Flying Fish

The **Exocoetidae** are a family of marine fish in the order Beloniformes class Actinopterygii. Fish of this family are known as **flying fish**. About 64 speciesare grouped in seven to nine genera. Flying fish can make powerful, self-propelled leaps out of water into air, where their long, wing-like fins enable gliding flight for considerable distances above the water's surface. This uncommon ability is a natural defence mechanism to evade predators.

The oldest known fossil of a flying or gliding fish, *Potanichthys xingyiensis*, dates back to the Middle Triassic, 235–242 million years ago. However, this fossil is not related to modern flying fish, which evolved independently about 66 million years ago.

## Etymology

The term Exocoetidae is both the scientific name and the general name in Latin for a flying fish. The suffix *-idae*, common for indicating a family, follows the root of the Latin word *exocoetus*, a transliteration of the Ancient Greek name ἐξώκοιτος. This means literally "sleeping outside", from ἔξω "outside" and κοῖτος "bed", "resting place", so named as flying fish were believed to leave the water to sleep on the shore.

A different etymological approach, more realistic, is that of Ancient Greek ἔξω "outside" + **κύτος "hull", which means not submerged in the water.**

## Distribution and Description

Flying fish live in all of the oceans, particularly in tropical and warm subtropical waters. They are commonly found in the epipelagic zone. This area is the top layer of the ocean that extends 200 meters from the surface down. It is often known as the "sunlight zone" because it's where most of the visible light exists. Nearly all primary production, or photosynthesis, happens in this zone. Therefore, the vast majority of plants and animals inhabit this area and can vary from plankton to the sharks. Although the epipelagic zone is an exceptional area for variety in life, it too has its drawbacks. Due to the vast variety of organisms it holds, there is high number of prey and predation relationships. Small organisms such as the flying fish are targets for larger organisms. They especially have a hard time escaping predators and surviving until they can reproduce, resulting in them having a lower fitness. Along with relationship difficulties, abiotic factors also play a part. Harsh ocean currents make it extremely difficult for small fish to survive in this habitat. Research suggests that difficult environmental factors in the flying fish's habitat have led to the evolution of modified fins.[7] As a result, flying fish have undergone natural selection in which species gain unique traits to better adapt to their environments. By becoming airborne, flying fish evade their predators and environment. This increase of speed and maneuverability is a direct advantage to flying fish, and has given them leverage when compared to other species in their environment.

Research has shown that the flying fish has undergone morphological changes throughout its history, the first of which is fully broadened neural arches. Neural arches act as insertion sites for muscles, connective tissues, and ligaments in a fish’s skeleton. Fully broadened neural arches act as more stable and sturdier sites for these connections, creating a strong link between the vertebral column and cranium. This ultimately allows a rigid and sturdy vertebral column (body) that is beneficial in flight. Having a rigid body during glided flight gives the flying fish aerodynamic advantages, increasing its speed and improving its aim. Furthermore, flying fish have developed vertebral columns and ossified caudal complexes. These features provide the majority of strength to the flying fish, allowing them to physically lift their body out of water and glide remarkable distances. These additions also reduce the flexibility of the flying fish, allowing them to perform powerful leaps without weakening midair. At the end of a glide, it folds its pectoral fins to re-enter the sea, or drops its tail into the water to push against the water to lift itself for another glide, possibly changing direction. The curved profile of the "wing" is comparable to the aerodynamic shape of a bird wing. The fish is able to increase its time in the air by flying straight into or at an angle to the direction of updrafts created by a combination of air and ocean currents.

Genus *Exocoetus* has one pair of fins and a streamlined body to optimize for speed, while *Cypselurus* has a flattened body and two pairs of fins, which maximize its time in the air. From 1900 to the 1930s, flying fish were studied as possible models used to develop airplanes. Exocoetidae feed mainly on plankton. Predators include dolphins, tuna, marlin, birds, squids, and porpoises.

### **Flight Measurements**

In May 2008, a Japanese television crew (NHK) filmed a flying fish (dubbed "Icarfish") off the coast of Yakushima Island, Japan. The fish spent 45 seconds in flight. The previous record was 42 seconds. The flights of flying fish are typically around 50 meters (160 ft), though they can use updrafts at the leading edge of waves to cover distances of up to 400 m (1,300 ft). They can travel at speeds of more than 70 km/h (43 mph). Maximum altitude is 6 m (20 ft) above the surface of the sea. Some accounts (e.g. Kon-tiki by Thor Heyerdal) have them landing on ships' decks.