Samoa Guide, 14. Manini and pone

Manini spawning is a spectacular event. When conditions are right, thousands will assemble to spawn at a particular time and place. They often spawn in or near the reef channel (ava) at dusk when the tide is high. Their behavior and coloration are noticeably different at this time, as they swim around in a agitated fashion and change color to white with wider black bars. This seething mass of fish mills about until they can't take the excitement any longer. A group of them will suddenly burst upwards in the water column, spawn, and return to the seafloor again, all in a split second. Although this happens fast, you can tell that the fish actually spawned because the milt expelled by the male fish looks like a puff of smoke from a gun. When the spawning action really gets going, it looks like an underwater version of popcorn popping.

After spawning, the fertilized eggs drift away with the currents. About one month later, the small manini that survived this larval stage are ready to settle back onto the reef. Pone (Ctenochaetus striatus, or the lined bristletooth surgeonfish) are a different type of surgeonfish in two respects. They are a dull brown color and they have funny teeth. Their lack of spectacular coloration is somewhat of an embarrassment in tropical waters which are renown for brightly colored fish. Pone are, however, one of the most abundant fishes on the reefs, so they must be doing something right.

Their teeth have evolved very differently from other surgeonfishes because what they feed upon is quite different. Instead of having actual teeth to bite off algae the way that alogo and manini do, pone have a mouthful of bristles which they use as a comb or brush to collect the detritus that lies on reef surfaces. The detritus they eat includes all the small bits and pieces of formerly living plants and animals. The detritus in your backyard, for example, might include grass clippings, old ulu leaves, decaying coconut husks, rotting papayas, and numerous unseen dead insects. Not a pretty meal, to be sure.

Detritus is found everywhere, but few large animals can make a meal out of it. Pone can, and that may account for their abundance and widespread distribution on coral reefs.

Every several years or so, pone have a very successful spawning event, and uncountable numbers of their young (pala'ia) settle onto the reef. Pala’ia are very pretty and look like small dark alogo. But their beauty fades as they grow, and in just a few weeks they turn brown in color.

Manini and pone are two favorite food fishes found just about everywhere in shallow waters around the islands of American Samoa. Like alogo, they belong to the family of fishes called surgeonfish because of their sharp knife blades that fit into grooves near their tail. Manini and pone are rather meek fishes, however, and they do not seem to wield their weapons much.

The manini (Acanthurus triostegus) is a small fish about 5 inches long. Its coloration is yellow with
vertical black bars, which looks a bit like a prisoner's uniform and that's why this fish is also called the convict tang.

The manini also cleverly use their schooling behavior to get food. They like to feed on the thin green algae turf that grows on reef rocks, but these algae patches are usually guarded fiercely by alogo surgeonfish and damselfishes (tu'u'u) who are nasty to intruders.

Just the sight of a manini gets them livid with rage. A single manini would not stand a chance to get by these guards, but a large group of manini can succeed. The alogo and damselfishes are simply overwhelmed when hundreds of manini descend into their territory to feed. While the alogo futilely chases one manini away, a hundred others are gobbling up its garden.

Manini often swim in large schools containing hundreds or thousands of individuals. There are two good reasons for this schooling behavior -- it helps them escape predators and it also helps them get access to food. First, when a large fish attacks a school of manini, the manini scatter in all directions like a shotgun blast. This commotion momentarily confuses the predator and the manini get away. Each manini thus has a better chance of not getting eaten if it stays in a group.