This week, I had a funny experience snorkelling with some guests at Los Arcos. One of my guest, who was snorkelling with his wife, was trying to describe a fish he kept seeing, but every time he went to show his wife this fish, it vanished. He started to describe it for her, but the description made her laugh at him and probably think he had perhaps had one too many tequilla´s. It´s about 3 foot long, green, no grey, no blue and it is clear with blue spots, and long pouting mouth and a long wire like thing sticking out from it´s bottom. She swam away from him in search of some normal people. I had to put him out of his misery and let his wife know he was not being silly. What he had seen was a cornetfish, also called Fistularia, meaning pipe in Latin. They are plentiful in the area and you see them every time you put your face in the water.
The Cornetfish is a stalking predator that actively hunts such ecologically diverse species as small blennioid fishes, halfbeaks, herrings and snake eels. It swims in the open day and night as they are so slim, they are hard to spot, and they have the ability to change color rapidly to blend into their surroundings. This explains our snorkelers inability to correctly describe the color of the fish. The blue spots are indeed stripes, but I did not mention this. As for the tail, some people once believed the cornetfish’s filament tail was a stinger, but that’s not true. I cannot find any explanation for the use this filament may have to the fish. My guess is that it makes the fish look bigger to potential predators.
Cornetfish get close to their prey in several ways. Sometimes they hang or drift motionless in the water like a stick. When an unwary fish swims by, the “stick” comes alive and vacuums up a meal. Fish that hunt like this are called water-column stalkers and include the cornetfish’s’ close cousins, the trumpetfish. Cornetfish also hunt by “riding” on top of a parrotfish. In this fashion, the cornetfish uses the herbivorous parrotfish as a mobile cover from which the cornetfish can ambush small fish. This is a good example of a type of symbiosis called commensalism, where one organism benefits and the other are unaffected. One researcher even found a lionfish inside the stomach of a cornetfish. Apparently, cornetfish are unharmed by the lionfish toxins. On the flip side, they are considered a tasty snack for other fish to eat and have no weapons to defend themselves with, which is probably the reason they appear to be slightly skittish and vanish in the blink of an eye at the slightest movement. I once saw a cornetfish sticking out of the jaws of a giant hawkfish. The poor little thing looked scared, and rightly so, as I was the last thing it saw!