A closer look at the quirky habits of the flying gurnard
There you are, finning across a rather ordinary bit of sea floor that's strewn with a few rocks and some patches of sea grass. Nothing remarkable going on here—until movement catches your eye, and what looked like a moss-covered chunk of debris suddenly sprouts neon-bright wings and glides away. No, you aren't narked. You've just seen a flying gurnard.
There are a number of fish lumped into the gurnard category, many of which have big frog-like heads and eyes, tapering elongated bodies and large pectoral fins. But the flying gurnards take the oversized fin thing to the next level, with pectoral appendages that measure almost a full body length when retracted and fan out into impressive and brilliantly-colored spans that resemble butterfly wings.
Despite the name, flying gurnards can't soar into the air like a flying fish, and actually spent most of their time on or close to the bottom. Most species have a somewhat dull and mottled coloration on their bodies, which help them blend into their surroundings. They have swim bladders but usually, maintain a slightly negative buoyancy. This helps them to remain stationary, or to hug the bottom as they move about unobtrusively in search of the small crustaceans, invertebrates and fish that make up their diet. In fact, it would be equally fitting to call these fish walking gurnards, because, in addition to their wing-like pectoral fins, they sport pelvic fins that sit far forward on the body, and resemble thin legs. They use these modified fins to push off the bottom in a walking-type motion.
Most of the time, flying gurnards keep their large wing-like pectorals folded back, and they may sometimes use the tips of these folded fins to help push along the bottom. The wings unfold when a gurnard feels threatened. It's partly a visual thing, as the sudden deployment makes the fish seem several times larger, and the typically bright, iridescent colors on the wings may cause a moment of confusion to a would-be attacker.
But the wings are more than defensive window dressing. They also provide lift and steering. When it decides to get up and go, a flying gurnard uses rapid sweeps of its tail to create forward motion and relies on the wings to keep it swooping along just inches off the bottom. These flights typically last just long enough to escape a threat, then the gurnard settles back onto the bottom. There are a number of videos posted on the Internet that show flying gurnards engaged in an escape behavior. In some cases, what is being shown borders on harassment. After startling the gurnard into flight, the diver with the video camera may keep following the fish for an extended period of time, forcing it to continue fleeing.
Though you are unlikely to hear it when on scuba, flying gurnards may talk to each other. These communications take the form of growling or grunt-like noises. In fact, the name gurnard comes from the medieval French word for grunt. The fish make these noises by thumping special muscles against their swim bladder. Scientists believe it is done to communicate with other gurnards. The fish only make these noises when there are others of their kind in the area, and the tones and patterns of the grunts vary throughout the day.
Don't look for gurnards among the corals. They are mostly likely to found in sandy or muddy bottoms broken up by isolated coral heads, rocks and patches of grass. Depending on the species, flying gurnards can grow to about 20 inches in length. There are several varieties found all across the Indian and Pacific Oceans, and one species that is common in the Caribbean and tropical Atlantic. If you do happen to spot one out foraging, and don't scare it into immediate flight. It can be entertaining to back off and watch the fish go about its bottom walking routine.
