Who’s Who: Juvenile Slender Filefish

Slender filefish on a sea rod. This one has the colors and design of a juvenile but doesn’t present the dewlap, or flap below its belly, often displayed by these fish. 

SLENDER FILEFISH (Monacanthus tuckeri) are only a few inches long and spend much of their time hiding out among gorgonians like this sea rod at the Turneffe Flats atoll off the coast of Belize.  They’re very good at camouflage and somewhat challenging to spot. They’re denizens of the Atlantic/Caribbean basin, found from the southeastern Caribbean as far north as North Carolina and Bermuda.

As adults, they tend to have white reticulated patterns on their bodies, with colors typically in variations of browns, yellow, tans and possibly grays.  But, they can change their color to blend in with their background.


Here’s a juvenile, its dewlap extended, photographed at Utila Island off Honduras, suggesting its camouflage capabilities.  As best I can tell, the white stuff is a variety of the free-floating fuzz ball algae, although Humann and DeLoach indicate it typically comes in variations of reds.

PRINCIPAL SOURCES: Reef Fish Identification Florida, Caribbean, Bahamas; Reef Coral Identification, Florida, Caribbean, Bahamas,  Paul Humann, Ned DeLoach; Peterson’s Field Guide to Atlantic Coast Fishes, C. Richard Robins, G. Carlton Ray, John Douglass.