You can easily think of dozens of land animals with big eyes. But what about fish with big eyes?
Having a pair of eyes is just as important to full-time sea animals as it is to animals on land – and even more so to fishes in particular.
But the presence of light is essential for sight. Light from the surface barely travels depths of 3,200 feet below the sea. At 650 feet, there is a sizeable amount of light penetrating the water.
So, at this stage, fish have to survive with little or no light. And to this effect, some body parts are modified to enable vision in dim light. Hence the development of larger than usual eyes.
In this article, we will get to know several species of fish with big eyes.
- Telescope Goldfish
- Horse-eye Jack
- Blue Shark
- Squirrel Fish
- Bigeye Tuna
- Bigeye Fish
- Spotted Ratfish
Types of Fish With Big Eyes
Scientific name: Carassius Auratus
Telescope goldfish is a fish with big eyes – really big eyes. They earned their name from their bulging eyes that have lenses that look like telescopes; they look so large that you’d think they were coupled with the wrong body.
Telescope goldfish is a result of years upon years of selective breeding. Now you might think that with this large pair of eyes, telescope goldfish should have the best eyesight on the planet – wrong.
Just as ridiculously big their eyes are, telescope goldfish have equally ridiculous poor eyesight. But they have other methods to flee from predators and hunt their prey; they depend on the silhouette of other animals and move vertically to detect movement properly.
Scientific name: Caranx Latus
Horse-eye jacks are your typical commercial and game fish. They are one of the many fishes that have adipose eyelids (a transparent film that covers most of a fish’s eye), and they also have big eyes.
Horse-eye jacks weigh about 30 pounds or more, and in relation to their body size, their eyes appear large. Apart from having big eyes, the vision of horse-eye jacks is pretty decent, which comes in handy when finding the prey.https://unsplash.com/photos/CPIxSGoAKOQ
They are regular game fish popular in-game fishing in Panama. When caught by a hook, horse-eye jacks are very resilient, putting up a good fight, which makes it the ideal game fish.
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Scientific name: Esox Sphyraena
Barracuda fish have moderately large eyes they use effectively for hunting. The eyesight of barracudas is not as outstanding as that of the swordfish or for its incredible size like the telescope goldfish.
Their eyes are highly sensitive to the reflected light, so they have the affinity to spot out prey by glint from parts of their bodies that is reflecting light.
For this reason, barracuda fishes are known to have attacked humans, not because humans are their natural prey but a glint of reflection from diving gear that sends off signals as prey.
Scientific name: Prionace Glauca
Blue sharks are beautiful fish identified by distinctive large pairs of eyes and blue sleek bodies. Like all sharks, they have a reputation for attacking humans.
However, their vision is not as great, as they can only see from the range of 30 to 50 feet. And according to animal experts, this is the main reason for their attack on humans – blue sharks do not see humans as prey.
Most blue shark attacks happen because people were mistaken with fish due to their artificial fins or the surfboards of surfers that are shaped like fish. Other than that, if a safe distance is kept from this shark, there is a 90 percent chance of no attack.
Scientific name: Megalops Atlanticus
Typically, the tarpon’s eye size varies as its ages. The adult-sized tarpon has big eyes. And according to the research, the tarpon’s color vision is 10,000 times better than human vision.
Tarpons have an amazing development that other animals don’t. They grow up in low light, and as they age, they emerge from the depth, and as they do this, they develop cone cells in their retina – where they had none but rods.
These cone cells are more sensitive to light and color and would reduce the effect that would occur if their usual rod cells were to be used in light.
Although this development aids in hunting and evading predators, it is of more importance to humans as scientists believe it might be a major break in curing blindness.
Scientific name: Holocentridae
The name ‘Squirrelfish’ is predominantly associated with the famous Chinese dish found in many cuisines. But the squirrelfish is also the general name for all fish in the sub-family, Holocentrus.
All squirrelfish are big-eyed fish. But while some squirrelfish are commercial fish, others are put in aquariums because of their vibrant colors.
In the wild, squirrelfish – especially the big-eyed squirrel fish move in groups, hunting together or fending predators.
Squirrelfish are usually found in coral reefs. Coral reefs do have a substantial amount of light to allow for efficient hunting. However, squirrelfish are nocturnal animals (they are more active at night than during the day), so they do need those pairs of large eyes for hunting in the dark.
Scientific name: Xiphias Gladius
Another fish with big eyes is the swordfish. However, in relation to body size, their eyes are not nearly as big as that of the telescope goldfish. For a fish that hunts predominantly in the depth of the sea where there is little to no light, the swordfish’s big eyes are an asset.
The special effect of the swordfish’s eyes is not in their incredible vision but the ability for their eyes to heat on their own! Now, this might not be as big of a deal as you think until you understand the concept of heat loss.
Heat is lost rapidly in water compared to air – swordfish heat their eyes to about 10 – 15 degrees above the temperature of the surrounding water and maintain this heat regardless of how rapidly the heat is been lost.
According to research, the retina of the swordfish collect flash-like movement and send nerve impulses faster when the temperature of their eyes is higher. The large eyes of swordfish go beyond merely seeing in the darkness – it goes as far as hunting like a pro.
Scientific name: Thunnus Obesus
The bigeye tuna is one of the most popular fish among others, and it is characterized by its large eyes and open mouth – its surprised look. These fish usually move in schools, hence they attract fishermen and large fishing boat fleets.
Bigeye tunas are used to make sashimi and many other kinds of food. Most fisheries are worth billions of dollars because of the in-demand commercial bigeye tuna.
This development had caused the population of bigeye tunas to decline as they were the hot cake of the fishery industry. But in recent years, a couple of laws have been put in place in order to elevate these numbers.
Read Also: Fish With Legs
Scientific name: Priacanthidae
As the name suggests, bigeye fish are another fish with big eyes. They look just like squirrel fish with their bright colors; they are usually red and gold-colored with spiny fins.
These fish live in depths higher than 100 meters, so they are not really light deprived, but just like squirrelfish, they are nocturnal animals, so their huge pair of eyes are very much appreciated in hunting in dim light.
There are 18 extant species of bigeye fish, and most of them are found in tropical and subtropical waters.
Scientific name: Sebastes
Under the sea, rockfishes do not have extremely large eyes. But when brought to the surface, the eyes of rockfish become large, like two bulging lenses of binoculars on each side of its body.
This is because of the gas pressure in the swim bladder. When the rockfish is deep inside the ocean, the pressure of the gasses in the swim bladder is the same as the pressure of the water around it.
But when they are suddenly brought up completely out of the water, the pressure in the swim bladder causes the eyes to bulge out. Their relatively large eyes are vision assets as they are found at depths of 9,000 feet.
Scientific name: Hydrolagus Colliei
Viewed from above, spotted ratfish on the sea almost give an illusion of a stingray. However, spotted ratfish have big eyes that stingrays do not, this sets them apart. But up close, spotted ratfish are very distinguishable from stingrays.
Their name spotted ratfish is coined from their rat-like tail and distributed spot. Their rat-like tail is sharp, and their dorsal fin is venomous.
It doesn’t pose a serious threat to humans, but it can be quite poisonous to other sea animals. Therefore they are used for defense.
Spotted ratfish are found at depths of 900m from the surface, therefore their large pair of eyes are very much appreciated.
Scientific name: Tetraodontidae
The last members on our list of fish with big eyes are pufferfish. Apart from their bulging eye appearance, pufferfish have acute eyesight. Their eyesight is a very important survival gift, as it has functions to identify a potential threat from a far distance, as well as a potential meal.
These fish are also referred to as blowfish, fugu, and globefish. All these names come due to their unique ability to puff up more than twice their normal size by gulping water.
They do this appearance metamorphosis when they are in danger, however, during this state they can swim at a much slower pace than usual.
These cute aquatic creatures are believed to be the second most poisonous vertebrates. In one fish, there is enough toxin to kill around 30 people.