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17. Decoy Scorpionfish (Iracundus signifier) (side view)



Subject:

Decoy Scorpionfish. Curiosity kills. The little Decoy Scorpionfish (Iracundus signifier), filmed here in the tropical waters of Mauritius, is one of the smaller members of the Scorpaenidae and can reach a length of 13cm/5.1inch. This cunning hunter who inhabits the waters the Indo-Pacific region, has a unique way of catching its prey.


It uses the movement of its dorsal fin as a lure. This dorsal fin has a strong resemblance of a small fish complete with an ocellated eyespot, a small black dot, located on the front of this fin representing the eye of a fish. This smart predator extends and wiggles this decorated fin in a figure-eight like pattern in a way that resembles a small swimming fish. Adding a subtle movement between the first two dorsal spines, which continuously move closer and then further away from each other, resembles the opening and closing of a fish's mouth.


Moreover, during the process of luring prey, the decoy scorpionfish actively changes the color of its fin and body. The dorsal fin, which is normally deep red in color, becomes more intense in hue, while the body of the fish appears duller, thus camouflaging it.


This behaviour adds to the effectiveness of its luring mechanism, making it difficult for prey to detect the decoy scorpionfish's true identity.


This mimicry, called aggressive mimicry, is used to lure in curious predators that are out to grab an easy snack, only to become a meal themselves.


The hunting technique of luring in prey is widespread in the living world. Carnivorous plants attract flies and other insects by making their traps resembling and/or smelling like flowers. Other fish species that uses this aggressive mimicry to their advantage frogfish and Stargazers. Just like the Decoy Scorpionfish who has several dorsal spines modified to resemble a small fish, frogfish have a single dorsal spine that terminates with a fleshy bait resembling worms or shrimp. In both cases the movement of the dorsal spine(s) results in fooling their prey. The Stargazer, a marine fish of the family of Uranoscopidae, uses its tongue, which resembles a worm, to attract his prey. The Stargazer lies buried under the substrate, wiggling its tongue above him on the sandy bottom to suddenly leap upwards when a curious or hungry critters moves close enough.


If you take a close look at the dorsal fin/lure of the Decoy Scorpionfish in this underwater video you will notice that spines and skin on the 6th and 7th dorsal spines are damaged. Why these spines are damaged we can only guess, but it is very likely that another predator was fast enough to attack the lure without being eaten himself by the Decoy Scorpionfish. It is not known if this damage will heal completely. Frogfishes however can regenerate their lure when the lure is accidentally bitten off.


Technique:

To accentuate the wiggling and movement of the dorsal fin that resembles a little fish, a matching sound effect was added to this video clip. Sounds (and music in general) are extremely important in storytelling videos, more than often a sound can insinuate things that are not visible in the clip.


Filming location:

This short underwater videoclip has been filmed in Mauritius 🇲🇺


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