Fish senses

Goldfish have highly developed senses. Six of them. Really.

1. Sight

Goldfish have vision superior to humans in some respects. We see three colors – red, green, and blue – and can tell light from dark. Our aquatic friends see those three colors plus ultraviolet light, giving them polarized vision. This capability allows them to resolve predators or prey through the surface of the water without troublesome reflections. If you ever wondered why your fish can recognize you and gather at feeding time even on a sunny day, now you know why. (This behavior also gives the lie to goldfish having a “three second memory,” a common legend.)

Their light and dark receptors work just like ours, with color resolution diminishing and luminance becoming the dominant part of vision as light diminishes. That explains why they are most at risk from predators at night. Lacking an iris, they also require time to adjust when light levels suddenly change. Fish kept outdoors have much healthier eyes than those housed in an aquarium, where artificial light is turned on and off frequently.

As air based animals, we evolved a need to see long distances. Humans can see with excellent resolution for up to a mile, while goldfish only see clearly about 15 feet. That is why your fish might react with fear and uncertainty if you move suddenly at a distance from the pond but be relatively calm if you make the same gesture right in front of them.

2. Hearing

Fish possess internal ears without openings. Sound travels three times as fast through the water as the air, so sonic waves easily penetrate the flesh to reach the ears. The swim bladder also conducts sound to the ears, allowing for higher frequencies to be heard. A third source of sound input is the lateral line, a system of canals running the length of the fish.

Fish have a hearing range equivalent to AM radio, which is not bad considering that humans can barely hear under water at all. Their complex hearing system makes them vulnerable to profound internal and nerve damage, however, when loud noises occur. That is why one must never ever break pond ice with a hammer during the winter. 160 decibels will destroy human ears; in the denser water much less is necessary to wreak havoc on the auditory and nervous systems of fish. Many ponders report that repeated loud low frequency noises like snow plows stress their fish.

3. Smell

Yes, goldfish smell and very well. Odor is the primary way they find food and mate. They can also sense injury and hence danger via the sense of smell. You might have noticed that a fish will sometimes seem to ignore a piece of food right in front of its eyes then suddenly gobble it up when it gets the scent.

They do have “nostrils” called nares, but not in the same sense as we do because they are not connected to any other orifice. They exist purely to conduct water to the olfactory receptors.

Unlike us, goldfish have olfactory bulbs that react more to small amounts of stimulation than to large. This results from their need to respond quickly to changes in their environment – the first whiff of blood or fear or food requires an immediate response.

4. Taste

Taste determines whether a goldfish will actually consume food or prey. As any ponder knows, certain fish favor particular foods and will quickly spit out any foreign object that smells like food but doesn’t taste right. Goldfish teeth are at the back of their mouths, so food is tasted before it is “chewed.”

Human taste combines input from the taste buds and the nose. In goldfish, the systems are separate. The basic components of taste – saltiness, bitterness, sweetness, sourness – all involve nutritional suitability, which helps the goldfish survive.

5. Touch

As far as we know, touch in goldfish has only a reflexive defensive function. Unlike mammals, they derive no comfort from being touched. Many people derive pleasure from handling their fish, but the feeling is not mutual.

6. Lateral line

The nerves arrayed along the system of canals known as the lateral line perform several valuable functions for goldfish. By monitoring subtle changes in current and pressure, the lateral line keeps the fish balanced and tells it what level it is in the pond, how fast the current is moving, and what is moving around and towards it. This unique sense allows fish to swim in schools, to dart quickly across the pond, and to avoid predators, nets, and other hazards. Damage to the lateral line through injury, parasites, bad water, or loud noises can cause decline and death.


One Response to “Fish senses”

  1. Laney White Says:

    well im doing a science fair project and this is very helpful for my goldfish memory project thank you ^ . ^

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