Piscis lapis (Stone fish)

Common names: stoning fish, lapidation swarm, pebble school, hunting stones

Basic info

Description: Stone fish are small greyish polymorphidae that change their forms between fish and stone. In fish form they have a rather flat nozzle, thick mouth layered with sharp little teeth, and six fins in addition to the tail fin. In stone form they are usually rounded and have grey, rather rough looking exterior. When changing into stone form, Stone fish condense their body, therefore their stone body is usually a little smaller than their fish body. In both forms they have grey colouring with a dull silver glint, the silver is much clearer in the fish form, but some Stone fish have silvery shimmer in their stone form as well.

Habitat: Oceans, with a preference to warm waters. They are most commonly found in the Indian Ocean.

Diet: Stone fish are carnivorous, and their diet consists mainly on other fish. Their unique hunting swarm technique allows them to feed on fish much larger than themselves, and would be enough to feed the entire school.

Habits & Culture

Stone fish live in shoals, the smallest include 20-30 members, the largest can reach over a hundred. The same shoal may fluctuate greatly in size around hatching season, as the hatchlings remain with their parental shoal until they are about a year old, at which time they reach adult size and can hunt and protect themselves. The young Stone fish then choose whether to remain with their parental school, or form a shoal of their own.

Stone fish reproduce by polygynandry spawning, is an area chosen by the shoal. During the summer months, as the water reach higher temperatures, the shoal will locate a secluded area that they can easily guard. They essentially build a nest by lying close together, while in their stone form, creating a tight circular shape. Once the nest is arranged, the females of the shoal deposit unfertilized eggs in the soil at the middle of it, then the males then release their sperm to fertilize them. The eggs hatch in about 48 hours, but it takes 2-3 days before the larva can swim and feed independently. The shoal remains close to their young throughout, until the eggs hatch the nest is kept constantly, so in small shoals the adults would often not move, even to eat, until the eggs hatch. Once hatched, the larva require feeding, so the adults change between watching over the young and hunting for food for the shoal. The larva usually stay in stone form, which makes feeding somewhat complicated, but keeps them safer.

Once the young stone fish are able to swim, the shoal will leave the nest area and move about, keeping the young ones in the middle of the school for their protection. The young Stone fish enjoy playing at hurtling themselves at rocks and at each other, which sometimes has distressing results if they don’t manage to change form fast enough. After a few weeks the larger of the young are big enough to join hunting parties, before that their stone form is simply too small to be affective.

Hunting is the main way Stone fish get food, although they can feed on plankton and other small marine beings, their preference is to get a large prey that will be enough to feed the shoal. Stone fish hunt by pelting their prey to death; while in fish form, they dash towards their target, gaining speed, and then shift to stone form just before hitting. The momentum of the hit usually through the Stone fish off some distance, where they shift again to fish form and begin again. The shoal coordinates the attack, and usually the hunt ends in a few minutes, with the meat of the prey softened from the pelting, and the shoal enjoying their meal.

Stone fish are deceptively small and delicate looking, and the few humans who encountered a shoal and deemed them ‘adorable’, soon changed their minds…