Can fish see in the dark? The quick answer is yes, many fish can see in the dark, but not all fish. Some fish can see in the dark without using their vision.
As we dive into how fish see, we will compare fish vision to human vision, look at how fish see in the dark, and then use it to help us fish at night.
Fish Vision vs. Human Vision
Fish vision and human eyes are very similar. Both sets of eyes have a retina that contains rods and cones. Fish have more rods and cones and use this to their advantage to see in the water at night. Both fish and human eyes have a lens, outer cornea, and an adjustable iris. Fish have ultraviolet receptors and a more dense spherical lens that bends light and focuses on the retina. The more dense spherical lens gives them an advantage in low light situations.
As you know, most humans can see all the rainbow colors, but fish can only see the world in reds, greens, and blues. Fish can see in any type of natural water because their eyes adapt to any available light source. Another characteristic of fish vision is that they have poor depth perception and have a semi-blind spot straight ahead of them. Unlike human eyes, fish have a protective eyelid that helps them see more clearly underwater. However, fish still live in a somewhat foggy world. Imagine driving your car through the fog; you don’t see the stoplight until you are almost at it. This hazy vision is why fish will come so close to your bait/lure to look at it before deciding to bite or not. When sight fishing, you can see the fish go and look at your bait sideways to examine it. This sideway examination is to help see it out of the blind spot. Unlike humans, many fish species have a second eyelid that helps when they swim at fast speeds. This second eyelid is to protect the cornea from damage at these higher speeds.
Fish have different eyes than land-dwelling animals because light waves behave differently in water. Water absorbs wavelengths at various speeds. For example, reds and oranges are absorbed in 30 meters, where blues and greens are absorbed in 200 meters. Many deep-sea fish are red because red wavelengths are absorbed, and this makes them appear black, which makes it difficult to see and less visible.
Fish Vision at Different Depths
As you may know, fish live at different depths of water. Epipelagic fish live in the top 200 meters of water. They use their vision for hunting and escaping. They do not have any adaptations for low light conditions. Herring, mackerel, tuna, and most sharks are epipelagic fish.
Mesopelagic fish live between 200 meters and 1,000 meters. At these depths, there is less light. These fish have large eyes with big lenses and are sensitive to small light signals. They fish up when hunting. Their upward-facing eyes are used to detect prey that is distinct against light sources such as the moon. These fish lack lateral or sideways vision because of the placement of their eyes. Lantern fish, barreleye, and bigeye tuna are mesopelagic fish.
The final depth is anything below 1000 meters. There is zero light at these levels of the bathypelagic zone. Sometimes called the midnight zone, the fish that live here do not rely on any vision. They count on the sense of smell, sound, and lateral line. Fish like the anglerfish use bioluminescence to attract prey or to mate. Bioluminescence is the ability to produce light. Other examples of bathypelagic fish are the bristlemouth, fangtooth, and barracuda.
Did you know that compared to other animals, fish have larger eyes compared to their body size so that more lights can be refracted from their lenses?
How Do Fishes See in the Dark?
Water clarity is a huge factor in fish being able to see and see in the dark. The time of the year, algae, and wind all play into water clarity that affects a fish’s ability to see clearly. When a dam releases water, the water becomes murky. When the snow melts into a river, the water can go from clear to dark and murky. In the most immaculate water conditions, fish can see 150 feet away, but remember, this is a foggy vision. In more cloudy water, fish vision is limited to just a few inches. When it is dark, the water clarity is just as important in aiding in the fish vision. Fish need the light to come through, and if the water is murky, they won’t have as much light.
Fish have excellent night vision because of the spherical lenses they have. They take advantage of the moon and stars to be able to see. They will also use lights from boats, parking lots, and docks to help their vision.
Fish do have more adaptations than just vision for seeing at night. They do not rely solely on sight, and these adaptations allow them to maneuver in low light. One of these adaptations is their lateral line. The lateral line is a line that runs down the length of their body that is a sensory system. This system is composed of neuromasts. The neuromasts are little organs that recognize vibration and pressure in the water around them. Knowing the vibration and tension in the water gives them the spatial awareness they have and helps them hunt from prey or hide from predators. It also helps them when they are schooling.
Two other adaptations that help them see is magnetoception and chemoreception. Catfish use chemoreception to taste and smell everything around them. This chemoreception is one reason catfish feed on the bottom so that they can taste and smell everything. It is another reason they have their whiskers, like cats, to help distinguish vibrations. Sharks and rays identify variations through electrical fields in the water.
Fish use multiple adaptations to see in the dark, and these adaptations don’t always involve their eyes. Knowing these adaptations and how fish see in the dark can help you be successful fishing at night.
How to Catch Fish at Night
Fish behave differently at night compared to during the day. This different behavior is because of their vision changes at night. It can take 20-60 minutes for fish’s eyes to adjust to the darkness. The number of cones and rods change in the fish’s eyes, allowing them to find the light. Many fish are more active at night, such as walleye, carp, and catfish. Because they behave differently, we should fish for them differently at night. Use loud baits, and this will help change the vibrations in the water. Fish will use their lateral lines while searching for these loud baits. Some noisy baits to try are chatter baits, buzz baits, and baits with moving parts. If you use live bait, keep the bait moving. Ensure they can swim when hooked and check it often to make sure it is always alive and moving.
It is prevalent for anglers to night fish during the spring and summer months. During the summer months, fish feed at night because it is too hot during the day. It makes them sluggish. To have the most success fishing at night, go during the summer. The wind tends to die down during the night. There is not as much boat traffic as during the day. The waters are calmer, and the fish are out feeding. The moon shines brighter, and the stars are more prevalent. Fish like to attack the top of the water during these conditions, so try using a topwater lure. Something that silhouettes against the moon will be more likely to catch a fish than something blended into the water.
Preparation is vital when night fishing. Rig up your rods in advance as there is not much light. A well-organized tackle box is essential, so you are not stabbing yourself with hooks you can’t see. Fish grippers are a necessary piece of equipment you should have while night fishing. These will allow you to handle the fish safely in the dark. This is for your safety as well as the fish’s safety. Another necessary piece of equipment is a headlamp. A headlamp will allow you to have a light but keep your hands free. Make sure this headlamp is a fishing headlamp or at least has the option for a red light. This red light will help keep from bugs attacking your face. Being prepared while night fishing will help make your trip more enjoyable and successful.
Fish can see in the dark by using their vision, lateral lines as well as other adaptations. We can take advantage of our knowledge of fish vision to target fish in different scenarios. Using loud baits at night is one of these scenarios. Using lures that are red, green, and blue is another scenario. The next time you go fishing, think about fish vision and adjust your game!
Also read: Do Fish Really Have Feelings?