Scientists learn red grouper operate as underwater architects
Monday, March 8, 2010
Red grouper are known for a few key characteristics -- their hue, which can range from pink to bright orange; their tastiness, whether they're grilled or sautéed; and their predation method, in which they ambush fellow sea creatures and swallow them whole.
But their least-known attribute might be the most valuable of all: They operate as underwater architects, transforming the seascape for myriad other forms of underwater life, rather than just residing there. That surprising discovery is forcing scientists and policymakers to recalibrate their approach to preserving the ocean's natural order -- and heightening tensions with those who fish for a living or as a hobby.
A team of scientists, led by Florida State University's Felicia Coleman, recently found that the red grouper off Florida's east and west coasts and throughout the Gulf of Mexico have created entire ocean communities by digging large holes in the sea's sandy bottom. In the same way beavers construct dams, red grouper excavate and maintain distinct holes whose rocky surfaces provide a place for coral, sponges and other marine life to congregate.
The discovery, published in January in the Open Fish Science Journal, highlights the extent to which researchers are just beginning to grasp the complexity of marine creatures' behavior.
"Our view of fish is changing," said Marine Conservation Biology Institute president Elliott Norse, whose group helped fund Coleman's research. "We now see fish as living, breathing entities, not only as meat."
This new understanding is changing the way federal and state authorities manage ocean habitats and is creating a stark new rift with fishermen. "The people who are in control want to prohibit fishing as much as possible," said Bob Jones, executive director of the Southeastern Fisheries Association. He added that the recent revelations about red grouper amount to an "excuse they can use to restrict fishing, commercial or recreational."
But to many researchers, fishery officials and even some fishermen, the fact that fish act as environmental engineers provides a compelling reason to protect them from exploitation.
"If you remove that fish, it puts into motion a whole chain of events," said Don deMaria, who used to fish for red grouper near Key Largo, Fla., but no longer does. "There's a whole lot of other critters that are affected. I'm not saying you can't catch them. But you can't do it to the extent we've been doing for the last 20 years."
Coleman didn't suspect initially that red grouper were capable of such engineering feats. Years ago, she was on a National Oceanic and Atmospheric Administration vessel in the Gulf of Mexico looking at images from a remotely operated camera and noticed the large holes on the sea floor.
"I was just sitting there, thinking, 'Why are there holes?' It came like a flash: The only thing it could be is red grouper," she said.
Coleman and a few colleagues, including her husband, Christopher Koenig, a fellow FSU professor, and Margaret Miller, an ecologist at the NOAA's Southeast Fisheries Science Center, tested her hypothesis. They trapped red grouper in a cage without a bottom; the fish dug out of it. The scientists placed black charcoal the size of sand grains on the sea floor to see whether the fish would move it; they scattered it everywhere.
"They started digging almost right away," Coleman said of the fish, adding that it was almost as if the scientists had offended the grouper's aesthetic sensibilities. "It was like, 'I just cleaned this place.' "
By building complex, three-dimensional structures that expose the hard rock beneath the sand, Miller said, red grouper create an environment in which seaweed, coral and sponges can thrive. These communities then attract everything from cleaner fish to female grouper seeking a mate.
"It's just a very cool ecological story," Miller said. "They really have this tremendous ability in getting these diverse communities of organisms to exist in a place that otherwise wouldn't be there."
Steve Bortone, executive director of the Gulf of Mexico Fishery Management Council, said he and other managers need to consider the environmental impact of red grouper digging patterns when they set future commercial and recreational catch quotas for the species. "We need to take into account this community aspect, which I think has been neglected," Bortone said.
Red grouper are not the only underwater architects. Tilefish construct some of the largest burrows in the sea, forming pueblos similar to those American Indians built on land centuries ago. In a 2002 scientific paper, Coleman and University of California at Davis professor Susan L. Williams described them as "virtual condominiums of burrows that are oriented horizontally in vertical cliffs."
Thomas Bigford, chief of NOAA Fisheries' habitat protection division, said researchers are looking in a different way at ecosystems they thought they knew. "We're learning the engineering happens at all sorts of different scales, at all sorts of different levels," Bigford said. "It changes the way we do things. It changes what we think of as protected habitat."