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Written by Margaret Griffis, BT Contributor   
July 2017

Two invasive damselfish make an appearance, and escape capture

FFish_1ishnets. Tickle sticks. Intoxicants. That might sound like a fun night on the town, but it’s really a Tuesday morning in early June, and it’s pouring buckets of rain at the Miami Beach Marina. Adjacent to Pier F, five snorkelers in full wetsuits slip quietly into Biscayne Bay in search of a three-inch fish.

They’re hunting Dascyllus aruanus, more commonly known as a humbug damselfish or whitetail damselfish. It’s not a Florida native; in fact, its natural habitat is in the Indian and western Pacific oceans.

Dial back the clock for a moment, though. If you had the chance, would you have stopped the release of Burmese pythons, giant African land snails, South American Tegu lizards, and other non-native pests? Among salt-water species, the red lionfish (Pterois volitans) may be the best-known invasive.

No one will ever know how that environmental disaster began. There were sporadic sightings of lionfish off Florida in the 1980s, but the National Oceanic and Atmospheric Administration (NOAA) hypothesizes that the main infestation began when a hobbyist on Key Biscayne lost a waterside aquarium to Hurricane Andrew. Studies suggest that most Atlantic Ocean specimens are descended from just a handful of fish, possibly from that single aquarium. Further releases by pet owners only padded their numbers.

Lionfish have few predators here. Other factors that naturally keep their numbers down -- parasites, disease, and competition from other fish -- are nearly absent in the Atlantic and Caribbean. In a year, a single female can lay two million eggs, which are carried off by the currents.

So the lionfish spread easily. Sightings now range from Rhode Island to Colombia, and at some reef locations, scientists have counted as many as 200 individuals per acre. Voracious eaters, lionfish easily decimate native fish populations by as much as 80 percent.

At this point, there is no solution. The goal now is merely to keep their numbers down, which is how they ended up in fish markets and on menus. The hope is we’ll eat enough of them to put a dent in the population until somebody figures a way out of this mess.

Fish_2Hindsight is 20/20, but what does foresight look like?

At lunchtime on Friday, June 2, I’m as hungry as a lionfish. Grabbing a bite at Publix, I pedal over to the Miami Beach Marina, just south of the MacArthur Causeway, to enjoy the view at one of the outdoor tables by the water. The parade of sea creatures here often includes parrotfish, snapper, tarpon, manatees, and even a resident great blue heron that hunts for minnows.

The water is clear, and I notice a distinctive fish hovering close to the surface. I don’t recognize it as one of the usual reef fish, so I snap a picture to help me identify it, and finish my meal. Later, after a bit of sleuthing, I find the humbug on the U.S. Geological Survey website, listed as a “nonindigenous aquatic species.”

The USGS website also notes that one humbug, a “possible aquarium release,” was found in Riviera Beach in 2009, collected by Reef Environmental and Education Foundation (REEF), and relocated to the National Aquarium in Baltimore. Excitedly, and thinking about lionfish, I report the new detection at the REEF website.

The humbug was considered eradicated in the Florida wild -- but the following Monday, Lad Akins, REEF’s director of special projects, sends me an e-mail to confirm my sighting. REEF is a nonprofit based in Key Largo whose stated mission is to “protect biodiversity and ocean life by actively engaging and inspiring the public through citizen science, education, and partnerships with the scientific community.” The volunteer REEF Fish Survey Project is its main ongoing program, but removing non-native species is another activity. He commends me for my “citizen science.”

The next day Akins and his intern, Claire Mullaney, arrive at the marina to capture this fish. Andy Dehart, vice president of animal husbandry at the Phillip and Patricia Frost Museum of Science, and his colleagues, Pat Kelly and Gregg McIntyre, join them. Dehart explains that the humbug is a cheap starter fish for the home aquarist, but owners often lose patience with its aggressive temperament and may consider freeing it in the wild, because pet stores usually won’t accept returns.

He hopes to add this humbug to a Frost Science exhibit that serves as a teaching tool, explaining the importance of keeping non-native pets out of the wild.

Fish_3At the marina, the steady rain tapers and then the sun peeks out, but it’s still chilly enough in the water to don wetsuits. The culprit is spotted soon enough, but five hours later, there’s still no capture. Imagine an agonizing game of hide and seek with a fish and a tiny scoop net in a home aquarium. A simple chase gives way to new strategies and many overturned rocks. Now scale it up to the outdoors. This is the day’s tableau.

Curious angelfish, some as big as Frisbees, swim close by, apparently hoping to grab a snack newly dislodged by all the activity. A nurse shark rests on the bottom nearby. Several night herons and a snowy egret wait motionlessly for their own distracted meal to swim past. As for the humbug, large scoop nets draw near...ever so close...and then it darts away between rocks. Over and over. Even an anesthetic fails to slow it down. The hide and seek lasts until sunset.

Meanwhile, though, Akins has caught a glimpse of another fish. It looks similar to other damselfishes that are native to South Florida, but its tail is markedly different -- and it likely is another foreign invader. Akins has tentatively identified it as a spiny chromis damselfish (Acanthochromis polyacanthus), a native of the Indo-Pacific.

The spiny chromis is also a common starter fish. The bad news? Two aquarium fish at the same location suggests that somebody intentionally dumped them. The good news? This release, unlike that of the lionfish, may have been caught in time. Although it’s impossible to know how destructive a particular species will be once established, it’s best never to find out, which is why extirpation is the necessary goal.

Fortunately, these two fish keep to their particular territories. The following Sunday, June 11, round two in the fish hunt involves three people and three hours. Akins and two interns, Mullaney now joined by Lawrie Mankoff, try to use a large cast net, laid out across the rocks, to lure either fish over it. The humbug earlier preferred to linger over a deep break in the riprap (the rocks used to reinforce the seawall) but now, alerted, changes strategies and moves for the shallows instead. No amount of prodding lures it back out. The spiny chromis, meanwhile, swims everywhere but near the netting.

At one point, Akins’ expression noticeably changes. He looks defeated, and I wonder if he’s thinking about euthanasia. He acknowledges that this amount of effort isn’t the norm, and that the geography here greatly increases the difficulty of live capture. However, on this day, the fish retain their lives and their freedom.

By press time, 34 man-hours have gone into this effort, and the group plans to return again. These are professionals whose time could be better spent. The week following the initial attempts, Akins was away on a business trip, and the Frost Science group was busy at their newly opened museum. However, the public can’t just go out and help catch them, as trapping requires permits from the state and permission from the marina. So the fish gain more time to find potential mates and breed.

What will happen if these fish continue to evade capture? That’s a question I put to the Frost Museum’s Dehart during his team’s visit. “The important thing is getting him out,” he said at the time. “Our first option is always to look at live collection efforts, but we have to be cognizant of the fact that if the first person who saw a lionfish had removed it, we might not be here, in 2017, with a Caribbean epidemic.”

 

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