Are toadfish and frogfish the same creature?

September 1999

Toadfish and frogfish are members of two separate families and are not nearly as alike as their respective amphibian namesakes.

The toadfish gets its name from the sounds it makes when agitated or guarding a nest of eggs.

The toadfish gets its name from the sounds it makes when agitated or guarding a nest of eggs.

The toadfish belongs to the family Batrachoididae. The frogfish is a member of the Antennariidae family. There are 69 species of toadfish and approximately 50 species of frogfish swimming in just about all of the world’s oceans.

Toadfish are small to medium in size with large, distinctly flattened heads. Their mouths are noticeably wide and their bodies are tapered so that they resemble a tadpole with fleshy fins.

Off the coast of North Carolina, divers sometimes spot an oyster toadfish (Opsanus tau) hidden in a crevice or perched on bottom debris. But a diver has to look hard to spot this master of disguise. Its camouflage allows the oyster toadfish to blend  perfectly with its surroundings, waiting for a meal of small fish or crustaceans to swim by its oversized mouth. This habit of not working hard for its living has earned it a reputation as a lazy fish by scientists who have studied it.

Some researchers say the toadfish is a fish with an attitude – it’s been called belligerent, ill-tempered and aggressive. The toadfish’s name, and perhaps part of its reputation, comes from the grunting sounds it makes when caught. The male fish also makes the sound during spawning season, possibly as a way to protect the nest of eggs it guards during incubation.

While it may sound like a disagreeable fish, Opsanus tau is actually very important to humans. The oyster toadfish has been used in studies of insulin and diabetes, drug metabolism, hearing, dizziness and motion sickness. In fact, two oyster toadfish were along for the ride when John Glenn made his famous return to space aboard the space shuttle. The fish were part of a continuing study to help scientists better understand the mechanisms that control our sense of balance.

There is one species of toadfish whose name sets it apart from its motley kin - Sanopus splendidus, the splendid toadfish. Indeed, its striking, colorful appearance presents quite a contrast to the other members of its family. Found only on the reefs around Cozumel, Mexico, the splendid toadfish has a zebra-striped head and fins accented with wide, yellow borders. Its ventral fin, located on the  underside closest to its head, is entirely yellow.

The toadfish gets its name from the sounds it makes when agitated or guarding a nest of eggs.

Frogfishes are bottom dwellers with great camouflage abilities.

Opsanus tau and the Atlantic midshipman (Porichthys plectrodon), which is a member of the toadfish family, are common to the North Carolina coast. The midshipman gets its name from the 600 or so button-like light organs  arranged in rows along its body like a midshipman’s coat.

The frogfish has a different shape than the toadfish and is a bit more proactive in its hunt for food. The frogfish is round with a mouth that resembles a trapdoor. Above that trapdoor is a dorsal spine that, when wriggled over the mouth, acts as a fishing lure for small fish and crustaceans. The frogfish’s mouth can expand to 12 times its normal size in about eight milliseconds, enabling it to quickly snap shut and capture prey mesmerized by the lure. Talk about fast food!

Frogfish species come in many different colors, including black and yellow. Like the toadfish, it is able to camouflage itself and blend with its habitat. Some frogfish may look like sponges, complete with patterns in the skin resembling the holes found in sponges. Others may look like clumps of seaweed or seaweed-covered rocks. In addition to its coloring, the frogfish’s gill openings are hidden behind its pectoral or side fins. That way, prey is not tipped off to its presence by outflowing water from the frogfish’s gills.

Three species of frogfish can be found off the North Carolina coast: the ocellated frogfish (Antennarius ocellatus); the singlespot frogfish (Antennarius radiosus); and the splitlure frogfish (Antennarius scaber). They range in size from 3 to 15 inches and can be found along the bottom in shallow waters.