From Herald Tribune: Questions about artificial reefs' effect on fish counts
Artificial reefs — long believed to boost fish populations — might be doing the opposite by concentrating fish and fishermen in the same places.
For decades, Gulf of Mexico fishing regulators have tried to rebuild depleted popular reef fish, including grouper and snapper, with limited success, despite increased restrictions.
Meanwhile, many coastal communities have looked to artificial reefs as a way to increase fish populations, to provide better fishing for the public and to dispose of large piles of refuse.
But while sunken ships, concrete rubble, Army tanks and oil rigs do a great job of attracting fish, they do not help them grow and reproduce, scientists and regulators say. Rather, they concentrate fish in widely publicized spots, making them more vulnerable to hooks and spears.
Despite their limitations, artificial reefs could still play an important role in helping select species survive to breeding age. But reefs designed for conservation are not likely to succeed if they also serve as fishing destinations.
"You can use them as a tool for economies. You may be able to use them as a tool for ecological benefits, but you can't necessarily do both simultaneously with the same reef," said William Lindberg, a fisheries science professor at University of Florida in Gainesville.
Artificial reef bonanza
With its vast shoreline, Florida has one of the nation's largest artificial reef programs, with about 2,600 statewide.
The program began in the 1970s, with counties taking the lead in deciding where to place the reefs and materials to use. With a few notable exceptions, most have become very popular fishing spots that contribute greatly to local economies.
From Pinellas County to Lee County, artificial reefs generate $253 million in spending each year, according to a recent University of Florida report.
Artificial reefs get tremendous support, and state grants allow counties to spend almost no money on them, said Laird Wreford, Sarasota County's coastal resources manager.
Sarasota County has several permits from the U.S. Army Corps of Engineers and the Florida Department of Environmental Protection to place material, such as old bridges and demolished buildings, off the coast as they become available.
That was the fate of the old Ringling Causeway, which is now part of the Lynn Silvertooth reef off the shores of New Pass. Wreford called the project a "glowing win" because it kept the bridge out of the landfill.
"It becomes basically a major fishery," he said.
Statewide it is up to each county to decide where to put reefs, within the confines of state and federal regulations. There is little collaboration with other counties, with scientists or with those who manage fisheries in state and federal waters.
Can reefs grow fish?
It is no secret that artificial reefs attract fish.
People have been using them for that purpose for hundreds of years, said James Cowan, a professor of oceanography and coastal science at Louisiana State University.
The question is whether they help fish grow and survive into adulthood, and several studies, dating as far back as the 1980s, consistently say they do not.
While reefs provide shelter for several species, including grouper and snapper, they do not provide a primary food source. For food, those fish need to travel.
Most natural reefs are small, providing limited shelter. Most artificial reefs, by contrast, are much larger, providing a great deal of shelter — perhaps too much.
In a 2006 study, Lindberg and eight other scientists found that grouper choose safety over sustenance by congregating on large artificial reefs. The result was that grouper of the same age on those larger reefs weighed significantly less than those on smaller, less sheltered reefs.
"They're willing to sacrifice a bit of growth so as to not be eaten," Lindberg said. The concern is that the grouper may not get sufficient food to reproduce if they choose to hide instead of eat.
Think of the overlarge reef as a city.
"You can have a city of several million people, but you better have some farmland out there producing food for them," Lindberg said.
Complicating the matter, people choose to place artificial reefs in places that are convenient for them, not for the fish.
"It turns out that some of those areas where reefs are deployed are areas that would be, in nature, the nursery habitat," Cowan said.
That encourages the adult fish, particularly snapper, to live among and compete with the juvenile fish. It also attracts more predators to what would naturally be nursery habitat. In the northern Gulf of Mexico, those shifts have brought large deep-sea fish, such as bluefin, closer to shore.
As a result, the sheltering fish face two threats instead of one: more natural predators and more baited hooks.
Because reefs attract fish, they can give fishermen the perception that they increase fish populations.
"If functioning properly, the number of fish on reefs farther offshore should increase," said Jon Dodrill, environmental administrator in the FWC division of fisheries management.
The key to the research — and for any other artificial reef that aims for conservation — is that it not be publicized as a fishing destination, Dodrill and other scientists said.
Recently, some communities in the Panhandle and Florida's east coast have expressed interest in building conservation reefs in undisclosed or hard-to-reach spots, Dodrill said. But no communities have made any reefs completely off limits.
Indeed, very few sites in the Gulf of Mexico are set aside as protected areas where fish can find refuge from fishing hooks.
But scientists and regulators said making fishing off-limits on some artificial reefs or even on natural reefs would probably produce the greatest benefit for exploited fish populations.
"That's just not a concept that is supported by the recreational fishing lobby — or even our own commissioners," Dodrill said.