Glassy sweepers can make a diver paranoid

Glassy sweepers gather on French Reef. The small fish live in anywhere from 18 to 80 feet of water.
Glassy sweepers gather on French Reef. The small fish live in anywhere from 18 to 80 feet of water.

You know how it can be in dark or shadowy places. Monsters or scary creatures are everywhere.

Finning through Christmas Tree Cave on French Reef, I had the eerie feeling that I was being watched. I turned my head to the right. Sure enough, I was being stared at by hundreds of beady little eyes — actually some not so little. 

The eyes seemed to be saying, “whataya doin’ in our turf dude?” Some of the eyes were attached to transparent creatures – eerie.

I mumbled “you lookin at me?” into my scuba mouthpiece, paraphrasing Robert De Niro’s iconic scene from the 1976 film Taxi Driver. I couldn’t let these tiny fish, known as glassy sweepers (parapriacanthus schomburgki), think they had the best of me just because I stumbled into their neighborhood. After all, I had to keep my image as a cool scuba instructor.

I sort of swagger-finned out of the swim-through trying to look “bad to da bone.”

I was diving with Wally Zimmerman (66) from Lakewood, Ohio. It was his second time in two years diving with us in the Keys. He looked to be at ease with the whole beady eye thing.

Our first dive of the morning had been on the USS Spiegel Grove (LSD-32), a purposely-sunk wreck sitting in about 130 feet of water off Key Largo, which draws divers from around the world. The Spiegel, a Thomaston-class dock landing ship 510 long and 84 feet wide, was scheduled to be sunk on Friday, May 17, 2002 at approximately 2 p.m., but it prematurely began to sink, rolled over, and remained upside down with her bow protruding from the water for several days.

A salvage team sank the ship three weeks later but the stubborn ship landed on its starboard side and efforts to right her failed. Three years later Hurricane Dennis finally completed the job up-righting the Spiegel to its current position.

With its numerous swim-throughs and abundant sea life, it is a fun dive for advanced divers who closely monitor their air gage, stay out of places that cut-out swim exits readily can’t be seen and who perform required safety stops to “vent-off” nitrogen buildup from breathing compressed air at depth.

Our second dive was on French Reef, a spectacular triangle shaped reef area with dozens of ledges and swim through tunnels to explore. The reef’s limestone cliffs are inhabited by many corals and the gullies and crevices that line them are home to yellowtails, porkfish, moray eels, grunts and many other critters.

French Reef is in a Sanctuary Preservation Area (SPA), a biologically important area in the Florida Keys National Marine Sanctuary with special regulations to help sustain critical marine species and habitats, located approximately six nautical miles southeast of Key Largo. The reef is marked by several buoys, which are inscribed with the letter "F." Be sure to use a mooring buoy if it is available. If not, don’t anchor on the reef structure. ( http://floridakeys.noaa.gov/zones/spas/frenchreef.html )

Some of the more notable tunnels are Hourglass Cave, located 50 feet inshore from buoy F1, Christmas Tree Cave, which is filled with its namesake Christmas tree worms and located 50 feet inshore of buoy F3, and the largest tunnel, White Sand Bottom Cave, located in the center of French Reef.

Back to glassy sweepers.

To avoid writing about the wrong fish, I sent a photo to Lad Akins, director of special projects for the Reef Environmental Education Foundation (REEF), an expert on fish identification.  He said it was the right critter — a glassy sweeper.

Glassy sweepers, or copper sweepers as they are also called, vary in color from tan-yellow to silver. These fish, which grow from 3 to 5 inches long, have a big head with large eyes and a very wide mouth.

Now back to the eerie part. Young glassy sweepers are so transparent that their backbones can be seen — some species even have fluorescent organs. And, as you might expect, glassy sweepers are night creatures that aggregate in dark crevices and caves during the day. 

Glassy sweepers live 18 to 80 feet deep in the ocean in the Western Atlantic from southeastern Florida and the Bahamas to south of Brazil.

They eat zooplankton (small animals and the immature stages of larger animals) and invertebrate larvae (a distinct juvenile form many animals undergo before growing into adults).

Fish that eat glassy sweepers include yellow goatfish, bar jacks, cardinal fish and bigeyes. People in Japan eat a variety of them. Sweepers also are a popular aquarium fish.

Two days later, I was diving on the Conch Horseshoe portion of Conch reef southeast of Plantation Key. I shined my underwater light into a crevasse and there they were again — more glassy sweepers, which also have been reported by the National Oceanic and Atmospheric Administration (NOAA) as living in healthy Elkhorn coral.

Many divers I guide seem to be on a race to see how much of the reef they can cover in a single dive. Next time you scuba dive, slowdown and look into the holes and cracks in the reef. You might see something very much unexpected — like a glassy sweeper.

“These eyes sitting on the wall; they watch every move I make; bright light living in the shade.” (Lyrics from “Ghost” by Ella Henderson).

To learn more about glassy sweepers see: https://keys-field-guide.wikispaces.com/Glassy+Sweeper or http://reefguide.org/glassysweeper.html.

For an excellent resource in helping you to identify fish that live in the Florida Keys see: http://www.dep.state.fl.us/coastal/programs/coral/documents/2012/FIM/04-13/RVC_FL_Keys_Study_Guide.pdf.

Don Rhodes, in addition to a career in government affairs, has taught scuba for 29 years. He and his wife retired to Tavernier four years ago, where he works as an instructor for Conch Republic Divers .