Many people think of members of the grouper family as a tasty main course, rather than a brilliant adornment to the coral reef community. However, reef crests throughout the Pacific to the Indian Oceans and even the Red Sea, are graced with a myriad of small brilliantly colored little fishes of this family (Serranidae), known to reef hobbyist as Fairy Basslets or Anthias.
redfinAnthias are smallish fish by general standards, most reaching only 4 to 6 inches in length at maturity. They all display brilliant colors: red, pink, orange, yellow and some even lovely purples. Their size makes them ideally suited for reefs, especially since they feed mostly on plankton and do not display any aggressive behavior towards any other reef inhabitant.
These colors are part of their territorial display features, and actually may aid in camouflage as the light fades and with it, the colors of the reef. They have lunate (half-moon shaped) tails and fusiform (bullet shaped) bodies which allow bursts of sudden speed when need for feeding or defense. Most of the time they are slow swimmers and may not even move much for great lengths of time, except when aggressed or when a sudden supply of food becomes availabe and they need to swim to reach it.
All anthias have, in varying distinctiveness, a bar that runs from the eye to the pectoral fin (tail fin). These fins are broad and soft, perfect for maneuvering through their coral homes. Overall the fishes shape is very characteristic and makes Anthias easy to differentiate from other fishes. Their mouths are large and in one genus Mirolabrichthys, the snout is very pronounced.
Anthias live in large colonies around branching and table corals (Family Acroporidae) among which they find shelter and a place to rest at night. They are generally diurnally active (meaning they are active during the daylight hours), and spend a great deal of time hovering above their chosen coral head, scooping up their plankton diet. The forereef and reef crest are rich in drifting plankton, and the currents bring the food right to the waiting fishes. On any given reef, Anthias colonies may be made up of thousands of specimens.
Colonies are made up of smaller groups which are structured like a harem with an approximate ratio of one male to anywhere from five to twenty females.
They are sequential, protogynous hermaphrodites, meaning they can change from sex to another – from male to female. They hatch as females, which are gently colored in pink and orange colors.
After about a year, some of the females will change to males. Out of that group of bachelor males some will become “supermales”. It is not possible to predict how many female will change to males. The fact remains though that some do.
These changes take only a matter of weeks as color and behavioral patterns change. The ovaries degenerate and give way to the appearance of testes. Male coloration is generally much more brilliant than that of the females. Male colors go from vivid reds to oranges to purples, or any patchwork combination of the above which is exactly what makes these fishes so colorful. The dorsal fin develops into an elongate filament, and the eye-to-pectoral fin bar intensifies in color.
Supermales defend their territories and their harem from neighboring supermales, while bachelor males hover around below the supermales and females. The juveniles remain towards the center of the colony. This behavior is typical of harems that are not yet ready to move to the spawning phase as, when that happens, behavior changes completely as we shall see.