Text of article ‘The TRUTH Behind That Fish Video’ published on website HolyMolyScience.com on March 30^th 2017.

We’ve all seen it by now but if you haven’t, take a minute out of your day and watch below (or watch for the hundredth time if you like!):

[video insert]

For those unable to watch right now, the video – taken by Belgian tourist Camille Lefevre – starts normal enough. Lefevre and husband Mathis are on a small boat enjoying the sun when they spot an odd sight.

The camera pans to show tens of fish leaping from the ocean and falling back in. Keen eyes will note a couple are in the air for quite a while but the first time the Lefevres get spooked is when a fish flies -yes, flies - right at them, landing in the boat!

Mathis Lefevre attempts to pick up the fish and put it back in the water but it runs away from him. That’s not a typo, the fish doesn’t flop around as he tries to grab it, it runs away with tiny legs just visible on its underside. After a brief freakout, the fish is tossed overboard and glides for a few seconds before turning sharply and dropping into the water.

What is happening? Have fish learned to fly? And walk? Are they going to learn to ride a bike and enter a triathlon? We asked Prof. Langdon, lecturer in Marine Biology at University of Portsmouth to explain.

“The first thing to say is that the fish in the video is called a Sea Frog and it lives in the reefs around the Papagaios islands in the Atlantic Ocean. The name is because at night they gather on rocks and make and noise that founds like a group of ribbiting frogs. If you listen carefully to the video, you can hear the fish in the boat make this grunting sound as it evades capture.”

The Professor continued, “Sea Frogs are part of a group of fish called Sea Robins. That name comes in part from their enormous wing-like pectoral fins which when fully spread out form a circle as big as the fish itself. Sea frogs are a little different. Their wings are actually quite a bit smaller in area, and more oval shaped. This allows the rays inside the fins to support it more, making it quite rigid when fully extended. When the fish builds up speed and leaps from the water, these fins form a wing surface to catch the air and allow it to glide.”

The fish more commonly known as ‘flying fish’ are an entirely unrelated group, but they have similar adaptations: strong, broad fins, and a strengthen spine to allow them to keep their rigid in flight, giving them an aeroplane shape. Sea frogs also do this though less well. Flying fish can glide for hundreds of metres, while sea frogs are at most fifty or sixty metres. The thing that makes them impressive however is their ability to change direction in the air, which is related to their other quirk: moving on land.”

We have seen other fish move around on land like mudskippers or epaulette sharks. Are these sea frogs doing the same thing? The professor says no.

“Most fish that move on land use their fins and push themselves along, kind of like a seal would use its flippers, or they push with their tails. Most fish are ‘ray-finned’ meaning their fins are a membrane of skin stretched between long, thin spines or rays. Sea frogs, and their sea robin relatives have lost the membrane between the front three rays of the pectoral fin giving them what look like six crab legs near to their heads. They use them for sensing prey but also have fairly specialised musculature allowing a good deal of control over them and so the fish can be seen to ‘walk’ along the sea floor using its free rays as legs.”

“Sea frogs have developed and strengthened this musculature more to allow them to move on land for short periods. Also, in addition to being able to move their free rays independently, sea frogs have good control over the rays in their gliding fins. They can therefore change the shape of the ‘wing’ in the air to gain a bit of height or change direction.”