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Invaders quickly became problem

Nov. 19, 2010


The inaugural Keys lionfish derbies are done, and the numbers are in — in three events, 53 teams of divers eliminated 654 of the venomous non-native fish from Keys waters.

The count:

Upper Keys, Sept. 11 (27 teams): 534 lionfish.

Middle Keys, Oct. 23 (five teams): 21 lionfish.

Lower Keys, Nov. 13 (21 teams): 109 lionfish.

Natives of the Indo-Pacific, lionfish have become the dominant fish on reefs in the Bahamas and Caribbean; in the United States, lionfish have been documented on the east coast from Rhode Island to Florida.

In January 2009, a diver off Key Largo documented the first lionfish in the Keys; within a year, the species had spread throughout the island chain.

Lionfish were probably introduced to the region through the aquarium trade, intentional or accidental releases of captive fish; another possibility is that lionfish arrived in ships’ ballast water.

With the species established, the Florida Keys Marine Sanctuary and Reef Environmental Education Foundation (REEF) decided to sponsor a series of lionfish derbies.

“We’re still in the initial stage of the invasion, but lionfish populations are really getting dense,” said Alecia Adamson, REEF’s field operations coordinator. “Obviously, densities are high enough for us to hold these events and have hundreds of lionfish brought in.”

In their native range, lionfish densities are about 80 fish per kilometer; in the Bahamas, where they have no enemies, densities of 200 per kilometer have been recorded.

Lionfish have been documented off Marco Island, Tampa, the Panhandle and Louisiana, but so far, none has been reported off Lee County.

“I’d say it’s inevitable they’ll get up there,” Morton said. “You have that warm water they feel comfortable in, so they’ll take hold. It’s something we’ll be watching.”

Lionfish are voracious predators, and their main threat is to native juvenile fish.
According to one study conducted in the Bahamas, a single lionfish can reduce recruitment of reef fishes on a small patch reef by 80 percent in five weeks.

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“Once they’re established, they don’t move around,” Keys sanctuary superintendent Sean Morton said. “They just hang around one spot and eat.”

Among the lionfish’s favorite targets are juvenile snapper, grouper, crabs and shrimp.
“They tend to eat smaller fish, but they eat a whole lot of them,” Morton said. “That’s a very worrisome thing. They’re eating the next generation of our fisheries.”

The Keys lionfish derbies had three purposes.

“First, obviously, to get rid of as many lionfish as possible,” Morton said. “Nobody has any illusions that we’re going to eliminate them in the Keys, but we can kill a lot of them.”

Second, the derbies were held to raise awareness.

“We want to let people know, if they see a lionfish, kill it or report it,” Morton said. “Another part of the outreach is to let folks know you can eat lionfish. It’s a delicious fish.”

Finally, the derbies were a chance for scientists to collect data.

All teams were asked to fill out data sheets, giving coordinates of where lionfish were seen and what kind of habitat the fish were in — nine habitat types were listed on data sheets, including patch reefs, rock bottom and artificial reefs.

As teams turned in their catch, scientists from the U.S. Geological Survey and National Oceanic and Atmospheric Administration removed each fish’s stomach and head. Stomach contents will show what lionfish are eating in the Keys; the fish’s ear bones will tell how old each fish is, which will indicate how fast lionfish are growing in the Keys and at what age they reach maturity. This, in turn, will show where and how fast the invasion is spreading.

Skin samples also were taken for DNA analysis.

At this point, researchers don’t know how lionfish will affect the Keys.

“The invasion happened really quickly,” Morton said. “It will take a while to gather the type of data where we can say, ‘OK, this is the impact on the coral reef and other habitats.’

“Then, if we want to take a whack at controlling them, where we can get the most bang for our buck, that’s where the science comes in.”

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