Frogfish form part of the Angler fish family, and are often described as the ‘Big Ugly Ones’ by divers who manage to spot them camouflaged against the coral. Although these creatures may not be the prettiest in the sea, they’re quite fascinating fish when it comes to how they attract and catch their prey. Angler fish make use of an illicium or fishing rod that is actually a modified dorsal spine. At the end of this appendage sits a soft, fleshy lure that brilliantly mimics smaller prey and attracts the prey of the angler fish dangerously close to where it lies hiding in camouflage.
Frogfish tend to stay in the same area for months and sometimes years, so it is possible for divers to revisit the same location and find the same frogfish time after time.
Because of their camouflage, frogfish are hard to find and even more difficult to identify. They mimic objects in their surrounding such as sponges, rocks and corals by changing to another colour, and can do so in a matter of days or minutes. Other concealment tricks include spots, stripes and fringes. Since frogfish are neither poisonous nor aggressive, their best defence is to avoid being seen.
The most interesting aspect of the frogfish, apart from his perfect camouflage, is the way he attracts his prey. Other fish wait until the prey swims close to their mouth, but the frogfish lures the prey (fish, crustaceans) to where it can strike. The lure is sometimes shaped like a worm, shrimp or a small fish therefore making it highly vulnerable to loss or damage by attacks or nibbling of potential prey as well as predators. Frogfish can regenerate their lure but might undergo a time of fasting until completion.
When feeding, the frogfish expands the mouth and engulfs his prey with a reflex that sucks it in whole by creating a vacuum pressure. They are so quick that they can actually catch a fish out of a school without the other fish noticing the disappearance. A frogfish will easily swallow prey that is larger than he is.
They are small stocky fish with loose prickly skin. The first dorsal spine is modified into a ‘fishing rod’ which is found just above their very large mouth. Just like any other fish, the frogfish has a dorsal fin, tail fin and pectoral fins.
Their limb-like pectoral fins assist in their locomotion. Frogfish don’t swim very often as most of them lack a swim bladder. To mobilise, they may walk or actually gallop. They can also move very quickly by sucking in large quantities of water through the mouth and forcing it out through the tiny gill openings.
Frogfish are widely found in tropical and subtropical waters of around 20°C temperature. They are shallow to deep-dwelling fish and live from 20m to 100m deep, max. 300m. They prefer sandy bottoms, rocks and coral reefs.
Keep your eyes wide open for these awkward yet adorable beings. As you can see, they are very photogenic so don’t forget to bring your underwater cameras.