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Home › Sea Creatures › Marine Animals › Vertebrates › Scorpionfishes › Stonefishes

Interesting Facts about Stonefish (Synanceia)

[Phylum: Chordata] [Class: Actinopterygii] [Order: Scorpaeniformes] [Family: Synanceiidae]

The stonefish is one of the top death-dealing fish on the planet. They thrive best in the Indo-Pacific coastal regions and some areas around the Caribbean.

This guide contains fun facts and interesting information about different species of stone fish, including where they are found, what they eat, and how they reproduce.

Reef Stonefish Habitat & Geographic Range

Synanceia (subfamily Synanceiinae) inhabit the tropical waters of the Indian and Pacific Oceans.

You could also spot these bottom-dwellers in parts of the Great Barrier Reef, the Persian Gulf, and even the Red Sea.

They are a ray-finned marine fish that tends to spend most time sitting in wait around shallow coral reefs and rock formations on the seafloor - especially large sunken shipwrecks.

Even though they prefer geographical locations with marine or brackish water, some scorpionfish families can survive in rivers and estuaries.

Pro Tip: Members of the venomous Synanceia genus produce overpowering neurotoxins (called verrucotoxin). The stonefish spine becomes erect if the fish feels threatened, and the venom is abruptly discharged from the base of the dorsal fin needles. Another section has more information about fish spike infection and puncture wounds from poisonous marine animals.

Stone Fish Characteristics and Behaviour

A compressed stout body, with a head that often has ridges and spines, helps to characterise most of the stonefish species.

In addition, like most scorpionfish species, the reef stonefish has a deadly sting contained inside the glands at the base of mucus coated sharp spines. For this reason, scientists consider them as being the most venomous fish in the ocean.

Here's the thing:

The operculum has no more than two (2) spines and the preoperculum (a bony gill cover) usually has five (5). The suborbital stay found in "mail-cheeked fishes" may also be attached to the preoperculum.

In fact, not all stonefishes have scales. But, the ones that do typically have ctenoid scales that have comblike teeth on the outer edges.

By and large, a single dorsal fin (often notched or incised) will contain up to seventeen (17) spines and seventeen soft rays.

The anal fin rarely has more than three (3) spines and up to nine (9) soft rays - though five is most common.

The pelvic fin features a single spine and usually two to five soft rays.

Some scorpionfish species do not have a swim bladder. This is one reason why you rarely see them swimming freely in the water column.

Stonefish Size and Weight

The largest stonefish can measure fifty (50) centimetres (20 inches) in length.

But, most adults will be about thirty five (35) centimetres long (14 inches) and weigh around two kilograms (5 pounds).

Stone Fish Camouflage

It could be a worthy contender for our list of funny fish names. But, the basis for the stonefish's common name is its strong resemblance to the "stones" and substrate in its natural surroundings.

They are experts at camouflaging themselves to match with mottled grey rocks. In fact, some even have algae growing on their body.

Scuba divers are usually aware of appropriate responses to any sightings of stonefish underwater. But, snorkelers and swimmers are more likely to step on one by accident and trigger a painful sting from stonefish spines.

Stone Fish Facts: The quantity of venom injected is commensurate to the "downward pressure" inflicted on the fish.

What Do Stonefish Eat?

Some stonefishes have muted hues (e.g. mottled brown or yellow). Whereas, others display a range of vibrant red or orange colours that render them close to undetectable when concealed among the rocks and reefs.

As a consequence, its physical structure and camouflage is vital for its survival. The feathery fins also help it blend in with the surroundings - often stony coral reef formations.

Perciformes are suction feeders. Hence, stone fish feed in the same manner by capturing its prey before projecting a suction zone to suck the food into its mouth.

Put another way:

Being a typical "sit-and-wait" predator, most of these spiny ray fish wait patiently in disguise. A sudden strike from their powerful jaw and mouth captures passing prey before they swallow it whole.

In general, the typical diet of stonefish includes aquatic crustaceans (e.g. crabs), bottom-dwelling invertebrates, sea snails, and small bony reef fishes.

Fun Fact: Stonefishes are typical examples of sedentary vertebrate animals that make very little movement - until the night time when they start hunting for food.

Synanceia Stonefish Species List

Reef Stonefish Reproduction

Even though they are solitary creatures, scorpionfish gather together and congregate in small groups to perform the mating process.

Some species engage in internal fertilisation. Whereas others will scatter around 15,000 eggs in a gelatinous "egg balloon" mass in the water column.

Following fertilisation by the males, the eggs float near the surface to avoid most egg-eating predators. The eggs hatch within a few days and the young will swim down to the relative safety of the reefs, once they have grown large enough to do so.

Stonefish Predators and Threats

One of the little-known facts about stonefish is that their deadly venom means they have few natural predators in the wild. Nonetheless, large snappers, sharks, and rays will hunt them down.

Pro Tip: The IUCN Red List of Threatened Species recently assessed many of the stonefish phylum and classified almost all of the species as being of "Least Concern" (LC).

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