Can Fish See In The Dark?

If you are curious about whether fish can see in the dark? Then don’t worry, you are not alone because many fishers wonder whether fish can see bait and lures in the dark. And aquarium owners always get confused whether they should leave a light on at night or not. To answer this question, we’ve gathered some information that might make you understand a little better about how does that work.

The Science Behind It

To understand this matter, you’ll need to go a little bit in-depth in the biology behind fish’s vision. The eyes of fish are similar to the eyes of most terrestrial vertebrates like mammals and birds, including humans; however, fisheye lenses are the more spherical lens. You might have noticed or heard that whenever humans want to focus on something, we usually adjust the vision focus by changing the shape of the lens. However, in fishes, they instead of doing what most mammals do they move the lens further away or closer to the retina when they want to focus on something.

The science behind a vision of a fish might be the same in most of the fish species, but not all of them have the same color of vision. Some fish species can see ultraviolet light while on the other hand, some are sensitive to polarized light. Some fishes have both photopic and scotopic vision, while most of the species have colored vision.

But in addition to all of this, many of the fish species have a lateral line that contains neuromasts. The function of these neuromasts is to sense the surrounding for any objects or predators. This function helps fishes find food and shelter in the deep dark water. So the answer to whether a fish can see in the dark could be answered in a way that fishes rather senses than actually seeing things in the surrounding. These are specially fishes living in the dark waters. Because they are adapted to moving around in the dark and so they don’t bump in anything.

Similarly, the fishes that you keep in the aquarium don’t need light because their bodies are adapted to the dark. Moreover, at night or in a sleep state, fishes lower the activity of their brains to 50 percent, which means half of their brains are asleep. However, they can still sense or see in such state. After a few hours later, they switch their brain sides, but they still stay alert. The senses might not be as strong as it would in daylight, but at least if they are aware of their surroundings.


The light in the water is different from the light outside. That’s why fishes living in the bathyal zone, the lower midnight zone and the abyssal zone have visions according to their habitats. Most importantly, fishes don’t just depend on their vision sensory system but also depends on their other sensory system as well i.e., smelling and hearing. Moreover, fishes have shown evolutionary changes in their visions. For example, studies have shown that deep seawater fishes have a vision more suitable for dark surroundings.

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