ToadfishesBatrachoididae

The whole family comes down to one species in this sea, and it is not a fish anyone finds on purpose. That thinness is the interesting part, because toadfishes are numerous elsewhere. Their home ground is estuaries, harbors, mud flats and river mouths, water that goes warm, still, brackish and short of oxygen, and a family built for those conditions has very little reason to be on a coral reef.

The build is unmistakable. A toadfish is mostly head: a broad flattened skull, eyes set on top of it, a mouth that opens nearly the width of the body, no scales, and a fringe of fleshy tags along the jaw. It does not pursue anything. It takes a cavity, under a rock or inside a shell or a discarded can, fills the entrance with its face and waits for something to come within a body length.

They are also among the hardest fish in the sea to kill, in the least glamorous sense of that. They tolerate handling, transport, filthy water and long spells stranded out of it, which is how one of them, the oyster toadfish of the American Atlantic coast, became a standard laboratory animal, and why toadfish have been carried into orbit on the space shuttle so that their balance organs could be used to work out why astronauts get motion sick.

The family's real distinction is noise, and the species page here covers it: toadfish call with the swim bladder, using the fastest muscle in any animal with a backbone. What the calling is for is a nest. A male occupies a cavity and hums from inside it, sometimes for weeks; females that come in leave a single layer of large eggs stuck to the roof, and he stays behind with them, guarding, fanning and still calling.

The one that lives here is seen mostly at night or as a face in a hole under coral, and any encounter with it is worth recording. Some members of the family carry venom in the dorsal and gill-cover spines, and the safe assumption with a fish this poorly known is that yours might.