Scientists probe secrets of marine reserve

Sea study: Scientists are on a reseach mission to learn more about several species of reef fish that congregate at specific places at certain times to spawn in Dry Tortugas, a marine reserve off Florida, the United States. - ?MCT photos

The rich sealife of Dry Tortugas, a marine sanctuary off Florida, provides research scientists with lots to study.

In the remotest part of Florida Keys, 112km 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 at an area called Dry Tortugas in masses when they are adults. Many species do so at specific spots and at specific times. The reason: to mate.

Recently, a group of scientists, a teacher, a marine sanctuary superintendent and two ROVs left Key West aboard the Nancy Foster 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 has been closed off with great controversy 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 US National Oceanic and Atmospheric Administration (NOAA).

Because of funding, it’s 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 510m.

The purpose is to learn more about fish populations, behaviours, corals and sea floor structure and to provide more data and information to justify the continuing existence of two large ecological reserves that closed down 391sqkm of prime fishing. This mission also is trying to help determine if recommendations made 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’s 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.

Loss of fishing grounds

Before the 9,616sqkm sanctuary was established in 1990, there was a bitter battle with residents distrustful of allowing the Federal Government to regulate the waters that provided many their livelihoods.

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 off another 391sqkm of prime fishing ground in Dry Tortugas, another battle ensued.

Scientists will use a remotely operated vehicle (ROV) to learn more about the structure of the sea floor more than 330m deep in Dry Tortugas.
Scientists will use a remotely operated vehicle (ROV) to learn more about the structure of the sea floor more than 330m deep in Dry Tortugas.

It was worth the fight for scientists, who said protecting the spawning grounds and nurseries there – called the “crown jewel of the reef” – was deemed critical for the sustainability of important reef fish species not only in this area but also Florida locations upstream. For decades, the area was being exploited by fishermen and damaged by large cargo freighters, which were dropping their large anchors on the corals and dumping their waste into the waters.

Most of what’s known about Dry Tortugas’ marine world has been discovered through a collaborative effort that has included scientists from the US National Park Service, which oversees Dry Tortugas National Park; the Florida Fish and 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 44km ecological reserve within Dry Tortugas National Park, which includes 259sqkm of marine waters, seven small islands and the national historic site Fort Jefferson. 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 US 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 the legal size of capture inside the protected area, while the measurements decreased or stayed the same in nearby areas of the Tortugas region open to fishing.

The report concluded that protection given these reef fish in this critical habitat was an important component for the recovery of their populations. It also strengthened the theory of inter-connectivity 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.”

Chris Bergh, who led the working group on regulations and marine zoning 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 that later will be analysed. In one project, scientists will go under water to perform surgery on fish, Donahue said. They will insert acoustic tags and sew them back up. In another project, a Mohawk ROV will go where divers cannot.

Seabed mapping

The Nancy Foster will methodically cruise back and forth on the ocean’s surface as if it’s “mowing the lawn” as a multi-beam sonar creates a high-definition map of the ocean floor by shooting a sound wave down at the bottom of the ocean and listening to its reflection. 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 time the science party is particularly interested in the west side of the Tortugas bank which is currently not protected, but the Sanctuary Advisory Committee has recommended 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 programme 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.” – The Miami Herald/McClatchy Tribune Information Services

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