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Here's a fun fish question I received by e-mail last week from a reader, Lynn: "I have been trying for years to find the name of a fish I saw a couple of times whilst snorkeling off the beach of Mahe in the Seychelles. Both times I tried to show it to my husband, it disappeared! It was long, about one meter, rather like a pipe, with a long 'snouty' nose, and incredibly, it had a long wirelike appendage hanging from its tail. ... I'm really curious because I feel that that particular fish was communicating with me."

That fish did communicate with Lynn, because the sighting happened nine years ago and she still remembers it.

The fish was a cornetfish, also called Fistularia, meaning pipe in Latin.

There are four types of cornetfish in the world, all growing to about 5 feet long including the "tail." This extension is a strand of soft tissue trailing from the rear of the fish.

Some people once believed the cornetfish's filament tail was a stinger, but that's not true.

Not one of my nine fish books mentions a theory about what use this filament may have to the fish.

My guess is that it makes the fish look bigger to potential predators.

Cornetfish have the same predators as other reef fish -- that is, carnivorous fish bigger than themselves -- but they also have to be careful about swimming close to the surface.

One early Hawaii researcher mentions finding skeletons of cornetfish on remote Necker Island, where seabirds carried them ashore.

Cornetfish are efficient predators themselves, eating small fish and shrimp by sucking them into their expandable mouths. One researcher even found a lionfish inside the stomach of a cornetfish. Apparently, cornetfish are unharmed by lionfish toxin.

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 is unaffected.

The most common cornetfish in Hawaii have greenish backs with light blue spots and lines. Below, they are silvery white.

These fish, however, can change color rapidly to blend into their surroundings.

At night or when resting on the bottom, Hawaii's cornetfish take on dark barred patterns.

Cornetfish are docile animals that sometimes allow swimmers to get close enough for an eye-to-eye encounter. Sudden movement, however, spooks them, and they dart into hiding so fast it seems they disappeared into thin air.

I suspect this is what happened when Lynn tried to show the fish to her husband.

Now, finally, after nine years of wondering, Lynn has proof that her odd fish really exists.