By Ryan Yousefi
By Chuck Strouse
By Terrence McCoy
By Terrence McCoy
By Terrence McCoy
By Michael E. Miller
By Kyle Munzenrieder
By Michael E. Miller
The fact that manmade reefs attract fish is not in dispute. The question, as it has often been formulated, is whether artificial reefs are discrete ecosystems that act as spawning grounds and nurseries and actually add to the overall fish population, or do they merely draw fish from elsewhere, concentrating them in a place where they can more easily be viewed by divers and killed by fishermen.
"Since day one there's been a philosophical battle," Mostkoff states. "Do they merely concentrate biomass, particularly fish, or do artificial reefs actually increase fishery resources? I think that if they're constructed properly, artificial reefs are capable of doing both."
Frost disagrees, and so do some local scientists. "The literature is full of mixed opinions on a lot of this," contends the park superintendent, who fears that artificial reefs may steal fish away from struggling natural reefs. "So far the scientific community has not reached any generalized conclusions about artificial reefs. In the face of that, I have to err on the side of caution. The premise behind a national park is that we leave the natural system alone."
"I have seen absolutely no evidence of any increased production," adds Bohnsack, the National Fisheries Service biologist. "There simply aren't any definitive studies."
The closest thing to a definitive study, Bohnsack and others suggest, is a 1989 Bulletin of Marine Science monograph by Jeffrey Polovina and Ichiro Sakai. The two researchers used 30 years of data from a large bay in Japan to draw some rough general conclusions about artificial reefs. Because of a fluke in political boundaries and differing regulations, one side of the bay was rife with manmade reefs, the other almost devoid of them. The only detectable enhancement in the overall aquatic population on the reef side of the bay versus the other occurred in a single species -- octopus.
Bohnsack likens artificial reefs to saltwater crack houses: They attract a lot of fish, but it may not be healthy for them. "They build 'em like mad but they don't spend any money to study them," he complains. "A lot of these things are strictly for public relations. Other times they're building artificial reefs because no one's catching fish like they used to. But it's probably not going to help the problem [of depletion], and if they're not done properly, they could actually cause harm. At the very least, it takes a lot of money that could be better spent elsewhere, on studying and preserving sea grass or mangroves, for example."
Bohnsack cites studies of sea otter extermination in Alaska to illustrate the delicacy of marine ecosystems. With the otters gone, sea urchins proliferated, gobbling up all the available kelp. In the same way, Bohnsack believes, the poverty of South Florida fisheries is due to the removal of too many so-called top predators -- larger, older fish, exactly the kind fishermen hope to find on artificial reefs. "For every problem there's a solution that's simple, obvious, and wrong," Bohnsack says.
Bill Lindburgh, a University of Florida marine biologist, agrees: "Artificial reefs are not a panacea. You're not going to promote these reefs as prime fishing locations and then expect them to add much to the surrounding ecosystem. It's easy to operate under the assumption that there's an ecological or biological benefit because you see more fish. It's a reasonable but false assumption to think there's an overall increase in the fisheries stock. That's the common step in logic that's taken by the public."
Lindburgh, who has just concluded a much-awaited five-year study of the gag grouper and its relationship to artificial reefs near the mouth of the Suwannee River, thinks it's time to refocus scientific thought about manmade marine habitats -- in part because the attraction-versus-production question now seems insoluble. "The attraction-versus-production question may be an inappropriate phrasing," he theorizes. "What we're really asking at this point is whether, if the fish are gaining a biological benefit from settling on the reef, that's benefit enough to offset the increased fishing."
Nova Southeastern University professor Richard Spieler echoes his colleagues. "I think the aggregation-versus-production question is mainly of historical interest," he says. "We had a lot of people putting in artificial reefs with a lot of assumptions that weren't correct. It pointed out a need for research. Now there's a real research impetus, and the result is a belief that it's going to depend a lot on the species, the location, and the natural history as to whether you're going to get production or aggregation of a particular animal in a particular season at a particular site. I don't think there is a general answer to the original question. Rather, the question has become more complex."
Spieler points to recent studies of Nassau grouper in the Virgin Islands. The fish not only settled on artificial reefs, but they seemed to prefer them to natural reefs, growing fatter than the cousins they left behind in traditional low-tech coral neighborhoods. The implication is that Biscayne National Park superintendent Frost could be right in his concern that artificial reefs might recruit some reef fish away from the park's natural habitat.