Boxfish

Quick Take

• Grilling a boxfish doesn't necessarily make it safe to eat, and the reason why defies everything you'd expect about cooking seafood. Cooking risks explained →
• A boxfish's brilliant yellow color isn't just decorative. It's sending a message that predators ignore at their peril. See the warning colors →
• Its boxy shape makes it one of the ocean's slowest swimmers, yet sharks still think twice before attacking. Here's why. Predators and defenses →
• Juvenile and adult boxfish look so different you'd barely guess they're the same species, a striking change that signals something important. Juvenile vs. adult changes →

It’s easy to see how a boxfish got its name. Its body is shaped like a small box! These are saltwater fish living on coral reefs in the Pacific and Indian Oceans, as well as the southeastern Atlantic Ocean. They’re sometimes sold as colorful additions to an aquarium.

3 Boxfish Facts

• Poison protection: Boxfish have a deadly neurotoxin in their skin that they can release when threatened by a predator.
• Lots of eggs: Though not much is known about the breeding habits of the boxfish, biologists have found that a female boxfish can lay eggs every day for one month.
• Sand blower: A boxfish sometimes blows water into the sand in search of the vegetation and prey in its diet.

Classification and Scientific Name

Ostracion cubicus is the scientific name of the Yellow boxfish. The Latin word Ostracion means shell, which refers to the carapace or shell structure of this fish. Cubicus means cube-like.

Trunkfish and cowfish are some of its alternate names. It’s in the Ostraciidae family and the class Actinopterygii.

Types of Boxfish: The Different Species

The Ostraciidae family of boxfish contains 23 species. Some of these family members live in the Atlantic Ocean, while others live in the Pacific or Indian Oceans. Here are some of the well-known species:

• Spotted boxfish (Ostracion meleagris): These fish live in the Pacific off the coast of Mexico. They are sometimes referred to as the white-spotted boxfish. This is due to their ornate, bright blue lower body, spotted with yellow.
• Roundbelly cowfish (Lactoria diaphana): It’s called a cowfish because of the two small horned structures sticking out of its head. They are found in the southeastern Atlantic Ocean on coral reefs as well as in the Pacific Ocean off the coast of California.
• Smooth trunkfish (Lactophrys triqueter): This fish is named for the shape and texture of its body. It’s dark brown and spotted with white. They live in the Atlantic Ocean off the coast of Mexico, Florida, and the eastern coast of South America.

Boxfish Appearance

The appearance of a boxfish changes as it grows older. If you see a brilliant yellow boxfish spotted with black, you know it’s a juvenile. But if you see one with a blue-gray, dull yellow, or even brownish body with faded spots, you know it’s an adult boxfish.

Their boxy shape is due to the shell structure beneath their scales. This odd shape makes them very slow swimmers. In fact, some describe their movement as hovering, instead of swimming.

Generally, these fish grow to between three and 16 inches. The longest recorded specimen is 18 inches.

Large fish and sharks are predators of the boxfish. Considering its small size, it would seem like easy prey. But one of the most interesting facts about the boxfish is that it has a few effective ways to defend itself.

First, this fish has a bright yellow body spotted with black. The brilliant, ornate color of its scales is a warning to predators that it contains poison. Indeed, if this fish becomes stressed, it releases poison into the water around it. This poison can make a predator sick or even kill it.

Some species of boxfish have horned structures that can deter predators.

The sturdy shell beneath the scales of a boxfish also makes this fish unappetizing to many types of predators!

Distribution, Population, and Habitat

These saltwater fish live in the Pacific, Indian, and southeastern Atlantic Oceans. They are found off the western and eastern coasts of Australia. Boxfish also live off the southeastern coast of the United States.

They have a coral reef habitat and occupy lagoons. These fish live at a range of depths from three to 920 feet.

Most of the boxfish species are classified as Least Concern by the IUCN Red List.

Boxfish Predators and Prey

Boxfish have an omnivorous diet. They hover over the rocky slopes and near the sandy bottom of a lagoon, looking for small prey.

What eats a boxfish?

Large fish, sharks, and humans are all predators of the boxfish. Some humans eat them while others keep these ornate, blue, yellow, and spotted fish in aquariums.

What do boxfish eat?

The diet of a boxfish includes marine algae and small fish, as well as krill and crustaceans.

Reproduction and Lifespan

These fish reproduce in the late spring in warm water. They form groups consisting of one male and two to four females. The females lay eggs that float near the surface. The male boxfish releases sperm to fertilize the eggs. A female boxfish can lay eggs every day for a month. The gestation period is unknown.

Boxfish live four years on average.

Boxfish in Fishing and Cooking

Boxfish are captured around coral reefs as food and exotic pets.

Some people successfully keep boxfish in aquariums. Of course, they are saltwater fish that need a water temperature between 72 and 78 degrees Fahrenheit. In addition, they require a water pH level between 8.1 and 8.4.

The horned, colorful, or otherwise unique appearance of this fish is a key reason why it is so popular with aquarium enthusiasts. Plus, they are available at a reasonable price online. As a note, the price of this fish varies depending on its coloration.

Some people do eat boxfish. In fact, many say grilled boxfish has a delicious flavor and contains healthy protein. However, caution is advised, as the toxin produced by some boxfish species is heat-stable and may not be destroyed by cooking, making consumption potentially dangerous.