Frogfish Masters of Camouflage | Frogfish Marine Life Guide of Similan Islands

Frogfish: Masters of camouflage

Frogfish are a true joy to encounter underwater; these are one of the hardest fish to spot underwater, in fact most divers who encounter them will usually tell you it’s a real stroke of luck to bump into a frogfish on a dive. There are plenty of different species of frogfish for you to find, and they range in size from the tiny Randall’s frogfish which grows to 1.5 to 2 cm to the truly enormous by frogfish standards Ocellated frogfish which can reach 38 cm in length. The one thing that is constant—whether it is a 1.5 cm fish or a 38 cm frogfish—is that they are incredibly difficult to spot underwater! That is why they are considered by many macro hunters to be one of the top prizes to find underwater.

Highly Adapted Physique

Frogfish have one of the most specialized and adapted bodies in the underwater world. Through evolution they have sacrificed body shape and hydrodynamics to become masters of camouflage. The frogfish can indeed exhibit a rainbow of colours, from black to yellow with all shades or orange, pink and brown in the middle, as well as body textures mimicking the bumps and patterns of substrates such as sponges, algae, seaweeds, rocks and encrusting corals. Besides being able to change colors to match their surroundings, they have also developed many extra appendages which hang off their body and make them more difficult to spot. When it comes to hunting, the frogfish has also evolved some neat tricks. Its forward dorsal fin has evolved from a fin into a fishing lure. The fin is now a long thin appendage that sticks out forward over the fish’s mouth. The end of the fin is fatter and rounder to mimic the shape of a juicy shrimp, attracting greedy predators within the grasp of the frogfish. Not only can the frogfish move its lure to make it resemble a shrimp, it can also completely retract it. As is often the case with lures, there is a strong possibility that the lure will get damaged or broken—well that is no problem for the frogfish since they can just regrow and regenerate the lure.

Not the Best Swimmers

Frogfish lack a swim bladder, which means that unlike other fish which can control their buoyancy and swim through the water column, a frog fish would just sink if it tried to swim forwards. That is why frogfish prefer to walk around on the reef. They use their pectoral fins to walk or even sometimes gallop around on the sea floor. They have the ability to swim very short distances using their fins, but they are not very good at it and prefer to walk.

Fluorescent Fish!

You would think being fluorescent goes against every rule of camouflage. But apparently not so for frogfish. Like many other marine creatures, several frogfish species can make their lure glow to attract prey especially in dark conditions. Recent research has found that not only the lures are fluorescent, but actually a big part of the frogfish’s body will fluoresce in certain lighting conditions. One of the best ways to experience this is to take part in a “Fluo night dive”, which uses a modified dive light and a special light filter for your mask. You will be amazed at how many fish boast this strange fluorescence. Up till now it is not clear why frogfish have this capability on their bodies.

Habitat and Range

Frogfish are tropical fish, they can be found in almost all tropical waters around the world. As a general rule, whenever you find a coral reef you will find some species of native frogfish. They are also considered like a prized species in some muck-diving, low visibility locations around the world. There is no specific species that completely circumnavigates the globe.

How many species of frogfish are there?

While you may have seen a few different types of frogfish, it would make sense to assume there are maybe about 10-12 different species of frogfish around the globe. Well you would be mistaken, there are over 50 different species globally. The distribution will vary greatly from the Sargassum frogfish, the Giant frogfish, the Hairy frogfish, and the Spotted frogfish, which circumnavigate the tropics and can be found from the Red Sea all through the Pacific and as far afield as Micronesia. On the other hand, you also have highly localised species which care only find in one small spot on earth. An example would be the Tasselled frogfish which is only found in the central section of southern Australia, and the Side-Jet frogfish which is only found on the reefs around Hawaii.

How can I improve my frogfish spotting?

Spotting frogfish can be very difficult, they are masters of camouflage and don’t move that often making them very difficult to spot. The first thing you need to do is learn where to look, research the types of frogfish around the area you are diving, and find out what kind of coral etc they like perching on. Once in the water when you do see one of these specific corals take it slow and spend some time slowly scanning it. Remember to go slow and spend time looking. One trick that can make your life easier is to ask divers who regularly dive the area, since they might be able to point you the exact spot, because frogfish tend to pick a spot and stay there for a few days before moving on.

How can they catch prey if they are so slow?

Frogfish are one of the ultimate ambush predators, whilst they use the modified dorsal fin/lure to attract prey, when they strike they are incredibly fast. The speed of a frogfish strike can be as fast as a mind-blowing 6 milliseconds, add to that the fact that they have the ability to not only throw their jaws and mouth outwards, they can expand the size of their mouth by up to 12 times, allowing it to catch very large prey relative to its body size. Once the hapless prey is in the mouth the excess water is squirted out through the gills, and the prey is swallowed alive. At that point, the frogfish’s oesophagus firmly shuts, closing off any escape route to the prey which is still alive. The key to the frogfish’s technique is camouflage and lightning-fast strikes.

What size fish am I looking for?

You need to do some research before getting in the water to find out what kind of frogfish inhabit the waters you are diving in. Although frogfish sizes vary widely from 1.5 cm to 38 cm the vast majority are in the 10 cm to 25 cm range and so can be easier to find. If you really want to go out hunting for one of the tiny ones, you need to be armed with excellent knowledge of the dive site, great eyesight and a large portion of luck. To put finding frogfish into perspective, on a typical dive site you are looking for a well camouflaged object the size of a small ball in an area the size of half a football field!