for National Geographic News
Although many fish populations are declining, a few species appear to be increasing their numbers, in particular those beyond the reach of fishing fleets.
These fish live in the abyssal plains, flat expanses of the ocean floor at depths of 10,000 to 20,000 feet (3,000 to 6,000 meters). Abyssal grenadiers, for example, have more than doubled in number between 1989 and 2004, according to a new study.
The fish also called rattails or deep-sea grenadiersgrow to about 2 feet (60 centimeters) long and are long-lived. But almost nothing is known about their reproductive habits.
Most experts agree that abyssal grenadiers are slow-growing animals, but estimates of their life spans vary from 6 to 60 years.
The deep-dwelling fish are extremely tough to study.
When they are brought up from the depths, gases in their bladders expand, popping the fish's stomachs and making their eyes bug out. No abyssal grenadier has ever been kept in captivity.
Why the Boom?
David Bailey, a research fellow at the Scripps Institution of Oceanography in La Jolla, California, is the lead author of the new study. He sees two reasons for the species flourishing.
"First," Bailey said, "natural climatic and oceanographic changes have increased food supply to the seafloor, triggering an increase in deep-sea fish abundances."
"Second, the absence of direct fishing pressure on the deep-sea fish has allowed these changes." The report appears in the March issue of the journal Ecology.
The abyssal plains, covering more than half the Earth's surface, are the world's largest habitat.
The researchers used a camera sleda camera-equipped rig towed behind and below a shipto survey the depths.
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