How can fish see in the dark

All fish, whether living in an aquarium or in their natural habitat, need periods of darkness. To find food in the darkness, fish rely on their senses of smell and sound along with whatever level of night vision they possess. The Lateral Line System or LLS — which is a group of sensory organs that give fish the ability to detect movement or vibrations through pressure changes in the water- is also necessary for fish to be able to feed in the dark.

Finding food in the dark is no easy feat for most fish. In the wild, they often adapt to their surroundings by using terminal rather than lateral vision. This means that their eyes face upwards instead of sideways, making it easier for them to see food silhouetted against the light reflecting off the surface of the water.

Feeding aquarium fish at night is a waste, for the most part, as most of it just ends up uneaten on the substrate. Darkness provides the chance for them to slow down their gill movements and regain much-needed energy.

Nocturnal aquarium fish, on the other hand, come to life in the darkness and become more active in cooler water temperatures. They may also feed more frequently and with greater success than other aquarium fish. If you leave a fish in the dark for too long, it may lose its vibrant coloring over time. Having a balance of both light and dark in an aquarium will provide fish with time to rest as well as prevent the overgrowth of algae in the tank, which can then lead to an increase in toxic bacteria.

Too much light can be just as detrimental for fish as too much darkness. In murkier water, their vision is limited to a few inches, similar to being in a perpetual dense fog. Structurally, fish eyes are similar to our own. The major difference is that fish lenses are generally more dense and spherical than human eyes. These rounded lenses give them better peripheral vision. They also are able to bend light and focus it on their retinas better than we are — which makes them able to take advantage of low light situations.

Fish that live in the surface waters within meters of the surface, known as egipelagic fish , primarily use their vision for hunting prey and escaping predator fish. These fish typically do not have adaptations for ultra-low light conditions. Some examples of fish at this depth would be herring, mackerel, tuna and most sharks.

The next level below is known as the mesopelagic zone. Light levels are greatly reduced at these depths and as a result fish here have large eyes with big lenses, which provide sensitivity to the smallest light signals. Many species have upwards facing eyes to detect prey animals silhouetted against the dim light above them. This adaptation means they sacrifice lateral sideways vision in favor of terminal vision.

Some fish that live at this level are lanternfish, barreleye and Bigeye tuna. No light from the surface can penetrate this deep. This layer is known as the bathypelagic or midnight zone. Fish living here have highly specialized adaptations to deal with the lack of light and high pressure. They do not rely on vision, and instead operate on sense of smell, sound and their lateral line. Many also incorporate bioluminescence producing their own light to hunt or find a mate.

Some examples of fish residing at these depths are the anglerfish , bristlemouth, fangtooth and barracudina.

Fish have a number of adaptations that make them less dependent on vision and better able to navigate in low-light environments. But they would not have as wide a range as the silver spinyfish. Nevertheless, scientists who were not involved in the study agreed that identifying fish with multiple rod pigment proteins was a novelty in itself. She joined the newsroom in and spent several years working on the criminal justice team.

She was also part of the team that was a Pulitzer finalist for its coverage of the Conception boat fire off the Channel Islands. This scientist is finding out. All Sections. About Us. B2B Publishing. Business Visionaries. Hot Property. Times Events. Times Store. Facebook Twitter Show more sharing options Share Close extra sharing options. A deep-sea lanternfish.

Some members of the lanternfish family were found to use multiple rod opsins within their eyes, allowing them to see colors in dark waters. By Leila Miller Staff Writer. The yellow light-filtering lens of a deep-sea oceanic basslet.

Yellow filtering pigments and lenses are found in a number of deep-sea fish eyes and are thought to enhance contrast against the residual daylight.