What family are the fish? Salmon fish names, features of the species. How long does the beluga live

Fish are classified according to a number of characteristics: lifestyle, fishing season, sex, physiological state, nutritional status, nutritional status, length or weight.

AB - fishing length of fish; AB - standard size; 1 - gill cover; 2 - hard dorsal fin; 3 - soft dorsal fin; 4 - tail fin; 5 - lateral line; 6 - anal fin; 7 - anus; 8 - pelvic fins; 9 - pectoral fins

The length of the fish is measured in a straight line from the tip of the snout to the beginning of the middle rays of the caudal fin (Fig. 20). Some small and low-value fish are classified as fines of I, II or III groups. A number of fish species listed in the standard are not subdivided in terms of length and weight. The smallest length of fish that is allowed to be caught is established by fishing rules and international conventions.

IN merchandising practicefish are classified by species and families.

A species is a collection of individuals occupying a certain geographic area and having a number of inherited traits that distinguish this species from closely related species. Species that are close in a number of characteristics are combined into genera, and the latter into families.

IN trade practicethe classification of fish by families is carried out mainly by external signs... The strictly scientific classification of fish by families is based on many criteria. The characteristics of the main characters of the families of the most common fish in commercial practice are given below.

Herring familyhas a laterally compressed body, covered with easily falling scales. There is no lateral line. The dorsal fin is single, the caudal fin has a deep notch. Herring is of commercial importance: Atlantic, Pacific, Danube, Donskaya, Dneprovskaya, Kerch, Volzhskaya, Chernospinka, Azov Puzanok, Baltic herring, Sardines, Sardinella, Sardi-nops (Ivasi); sprat: Caspian, Baltic (sprats), Black Sea, Tyulka.

Anchovy familyhas a cigar-shaped body, similar in size to small herring. This family includes the Khamsa of the Azov-Black Sea, Anchovy.

Sturgeon familyhas an elongated fusiform body, with five rows of bony formations - scutes: two abdominal, two thoracic, one dorsal. The snout is elongated, fromfour antennae. The dorsal fin is single, the caudal fin is unequal. Commercial value are: beluga, kaluga, sturgeon, thorn, stellate sturgeon, sterlet. Soviet scientists, by crossing beluga and sterlet, obtained a bester, which is bred in water bodies.

Carp familyhas a high, laterally compressed body, covered with densely sitting scales, sometimes naked. The dorsal fin is single, soft, the lateral line is well pronounced, the pharyngeal teeth. This family includes fishes of inland waters: carp, carp, crucian carp, roach, roach, roach, ram, bream, white-eye, blue bream, barbel, silver carp, grass carp, buffalo, vimets, shemaya.

Salmon familyhas a high body, laterally compressed, covered with small scales. There are two dorsal fins, the second is adipose. The lateral line is well defined. Chum salmon, pink salmon, salmon, chinook salmon, Caspian salmon, salmon, trout, whitefish, vendace, muksun, omul are of commercial importance.

Family smelthas an elongated body, with easily falling scales, an incomplete lateral line. There are two dorsal fins, the second is adipose. Main species: European smelt, smelt, capelin.

Perch familyhas two dorsal fins, the first is spiny, in the anal fin there are three spiny rays, the lateral line is straight, on the sides there are transverse stripes. Common species: perch, pike perch, ruff.

Horse mackerel familyhas a flattened body shape. The lateral line has a sharp bend in the middle, in some species it is covered with bony spines. There are two dorsal fins, the first is spiny, the second is soft, long. There are two spines in front of the anal fin. The caudal peduncle is thin. The Azov-Black Sea mackerel, oceanic mackerel, caranx, seriola, pompano, lichiya, vomer are of commercial importance.

Cod familysubdivided into subfamilies of cod-like and burbot-like. The former have three dorsal and two anal fins, the latter two dorsal and one anal. These are marine fish, with the exception of burbot. They have a well-defined lateral line. The pelvic fins are located under the pectorals or in front; many have an antennae on the chin.

The body shape is close to torpedo. Cod, haddock, navaga, pollock, pollock, blue whiting, burbot, Arctic cod are of commercial importance.

Mackerel familyhas an elongated fusiform body, a current caudal peduncle. There are two dorsal fins; behind the second dorsal and anal fins there are four to seven additional fins. Black Sea mackerel, common mackerel, Japanese mackerel are of commercial importance. Mackerels are sold under the names Azovo-Black Sea Mackerel, Far Eastern Mackerel, Kuril Mackerel, Atlantic Mackerel.

In terms of body shape and location of fins, tuna, bonito, mackerel are similar to mackerel, the latter have one dorsal fin and additional fins.

Flounder familyhas a flat body, flattened from back to abdomen, eyes are located on one side of the head. Dorsal and anal fins along the entire length of the body. Black halibuts, common, arrowtooth halibuts are of commercial importance; flounder sharp-headed and river.

Of the fish of other families, the following are of commercial importance.

Sea bassgolden, beaked, pacific from the scorpion family have a large head, an oblong, laterally compressed body, often red in color, one dorsal fin, often prickly in the front.

Catfishstriped and spotted from the catfish family

they have one long soft dorsal fin, a round large head, the body is laterally compressed in the back.

Terpuginorthern, southern, toothed have a spindle-shaped body, one spiny dorsal fin, strongly developed anal AND pectoral fins.

Ice fishfrom the family of lemons has a large head with an elongated snout, two lateral lines, the color is light green, the blood is colorless, since it contains copper instead of iron.

Butterfish and oily small fishfrom the stroma-thia family have a flattened high body, one soft long dorsal fin of the same size and shape as the anal one, the lateral line repeats the bend of the ridge.

Notothenia marble and green, squama, toothfish from the Notothenia family have a large head, two spiny dorsal fins, a long anal, large pectoral fins, the body is thickened in front.

Croaker, captain, umbrina- fishes from the family of humpbacks, have a high body, a back humped in front, one dorsal fin, separated by a deep notch, the front part is prickly, the lateral line is well expressed.

Macrousesfrom the family of macrourids have an elongated, tapering body in the tail in the form of a thread. There are two dorsal fins.

Fish species such as catfish, pike, lamprey, eel, gobies, argentina, mullet, eelpout, pristipoma, bluefish from families with similar names, sea bream from the Brahm family are also caught; merrow, rock perch - from the serran family.

Pisces class - this is the most numerous group of modern vertebrates, which unites more than 25 thousand species. Fish are inhabitants aquatic environment, they breathe with gills and move with the help of their fins. Fish are common in different parts of the planet: from high-mountainous reservoirs to ocean depths, from polar waters to equatorial ones. These animals inhabit salt water seas, found in brackish lagoons and estuaries large rivers... They live in fresh rivers, streams, lakes and swamps.

External structure of fish

The main elements external structure The bodies of the fish are: head, operculum, pectoral fin, pelvic fin, trunk, dorsal fins, lateral line, caudal fin, tail and anal fin, as can be seen in the figure below.

Internal structure of fish

Fish organ systems
	1. Skull (consists of the cerebral box, jaws, branchial arches and operculums) 2. The skeleton of the trunk (consists of vertebrae with processes-arcs and ribs) 3. Skeleton of fins (paired - pectoral and abdominal, unpaired - dorsal, anal, caudal)	1. Brain protection, food capture, gills protection 2. Protection of internal organs 3. Movement, maintaining balance
Musculature	Wide muscle bands, divided into segments	Traffic
Nervous system	1. Brain (sections - anterior, middle, oblong, cerebellum) 2. Spinal cord (along the spine)	1. Control of movements, unconditioned and conditioned reflexes 2. Implementation of the simplest reflexes, conduction of nerve impulses 3. Perception and conduct of signals
Sense organs	3. The organ of hearing 4. Tactile and taste cells (on the body) 5. Side line	2. Smell 4. Touch, taste 5. Feeling the direction and strength of the current, the depth of immersion
Digestive system	1. Digestive tract (mouth, pharynx, esophagus, stomach, intestines, anus) 2. Digestive glands (pancreas, liver)	1. Capturing, chopping, moving food 2.excretion of juices that aid in the digestion of food
Swim bladder	Filled with a mixture of gases	Adjusts the immersion depth
Respiratory system	Gill lobes and gill arches	Carry out gas exchange
Circulatory system (closed)	Heart (bicameral) Arteries Capillaries	Supply of all body cells with oxygen and nutrients, removal of decay products
Excretory system	Kidneys (two), ureters, bladder	Isolation of decay products
Breeding system	In females: two ovaries and oviducts; In males: testes (two) and vas deferens

The figure below shows the main systems of the internal structure of fish.

Pisces class classification

Currently living fish are divided into 2 main classes: cartilaginous fish and bony fish. Important distinctive features cartilaginous fish - the presence of an internal cartilaginous skeleton, several pairs of gill slits that open outward, and the absence of a swim bladder. Almost all modern cartilaginous fish live in the seas. Among them, sharks and rays are the most common.

The vast majority of modern fish belong to the class bony fish... Members of this class have an ossified internal skeleton. A pair of external gill slits are covered with gill covers. Many bony fish have a swim bladder.

The main orders of Pisces

Orders of fish	The main signs of the detachment	Representatives
	Cartilaginous skeleton, no swimming bladder, no operculum; predators	Tiger shark, whale shark, katran
	Manta stingray
Sturgeon	Bone-cartilaginous skeleton, scales - five rows of large bone plates, between which there are small plates	Sturgeon, beluga, sterlet
Dipnoi	They have lungs and can breathe atmospheric air; notochord is preserved, no vertebral bodies	Australian horntooth, African flake
Kistepery	The skeleton is mainly composed of cartilage, there is a notochord; poorly developed swim bladder, fins in the form of fleshy outgrowths of the body	Coelacanth (the only representative)
Carps	Mostly freshwater fish, there are no teeth on the jaws, but there are pharyngeal teeth for grinding food	Carp, crucian carp, roach, bream
Herring	Most are schooling sea fish	Herring, sardine, sprat
Cod	A distinctive feature is the presence of a mustache on the chin; the majority are cold-water marine fish	Haddock, herring, na-wag, burbot, tres

Ecological groups of fish

Depending on the habitat, ecological groups of fish are distinguished: freshwater, anadromous, brackish and marine.

Ecological groups of fish	Key features
Freshwater fish	These fish constantly live in fresh water. Some, such as crucian carp and tench, prefer stagnant bodies of water. Others, such as gudgeon, grayling, chub, have adapted to life in the flowing waters of rivers.
Anadromous fish	This includes fish that move from sea \u200b\u200bwater in fresh water (for example, salmon and sturgeon) or from fresh water they go to breed in salt water (some types of eels)
Brackish fish	They inhabit desalinated areas of the seas, the mouths of large rivers: such are many whitefish, roach, goby, river flounder.
Sea fish	They live in the salty water of the seas and oceans. The water column is inhabited by such fish as anchovy, mackerel, tuna. Stingray and flounder live at the bottom.

_______________

Sourse of information:Biology in tables and diagrams. / Edition 2e, - SPb .: 2004.

When a person looks into the water from his familiar world, filled with light and air, the world in which fish live seems to him cold, dark, mysterious, inhabited by many strange, unusual creatures. He himself in this environment can only move with great difficulty and in a very limited space. The need to put on heavy, bulky equipment in order to see, breathe, keep warm and move at a speed that fish should seem to be a turtle hides from humans some of the undoubted advantages of fish over land inhabitants.

The advantages are given by the very existence in the aquatic environment, which played an important role in the formation of fish. The water is not subject to sudden temperature changes and therefore can serve as an excellent habitat for cold-blooded animals. Changes in the water are slow and provide an opportunity to go to more suitable places or to adapt to changed conditions. The problem of maintaining your own body weight in water is also much easier than on land, because protoplasm has about the same density as water, and therefore fish in their environment are almost weightless. This means that they can get by with a simple and light skeleton and at the same time sometimes reach considerable sizes. A big fish like the whale shark moves with the same freedom and ease as a small guppy.

But there is one significant difficulty that is associated with life in water, and which, more than anything else, has shaped fish, is the incompressibility of water. Everyone who has ever wandered through the water a little higher than the ankle has felt the difficulty that fish have to overcome constantly: the water must be moved apart, literally pushed to the side, and it immediately closes behind you again.

Flat and angular bodies hardly move through such an environment (if you push a board lying on the water straight down, it will definitely wiggle from side to side), so the shape of the fish body is remarkably consistent with this property of water. We call this shape streamlined: sharply pointed from the head, the most voluminous closer to the middle and gradually tapering towards the tail, so that the water can flow smoothly from both sides with the least swirl and, when approaching the tail, even give a fast-swimming fish some additional push. Of course, there is a certain variety of outlines, but in general, this is the initial form for all free-swimming fish, whatever form they acquire in the process of evolution.

The body of a fish, like any vertebrate animal, has bilateral mirror symmetry and is built according to the same simple scheme: a hollow cylinder with an alimentary tract open on both sides, which extends from one end to the other inside. The mouth opening is located at the front end, the anal opening at the opposite end. On the upper half of the cylinder there is a spinal column, a row of bone or cartilaginous discs, which give rigidity to the entire structure. The canal formed by the vertebrae contains the spinal cord, which expands at the anterior end to form the focal point, or brain. The walls of the cylinder along its entire length from head to tail are divided into numerous identical segments; the strong motor muscles of these segments act on the bone or cartilaginous skeleton and enable the entire body to make wave-like movements from side to side.

Since fish are cold-blooded animals, life in the aquatic environment, as already mentioned, is especially favorable for them, but still it has its limitations. When the temperature drops below the limit that fish can tolerate, they have to leave these places - this is why many temperate fish make seasonal migrations. With a strong and sharp change in temperature, the fish become too lethargic and do not have time to leave, and if conditions do not improve, they die. Some freshwater fish, which, when the seasons change, cannot make migrations, bypass this danger by plunging into hibernation or summer hibernation - they stop eating and winter time lie inertly at the bottom, and in summer they burrow into silt until the temperature becomes favorable again.

The circulatory system in fish is the simplest of all vertebrates. The blood travels in one circle - from the heart through the gills, where it is saturated with oxygen, to the various organs and parts of the body that take oxygen, and back to the heart. The heart itself consists of only two chambers, the atrium and the ventricle (in contrast to the three-chambered heart of amphibians and the four-chambered mammals), and works, so to speak, in line with the entire system.

A characteristic feature of fish is fins, large or small pterygoid formations, which give them stability in the water, help to move and control movements. Most fish have two types of paired fins - the pectoral fins on the sides of the head just behind the gills, and the ventral fins, which are usually pushed back. A dorsal fin passes through the middle of the back, it can be subdivided into two parts, the front spiny and the back soft. On the ventral side of the body, behind the anus, there is the anal fin, and at the very end, the caudal.

All fins have their own special purpose, they are all mobile and set in motion by muscles located inside the body of the fish. The dorsal and pectoral fins work together to play a major role in building stability. The straight up dorsal fin acts as a stabilizer to keep the fish upright; The pectoral fins are set apart to help maintain balance and make turns. The pelvic fins are also used as stabilizers. The tail serves for control and in the fastest fish it also plays the role of a stabilizer and a motor. The fish forcefully beats it from side to side, and the entire back of its body makes undulating swimming movements. In fast swimmers, the dorsal and anal fins are pressed against the body or even retracted into special notches, which increases streamlining.

The location and structure of fins in fish can be very diverse. In most benthic species, the paired fins are very close together and the ventral pair, strongly shifted towards the head, is sometimes even in front of the pectoral fins, just under the lower jaw. This arrangement allows the head and gills to be kept above the bottom surface. In other fish, the pelvic fins are greatly reduced or even completely disappeared, for example, in eels. In triggerfish and other more or less disc-shaped fish, the pectoral fins assume the role of engines in whole or in part. In the sea rooster leading a bottom lifestyle, the lower rays of the pectoral fins are separated and act like the legs of an insect. And the pectoral fins of the striped lionfish serve it mainly for camouflage: their long and widely spread rays resemble a bundle of algae among the coral reefs where this fish lives.

The shape of the body of the fish is also noticeably different from each other. The most surprising changes occurred with those of them that lie at the bottom almost all the time: they have become flat. Some fish lie on the belly and are flattened from above, while others lie on their sides and are flattened from the sides. Flattening in such fish occurs during the growth of juveniles and ends in an unusual process of moving the eyes to one, upper, side of the head. Winter flounder ( Pseudopleuro-nectus americanus), for example, lies on the left side, and her eyes are on the right side, and her close relative, the summer flounder ( Paralichthys dentatus), on the contrary, the eyes are on the left side, as it lies on the right side.

Among the fish, flattened on top, is the monkfish. This fish rarely moves and catches its prey using its own fishing rod with bait - a fleshy lump on a thin flexible rod hanging from its head. His close relative, the sea clown, is more active: his pectoral fins have turned into a special kind of limbs, and with their help he moves in leaps.

Various stingrays are in essence sharks that have moved on to a sedentary bottom life and become flat. During swimming, their wide pectoral fins make wave-like movements and the fish seem to float in the water. In many stingrays, the tail is elongated like a whip and has no motive power.

Even in water, besides swimming, there are other modes of movement, and fish use all of them to varying degrees. They crawl along the bottom like gurnard and dol-goper, and can even come out of the water to the shore, like a mud jumper. The Malay crawler and Chinese snakehead easily walk along the ground from reservoir to reservoir, crawling in exactly the same movements as most fish swim. In order not to tip over, the slider supports its narrow nimble body with pectoral fins, like props.

Some fish can also move through the air, albeit over short distances. The Mississippi carapace pike glides on the surface of the water using its tail as the propeller for an outboard motor But flying fish do fly - they can fly through the air for almost a full minute and, if a strong wind blows, they rise to a height of three to six meters and glide over the waves on large front fins, stretched out like wings. There are flying fish of the biplane type, those that use the pectoral and pelvic fins for flight, there are monoplane ones that fly only on the pectoral fins, and there are even freshwater species fish that fly like birds, flapping their pectoral fins over the water surface.

One remarkable feature of fish immediately attracts attention: from head to tail, fish are covered with a flexible, usually shell of round, overlapping bony plates, or scales. These scales are anchored in the inner layer of the skin and form the protective cover that fish needs. In addition to the armor made of scales, the fish is also protected by a layer of mucus secreted by numerous glands scattered throughout the body. Antiseptic mucus protects fish from fungi and bacteria and lubricates the surface of the body. Differences in the size and thickness of the scales can be very significant - from the microscopic scales of an ordinary eel to very large, the size of a palm, the scales of a three-meter barbel living in Indian rivers. Only a few species of fish, such as lampreys, have no scales at all. In some fish, the scales have merged into a solid, immovable shell like a box, like in box bodies, or formed rows of closely connected bone plates, like in sea horses and sea needles.

The scales grow as the fish grows, and some fish have distinct annual and seasonal marks on the scales. The substance necessary for growth is secreted by the layer of skin that covers the scales from the outside, and builds up along its entire edge. Since in temperate zones scales grow fastest in summer, when there is more food, then the number of annual rings on the scales can sometimes determine the age of the fish.

The fish's mouth is the only tool for grabbing food, and in all fish species it is perfectly adapted for its business. In the parrot fish, as already mentioned, a real beak has formed for plucking off plants and corals; the small American gerbil is equipped with a burrowing tool - a hard, sharp projection on the lower jaw, with which it digs sand in search of small crustaceans and worms.

In fish feeding near the surface, the mouth is usually directed upward, the lower jaw is sometimes strongly elongated, as, for example, in half-fish. Bottom fish, such as the stargazer and anglerfish, which grab prey floating above them, have their mouths upward. And in those fish that are looking for food at the bottom, for example, in stingrays, haddock and the common Chukuchan, the mouth is located on the underside of the head.

Well, how does a fish breathe? To maintain life, she, like all animals, of course, needs oxygen - in fact, her respiratory process is not so much different from that of terrestrial animals. To extract the oxygen dissolved in the water, the fish run the water through their mouths, pass it through the gill cavity, and push it through the holes located on the sides of the head. The gills act in much the same way as the lungs. Their surface is permeated with blood vessels and covered with a thin layer of skin that forms folds and plates, the so-called gill lobes, which increase the absorption surface. The entire branchial apparatus is enclosed in a special cavity, covered by a bony shield, a branchial cover.

The branchial apparatus is distinguished by high functional adaptability, so that some fish can even get the oxygen they need not only from water, but also from the atmospheric air. Common carp, for example, during the hot summer months, when the pond is dry or lacking in oxygen, traps air bubbles and keeps them in the mouth next to moist gills. The creeper, snakehead and Indian catfish have special air cavities with folded walls near the gills. Doubling fish, if necessary, use fully developed lungs with the same network of blood vessels as in frogs and newts. In some ancient fish, the rudimentary lung, which later turned into a swim bladder, is still connected to the esophagus, and in essence these fish - silt fish, shell pike - have spare lungs.

However, the swim bladder of modern fish, if any, no longer performs respiratory functions, but acts as an improved lifting balloon. The bladder is located in the abdominal cavity below the spine and is an airtight sac, equipped with glands that can, if necessary, extract gas directly from the fish's bloodstream and fill the bladder with it. The amount of gas is regulated with great precision, and the fish receives just the lifting force that it needs to stay at its usual horizon, whether it be near the surface or at a depth of four hundred meters. Many fish living at great depths or leading a near-bottom lifestyle do not need a swim bladder, and they do not have one. The swim bladder limits the fish's ability to move arbitrarily to any depth, as adaptation to depth and pressure occurs gradually. Most fish living at considerable depths cannot rise to the surface, because their swim bladder would swell to an unbearable size for a fish - if such a fish is caught and pulled out of the water, the swollen bladder can squeeze its stomach through the mouth. There are fish, for example the mackerel family, with a very small bubble or no bubble at all. For them, there is no such restriction, and they can fish for food at different depths. However, they pay a dear price for this: in order not to drown, they need to be in constant motion.

There are fish that live alternately in fresh water, then in salt water, they have special difficulties - salt barriers that they need to overcome. Since the fish lives in water, it needs to maintain a balance between the salts dissolved in its blood and lymph, and the salts that may or may not be in the surrounding water. In freshwater fish, the concentration of salts in the blood is higher than in the surrounding waters, and therefore water constantly tends to penetrate the fish's body through the skin, gill membranes, mouth and other open areas of the body. Under such unremitting pressure, the fish must constantly release water in order to maintain proper balance. In marine fish, the difficulty is just the opposite: they constantly release water into a saltier environment and therefore must absorb it all the time so as not to shrivel like a baked apple. And for the release of excess salts that get along with the water, marine fish have special cells on the gill lobes.

Since the aquatic environment differs sharply from the air, we have the right to ask ourselves the question of how the senses in fish act to notify it of where it is and what is happening around. What does the fish see? How does she hear? Does she have a sense of smell similar to ours, a sense of taste, a touch?

You can answer that the fish have all these five senses, and in addition they have another, truly sixth sense, which allows them to very subtly perceive the slightest change in the movement of water around. This sixth sense is unique to fish (This organ system is also characteristic of amphibians living in water.), And its organs are located in a system of channels under the skin.

Let's start, however, with the organ of vision - in fish it acts in the same way as in humans, with the difference that the fish that feed themselves above the surface of the water have to deal with the phenomenon of refraction. Due to the refraction of light rays when they pass from air to water (or vice versa), objects observed in water seem to be displaced if you do not look at them directly from above. A person who wants to hit a fish with an arrow from a bow must aim much lower than the place where he sees it, otherwise he will miss, and long practice has taught him to do this. Likewise, a trout, long-eared perch or salmon, preparing to grab an insect fluttering over their pond, must jump out of the water somewhat ahead of the intended goal - and for a very long time in the process of evolution this skill has turned into a reliable skill based on instinct.

Fish that forage in the water do not have to overcome this difficulty, because light under water travels in the same way as in the air, in a straight line. There are, however, other factors that affect the mechanism of visual perception in their underwater world, and hence the structure of their eyes. Chief among these factors are the amount of light available under the water and the limit of visibility, due to the fact that even the most transparent water cannot match the air.

The lack of bright light in the underwater world has contributed to a significant simplification in the structure of the eyes of most fish in comparison with the eyes of land animals: they can do with little or no contraction of the iris, they also do not need eyelids, because the water constantly flushes foreign particles from their eyes ... They have an iris - a metallic-colored ring around a dark pupil, but to regulate the amount of light rays entering the eye, it does not need to expand and contract to the same extent as our iris, so in most fish it is motionless.

Since underwater visibility does not exceed thirty meters at best (and often much less), fish do not need to adjust their eyes to too much difference in distance. Most of the time, they only have to look at objects in close proximity, and their eye structure matches this. Their lens is not a lens with an adjustable curvature, like the human eye, but an incompressible ball. In the usual position, the fish's eyes see only close objects, and if you need to look at an object at a distant distance, a special muscle tightens the lens.

There is also another, more important reason for the spherical shape of the lens of the fish, and this again has to do with refraction.

Since the lens contains a substance of almost the same density as water, light, penetrating from the surrounding aqueous medium into the lens, is not refracted - according to the laws of optics, this means that for a clear image of an object on the retina, the curvature of the lens must be significant, and the greatest curvature has ball. But, according to some scientists, even with such a curvature, the image is not really clear, and it is possible that the fish, even under the most favorable conditions, does not see objects clearly under water.

But fish have an advantage that land animals do not have: they can see in more than one direction at a time. Their eyes are not located in front, but usually on the sides of the head, and what each eye sees is fixed in the brain from the opposite side, that is, objects on the right are fixed by the visual center located on the left side of the brain, and vice versa.

This monocular vision of fish has its limitations, especially in the estimation of distance. Nevertheless, it is not at all excluded that there is a relatively narrow space directly in front of the fish, which both eyes can see at the same time, therefore, to some extent, binocular vision (and therefore a sense of perspective) is inherent in fish, such as ours. Indeed, when something aside attracts the attention of the fish, it seems to be really trying to replenish its monocular vision: it quickly turns so that the object is in the field of view of both eyes and it would be possible to better estimate the distance to it.

DOUBLE VISION. The eyeball of the four-eyed, living in the rivers of Central and South America, is designed so that the fish can simultaneously and equally clearly see both in the water and above its surface. The four-eyed eyes are both located at the top of the head, and it can swim with them halfway out of the water. True, from time to time she has to dive in order to wet the upper, "above-water" part of the eye.

To what extent fish can distinguish colors is unknown. The main tone of the underwater world of fish is greenish-blue, since all other colors are absorbed and disappear already at a short distance from the surface. The perception of color is therefore not particularly important for fish; the only exceptions are those fish that swim near the surface. However, we know that all fish except sharks can perceive certain colors. Microscopic examination of the fish retina has shown that it contains cones, color-discriminating nerve cells and rods that function mainly at night and are insensitive to color.

But what does the color mean in everyday life fish, remains a mystery. Some fish prefer one color to another: trout, for example, distinguishes artificial flies by color. If a darkened aquarium is illuminated with all the colors of the spectrum, the fish will swim to the green and yellow stripes and stop there, but if you leave only the red color, they will behave like in the dark.

Bright and sharply contrasting colors, of course, can be a certain means for fish to recognize each other, but here again we are not sure that this is actually the case. The bright, colorful outfit of some tropical fish makes, of course, think that it must have some significance for other inhabitants of the underwater world. For example, does a shark recognize a pilot fish by contrasting transverse stripes on its dark back and sides? This would explain to us why such a small fish, a little more than twenty centimeters long, can fearlessly swim next to its huge and voracious companion, and he will never swallow it by mistake.

It is also possible that bright colors serve as an identification mark warning of the inedible or poisonous fish. There are fish that probably do not represent a tasty prey for other fish, and in the shallow waters of tropical coral reefs, where visibility under water is relatively high, the bright color, so sharply distinguishing them from their underwater counterparts, can serve as protection.

If anything, it seems likely that some species of fish recognize each other by color. In their greenish-blue world, a bright color catches the eye faster than a gray, barely perceptible shadow that flickered somewhere nearby. This conjecture is supported by the fact that most species of fish, which usually swim in dense schools, are rarely brightly colored, while fish that live separately, among a rather monotonous environment, usually have a noticeable appearance, and other individuals of this species can identify them.

The dyes themselves are produced by a layer of cells in the skin under the transparent scales. These cells are called chromatophores, or color carriers, and contain a variety of pigment grains.

First of all, these are orange, yellow and red pigments, very similar to pigments in red or yellow flower... Then black pigment, which is essentially unnecessary waste of the body and can be found not only in the skin (the internal organs of fish with black skin also usually have a black shell), and finally, the substance guanine, which is contained in the form of crystals, which, depending on their numbers and locations can give white, silver or rainbow colors. In combination with a black pigment, guanine produces blue and green metallic sheen.

Of course, the main thing in the color of most fish is its protective properties. The protective coloration of the fish living in the upper layers of the sea - a dark back and a white or silver underside - makes them unobtrusive from wherever you look at them. Camouflage in bottom fish is very skillful - their color matches the color of the bottom or, like a zigzag pattern of camouflaged warships, breaks the contours of the fish's body. To this "tearing" color is added the so-called "deceit", which completely changes the appearance of the fish.

Sometimes the surrounding objects are imitated not only in color, but also in shape. The Amazonian leaffish is remarkably similar to a leaf floating in water. Fish can even change their disguise at different periods of life - in tropical waters off the coast of Florida there are, for example, fish that, at a young age, take the shape and color of a mangrove pod lying on a white sandy bottom, but when they outgrow, so to speak, a pod, This disguise becomes useless, the fish then go into deeper waters, becoming striped. One of the most skilled craftsmen camouflage is an ordinary flounder, it is easily forged by a chameleon under stones, sand, dark silt.

Disguise can even affect the structure of the fish. The sargassum sea clownfish is covered in skin outgrowths like threads and patches that mimic algae where it hides, while the rag-picking seahorse has long outgrowths like seaweed leaves that it clings to.

Most fish retain the same basic color for life, but in some it changes with age. Young salmon and trout are streaked with dark stripes, while in adult fish the stripes disappear. Male salmon, trout, sticklebacks and many other fish change their color during the breeding season. Once Dr.William Beebe discovered coral fish, which changed their color combination seven times in a day.

Even males and females can differ in color. Male gudgeons, or lyre fish, and European wrasse look like exotic birds with brilliant plumage, while females of both species are completely inconspicuous. There are fish that become darker at night or, like barracuda, take on a completely different color. Many fish change color when scared or hooked.

After death, the color of the fish usually changes immediately and often becomes completely different from what it was during life. The most amazing changes are probably taking place in the bright green-gold luminary, or dorado. During the death throes, the green and gold colors turn to blue and pure white, and then gradually, when the last cramps stop, the whole body acquires a dull brownish-olive tint.

For a long time, scientists have studied the hearing of fish, trying to find out if they can perceive sounds. It was believed that they could not, but what we call the ear serves as an organ of balance in fish. But since some fish still make sounds under water (these can be calling and response signals in mating season or identification signals), it is logical to conclude that they still perceive them. Most likely, when sound waves are perceived, the swim bladder serves as a resonator. Since they do not have the tympanic membrane and the auditory ossicles of the inner ear, which are the real hearing apparatus of higher animals, it is believed that the role of an organ of hearing that perceives sound in the form of wave vibrations is played by the swim bladder and the so-called Weber apparatus - a series of small bones connecting the swim bladder to the inner ear. Some fish are certainly very sensitive to vibrations, including the simple movement of water. They can hear the sound of the propeller at a great distance, and the steps of a person on the shore, shaking the earth and thus the water very slightly, are quite enough to scare away the trout in the pond, the touching sensitivity in fish is carried out by nerve endings distributed throughout the skin. Most of them are on the head and around the lips, and in many fish they are located, in addition, on special antennae. Cod and red mullet examine the bottom with rather short antennae sitting on the chin; catfish have very long whiskers.

Almost all fish are characterized by a finely developed sense of smell. They have somewhat similar nostrils to ours - a pair of small, outward opening and located directly on the snout of the grooves, lined inside with folded tissue, which greatly increases their surface. This tissue contains nerve cells that sense smell.

The sense of smell in most fish is developed so much that when looking for food, it means much more to them than sight. Sharks can smell blood from afar and appear near a wounded fish or animal from out of nowhere. Sports anglers have successfully used fish blood to attract bluefish and other predatory fish. If you pour only one glass of water into a pool with lampreys, in which another fish was swimming, lampreys will immediately be on the alert and begin to look for the source of this aroma that suddenly appeared pleasant for them.

As for gustatory sensitivity, it probably does not play a big role in the life of fish. First of all, none of them, except for lungfish, have taste organs in the mouth. They have taste buds, but they are located on the head, torso, tail, modified fins or antennae, and therefore if fish do taste food, it happens before it gets into their mouth. Many fish simply swallow food, it goes directly into the stomach and is digested there.

The most remarkable feature of the fish is its unique "sixth sense", which allows it to subtly perceive all movements and currents of water. The perfectly arranged system of channels under the skin is quite clearly marked on the sides of the fish as a series of scales of a different form. This is the side line. In the main channel, specialized senses are located at a certain distance from each other. The same channels diverge throughout the head.

Scientists have yet to reveal all the secrets of the lateral line, but it is already clear that its main function is associated with capturing the movement of water. If you cut the base of the nerve going from the lateral line to the brain, then the fish clearly loses the ability to respond to disturbances in the water or a change in the direction of flow. Apparently, it is this special sense organ that allows the coral fish to sweep like an arrow through a narrow crevice, which it probably cannot see properly, or allows the fish to bypass obstacles invisible in muddy water during floods. And, probably, it is the lateral line that allows huge fish schools of many thousands of individuals to swim in such a coordinated formation.

Anyone who has ever caught fish or seen others catch fish probably wondered if the fish felt pain. This question is too difficult to give an unequivocal answer to it. Pain is not only a physical reaction, but also a mental one, and we cannot find out from the fish what exactly it feels. But we can almost be sure that mentally fish do not feel pain.

Well, are they physically in pain? In humans, pain is born in the cerebral cortex as a result of information sent by sensory nerves, but fish do not have a formation comparable to the cortex of the human brain, or any other part of the brain that would perform its functions.

The force of irritation of certain senses, necessary in order to induce a sensation of pain, is called the pain threshold. In some species of animals, as well as in some individuals, it is much higher than in others. The lower we go down the evolutionary ladder, the higher the pain threshold becomes, the more irritation is needed to trigger a pain response. We can be quite sure that it is high in fish. In response to too much irritation, they simply walk away or try to walk away.

That is why a fish can safely swim away with a hook in its mouth or a harpoon in its back, and a wounded shark will continue to attack, even if its brethren are ripping out its entrails.

Fish classification (from Latin classis - category - class and ..., fication) is, simply speaking, the division of fish by lifestyle, structural features, breeding method and appearance... There are many different classifications, and the main aquarist needs to know.

Let's start with the fact that of all vertebrates, fish are the most numerous in terms of the number of animal species. If you combine all mammals, birds, amphibians and reptiles, then the number of their varieties will be less than fish, of which there are over 20 thousand species!

Fish inhabit almost all water bodies of the world. Through evolution, these animals have adapted to various conditions of existence, which led to the emergence of many of their species. All of them are combined into one general class of "fish".

According to this system, the class "fish" is divided into subclasses, subclasses, in turn, into orders, orders into suborders, suborders include superfamilies, superfamilies - families, families - subfamilies, subfamilies - genera that already include species.

The Latin name for fish usually has a definite ending. Thus, the order usually ends in -formes, the suborder in -oidei, the name of the superfamily is written with the ending -oidae, the family ends in -idae, and the subfamily ends in -ini.

Other not specified systematic units fish classification do not have a definite ending and can end in different ways.

Fish classification is carried out as follows. Very similar fish species in structure and lifestyle, as well as in their relationship, are combined into a genus. The genus, in turn, belongs to a subfamily, the subfamily belongs to a specific family, and so on. In some cases, the species are still subdivided into subspecies.

The scientific name of the fish is indicated on the letter in two words. The first of them is the genus, and the second is the specific name. In addition, the surname of the author who first described this species is indicated, as well as the year in which the description was created, if this year, of course, is known.

For example, the Latin name for a fish zebrafish rerio looks like this: Brachydanio rerio Hamilton-Buchanan, where Brachydanio is the name of the genus, rerio is the name of the species, and Hamilton-Buchanan, respectively, is the author's surname.

In addition to the division described above, there are other fish classification... First of all, fish are always divided according to their habitat into marine and freshwater species.

Then, according to the method of reproduction, they are divided into viviparous and spawning.

Further, which is no less important, classify fish according to the temperature regime that is optimal for their life: fish are warm-water, tropical and cold-water. Typically, aquariums contain tropical species, which are most easily provided with suitable temperature conditions.

There is also fish classification by their shape and features of the body structure. Usually, there is no separate Latin name in this case, and aquarists call different forms of fish species breeds.

For example, if the fish is called danio rerio veil, then such fish have elongated fins, similar to a veil.

Besides, classify fish depending on the color form. In general, it might look something like this: black forked guppy, where guppy is the name of the fish species, black is the color of the body and fins, fork is the forked shape of the caudal fin.

Aquarists can call these same guppies, for example, "the black prince", although this species with this name is scientific men in fish classification not described or "patented", but the aquarists themselves came up with the name of the fish, after they brought out this form.

Figure: 1. The structure of fish ()

Fish have a head, body, tail, and fins. Primarily the shape of the body is elongated, streamlined(fig. 1). The body of the fish is without protrusions, covered with mucus, which facilitates movement in the water. The pointed head is tightly covered with gill covers, it helps to move well in the water and cut the water. The tail and fins determine the direction of movement of the fish in the water.

Fish body In most cases scalythat sits in folds of skin like nails. The free ends of the scales overlap each other, resembling roof tiles. It grows with the fish itself. Fish scales come in different shapes. But there are species that have a body as smooth as a catfish.

Another feature is the structure of fish eyes. They have no eyelids, the eyes are on both sides of the head, but in the flounder they are shifted to one side. Pisces cannot cry, the eyes are hydrated naturally. They see at a distance of one meter. Fish do not tolerate bright light, some species are color-sensitive.

The fish have gillsBasically, they all breathe like this: the fish swallows water through the mouth, it passes through the gills and pours out through a special hole. The water contains oxygen, and through the gills it enters the fish blood. But in nature there is lungfish... They use both gills and lungs for breathing. This is the Horntooth (Fig. 2).

In most cases, fish spawn, from which future offspring emerge. In the water, they lay eggs in various places: special nests, stones, sand, plants. But fish can be viviparous... An example of this is the guppy fish (Fig. 3).

These fish give birth to fry immediately.

One of the most curious differences between fish and other vertebrates is their special feeling. You are also interested to know why the joint first floats together in one direction, and then suddenly, as if at someone's command, it all at once turns in the other direction. It helps to do lateral line on the body of the fish... It consists of sensitive cells that detect the slightest fluctuations in the water flow.

The fish also have a unique adaptation - swim bladder... It serves as a lifeline that does not allow to fall to the bottom. By filling with oxygen or blowing it off, fish change the depth of their immersion in the water.

It is worth saying that fish feel pain, they have an organ of hearing - inner ear... They have a delicate sense of touch - they feel everything with their skin. Animals have nostrils, distinguish smells. Fish themselves can smell, there are special glands.

The body shape of fish is very diverse. The serpentine shape of the body, like that of an eel, makes the fish elusive (Fig. 4).

Spherical shape with needles, like a fish-hedgehog, - invulnerable (Fig. 5).

Its wide and flat shape, like a slope, allows it to spread flat on the bottom (Fig. 6).

The seahorse looks a little like fish, it merges well with algae (Fig. 7).

Figure: 7. Seahorse ()

The needlefish is so thin that you can't immediately notice (Fig. 8).

Figure: 8. Fish-needle ()

Fish of completely different sizes are found in nature. The smallest known fish is the dwarf goby. It can be up to 1 cm long (Fig. 9).

Figure: 9. Dwarf goby ()

The largest is the whale shark - up to 18 m (Fig. 10).

Figure: 10. Whale shark ()

Some species fishes emit a cold light... These are mainly deep-sea fish. It is very dark at the bottom and it is necessary to attract prey. The glow is provided by special glands, they are found in the angler fish (Fig. 11), the midshipman fish (Fig. 12).

Figure: 11. Angler fish ()

Figure: 12. Fish-midshipman ()

Nature has taken great care to make the fish comfortable and comfortable to live in their habitat. In this case, the habitat can be in different places. Fish can be found where it is very warm and where it is very cold. They are found at high altitudes, as well as where very low. Of course, they had to adapt well to all these conditions, therefore, along with common features, they have many differences.

Figure: 13. Drummer ()

Figure: 14. Spinhorn ()

Some thus draw attention to themselves during the breeding season.

Many fish have adopted electricity and poison for their safety and for catching prey. Send electrical discharge can the Nile elephant, the European astrologer, the marble stingray (Fig. 15-17).

Figure: 15. Nile elephant ()

Figure: 16. European astrologer ()

Figure: 17. Marble slope ()

Some fish sting no less dangerous than snakes. This is a sea dragon, scorpion fish, lionfish (Fig. 18-20).

Figure: 18. Sea Dragon ()

Figure: 19. Scorpion ()

Figure: 20. Lionfish ()

Fish coloringstrikes the imagination. The color palette is diverse. The bright color either attracts the attention of the victim, or is needed, on the contrary, to scare away. Appropriate coloring is also needed for camouflage. The angelfish, mandarin duck, and clown fish have a very colorful appearance (Fig. 21-23).

Figure: 21. Angelfish ()

Figure: 22. Mandarin duck ()

Figure: 23. Clown Fish ()

Some fish need to be able to fly and have sharp teeth. Some of the fish can crawl and bury themselves in the sand. There are fish that have special suction cups in order to stick to another animal. There are completely blind fish, other senses help them in life. There are many devices, each fish needs its own individual.

The role of fish in human life is simply invaluable. Since ancient times, people have eaten fish. In our diet, it is a supplier nutrients, minerals: proteins, fats, vitamins. Even in the ancient world, people began to breed fish for beauty. In any modern home, you can see an aquarium with beautiful and amazing fish. Fish is also used in industry and medicine. Man copied the streamlined shape of fish during the construction of ships and submarines. Unfortunately, in recent years, industrial fishing has become more frequent, there are cases of poaching, so some species of fish simply disappear. In this regard, many civilized countries have entered into an agreement in which it is strictly spelled out where you can fish and how much.

Every person on Earth should think about the preservation of this class of animals.

Bibliography

1. Samkova V.A., Romanova N.I. The world around you 1. - M .: Russian word.
2. Pleshakov A.A., Novitskaya M.Yu. The world around us 1. - M .: Education.
3. Gin A.A., Faer S.A., Andrzheevskaya I.Yu. The world around us 1. - M .: VITA-PRESS.

1. Festival pedagogical ideas "Public lesson" ()
2. Pro-ryb.ru ()
3. Kindergenii.ru ()

Homework

1. Who are fish?
2. Tell us about the structure of fish.
3. What is the role of fish in human life?
4. * Draw the fish that you remember the most and tell us about it.