Fish Identification: Glassy Sweeper

Video Transcript

The marine organism we're going to identify now is the glassy sweeper. Glassy sweepers are also frequently referred to as copper sweepers. This is because their bodies are a shiny copper color. The distinctive marking that differentiates the glassy sweeper from the other Caribbean sweeper, the short fin sweeper, is a dark band that is found at the base of the glassy sweeper's anal fin. Glassy sweepers have a very distinctive body shape, its deeply keeled almost hatchet-shaped. They have large dark colored eyes and they range in size from three to six inches with most specimens being five inches or shorter. Glassy sweepers can be found throughout the Bahamas, Florida and the Caribbean but the frequency with which they are found varies considerably throughout the range. Part of the reason is the type of habitat in which they are found. Glassy sweepers are cave dwellers, this means they are always in dark areas, hence the large eyes. They can be found in caves, in ship wrecks, under reef ledges, and even sometimes under docks, wherever little light penetrates during the day, you could find glassy sweepers. They're also generally found in relatively shallow waters, often in fifteen feet or less. This school was found in the Bahamas in a coral cave, the bottom of which was about twenty-five feet deep and the top was about five feet below the surface. Glassy sweepers are also schooling fish. Schools can range in size from a few dozen fish to hundreds of fish. If one moves slowly into the cave or structure they inhabit during the day, the glassy sweepers will move aside and let the diver into their midst. Once in the middle of the school, if you remain motionless, the schooling fish will closely approach, apparently, unafraid. Glassy sweepers are nocturnal fish, another reason for the large eyes and why they hang out in dark areas during the day. At night, the school will emerge from their daytime lair to feed on zooplankton. One of the favorite zooplanktonic foods are the larval stages of invertebrates. That's the glassy sweeper.

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