In the Water: Fishes

Flying Gurnard

Dactylopterus volitans

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About

Known for massive pectoral fins that are phosphorescent blue along their border, the flying gurnard is a mid-sized fish (growing up to 50 cm/20 inches in length) that can be found on sandy and rocky seafloors around Saba. Flying gurnards are ray-finned fish, meaning their fins are supported by bony spines connected by skin. Much like the ribs of an umbrella, these rays, when spread, make the webbing between them expand. Their impressive fins are dual-purpose: When expanded, they can make the fish nearly double in size, tricking predators into thinking they’re too big to be food. For yet more intimidation, it’s also hypothesized that by ballooning the front half of itself, the gurnard may look more like a stingray (barbed stinger included).

The rays in the front segment of each pectoral fin can also move independently, allowing them to scour the seafloor. These fish can even use their pelvic fins like legs to “walk” across the seafloor, which is a lot less energy-intensive than swimming. When they need to swim quickly instead, these handy fins can be folded neatly to their sides, allowing for a much more typical fish-like range of movement. What can’t these fins do?

The flying gurnard (which can range in color from shades of yellow to green and brown) eats small shrimp, crabs, and other invertebrates off the seafloor, using their relatively large eyes to hunt for food. They can even use their faux “legs” like probes, sticking them into deep sand to detect their prey’s movement before digging up a tasty treat.

Since they don’t literally fly, some people prefer to call these fish “helmet gurnards,” due to their hard, blunt heads. But what’s a “gurnard”? They get this part of their name from the French word gronger meaning “to grunt,” which they do! More specifically, they have two muscles that can contract around their swim bladder to produce a noise that’s reminiscent of a chicken clucking. They make this sound when being pursued by predators, often while their fins are stretched out in the hopeful “I’m too big to eat” position.

This species is:
Native

Why that matters:
Native species are those that evolved in the region naturally, without human influence. That means they’re specifically adapted to Saba’s habitat, and play a key role in island biodiversity. When we lose native species, gaps appear in the ecosystem. That leads to cascades of additional extinctions, and to the loss of the ecosystem services (food, clean air and water, flood and coastal protections, and more) that we humans rely on.

Credit: @zahnerphoto, iNaturalist (CC-BY-NC).

iNaturalist Observations

Flying gurnard

iNaturalist user @zahnerphoto (CC-BY-NC)

Where locals, researchers, and visitors have seen this species.

Saba Island Map and Pins: iNat Taxonomy ID 55016

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Ask a Scientist

Question: How does the flying gurnard's coloration help it to survive in the wild?

Answer: Flying gurnards typically lie on the seafloor with their wings tightly appressed to their bodies, blending in due to their dusky red, drab white, brown, and black pigmentation. However, when they sense danger or sudden disturbances, they quickly expand their brightly colored pectoral fins, which are adorned with distinctive blue-and-white patterns. This not only makes them appear larger, but also draws the attention of potential predators away from their body, allowing them to escape quickly.

Ryan Schaeffer
Senior Biologist at Steinhart Aquarium, California Academy of Sciences