Fish belong to the group. Salmon fish names, species features. The internal structure of fish
Fishes common in all types of water bodies, from marine water spaces to the smallest ponds, eriks and rivers. The tropics and eternal ice are also rich in unusual varieties of fish. In the reservoirs of Russia, aquatic inhabitants are very diverse and distinguished by their beauty. On the territory of the Russian Federation there are more than 120 thousand rivers, about 2,000,000 lakes, 12 seas, 3 oceans, and all of them are habitats fish. Even in fresh Russian reservoirs, more than 450 fish species, and many live permanently, and some arrive temporarily until a certain period.
general information
According to the presence and nature of the rays in the fins of most bony fish, a fin formula is compiled, which is widely used in their description and definition. In this formula, the abbreviated designation of the fin is given in Latin letters: A - anal fin (from Latin pinna analis), P - pectoral fin (pinna pectoralis), V - ventral fin (pinna ventralis) and D1, D2 - dorsal fins (pinna dorsalis). Roman numerals give the numbers of prickly, and Arabic - soft rays.
Gills absorb oxygen from the water and release carbon dioxide, ammonia, urea and other waste products into the water. Teleost fish have four gill arches on each side.
Gill rakers are the thinnest, longest, and most numerous in plankton-feeding fish. In predators, gill rakers are rare and sharp. The number of stamens is counted on the first arch, located immediately under the gill cover.
The pharyngeal teeth are located on the pharyngeal bones, behind the fourth gill arch.
FISHES
(Pisces),
An extensive group of jawed vertebrates that spend all or most of their lives in water and breathe with gills. This definition immediately excludes from the number of fish vertebrates that breathe with lungs, i.e. whales, seals, dolphins and other aquatic mammals. All of them also feed their offspring with milk, and the fish do not have either mammary glands or hairline characteristic of mammals. Frogs, toads, newts and salamanders in the early stages of development breathe with external gills, and then lungs. These amphibians (amphibians) also differ from fish in the presence of paired limbs in adults, which are homologous to the fins of fish.
Anatomy. The external structure of fish is complex and varied. In principle, each structure of the organism ensures its adaptation to specific living conditions. However, some features are common to most fish, such as dorsal, anal, caudal, pectoral, and ventral fins.
Digestive system. In terms of internal structure, fish are similar to other vertebrates. The body is bilaterally (bilaterally) symmetrical, except for the digestive tract. The latter consists of the mouth, jaws, usually covered with teeth, tongue, pharynx, esophagus, stomach, intestines, pyloric appendages, liver, pancreas, spleen, rectum or colon, and anus or anus. In the intestines of sharks and some other primitive fish there is a spiral valve, a unique organ that increases the "working" surface of the digestive tract without increasing its length. In predatory fish, the intestines are usually short, forming one or two loops, while in herbivorous species it is long, tortuous, with many loops. The respiratory system consists of gill arches covered with delicate, fleshy gill filaments, richly supplied with blood through capillaries and larger vessels. In front of the mouth there are special oral valves that prevent the return of water. When the mouth is closed, it enters the pharynx, flows between the gill arches, washes the gill filaments, and exits through the gill slits (in cartilaginous fish) or the opening under the gill cover (in bony fish). The nervous system - the brain, nerves and sense organs - coordinates the functions of the body and connects it with the outside world. Like other vertebrates, the nervous system of fish includes the brain and spinal cord. The brain consists of the olfactory lobes, forebrain hemispheres, diencephalon with pituitary gland, visual lobes (midbrain), cerebellum and medulla oblongata. Ten cranial nerves depart from these departments. The eye consists of the cornea, lens, iris, retina, and sharks also have an eyelid - a nictitating membrane that can move from below to the cornea. Fish have no external ear. The inner ear consists of three semicircular canals with ampullae, an oval sac and a round sac with a projection (lagena). Fish are the only vertebrates with two or three pairs of otoliths, or ear pebbles, which help maintain a certain position in space. In some groups, the swim bladder communicates with the inner ear with the thinnest tube, and in minnows, carps, catfish, characin and electric eels, it is connected to it by a complex bone mechanism - the Weberian apparatus. This allows you to better perceive ("hear") the vibrations of the environment. The lateral line system is a unique sensory organ in fish. Usually it is a network of depressions or channels in the skin of the head and trunk with nerve endings in depth. These canals in bony fish usually open with pores on the surface. The entire system is connected by nerves to the inner ear. It serves to perceive low-frequency vibrations, which allows you to detect moving objects.
anatomical adaptations. Fish are extremely diverse in structure and adaptations. They walk, swim and fly (plan). Some are able to see both in water and in the air, make various sounds, emit light, and even generate a strong electric charge. Each structure fulfills its purpose - it serves for protection, obtaining food or reproduction.
Mouth, jaws and teeth. The jaws of fish are diverse - from toothless to equipped with chisel-shaped incisors and long sharp fangs. Some herbivorous forms, such as surgeonfish and South American catfish, have teeth on long thin stalks with a cupped top. Parrotfish are remarkable for their beak-forming teeth, which gives them a resemblance to birds, hence the name of the family. The mouth can point down like a shark, forward like a salmon, or up like a stargazer. The lips are covered with long hair-like outgrowths, like those of the hair-tooth (Trichodon), which, having dug into the ground, with the help of this filter cleans the inhaled water from sand. Gill openings are of two types. For sharks and rays, five external gill slits are typical, and for bony fish - four or five holes covered with a gill cover, which directs the water pushed through the gills into one common slit that opens outward.
Eyes. In general, the eyes of fish are arranged in the same way as those of other vertebrates. Outside, they are covered with a cornea. Light passes through the pupil - a hole in the iris - and is focused by a spherical lens on the retina, which occupies the back wall of the eye. Visual stimuli are transmitted from the retina along the optic nerve to the brain. Since both rods and cones are present in the retina of fish, it can be concluded that they distinguish colors. In the four-eyed (Anableps), living in Central and South America, the eyes are divided into two parts: the upper one is adapted to see in the air, and the lower one - under water. The lens here is oval and angled to focus light rays from both sources onto the retina. Since bony fish do not have eyelids to moisten their eyes while in the air, the four-eyed fish solves this problem by periodically dipping its head into the water.
Luminescence. The ability to emit cold light is widespread in various, unrelated groups of marine fish. The glow is usually provided by special glands located in the skin or on certain scales. The glands consist of luminous cells, behind which there may be a reflector, and in front - a lens. Pisces are able to arbitrarily "turn on" and "turn off" their glow. The location of the luminous organs is different. In most deep-sea fish, they are collected in groups and rows on the sides, belly and head, resembling pearl buttons or modern road markings that reflect light at night. The purpose of this cold glow is not entirely clear. In the absolute darkness of the ocean depths, where some angler fish live, it is probably used to attract small prey and individuals of the opposite sex.
Sounds. The sounds made by some fish can be clearly heard by the human ear for many meters. They vary in height and intensity. Among the many "vociferous" fish, the most famous are croakers, drummers, ronks, triggerfish, toad fish and catfish. Their sounds are reminiscent of grunting, squealing, creaking, barking, and in general, the noise of a barnyard. The origin of the sounds produced is different. In some catfish, the back and forth movement of gas in the swim bladder causes the tightly stretched membranes to vibrate. The roncs rub their pharyngeal teeth together. Croakers and drummers make a particularly loud noise with the help of the vibrations of the swim bladder: there is something like the muffled sound of a jackhammer on the pavement. Some triggerfish make sounds by rotating their fin rays. Usually, the most frequent and intensive use of sound signals by fish is during the breeding season.
I. Some fish are able to sting no less dangerous than poisonous snakes. The action of their poison is similar to the bite of cobras, rattlesnakes or bees. The most famous of these fish are stingrays (Dasyatidae), scorpion fish (Scorpaenidae), toad fish (Batrachoididae) and dragon fish (Trachinidae). Less poisonous are catfish, tropical perches from the Pacific Ocean belonging to the Siganidae family, some sharks (Squalus, Heterodontus) and chimeras. In stingrays, the sting is located on the upper side of the tail, about a third or half of its length from the end. It reaches 30 cm in length, serrated on the sides and surrounded at the base by poisonous glands. Stingrays are found in shallow waters, near sandy and muddy beaches of warm seas, in river mouths and quiet bays, and some species even in the rivers of Asia and South America 1600 km from the sea. Stingrays hide in soft ground. If stepped on, they swing a powerful tail, which raises a poisonous sting, and it sticks deep into the victim, causing piercing pain. This device is used for both defense and attack. Stingrays feed on invertebrates living in silt and sand. In most other poisonous fish, such glands lie along the dorsal and pectoral fin spines and at their base. When the spike pierces the body of the victim, poison is squeezed out of the tissues surrounding it and enters the wound through a special groove. Siganus has two grooved venomous spines in each pectoral fin. The most developed stinging organs are in sea dragons and toad fish. The spines on the gill covers and the first two dorsal rays are hollow, like the teeth of poisonous snakes. The base of such a spike is surrounded by a poisonous gland.
Electricity. Five groups of fish are capable of generating an electric charge: sea stargazers (Astroscopus), freshwater hymnarchs (Gymnarchus) living in Africa and electric catfish (Malapterurus), marine electric rays (Tetronarce) and the famous South American electric eel (Electrophorus electricus). The latter lives in the slowly flowing waters of the Amazon and Orinoco, reaching a length of 180 cm. Experiments carried out at the New York Aquarium showed that this wonderful creature generates a voltage of 600 volts and can release electricity at will at intervals of two to three seconds, after which the discharge power drops for several hours. The voltage generated by electric catfish and stingrays is much less, and in stargazers and hymnarchs it is even weaker.
Coloring. Modern aquariums give a good idea of the magnificent coloration of many freshwater and saltwater fish. Some freshwater species take on a dazzling brilliance with crimson, bright yellow and blue spots during the breeding season, and are much more modestly colored the rest of the time. Among the coral reefs in tropical seas, several hundred species of fish live, competing in their colors with butterflies and birds. Here you can find almost every conceivable type of color: from gray and silver to contrasting black with yellow, blue, red lines, rings, stripes, strokes or green, yellow and purple speckles, spots, blots and circles encircling the body. Pigments corresponding to black and brown shades are called melanins. Bright colors provide fat-soluble lipoids. Both types of pigments are located in special cells, chromatophores, deep in the skin. In addition, special reflective granules - iridocytes - give the fish a milky white and silvery color. The ability of the chromatophores to expand and contract allows the fish to change their body pattern, which aids in camouflage. The nature of the environment is perceived by sight and purely reflex changes the state of the chromatophores. As a result, many fish become almost invisible. Known examples of species with this protective coloration are clownfish living in thickets of Sargassum algae, sea needles among the green grass of eelgrass, poisonous warts (Synanceja) at the bottom of pits in coral reefs, and rag-pickers (Phyllopteryx) resembling branched thalli of algae.
Number and size. Fish are the most numerous vertebrates. Known ca. 40,000 different species, more than double the total number of mammals, birds, amphibians and reptiles combined. As for the number of individuals, there are truly a myriad of them in the waters. For many years, the smallest of the fish was considered the species Heterandria formosa 19 mm long, from the southeastern United States. However, in the Philippines, a species of Pandaka pygmaea has been found, the name of which is much longer than the animal itself (9-11 mm). It is the smallest known vertebrate. The largest species of catfish is Pangasius sanitwongsei from Siam at 3 m long, and the largest freshwater fish is the North American white sturgeon from the Columbia and Fraser rivers in the northwest United States, which reaches a length of 3.8 m and a record mass of 583 kg. However, the beluga (Acipenser huso), caught in the Volga near Astrakhan, turned out to be even larger: its length was 4.4 m, and its weight was 1022 kg. However, even these giant sturgeons are pygmies compared to the champions among marine fish. Man-eating sharks 9-12 m long give way to two harmless species. One of them, the giant shark (Cetorhinus maximus) from the Arctic waters, reaches more than 12 m in length. But the largest of the fish is the whale shark (Rincodon typus), broad-headed, blackish, with white spots on its back the size of silver dollars. This giant feeds on plankton - small animals and algae that drift with ocean currents. The maximum accurately recorded length of such a shark is approx. 13.5 m, but, according to rough estimates, it can be more than 21 m with a mass of approx. 68 tons
Ecology. Fish occupy almost all aquatic habitats. They are found in polar and tropical seas, in cold mountain lakes and streams, and in hot springs with temperatures up to 43 ° C. Many species live in the open sea, away from the coast, some live in great ocean depths, in complete darkness. Fish live in thickets of aquatic vegetation, rock crevices and among stones; they can burrow into silt, sand, and pebbles. Some are nocturnal, but most hunt during the day. Several species live in dark caves: they are almost or completely blind.
Spreading. Fish are found in all large rivers, in almost all large lakes and are absent only in a few reservoirs. Marine fish are divided into coastal, oceanic and deep-sea forms. The former live in shallow waters off the coast, among them are herring (Clupea), mackerel (Scomber), sea bass (Sebastodes), pomacentrids (Pomacentridae), flounders (Pleuronectes), borracites (Salarias), etc. Halibut (Hippoglossus) and cod (Gadus) are found on the continental shelf. Oceanic fish live in the open seas to depths of 90-150 m. They are called pelagic. These include large sport fish such as tuna (Thunnus), swordfish (Xiphias), marlin (Makaira), and small glowing anchovies (Myctophidae) and mackerels (Scomberesocidae). At depths from 135 to 540 m, there are many small fish with huge eyes and a silvery color. Even deeper are bathypelagic species with small eyes and luminous organs, such as stomiids (Stomiatidae) and deep-sea anglers (Ceratiidae). The color of these fish is mostly black. Abyssal fish, in particular long-tailed fish (Macrouidae), spend their whole lives at the ocean depths near the bottom. Freshwater fish are distributed throughout all continents and large islands. They are often divided according to their belonging to seven zoogeographic regions: 1) Nearctic - Canada, the USA and most of Mexico; 2) Neotropical - Central and South America; 3) Palearctic - Europe and Asia north of the Himalayas and the Yangtze River; 4) Indo-Malay - India, Southeast Asia, the islands of Java, Sumatra, Borneo; 5) Ethiopian - Africa; 6) Australian - Australia, New Guinea and the islands of the Malay Archipelago to the east of the Wallace line, passing between the islands of Borneo and Sulawesi, Bali and Lombok; 7) Madagascar. Some areas, for example, the Nearctic and Palearctic, are very similar in terms of ichthyofauna - in both regions there are cyprinids (Cyprinidae), chukuchans (Catostomidae), perches (Percidae) and eudoshkids (Umbridae). Similarly, characins (Characinidae), nematognathoid catfishes (Nematognathoidea) and cichlids (Cichlidae) live in both the Neotropical and Ethiopian regions. In terms of the composition of the freshwater fish fauna, Europe, North Asia and North America are closer to each other than North and South America, and there are more similarities between South America and Africa than between Africa and Eurasia.
Reproduction. Fish breeding methods are different. Some are viviparous - active juveniles come out of the mother's body. The rest are oviparous, i.e. they lay eggs that are fertilized in the external environment. The reproductive behavior of some fish is very peculiar. It is difficult to see a clear evolutionary sequence in their methods of reproduction. Sharks and rays, primitive in their anatomy, are mainly viviparous or lay horny egg capsules. In more highly developed fish, both viviparous and oviparous species can be found in the same group.
Atherine Grunion. Atherine Grunions (Leuresthes) can be seen in spring and summer along the southern coast of California, where on the second, third and fourth night after the highest (syzygy) tide, they splash in the moonlight on wide sandy beaches. As soon as the surf hits the shore, churning the water into white foam, and then spreads over the sand, the atherines rush to land. For some time, these fish 15-20 cm long are out of the water. Females, as it were, "stand" on the tail, plunging it into the sand and leaving 2/3 of the body outside. Males swarm around them. At this point in the sand to a depth of approx. 5 cm fertilized eggs are laid. The next wave captures the spawned atherine grunions and drags them back into the ocean. Under the influence of the surf, the egg laying sinks even deeper into the sand, and in the next few days the tide recedes and it ends up on the shore. Here, under a sandy blanket, the caviar of the grunion atherina is not afraid of the hot rays of the sun and predators. Two weeks later, the spring tide comes again, the waves flood the beach and free it from the sand. At this moment, the juveniles hatch from the eggs and leave for the ocean.
Salmon and trout. All types of salmon spawn in nests on the pebbly bottom of cold rivers or spring lakes. Most of these fish migrate to spawn from the sea to fresh waters: they are called anadromous or anadromous. The female, sometimes with the participation of the male, digs the nest. To do this, she lies on her side and begins to bend her tail up and down, moving slightly upstream. So she "irons" the same place several times in a row. With each stroke of the tail, pebbles and sand rise from the bottom, carried downstream until a saucer-shaped hole is ready. During the construction of the nest, the male and female protect their territory from encroachment by other fish. When a male of the same species and similar size approaches, the legal owner of the territory swims out to meet him, may attack or simply send the uninvited guest out. In the latter case, the fish, before dispersing, swim a certain distance parallel to each other. The rest of the time the male devotes to courting the female, which consists in lightly pushing her with his nose and simultaneously trembling with his whole body. Fertilization occurs when both fish lie on the bottom of the nest side by side with their heads against the current. At the same time, shuddering, the male and female spawn eggs and milk and immediately cover the masonry with soil raised from the bottom a little upstream. At all stages of spawning, the actions of the parents are strictly synchronized. If male and female germ cells do not appear in the water at the same time, fertilization will not occur. The caviar will swell due to the entry of water into it, and after a few minutes the micropyle, i.e. the pore through which the spermatozoon can penetrate will close. Trout is able to breed several times in its life, and Pacific salmon dies shortly after spawning.
River eel. Well-coordinated and specialized reproductive behavior is characteristic of many fish, including the common eel (Anguilla). The European eel migrates over a distance of approx. 3220 km across the North Atlantic to spawn northwest of Bermuda in the Sargasso Sea. Spawning of the American eel takes place in approximately the same place. Juveniles of the European species develop within two years, drifting back to the shores of Europe, where they enter fresh waters. American eel fry reach the rivers in the next spring.
Origin of fish. The oldest fossilized remains of real fish have been found in the Ordovician deposits. The next four periods (Silurian, Devonian, Mississippian and Pennsylvanian) are called the "age of fish" - these were the largest and most diverse animals on Earth. In later geological epochs, their species richness and abundance remained high, but more evolutionarily advanced groups appeared - amphibians and reptiles, then birds, mammals, and, finally, humans. The most primitive of modern fish are sharks, rays and chimeras with a cartilaginous skeleton. It partially ossifies in sturgeon, silt and some other fish. Finally, species with a completely ossified skeleton appear, they are called bony (Teleostei).
See also COMPARATIVE ANATOMY.
Fish classification. Fish belong to the chordate phylum, which also includes amphibians, reptiles, birds, and mammals. This type is variously subdivided into taxa of lower rank. The system below distinguishes two of its subtypes: non-cranial (Acrania), devoid of a real head section (lancelets), and cranial (Craniata), or vertebrates, which include fish. Among the latter, several subclasses and orders are distinguished. Type Chordata (chordates)
Subphylum Acrania (craniless)
Class Cephalochordata (cephalochordae)
Order Branchiostomoidea (lancelets)
Subphylum Craniata (cranial)
Superclass Agnatha (jawless)
Class Marsupobranchii (sacgills)
Order Petromyzonoidea (lampreys)
Myxini class (mixins)
Order Myxinoidea (hagfishes)
Superclass Gnathostomata (jaws)
Class Elasmobranchii (plate gills)
Subclass Selachii (sharks and rays)
Superorder Selachoidea (sharks)
Order Heterodontoidea (Odd-toothed)
Order Hexanchoidea (polygilloides)
Order Lamnoidea (lamniformes)
Order Squaloidea
Superorder Hypotremata (rays)
Order Batoidea (stingrays)
Class Holocephali (whole-headed)
Order Chimaeroidea (chimaeriformes)
Class Osteichthyes (bony fish)
Subclass Choanichthyes (Choans)
Order Dipnoidea (lungfish)
Order Crossopterygoidea
Subclass Actinopterygii (ray-finned)
Superorder Chondrosteoidea (cartilaginous)
Order Cladistioidea (multifeathers)
Order Acipenceroidea (sturgeons)
Superorder Holostei (bony ganoids)
Order Semionotoidea (shell-shaped)
Order Amioidea
Superorder Teleostei (bony fish)
Order Isospondyloidea (herring-like, or soft-finned)
Order Esociformes (pike)
Order Bathyclupeoidea (deep sea herrings)
Mormyroidea detachment (klyuvoryloobraznye) Ateleopoidea detachment (lozhnodolgohvostoobraznye) Gyanturoidea detachment (giganturoobraznye) Lyomeroidea detachment (saccopharyngiformes) Ostariophysoidea detachment (carps, or kostnopuzyrnye) Apodoidea detachment (eel) Heteromoidea detachment (notacanthiformes) Synbranchioidea detachment (synbranchiformes) Synentognathoidea detachment (sarganoobraznyh) Order Cyprinodontoidea (cypriniformes) Order Salmopercoidea (percopsiformes) Order Berycomorcomorphoidea (beryxiformes) Order Zeomorphoidea (sunniformes) Order Anacanthoidea (cod fishes) Order Thoracostoidea (sticklepiformes) Order Solenichthyoidea (acidiformes) Order Allotriognathoidea (opiformes) Order Percomorphaoidea (perciformes) Order Skocleroparelacide (Long-finned) Order Hypostomosoidea (Pegasiformes) Order Pleuronectoidea (Flounders) Order Icosteoidea (Rag-shaped) Order Chaudhurioidea (Chaudhuriformes) Order Mastocemb eloidea (probosciformes) Order Discocephalioidea (sticky-like) Order Plectognathoidea (rock-toothed) Order Gobiesociformes (sucker-like) Order Bathrachoidea (toad-like) Order Pediculatiformes (angler-like)
Rice. 1. The structure of fish ()
Fish have a head, body, tail and fins. Mostly body shape elongated, streamlined(Fig. 1). The body of the fish without protrusions is covered with mucus, which facilitates movement in the water. The pointed head is tightly covered with gill covers, it helps well to move in the water and cut through the water. The tail and fins determine the direction of movement of the fish in the water.
fish body In most cases scaled, which sits in the folds of the 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 in which the body is smooth, like a catfish.
Another feature is the structure of the eyes of fish. They do not have eyelids, the eyes are on both sides of the head, but in the flounder they are shifted to one side. Fish can't cry, moisturizing the eyes happens naturally. They see at a distance of one meter. Fish do not tolerate bright lighting, some species distinguish colors.
The fish have gills, basically, 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 blood of the fish. But in nature there is lungfish. They use both gills and lungs for breathing. This is Horntooth (Fig. 2).
In most cases fish spawn, from which the future offspring appears. In the water, they lay eggs in a variety of places: special nests, stones, sand, plants. But fish can be viviparous. An example of this is the guppy fish (Fig. 3).
These fish are born immediately fry.
One of the most curious differences between fish and other vertebrates is their special sense. You are also interested to know why the school first floats together in one direction, and then suddenly, as if on someone’s command, turns all at once in the other direction. It helps to do lateral line on the body of the fish. It consists of sensitive cells that pick up the slightest fluctuations in the water flow.
Fish also have a unique adaptation - swim bladder. It serves as a lifeline that does not allow falling to the bottom. Filling with oxygen or deflating it, 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 subtle sense of touch - they feel everything with their skin. Animals have nostrils distinguish odors. Fish themselves can smell, on their body there are special glands.
The body shape of fish is very diverse. The serpentine body shape, like that of an eel, makes the fish elusive (Fig. 4).
Spherical shape with needles, like a hedgehog fish, - invulnerable (Fig. 5).
A wide and flat shape, like a stingray, allows you to spread out along the bottom (Fig. 6).
The seahorse bears little resemblance to fish; it merges well with algae (Fig. 7).
Rice. 7. Seahorse ()
The needlefish is so thin that you won't notice it right away (Fig. 8).
Rice. 8. Needle fish ()
In nature, there are fish of absolutely different sizes. The smallest known fish is the pygmy goby. It can be up to 1 cm long (Fig. 9).
Rice. 9. Dwarf goby ()
And the largest is the whale shark - up to 18 m (Fig. 10).
Rice. 10. Whale shark ()
Some species fish emit cold light. Mostly deep sea fish. It is very dark at the bottom and it is necessary to attract prey. Glow is provided by special glands, they are found in angler fish (Fig. 11), midshipman fish (Fig. 12).
Rice. 11. Anglerfish ()
Rice. 12. Midshipman fish ()
Nature has taken great care to ensure that the fish are comfortable and convenient to live in their habitat. In this case, the habitat can be located in different places. Fish can be found where it is very warm, and where it is very cold. They are found at high altitude and also where it is very low. Of course, they had to adapt well to all these conditions, therefore, along with common features, they have many differences.
Rice. 13. Drummer ()
Rice. 14. Trigger ()
Some, thus, attract attention to themselves during the breeding season.
Many fish have adopted electricity and poison for their safety and to catch their prey. Send electrical discharge the Nile elephant, the European astrologer, the marble slope (Fig. 15-17) can.
Rice. 15. Nile elephant ()
Rice. 16. European stargazer ()
Rice. 17. Marble slope ()
Some fish sting no less dangerous than snakes. This is a sea dragon, scorpion fish, lionfish (Fig. 18-20).
Rice. 18. Sea dragon ()
Rice. 19. Scorpio ()
Rice. 20. Lionfish ()
Fish coloring strikes the imagination. The color palette is varied. A bright color either attracts the attention of the victim, or, on the contrary, is needed to scare away. Appropriate coloring is also needed for camouflage. It has a very colorful appearance angel fish, mandarin duck, clown fish (Fig. 21-23).
Rice. 21. Angelfish ()
Rice. 22. Tangerine ()
Rice. 23. Clownfish ()
Some fish need to be able to fly and have sharp teeth. Some of the fish can crawl and burrow into the sand. There are fish that have special suckers in order to stick to another animal. There are completely blind fish, they are helped in life by other senses. There are many adaptations, each fish requires its own individual ones.
The role of fish in human life simply invaluable. Since ancient times, people have eaten fish. In our diet, it is a supplier of useful substances, minerals: proteins, fats, vitamins. Even in the ancient world, people began to breed fish for beauty. In any modern house you can see an aquarium with beautiful and amazing fish. Fish is also used in industry and medicine. The streamlined shape of fish was copied by man in the construction of ships and submarines. Unfortunately, industrial fishing has become more frequent recently, there are cases of poaching, so some fish species simply disappear. In this regard, many civilized countries have concluded an agreement in which it is strictly prescribed where you can fish and how much.
Every person on Earth should think about the conservation of this class of animals.
Bibliography
- Samkova V.A., Romanova N.I. The world around 1. - M .: Russian word.
- Pleshakov A.A., Novitskaya M.Yu. The world around 1. - M .: Education.
- Gin A.A., Faer S.A., Andrzheevskaya I.Yu. The world around 1. - M .: VITA-PRESS.
- Festival of Pedagogical Ideas "Open Lesson" ()
- Pro-ryb.ru ()
- Kindergenii.ru ()
Homework
- Who are the fish?
- Tell us about the structure of fish.
- What is the role of fish in human life?
- * Draw the fish you remember the most and tell us about it.
Everyone has heard the expression “roaring like a beluga”, but not everyone clearly imagined what this animal looks like. What kind of beluga is this and what else besides the roar can it be famous for? Let's try to figure this out. Well, for starters, let's say right away that a beluga cannot roar at all. If only because it belongs to the class of fish, and fish, as you know, are silent.
Description of the Beluga
Beluga is the largest freshwater fish living in the waters of our country.. It lives on Earth for almost 200 million years and, like all other sturgeons, has learned to adapt to a variety of habitat conditions. These fish do not have a backbone, and instead of a skeleton there is a flexible chord.
Appearance
Beluga is large in size: its weight can be equal to one and a half tons, and its length is more than four meters. Some of the eyewitnesses even saw beluga reaching a length of nine meters. If all of this unconfirmed evidence is true, then the beluga can be considered the largest freshwater fish in the world. She has a thick and massive body.
With its head and muzzle shape, the beluga resembles a pig: its snout, which looks like a snout, is short and blunt, and its huge toothless mouth, which occupies almost the entire lower part of the head, surrounded by thick lips, has a crescent shape. Only beluga fry have teeth, and even those disappear after a short time. The antennae hanging down from the upper lip and reaching the mouth are slightly flattened downwards. The eyes of this fish are small and blind, so it is oriented mainly with the help of a well-developed sense of smell.
This is interesting! From the Latin name of the beluga (Huso huso) is translated "pig". And, if you take a closer look, you can really notice that these two creatures are similar in some way both externally and in their omnivorousness.
Beluga males and females differ little in appearance, and both of them have the body covered with equally large scales. The scales look like rhombuses and nowhere overlap each other. This type of scale is called ganoid. The back of the beluga is gray-brownish, the belly is lighter.
Behavior and lifestyle
Beluga is an anadromous fish, mainly it leads a benthic lifestyle. The very appearance of this amazing creature, reminiscent of the appearance of ancient armored fish, indicates that the beluga rarely appears on the surface: after all, with such a massive body it is more convenient to swim in deep water than in the shallows.
She continually changes her habitat in the reservoir and often goes to the depths: there the current is faster, which allows the beluga to find food, and there are deep holes that this fish uses as places to rest. In spring, when the upper layers of water begin to warm up, it can be seen in shallow water. With the onset of autumn, the beluga again goes to the sea or river depths, where it changes its usual diet, eating mollusks and crustaceans.
Important! Beluga is a very large fish, it can only find enough food for itself in the seas. And the very presence of beluga in the reservoir is evidence of a healthy ecosystem.
The beluga travels great distances in search of food and spawning grounds. Almost all beluga tolerate both salt and fresh water equally well, although some species can live exclusively in fresh water.
How long does a beluga live
Beluga is a real long-liver. Like all other sturgeons, it slowly matures: up to 10-15 years, but it lives a very long time. The age of this fish, if it lives in good conditions, can reach a hundred years, although now beluga live for forty years.
Range, habitats
The beluga lives in the Black Sea, in the Sea of Azov and in the Caspian Sea. Let less often, but also found in the Adriatic. It spawns in the Volga, Don, Danube, Dnieper and Dniester. Infrequently, but you can meet her in the Urals, Kura or Terek. There is also a very small chance to see a beluga in the Upper Bug and near the Crimean coast.
There was a time when the beluga walked along the Volga to Tver, along the Dnieper to Kyiv, along the Ural River to Orenburg, and along the Kura to Tbilisi itself. But for some time now, this fish has not been taken so far upstream of the rivers. This is primarily due to the fact that the beluga cannot rise upstream due to hydroelectric power stations blocking its path. Previously, she also appeared in such rivers as the Oka, Sheksna, Kama and Sura.
Beluga diet
Recently born fry, weighing no more than seven grams, feed on river plankton, as well as larvae of mayflies, caddisflies, caviar and fry of other fish, including sturgeon species related to them. Grown up Belugas eat juveniles of stellate sturgeon and sturgeon. Young Belugas are generally characterized by cannibalism. As the young beluga grows up, her diet also changes.
After the young of the year move from the rivers to the sea, they feed on crustaceans, molluscs and small fish, such as gobies or sprats, as well as herring and cyprinids until the age of two. Upon reaching two years, beluga cubs become predators. Now approximately 98% of their total diet is fish. Beluga food habits vary depending on the season and feeding grounds. In the sea, this fish feeds year-round, although with the onset of the cold season, it eats less. Remaining for the winter in the rivers, she also continues to feed.
This is interesting! The food of many adult sturgeons is various small living creatures that live on the bottom, and only the largest of them - beluga and kaluga - feed on fish. In addition to small fish, their victims may be other sturgeon and even small seal pups.
In the belly of one of the caught sturgeons, a rather large sturgeon, several roach and bream were found. And in another female of this species, the catch was two large carps, more than a dozen roach and three bream. Also, a large pike perch became its prey even earlier: its bones were found in the stomach of the same beluga.
Reproduction and offspring
Beluga starts breeding late. So, males are ready to breed at the age of at least 12 years, and females do not breed before they are 16-18 years old.
The females of the Caspian beluga are ready to continue their race at the age of 27: only by this age do they become fit for reproduction and accumulate sufficient weight for this. Most fish die after spawning is over. But the beluga spawns repeatedly, though with interruptions of two to four years.
In total, 8-9 spawnings occur during her long life. She spawns on a sandy or pebble bottom, where there is a fast current, which is necessary for a constant supply of oxygen. After fertilization, the eggs become sticky and stick to the bottom.
This is interesting! A female beluga can lay several million eggs, while the total mass of eggs can reach up to a quarter of the weight of the fish itself.
In 1922, a five-meter beluga weighing more than 1200 kg was caught in the Volga. It contained approximately 240 kg of caviar. The hatched larvae, later turning into fry, set off on a difficult journey - in search of the sea. "Spring" female beluga, entering the river from the middle of winter to the end of spring, spawn in the same year. The “wintering” beluga in order to find and take a place convenient for spawning, comes to the rivers in August and stays there for the winter. She spawns only the next year, and before that she lies in a semblance of hibernation, having gone to the bottom and covered with mucus.
In May or June, the "winter" beluga comes out of hibernation and spawns. Fertilization in these fish is external, like in all sturgeons. Caviar attached to the bottom of the reservoir, for the most part, becomes the prey of other fish, so the percentage of survival among beluga juveniles is very small. Belugas live in shallow water warmed by the sun. And after they grow up enough, they leave their native rivers and go to the sea. They quickly increase their size and by the year their length becomes approximately equal to a meter.
natural enemies
There are practically no natural enemies in adult beluga. But their caviar, as well as larvae and fry living in the rivers, are eaten by freshwater predatory fish.
This is interesting! Paradoxically, one of the main natural enemies of the beluga is this fish itself. The fact is that the Belugas that have grown up to 5-8 cm are happy to eat the caviar of their relatives in the spawning grounds.
Population and species status
By the beginning of the 21st century, the beluga population had declined significantly, and this species itself was considered endangered and was listed in Russia and in the International Red Book.
In the natural environment, due to the small number of livestock of its species, the beluga can interbreed with other related sturgeon fish. And in 1952, through the efforts of scientists, an artificial hybrid of beluga and sterlet was bred, which was called bester. It is bred, as a rule, in artificial reservoirs, since Bester is not released into natural reservoirs, where other sturgeons are found, in order to keep the natural populations of other species clean.
Fish are classified according to a number of criteria: lifestyle, fishing season, sex, physiological state, fatness, nutrition, length or weight.
AB - commercial length of fish; AB - standard size; 1 - gill cover; 2 - dorsal fin hard; 3 - soft dorsal fin; 4 - tail fin; 5 - side line; 6 - anal fin; 7 - anus; 8 - ventral fins; 9 - pectoral fins
The length of the fish is measured in a straight line from the top 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 small things of groups I, II or III. A number of fish species listed in the standard are not subdivided according to length and weight. The smallest length of fish that is allowed to be caught is set by fishing regulations and international conventions.
IN commodity practice Fish are classified according to species and families.
A species is a collection of individuals occupying a certain geographical area and having a number of inherited traits that distinguish this species from related species. Species close in a number of characteristics are combined into genera, and the latter into families.
IN trade practice classification of fish by families is carried out mainly according to external features. Strictly scientific classification of fish by families is made according to many features. The characteristics of the main features of the families of fish most commonly found in commercial practice are given below.
herring family has a laterally compressed body, covered with easily falling scales. Lateral line is absent. The dorsal fin is single, the caudal fin is deeply notched. Herring is of commercial importance: Atlantic, Pacific, Danube, Don, Dnieper, Kerch, Volga, Chernospinka, Azov Shade, Salaka, Sardines, Sardinella, Sardinops (Ivasi); sprats: Caspian, Baltic (sprats), Black Sea, Tyulka.
anchovy family has a cigar-shaped body, similar in size to small herring. This family includes the Hamsa of the Azov-Black Sea, Anchovy.
Sturgeon family has an elongated-fusiform body, with five rows of bone formations - bugs: two abdominal, two thoracic, one dorsal. Elongated snout, from four mustaches. Dorsal fin single, caudal fin unequally lobed. Of commercial importance are: beluga, kaluga, sturgeon, spike, stellate sturgeon, sterlet. Soviet scientists, by crossing beluga and sterlet, obtained bester, which is bred in reservoirs.
Carp family has a high, laterally compressed body, covered with tightly fitting scales, sometimes naked. The dorsal fin is one, soft, the lateral line is well expressed, the teeth are pharyngeal. This family includes fish of inland waters: carp, carp, crucian carp, roach, vobla, ram, bream, white-eye, blue bream, barbel, silver carp, grass carp, buffalo, fish, shemaya.
salmon family has 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, sockeye salmon, chinook salmon, Caspian salmon, salmon, trout, whitefish, vendace, muksun, and omul are of commercial importance.
Family smelt has an oblong body shape, with easily falling scales, an incomplete lateral line. There are two dorsal fins, the second is adipose. Main species: European smelt, smelt, capelin.
perch family has two dorsal fins, the first one is spiny, the anal fin has three spiny rays, the lateral line is straight, there are transverse stripes on the sides. Common species: perch, pike perch, ruff.
scad family has a flattened body shape. Lateral line with a sharp bend in the middle, in some species covered with bony spines. There are two dorsal fins, the first is prickly, the second is soft and long. There are two spines in front of the anal fin. The tail stalk is thin. The horse mackerels of the Azov-Black Sea, oceanic, caranx, seriola, pompano, lychia, vomer are of commercial importance.
cod family subdivided 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 pectoral or in front, many representatives have a mustache on the chin.
The body shape is close to torpedo-shaped. Cod, haddock, navaga, saithe, pollock, blue whiting, burbot, polar cod are of commercial importance.
mackerel family has an elongated fusiform body, a thin 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, and Japanese mackerel are of commercial importance. Mackerels are sold under the names "Mackerel of the Azov-Black Sea", "Mackerel of the Far East", "Mackerel Kuril", "Mackerel Atlantic".
In terms of body shape and arrangement of fins, tuna, bonito, mackerel are similar to mackerel, the latter have one dorsal fin and additional fins.
flounder family has a flat body, flattened from the back to the abdomen, the eyes are located on one side of the head. Dorsal and anal fins along the entire length of the body. Commercial value halibut black, common, arrow-toothed; flounder sharp-headed and river.
Of the fish of other families, the following are of commercial importance.
sea bass golden, 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.
catfish striped and spotted from the catfish family
have one long soft dorsal fin, a round large head, the body in the back is laterally compressed.
Terpugi northern, southern, toothed have a spindle-shaped body, one spiny dorsal fin, highly developed anal and pectoral fins.
ice fish from the white-blooded family, it 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 butterfish small fish from the stromatiaceae family, they 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.
Marble and green notothenia, squama, toothfish from the nototheniaceae family have a large head, two spiny dorsal fins, a long anal, large pectoral fins, the body is thickened in the front.
Slab, captain, umbrina- fish from the croaker family, have a high body, a humpback in front of the back, one dorsal fin, divided by a deep notch, the anterior part is prickly, the lateral line is well expressed.
grenadiers from the macrourid family, they have an elongated, fading body in the tail section in the form of a thread. There are two dorsal fins.
They also catch such species of fish as catfish, pike, lamprey, eel, gobies, Argentina, mullet, eelpout, prystipoma, bluefish from families with similar names, sea bream from the Brahm family; merrow, stone perch - from the serran family.