How do fish visual organs adapt to aquatic life?

Many ichthyologists believe that fish mainly rely on visual observation to find bait. In other words, vision plays a very important role in the foraging activities of fish. Therefore, when fishing, the fish must first see the bait carefully set by the angler. When talking, the fish must not see the trap-the hooks and lines set inside and outside the bait.

Fish eyes are basically similar to human eyes. Fish live in water and people live on land. Both of them observe two completely different worlds with almost the same eyes, one surrounded by water and the other by air. W Therefore, fish's eyesight is inevitably affected by many objective factors such as water density, water turbidity, water illumination intensity and so on.

(1) fish's eyesight. How far can a fish see? This is a question that fishing enthusiasts are interested in.

In the past, it was generally believed that fish were extremely nearsighted. The reason is that the lens of fish eyeball is spherical, and the curvature cannot be adjusted to change the focal length. Secondly, the fisheye must observe the objects piled up in the water to penetrate the light, so it is very close.

See (this conclusion is widely quoted in many published fishing books). In fact, we can't just assume that it is myopia. Although the lens in fish's eyeball can't adjust the focal length by itself like the human eye, fish

The eye can adjust the distance between the aquatic body and the retina through the contraction and relaxation of special muscles. The lens is initially connected to the retina through a small contractile muscle band. If you need to look east, this muscle will

Hold the mushroom tightly and put the water near the retina, so that the focal length can be adjusted to a far place. If you look carefully, the lacing muscles don't need to contract. However, the degree and speed of this adjustment vary with the species of fish. Usually.

Fierce carnivorous fish come faster than tame fish such as grass carp and filter-feeding sewing fish. Experiments show that many fish can see far because of this adjustment. According to the true class, class, grouper, Japanese bamboo pod fish

Through the comparative analysis of eye accommodation of 13 species of marine fish in six visual fields, it is proved that these fish have quite strong visual accommodation ability in normal state and can see far.

In addition, the round lens of fish also increases the favorable factors for improving vision. As we all know, in the case of the same size. The focal length of spherical lens is shorter than that of flat spherical lens, so the spherical lens of fisheye is out of focus.

The short-distance oblate lens has a larger visible and clear area than other land ridge propellers. Of course, we can't live in water with fish at a distance that people or some land ridge propellers can clearly see when the air visibility is high.

Comparative visual ability. For example, snakehead can clearly see the bait 50 meters away when the water quality is good, but human vision is far behind under the same conditions in water. Similarly, we are not stupid, so we conclude that,

The human eye is nearsighted.

However, just as any animal of the same species has different functional levels of the same organ in different species, some fish have poor eyesight, such as fish whose eyes are degenerating or in the process of degeneration, and some fish have hair.

Fish with poor culture have poor eyesight and even myopia. Freshwater frog fish is an example. It can see the early body at a distance of no more than 30.40 cm, even if the lens is pulled back with the adjustment function in the fish eye.

Near the retina, only the distance less than 10- 12 cm can be seen.

Which fish eats more by sight? Generally speaking, fish that feed in the upper layer of water with white color are more dependent on eyesight than those that feed in deep water at night, such as crustaceans, swordfish, mandarin fish, pike, mandarin fish and mullet. So these fish can be caught not only with live real bait (real bait), but also with fake bait (simulated bait).

(2) Fish's visual field: Most of the color eyes are on both sides of the head, protruding from the orbit, so the visual field is quite wide. Looking down at the fish's back, you can see its prominent eyeball, and its single eye can

See horizontal plane 60- 170 degrees. The visual field is 150 degrees on the vertical plane. This is the monocular vision of fish. Generally, fish only have a small area directly behind their bodies as eyes.

Blind spot of vision. It is of great significance to find bait to adapt to the water city environment and find out the sudden enemy damage from any direction in time. On the other hand, the light in such a large space can be transmitted to the fish's eyes, so it can

Search and dye light as much as possible to increase vision, which is obviously an excellent adaptation to weak or even weak light in water. Otherwise, when we go bottom fishing in deep water, the fish will definitely find the bait and swallow it.

In front of the fish, the intersection field of vision formed by its eyes is about 45 degrees, which is the stereoscopic binocular field of vision of the fish. In this view, the fish can show the exact depth of the scene in front, but the clarity is poor because it is right in front of it.

The focus of the front image falls on the edge of the front end of the retina (see Figure 2-2). Therefore, when fish see what they want to see clearly, they should not look at it positively, but choose a suitable angle, not a positive angle. We observe the fish in the water.

When chasing prey and bait, they will find that once they find the target they are chasing, they will attack from the front, keep the prey and bait in a three-dimensional field of vision, then shake their heads and tail, and observe their eyes with a "Z"-shaped attack action.

Standard, and achieve the purpose of bait.

(3) fish's bending vision: the light entering the water is weakened by scattering, so the change of underwater light will be completely clear. But the change between water surface and air is very strong, and light is refracted and reflected by water surface.

Most of the light is reflected back to the sky, and only a part of the light enters the water. When the lake is as flat as a mirror and the weather is clear, it looks like a mirror from the water. In this case, the fish can not only see it by looking up.

The object above can also see the object below through the reflection of the "mirror". Even in calm shallow water, you can see the object on the back of another body with obstacles. As far as fishing is concerned, the waves are calm.

On the surface of the water, the fishing line cast by the fisherman will make the fish at the bottom of the water feel that there is a crack in the mirror or that the mirror reflects a shadow. This will have a great influence on very alert fish.

In addition, fish in the water towel, especially when the waves are gentle, can also see the scenery on the shore or front through the "mirror". in?that?case

In the morning, even the slightest action of the fisherman may scare the fish away. In other words, the vision of fish resting in water also has potential function. Things on shore are refracted by water and enter the bottom of the water. Therefore, underwater fish have the function of diving.

Anglers can't see fish, but fish lists anglers. The effect of diving depends on the sight of the fish, the angle between the shore and the water surface and the weather. Take 4 as the line of sight of a fish.

2 degrees, you can see the image of the object entering the water at the angle of 10. However, the light entering the water at an angle less than 10 degree avoids the fish's vision. In fact, the light below 30 degrees has good penetration and must be very clear.

The fish can't see the coast until tomorrow. Something under the corner shelf. Even so, anglers can't help fishing.

Keep your body down, use short poles, wear camouflage clothes and try to avoid walking on the shore. In America, some excellent trout fishermen will compete with others.

Climb to a thousand-water path and fish for trout in supine position.

(4) Light perception of fish: There are two extremely important visual cells in the retina of fish eyes, namely, pao and prop-pulling cells. Conical fine bubbles play a visual role in strong light, while cylindrical fine bubbles play a role in weak light. pass by

In this way, fish can not only live in an environment where the light is enhanced during the day and dim at night, but also swim in water layers with different light intensities at the same time. However, fish's vision changes from cone-shaped cell function to cylindrical cell function during the day.

The effect will not be completed soon. It's like a person who has just walked into the cinema from the bright outdoor, and there is darkness in front of him. It takes some time to get used to this darkness. It usually takes two hours for fish to smell at this time. if

Sunset time is 6 pm and sunrise time is 8 am, so fish can adapt to night vision at 8-9 pm. At about 1 1 in the evening, fisheye will begin to prepare for daytime vision in advance. This is a completely automatic,

A wonderful process that happens according to a certain law. According to the lateral measurement, the round filler of this fish is extremely sensitive to weak light. After adapting in the dark, its round cells can feel one tenth of 100000 to one tenth of 100000 (lux

Is the unit of lighting. The illuminance of the object surface is expressed by the light passing through the basin per unit area of the object surface. Because I am eating bait at the moment. Therefore, anglers regard Yao Ming and Huang Qing as the golden moment of fishing. Sure, by

Due to the influence of meteorology and water turbidity, there will be exceptions to this law.

(5) Fish's color vision: Is fish the color Ff? This question is often debated among anglers. Because pong fishermen are very concerned about the color of the bait, they also want to choose a more attractive color bait to lure them.

From the aspect of fish anatomy, it is proved that fish can see considerable colors. Circular injection cells in fish eye retina and circular silo have different functions, among which circular cells are not only suitable for vision under strong illumination, but also can

Feel and distinguish different wavelengths of colored light. But marine fish is an exception, it can only distinguish X-white cylindrical cells, and four families of fish living at the bottom of the deep sea can't distinguish colors.

The important thing is that fish live in water, and the color it observes is very different from the color of objects we see on land, in the air and in the sky. Water is a very effective color secreting agent for light. When light enters the water and reaches an object in the water,

That is, it has been partially absorbed and then reflected from the surface of the object through the water body to the eyes of the fish, and the color tilt of the light is eliminated again. The filtered light, first long-wave red light, is absorbed, and then with the increase of water depth. light

The distance through water absorbs light of other wavelengths in turn. The rescue color and green color with the shortest wavelength are finally absorbed. So in water, especially in deep water, warm red light can't be preserved, only blue-green cold light is left.

Color, most fish live in a dark, quiet and silent world.

Under the water of about 6 meters, the color will regard the pure red simulated bait or live bait as black. If it is not golden red, the center is green or blue, and it will turn blue or grayish green in the same depth of water. Yellow is composed of shorter wavelengths.

Light components, strong permeability to water, can keep the primary color better than red in deep water, but the color is darker. Blue or green can keep its primary color at a considerable depth, but in the depth, it will be the same as the dark green background under water.

Mixed together, it is not easy to be found by fish. What anglers should pay special attention to here is that orange, which is close to red, has good penetration, and it still has 20% penetration in water near 10 meters deep.

At dusk, the first color that disappears in the water is red, followed by orange and yellow, and finally green and blue. When the luminosity drops below 1 lux, the world in the eyes of fish is completely black and white, even if there is a bright moon.

Light, the fish still can't see any color. At dawn, green and blue recover first, and red comes last. So when we fish at dawn and dusk, the color of the bait is not important, but the bait should be considered.

The light and darkness. At dusk, the earth is crisp and black, but the sky is still bright. At this time, under the bright sky background, if you choose gray bait, it will be easily found by thousands of fish when it falls into the bottom of the water. Of course, for example

If a luminous ball with laser luminous effect is installed at the upper end of the hook handle or a simulated bait coated with noctilucent powder is selected, it will also have certain effect.

This article is published by Quhai Fishing Net, an authoritative fishing net.

Please keep the source when reprinting.