Scientists have developed a new weapon in the war against poaching great white
sharks. As this ScienCentral News video reports, this new test will make it
easier to spot sales of the endangered species.
Great White Myth
Thanks to movies like Jaws, most people think of great
white sharks as vicious hunters. But the truth is, you're more likely
to get killed
by a falling coconut than a shark, and humans are hunting the great whites
right out of existence, selling everything from their teeth (for jewelry)
to their fins (for soup).
"Just in the Northwest Atlantic alone, the population of the great white
has plummeted by 79 percent just since 1986," says Ellen
Pikitch, director of ocean strategy for the Wildlife
Conservation Society (WCS). "It's ironic that great white sharks
have been thought of as being man-eaters. They've been maligned in the press,
and what is really happening is that humans are hunting the great white out
of existence, and not the other way around."
Great whites are among the world's most legally
protected shark species, but the laws are hard to enforce, partially because
of the lack of means to identify the sharks from their marketed parts. "Oftentimes
great white sharks appear just as either fins alone, cartilage pills or in
ground up flesh, possibly even mixed in with other species," explains
Pikitch. "So, it's really hard to tell from those shark products whether
or not you've got a great white shark."
image: Wildlife Conservation Society
So Pikitch and her WCS team, along with researchers
from Nova Southeastern University in Florida,
came up with a way to better protect these toothy beasts by developing a faster
way to find out whether great whites are being hunted illegally for their
meat—a DNA test.
DNA Taste Test
Most people are familiar with DNA tests from criminal investigations, and this
test is similar. But in this case, scientists must be able to rely on DNA
to distinguish one shark species from another.
Writing in the August issue of the journal Conservation
Genetics, Pikitch reported that the new test not only cut test time
from three days to 24 hours, but also is very accurate. "There are other
genetic tests that have been used to detect other species of wildlife, but
what’s different about this one is that it’s very sensitive, it
is very inexpensive to use, and it’s very rapid," says Pikitch.
"This is the first genetic test that has ever come out that enables the
person to tell great white sharks definitively, even from the tiniest bit
of tissue."
The researchers used a technique called polymerase
chain reaction, or PCR. The new test uses DNA from shark cell nuclei and
mitochondria, the "powerhouses" of the cells. The team tested 53
samples of great white and 68 samples of other shark species from all over
the world. None of the tests wrongly confused great whites with other sharks.
Sand tiger shark. image: Wildlife Conservation Society
"In order to know that this test is really valid,
really accurate, you need to be able to test it looking for false positives
and false negatives against other closely-related shark species," says
Pikitch. "We are able to distinguish between a false negative and a test
that wasn’t done properly. And that’s one of the beauties of this
test that makes it really unique—that we know for sure whether we have
a failure of the test itself, or there just aren’t any great white sharks
in the sample.”
The test can detect the presence of great white DNA in a mixture of DNA from
up to ten different commercially fished shark species. Pikitch points out
that although her test is just for great white sharks, the method could be
streamlined and used to develop similar tests for other species.
delicious
digg
magnolia
reddit
newsvine
netscape
netvibes
