Monday, December 1, 2008

There are a minimum of 11,750 propeller scars in Florida Bay, according to the findings of a peer-reviewed Everglades National Park study scheduled for release next month.

"You can pretty much map the banks of Florida Bay based upon the scarring," said David Hallac, chief of the park's natural resources branch, while previewing the study at a recent workshop hosted by the Florida Keys National Marine Sanctuary.

The study, titled "Patterns of Propeller Scarring of Seagrass in Florida Bay," was funded by the park, the National Parks Conservation Association and the South Florida National Parks Trust.

Researchers also found that at least 8,000 acres of bay bottom are scarred by propellers. The actual number, though, could be up to 10 times higher, Hallac said, because scientists did not use high-resolution cameras to record their aerial surveys. Lower resolution lenses miss many of the submerged scars.

Propeller groundings wreak havoc with the Florida Bay ecosystem, especially by damaging seagrass, which serves as a nursery for species ranging from shrimp to stone crab to yellowtail snapper.

Once damaged, some of Florida Bay's seven seagrass species can take several years to recover.

Park officials took prop scar damage into effect in spring 2007 when they released a series of alternatives for managing Florida Bay and the rest of Everglades National Park waters over the coming decades. Those proposals, which in general terms would have scaled back motorboat access in park waters, set off an avalanche of criticism from South Florida fishing and boating interests.

Among other things, critics questioned the scientific basis for the park proposals, especially as they related to boat use and propeller scars.

Out of the carnage came plans for two studies -- one measuring propeller scars, and another tracking changes over the years in Florida Bay boat traffic, which also is scheduled for release next month.

The two studies are playing a role in the shaping of a new and much-delayed set of Florida Bay management alternatives. Park Planner Fred Herling now says those proposals will be out by January, more than a year after originally planned.

During his presentation last week, Hallac showed slides of three spots where researchers were able to compare recent photographs with pictures of similar quality taken five years ago.

"Our analyses suggests that from 1999 to 2004, total length of scars at all three sites increased by a factor of three," Hallac said.

The findings of the park service study are in rough congruence with a less scientific study undertaken by local fishing captain John Kipp over the past year.

In November 2007 and again in July, Kipp poled identical regions around the Buchanan Keys just west of Lignumvitae Key. During that span, the number of sites where he counted prop damage increased from 59 to 155.

In the area a bit further north around Twin Key, Kipp recorded 28 GPS sites with prop scars in November 2007. He recorded 78 such locations in August.

Jerry Lorenz, a biologist who heads Audubon of Florida's Tavernier Science Center, presented Kipp's findings at the Nov. 18 workshop as part of a push for baywide caps on boat and engine size. Lorenz said multi-engine boats with powerful motors are causing massive damage to the bay.

"Clearly education is the most important thing, but there are some people who just aren't going to bother," he said.

In what could be a preview of the debate that will follow the park service's release of the new management alternatives, Lorenz's presentation drew a rebuke from fishing enthusiast Jim Trice, one of the architects of Alternative E, a management strategy supported by a cross section of Florida Bay users. In an e-mail, Trice called Kipp's prop scar study, and Lorenz's use of it, "Totally anecdotal evidence being supported by a Ph.D."

Alternative E calls for a boater certification program that would seek to protect the shallow and tricky-to-navigate waters of the park through mandatory education. It also calls for idle speed zones along the shorelines and a noncombustible motor zone on the Snake Bite flats near Flamingo.

But Trice opposes limiting boat sizes.

Park planner Herling confirmed at the workshop that all the proposals in the next round of alternatives would include mandatory education and permitting.

Trice urged people to "think big, start small, scale up."

rsilk@keysnews.com