One of the never-ending debates among anglers, fishers and scientists is, fish can see water? Fish are incredible and resilient creatures that have been around for more than 450 million years and have evolved to adapt to the ever-changing environment. Scientists believe that there are more than 3.5 trillion fish in the world. This means that their population is about 450 times that of humans. Fish eyes are quite similar to the human eye and many other vertebrates. However, their eyes components work slightly different from that of humans due to the nature of the environment that they live in and how light behaves underwater. For instance, a fish cornea is more rounded, a feature that allows them to receive more light information. Additionally, fish have up to 360 degrees field of view, which is by far much superior to that of humans. But the big question is; can fish see water? Please continue reading to find out more about fish vision, including whether they can see the water.
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Can fish see water?
Can fish see water that they are in? The answer is NO; fish do not see water that they are in. However, they have a complex sensory system that enables them to sense changes in water.
Just the way humans cannot see air; the same also applies to fish; they cannot see water. Of course, you may argue that air is naturally invisible while water is visible. Yes, you can see water in a glass, in puddles, in the ocean, in lakes and so on. However, you cannot see water when you are in water. The same thing also applies to fish. They cannot see water become they lie in water.
You can also argue that if humans cannot see air but can see water, then can fish see air? The answer is NO; fish cannot see air for the obvious reason that air is invisible. Additionally, fish vision mainly depends on reflective light, and air does not have a reflective surface. So fish don’t see air.
Can fish see in the water?
Now because fish cannot see water, do they see in the water? The fact that fish don’t see water does not mean that they don’t see in the water. Of course fish see in the water. If they didn’t, then they would be crashing on the rocks and bump on each other all the time. But the fact that they don’t mean that they see in the water. Most fish have incredible eyesight and see well in water. That is why they can navigate through narrow paths underwater and capture their prey in split seconds. Fish see well during the day, but a majority of them don’t see well during the night.
Fish that hunt during the night depend mostly on their incredible sense of smell and taste to stalk and catch their prey. Research has shown that fish have a special sensory organ known as ampullae of Lorenzini that they use to navigate through dark water with ease. This special sensory organ is mostly used by fish living in deep water where there is minimal light.
How do fish see the light in water?
Fish eyes are similar to other mammal’s eyes. However, there have additional features that enable them to see clearly in the water. For instance, the human eyes cannot see underwater without wearing goggles, but the fish can see clearly in the water.
Fish have no eyelids; Instead, they have cones and rods that help them to adjust the light intensity in water. Unlike humans and other animals that adjust the focus by changing the shape on the lens, fish usually change focus by moving the lens closer or further away from the retina, just the way camera do. A vast majority of fish have fixed iris meaning that they cannot control the amount of light that enters their eyes. That explains why most fish in aquariums often hide for a short period when lights are turned on.
However, predator fish eyes can adapt faster to changing light, thus giving them an upper hand over the prey. Most predatory fish like shark feed mostly during dusk and down because they have sight advantage over their prey. Just like humans, the quality of fish eyesight is highly dependent on diet. For instance, fish that are deficient on vitamin B1 have decreased visual ability than those that are well-nourished and have an adequate supply of this important vitamin.
Nine interesting facts about fish eyes
1. The fish eye is very similar to human eyes. They have many similar parts, including the cornea, pupil, retina and lens. However, most fish have superior eyesight than humans. They also have a wide field of view and use their cornea as goggles. The way their cornea is built allows ten to see clearly in the water.
2. Some fish have eyes while young but disappear by the time they reach adulthood while others have non at birth but develop the by the time they reach adulthood.
3. Fish tend to have stronger rods and sensitive cones to improve their visibility, especially in water with poor visibility or during the night.
4. There are fish with cones and no rods, and there are others with rods and no cones.
5. Some fish such as eel usually change their eyes during migrations. They increase both the cones and lens to enhance their visibility.
6. Fish that live close to the water surface have retina that is specially adapted to handle more light and hence see more color. On the other hand, those that live in the middle of the ocean are not good at distinguishing colors but are good at differentiating sizes and shapes. Fish in deep water rely more on noise and motion.
7. Unlike human lens that can focus on objects at varying distance, fish don’t have this ability. As such, most fish are short-sighted. However, some fish such as shark are known to spot prey from a distance.
8. Fish do sleep, but they cannot close their eyes because they have no eyelids. When sleeping, fish usually pull their pupil up inside the socket to lessen the entry of light while they are asleep.
9. Fish can see colors such a violet that human eyes cannot.