National Geographic Daily News
A novel batfish.
One of the new batfish species found in the Gulf of Mexico (file photo).

Image courtesy AMNH

Ker Than

for National Geographic News

Published July 9, 2010

Two new species of bottom-dwelling "walking" fish have been found in the Gulf of Mexico—right in the path of the Gulf oil spill, experts say.

Small enough to fit in a person's palm, members of the two species of pancake batfish might already be threatened by the ongoing Deepwater Horizon spill and the oil-dispersing chemicals being used in its cleanup, experts say.

(Related: "Oil Spill to Wipe Out Gulf's Sperm Whales?")

The new fish are so named because they are flat and can use their stout, arm-like fins to shamble along the seafloor with a stilted gait, reminiscent of a walking bat. (See pictures of other newfound fish that walk on their "hands.")

Once thought to be part of a known, widespread species, the batfish are actually three separate species, according to a recent physical reexamination of museum specimens. The species discoveries—to be described in an upcoming issue of the Journal of Fish Biology—were made before the Gulf oil spill began on April 20.

One of the new species, H. intermedius, is found only in the Gulf of Mexico (see map), including parts—such as coastal Louisiana—that are already heavily affected by the oil spill.

The other new batfish, H. bispinosus, lives along the northeastern Gulf coast, as well as along the eastern coasts of Florida, Georgia, and the Carolinas. Oil has begun to dirty the western coast of Florida in recent weeks. (See pictures of oiled Florida beaches.)

"If we are still finding new species of fishes in the Gulf, imagine how much diversity ... is out there that we do not know about," study co-author John Sparks, a fish biologist at the American Museum of Natural History in New York City, said in a statement.

Toxic Oil Poses Many Threats to Batfish

There are several ways the oil could harm the newfound fish.

For one, floating slicks of oil may be killing the pancake batfishes' plankton food supply.

Adult pancake batfish on the seafloor could be immediately harmed by oil gushing from the broken wellhead.

And the toxic crude may also kill off the fishes' eggs and larvae, which travel on the ocean's surface, said study co-author Prosanta Chakrabarty, a fish biologist at Louisiana State University.

What's more, chemical dispersants used to break up the oil into smaller droplets for easier digestion by microbes may be toxic to the fish, he said.

As a drastic measure to contain the disaster, cleanup crews have been applying dispersants underwater directly at the source of spill. However, it's unknown how—or even if—dispersants applied at depths biodegrade in the same way that they do at the surface.

Dispersed Oil's Impact on Fish Unknown

It's also unclear whether the right kinds of microbes exist in deep ocean to digest the oil once it's broken up by dispersants, Chakrabarty pointed out.

"How the oil breaks down and how it's affecting the fish is totally unknown. This shouldn't have been done without a study beforehand," he added.

(See "Gulf Oil Spill a 'Dead Zone in the Making'?")

"I'm afraid that next year when there's no oil on the surface, people will forget about it.

"People are going to say everything's fine in the Gulf," he said, "when in fact terrible things are still going on below the surface."

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