species, they are finding a predictable overlap with marketable species. Predators, not surprisingly, concentrate near prey, making it tough to sort plate-bound predators from endangered ones.
In the Atlantic, for example, loggerhead turtles move
northeast from the Carolinas along the Gulf Stream, toward the once-plentiful
fisheries south and east of Nova Scotia. Here, at the junction between
the warm Gulf Stream and colder, southbound currents, nutrient-rich
bottom water feeds blooms of plankton, starting a rich food chain
that attracts many large predators. The edge of the Gulf Stream,
turtle-tracker Andrew Read says, "is extraordinarily rich with many
large pelagic [open-ocean] organisms, swordfish, tuna, sea turtles
and marine mammals."
For centuries, fishermen have fished such hotspots as
the Flemish Cap, the Grand Banks, and Georges Bank, and that has
played havoc with the population of such large predators as tuna
and sea turtles. The population crash of sea turtles, says Read,
has impacted the American (but not international) swordfishing industry.
"The Grand Banks was extremely important for sea turtles, and it
was closed to American swordfishermen because of bycatch of sea
A: A pop-up satellite archival tag on a pole
used to attach it to a fish. Pop-up tags release from the animal,
pop to the surface, and send stored data to a satellite.
B: Two small archival tags.
C: A pop-up satellite tag rigged to a shark harness.
D: Small plastic tags, once the mainstay of fish tagging, are still
handy for some research.
Could technology come to the rescue? Already, shrimp boats in the Gulf of Mexico use turtle-excluder devices to prevent sea turtles from drowning in their nets. Knowledge of turtle behavior derived from satellite tagging could spawn other techniques for sparing sea turtles. For example, it's now known that sea turtles spend 90 percent of their time in the top 40 meters of water. If fish hooks are placed below that level, turtle bycatch should decline.
Could the new understanding also hatch a revolutionary