BLACK DURGONS (MELICHTHYS NIGER) HAVE LONG BEEN BOTH A FAVORITE FISH OF MINE and a challenge to photograph. A favorite because I like their dramatic effect – all that blackness with blue stripes along their anterior dorsal and anal fins – and their wiggly technique of swimming powered by those fins.
A challenge because, well, they’re black. They suck up light like a black hole. And (see above), they’re wiggly. I’ve shot more black, blobby photos of black durgons wiggling away from me than I care to count.
LOCK AND LOAD
Black durgons are triggerfishes, members of family Balistidae, famous for having strong, hefty spines on their front dorsal fins they can erect and lock in place with a shorter, second spine – the “trigger.” The trigger spines are usually described as weapons of self-defense – predators that grab triggerfishes can expect significant injury.
But the spines are also handy for wedging themselves in place in crevices and holes for sleeping or hiding. When not in use, these spines are kept in a groove along the front dorsal fin.
WORLDWIDE. AND NOT
Melichthys niger is found in tropical waters around the world. The black durgon isn’t. While M. niger lives in apparently great quantity and happiness throughout the Indo-Pacific Oceans, in that basin it’s just called the black triggerfish. Only in the Atlantic-Caribbean basin is it the black durgon.
Where the name comes from is hard to pin down. The only non-triggerfish definition of “durgon” I could find is an old English term meaning “an undersized person or animal.” The Oxford English Dictionary does indicates that the “g” in durgon is a hard g.
NOT REALLY BLACK
Surprisingly, although M. niger usually appears completely black at a distance, the right lighting reveals rich subtleties in its coloration – a network of blue streaks between their eyes and their foreheads, corresponding yellow pattern toward their beaks. Also, they can change colors. Photographers more patient than me have captured images of the black durgon looking almost uniformly blue.
Like all triggerfishes they’re animals with compressed, oval bodies and thick scales that add to their defenses against predators. Their wiggly swimming reflects the fact that they move primarily with motion of their long anterior dorsal and anal fins – their caudal fins are not usually involved. They’re not the fastest fishes in the ocean but they have pretty precise control of their movements. In fact, by reversing their fins’ undulations, they can move backwards.
A random factoid is that they can rotate the eyeballs on each side of their heads independently.
They have small mouths equipped with strong jaws and chisel-like teeth. This is good. They’re omnivores, eating anything and everything from algae and seagrasses to sea urchins. They uncover crabs, worms and clams in the seafloor by dislodging sand with puffs of water. They attack sea urchins the same way, sometimes, reportedly, with several jointly puffing streams of water to overturn the urchins to get at their vulnerable undersides. They’re reputedly so good at hunting that other, smaller fishes shadow them to dine on sloppy seconds.
WHEN & WHERE
Black durgons are described as benthic/pelagic fishes – that is, they may be found above the reef or near the bottom, feeding. They may sometimes be found in loose aggregations of fellow M. niger’s, but basically they’re loners.
Except when mating, which is governed by lunar cycles and tides. Males and females prepare nests in the sandy bottom together, blowing sand away to create a foot-wide, inch-deep basin for thousands of eggs. Black durgons are singular in that the females then care for the eggs, making sure they’re well-supplied with oxygen by puffing water on them.
Naturally, the mass of gelatinous eggs attract predators like wrasses and damsalfishes, so they also stand guard. According to some sources, the male may patrol the area to protect the nest from above. It’s not a lengthy vigil. The eggs hatch within a day or two of being laid.
PRINCIPAL SOURCES: Reef Fish Identification Florida, Caribbean, Bahamas, Paul Humann, Ned DeLoach; Reef Fish Behavior, Ned DeLoach; Marine Life, Caribbean, Bahamas, Florida, Marty Snyderman & Clay Wiseman; Eyewitness Books – Fish, DK Publishing; Encyclopedia of Fishes, John Paxton and William Eschmeyer; Watching Fishes, Roberta Wilson and James Q. Wilson; “Black Durgon,” Mexico – Fish, Marine Life, Birds and Terrestrial Life website; “Triggerfish,” nationalgeographic.com.