TigerperchesTerapontidae

This is an Australian freshwater family that got out.

Most terapontids live in rivers, floodplains and waterholes across 🇦🇺 Australia and 🇵🇬 New Guinea, where they are known as grunters and where almost the whole family stayed. A small minority never left salt water, and it is that handful, the terapons and their relatives, that spread along the coasts of the Indian and Pacific Oceans and reached this one. Four are listed here, which is a fair reflection of a group whose center of gravity is a continent away and inland.

The ones that travel are built to tolerate almost anything. They are small, silver, marked with dark stripes or arcs, omnivorous to the point of eating whatever the tide left, and comfortable in water that swings between fresh, salt and warmer and saltier than either. That is the profile of a colonist, and it explains both how far they got and where you find them: the sandy surf line, the mouth of a lagoon, a harbor wall, the shallow silty water inside a bay. None of that is reef, which is why divers on this coast almost never see them and anyone wading does.

They are noisy fish, and this family makes its sound a different way from the grunts. Rather than grinding tooth plates in the throat, a terapontid has muscles attached to the wall of the swim bladder that contract fast enough to drum it, and the result is loud enough that fishermen name the animals after it. Hold one out of water and it complains.

The young of one of them do something worth knowing: juvenile crescent grunters have been recorded taking scales and pieces of fin off larger fish, a living the reef's fangblennies make a full-time profession of. They grow out of it. And one of the four here, the fiveband flagtail, is not a terapontid at all but a member of a neighboring family, filed alongside them because it lives in the same broken water and looks the part.