Florida Keys

Scientists probe secrets of Dry Tortugas

In the remotest part of the Florida Keys, 70 miles west of Key West and accessible only by boat or seaplane, there’s an underwater world filled with habitats as happening as Miami’s hottest nightclubs.

Several species of grouper, snapper and other reef fish congregate to the Dry Tortugas in masses when they are adults. Many species do so at specific spots and at specific times. The reason: to mate.

On Monday, a group of scientists, a teacher, a marine sanctuary superintendent and two remotely operated vehicles (ROVs) left Key West aboard the Nancy Foster federal research ship for a 14-day mission to the isolated area — where the only buildings are a Civil War-era fort and a lighthouse. They are continuing studies, monitoring and mapping of a magical and still-mysterious marine world that, with great controversy, has been closed to fishing, anchoring and, in some parts, diving since 2001.

“Everybody always wants to know: Where’s the science?” said Sean Morton, superintendent of the Florida Keys National Marine Sanctuary, which is part of the National Oceanic and Atmospheric Administration (NOAA).

Because of funding issues, it is only the sixth such research trip since 2005.

Time on the Nancy Foster, one of NOAA’s 16 research vessels, is competitive and precious. Chief sanctuary scientist Scott Donahue said he has crammed as many projects as he can into the itinerary, including fish-tagging, mapping of the sea floor for structure and fish abundance, and ROV exploration of Riley’s Hump, the deepest part of the sanctuary with a maximum depth of about 1,700 feet.

The purpose is to learn more about the fish populations, behaviors, corals and sea floor structure and to provide more data and information to justify the continuing existence of two large ecological reserves that closed 151 square miles of prime fishing: 91 around the northern area known as Sherwood’s Forest and 60 in the southern portion around Riley’s Hump.

This mission also is trying to help determine whether recommendations made last month by the Sanctuary Advisory Council to move the boundaries of the southern reserve are scientifically sound.

“Part of the reason we keep doing the science: Are we protecting the right areas?” Morton said.

It is all part of a comprehensive review that formally began in September 2011 with a sanctuary condition report and is scheduled to be completed in 2016.

Before the 2,800-nautical-square-mile sanctuary was established in 1990, there was a bitter battle with independent Keys residents distrustful of allowing the federal government to regulate the waters that provided the livelihoods of many of them.

In 2001, fishing was allowed in most of it, but there were 23 small no-take zones that still angered many. So when the sanctuary managers proposed closing 151 additional square miles of prime fishing ground in the Dry Tortugas, another battle ensued.

It was worth the fight for the scientists, who said protecting the spawning grounds and nurseries in the Dry Tortugas — called the “crown jewel of the reef” — was deemed critical for the sustainability of important reef fish species not only in this area but in other Florida locations as well.

For decades, the area was exploited by fishermen and damaged by cargo freighters, which were dropping their large anchors on the corals and dumping their waste into the waters.

Most of what is known about the Dry Tortugas’ marine world has been discovered through a collaborative effort that has included scientists from the National Park Service, which oversees Dry Tortugas National Park; the Florida Fish & Wildlife Conservation Commission (FWC); and the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, led by marine biology and fisheries professor Jerry Ault.

In 2007, the state established a 46-square-mile Research Natural Area (basically what the feds call an ecological reserve) within Dry Tortugas National Park, which includes 100 square miles of marine waters, seven small islands and the Fort Jefferson national historic site. The goal was to protect shallow-water habitats and reef species near the two existing ecological reserves, which all were believed to be interconnected.

“The state gave them five years to prove their case to see if it would stay a reserve,” Morton said. “It was all guns out to try to characterize corals, birds, turtles and fish, fish, fish. It took a whole bunch of people working together. But five years later, [FWC] said: ‘OK, you’ve proven your case.”

The National Park Service’s five-year report on the Research Natural Area found that both abundance and size increased in red grouper, mutton snapper, yellowtail snapper and hogfish at or above legal size of capture inside the protected area, while the measurements decreased or stayed the same in nearby areas of the Tortugas region that were open to fishing.

The report concluded that protection given the reef fish in the critical habitat was an important component for the recovery of their populations.

The report also strengthened the theory of interconnectivity between the reserves thanks to an acoustically tagged mutton snapper.

“We have fish listening stations [like cell towers] all over to see the movement back and forth between the Tortugas,” Donahue said. “We could see the most famous mutton snapper in the world. It hangs out in the North Tortugas reserve and three times in one summer goes down to Riley’s Hump on the same lunar cycles to spawn, spawn, spawn.”

One FWC biologist nicknamed this migration corridor the “sexual highway.”

Longtime commercial fisherman Manny Herrera said he is among the many anglers in the Keys who are skeptical of the science that has been provided in the past.

“But I didn’t accept being part of the working group [involved in the sanctuary review] because I’m an anti-conservationist,” he said. “I’m very much for conservation. You see what happens in places like Japan that don’t have fisheries because they were not managed and taken care of.”

Herrera said he believes the preserves in the Tortugas are successful, especially because of their remote location with superior water quality and limited human presence. Higher gas prices also have helped reduce fishing in the area. He would like to see at least one other “true reserve with no users and good law enforcement” in another part of the Keys as a test.

Chris Bergh, who led the working group on regulations and marine zoning that Herrera participated in for the sanctuary’s comprehensive review, said there has not been much resistance to the Tortugas reserves now because “they have not unduly harmed people’s businesses or recreation.”

The current battles have been over the protection of other habitats in the Keys where there is great demand by commercial and recreational fishermen, divers and boaters.

Evaluation of the Dry Tortugas reserves can help make the case for the importance of other no-take zones in environmentally sensitive waters where the marine world also is battling climate change, ocean acidification and pollution.

During this research trip on the Nancy Foster, divers, ROVs and high-tech sonar equipment will gather information to be analyzed later.

In one project, scientists will go underwater to perform surgery on fish, Donahue said. They will insert acoustic tags and sew them back up.

In another project, a Mohawk ROV will be used to help answer a question Morton said he hears often: “Why are you protecting the super-deep areas in the Tortugas South Reserve that go down about 1,700 feet?”

The ROV is going where divers cannot.

The Nancy Foster will methodically cruise back and forth on the ocean’s surface as if it’s “mowing the lawn” while a multibeam sonar creates a high-definition map of the ocean floor by shooting sound waves to the seabed and listening to their reflections.

Simultaneously, another machine that is like a “fish finder on steroids” is superimposing information about the marine life over an ocean-floor structure map.

“This is a collaborative effort to look for critical bathymetric features that fish might be using as cues for an aggregation site,” Donahue said.

Morton added: “This information doesn’t have the ‘wow’ factor of fish-tagging and ROVs, but it’s what really tells the story: ‘What is the place and what is the type of habitat? What is the depth? What are the features? Is it flat ledges or deep drop-offs?’”

This time the science party is particularly interested in the west side of the Tortugas bank, where large snowy grouper hang out. This western area is currently not protected, but the Sanctuary Advisory Committee has recommended that it be added to the no-take zone. In exchange, the committee also recommends giving a southern portion of the reserve back to fishermen.

“There’s a perception in the community that the sanctuary only takes and never gives back,” said Bergh, the Florida Keys progam director for The Nature Conservancy. “I’d like to see the sanctuary prove that wrong. As new information becomes available, the sanctuary can adapt, and it does listen to science and the public.”