Ministry of Agriculture

Russian Federation

FSBEI HPE "Yaroslavl State Agricultural Academy"

Department of Private Animal Science

Control work on discipline

FISH FARMING

Yaroslavl, 2013

QUESTIONS FOR PERFORMANCE OF CONTROL WORK.

4 . Swim bladder.

24 . Earthen dams and dams.

49 . Characteristics of compound feed.

Question number 4.

SWIMMING BLADDER.

An important role in ensuring the movement of fish in the water column is played by a special hydrostatic organ - swimmingbubble. This is a single-chamber or two-chamber organ filled with gases. It is absent in deep-sea fish, as well as in fish that quickly change their swimming depth (tuna, mackerel). In addition to hydrostatic buoyancy, the swim bladder performs a number of additional functions - an additional respiratory organ, a sound resonator, a sound-producing organ (Privezentsev Yu. A., 2000).

Figure 1 - Organs of water and air respiration in adult fish:

1 - protrusion in the oral cavity, 2 - supragillary organ, 3, 4, 5 - sections of the swim bladder, 6 - protrusion in the stomach, 7 - oxygen absorption site in the intestine, 8 - gills

The swim bladder develops in the fish larva from the foregut and remains in most freshwater fish throughout their lives. After hatching, fish larvae do not yet have gas in the swim bladder. To fill it, they have to rise to the water surface and suck in air there.

Depending on the anatomy of the bladder, fish are divided into two large groups: open bubble(most species) and closed-vesical(perch, cod, mullet, stickleback, etc.). In open bladders, the swim bladder communicates with the intestines by a duct, which is absent in closed bladders. Since the pressure equalization of the occluded bladder lasts much longer than that of the open bladder, they can only slowly rise from deep layers of water. Therefore, in these fish, the foregut, due to the greatly swollen swim bladder, protrudes from the mouth if they are hooked at a depth and quickly removed to the surface. The most famous blisterfish are perch, pike perch and stickleback. In some fish living near the bottom, the swim bladder is greatly reduced or completely absent. Catfish, as a typical representative of demersal fish, has only a poorly formed swim bladder. The sculpin, which keeps between and under rocks in streams and rivers, has no swim bladder at all. Since he is a poor swimmer, he moves along the bottom with pectoral fins spread apart (www.fishingural.ru).

Figure 2 - Swim bladder: a) swim bladder associated with the intestines; b) a swim bladder that is not connected with the intestines.

In cyprinids, the swim bladder is divided into anterior and posterior chambers, which are connected by a narrow and short canal. The wall of the anterior chamber consists of the inner and outer shells. There is no outer shell in the posterior chamber. The inner lining of both chambers is formed by a single layer of squamous epithelium, followed by a thin layer of loose connective tissue, muscle cords and a vascular layer. Next are 2-3 elastic plates. The outer shell of the anterior chamber consists of two layers of dense fibrous (acicular) connective tissue, giving it a pearly sheen. Outside, both chambers are covered with a serous membrane (Grishchenko L.I., 1999).

In juveniles, the bladder is completely transparent and clean, and becomes cloudy with age; consists of connective tissue. The bubble is filled with various gases, the quantitative ratios of which are different. A filled swim bladder is a hydrostatic apparatus that promotes the vertical movement of fish as a result of the movement of gases into the anterior or posterior chamber (with a two-chamber bladder). If the carp is forced to inhale air for a longer time, then the anterior chamber of the swim bladder increases significantly (Koch V., Bank O., Jens G., 1980).

The swim bladder is an organ that is reflexively connected to the muscles of the body and affects the tone and coordinated movements of the muscles. The tension of the gases in the swim bladder creates certain impulses to the behavior of the fish. So, for example, if you fill the swim bladder of a sea bass with an indifferent fluid under increased pressure so that the walls of the bladder are somewhat stretched, the fish swims near the bottom; if the pressure of the liquid on the wall is lowered, then the fish tends upward, due to compensatory movements of the fins. Simultaneously with the compensatory movements of the fins, which are different in both cases, either resorption or secretion of gas occurs in the swim bladder, respectively (Puchkov N.V., 1954).

The swim bladder helps the fish to be at a certain depth - one at which the weight of the water displaced by the fish is equal to the weight of the fish itself. Thanks to the swim bladder, the fish does not spend additional energy to maintain the body at this depth.

The fish is deprived of the ability to voluntarily inflate or compress the swim bladder. But on the other hand, there are nerve endings in the walls of the bladder that send signals to the brain as it contracts and expands. The brain, on the basis of this information, sends commands to the executive organs - the muscles with which the fish moves (www.fishingural.ru).

In some fish, the swim bladder has other functions. So, for example, carps have a kind of mobile connection between the swim bladder and the labyrinth through Weber's bones. The anterior section of the swim bladder of carps is elastic and can expand greatly with changes in atmospheric pressure. These extensions are then transferred to the Weberian bones, and from the latter to the labyrinth.

Similar connections are found in catfish, and are especially pronounced in chars, in which the entire posterior part of the bladder is lost, as well as its hydrostatic function; the bubble at the same time is enclosed in a bone capsule. From the skin on both sides of the body, channels closed from the outside with a membrane, filled with lymph, stretch and approach the walls of the swim bladder in the place where it is free from the bone capsule. Changes in pressure are transmitted from the skin through canals and the swim bladder, and from the latter through the Weberian apparatus to the labyrinth. Thus, this device is similar to an aneroid barometer, and the function of the swim bladder is primarily to sense changes in atmospheric pressure.

In most fish, the respiratory function of the bladder does not play a significant role. The amount of oxygen that is available in the swim bladder of tench and carp, as calculations show, could cover the normal need of fish for this gas only for 4 minutes and, thus, cannot be of practical importance for respiration. But in some fish, breathing with the help of the swim bladder takes on an important role. Such fish include, for example, dogfish (Umbra crameri), found in Europe in the region of the Danube and Dniester rivers. It is able to live in oxygen-poor water of ditches and swamps. If this fish, which is in ordinary water with plants, is prevented from reaching the surface and deprived of its ability to capture atmospheric air, it dies of suffocation in about a day. Experiments have shown that dog fish in humid air without water can remain alive for up to 9 hours, while in boiled and oxygen-poor water it dies after 40 minutes if it is prevented from capturing air from the atmosphere. If it is allowed to rise to the surface, then the dogfish endures the content in boiled water without harm to itself and only more often than usual captures air.

Air breathing is most pronounced in lungfish, which instead of a swim bladder have real lungs, very similar in structure to the lungs of amphibians. Lungs of lungfish consist of many cells, in the walls of which are located smooth muscles and a rich network of capillaries. Unlike the swim bladder, the lungs of lungfish (as well as multifins) communicate with the intestine from its ventral side and are supplied with blood from the fourth branchial artery, while the swim bladder of other fish receives blood from the intestinal artery (Puchkov N.V., 1954) .

Question number 24.

EARTH DAMS AND DAMBS.

Dams are built to hold and raise the water level. They block the channels of rivers, ravines and beams. Dams are earthen, concrete, stone, etc. In fish farms, earthen dams are mainly built with or without slopes. When designing a dam, the dimensions of its main elements are set: the width of the crest, the excess of the crest above the normal retaining level, the slopes of the slopes. The head dam is built at such a height that a head pond is formed with a volume of water that guarantees the satisfaction of the needs of the economy at a constant flow of water. The dam site is chosen in the narrowest place of the floodplain with dense waterproof soil, where there is no outlet for springs and springs. The width of the crest of the dam is determined based on the operating conditions of the structure, but not less than 3 m.

Dams are erected during the construction of floodplain ponds. Depending on the purpose, they are contour, water-protective and dividing. Contour dams diversify the territory of the floodplain, where fish ponds are located. They are designed to protect ponds from flood waters. Dividing dams are arranged between two adjacent ponds. To protect the territory of the fish farm from flooding, water protection dams are built.

During operation, earthen dams and dams can be deformed and destroyed. The greatest danger in this case is filtration and wave run-up, as a result of which breakthroughs, landslides and other destruction can occur. With strong waves, the slope of the dam from the side of the prevailing winds can be destroyed and it is additionally protected by special fasteners. Prefabricated and monolithic reinforced concrete slabs and other fasteners are used to fasten the upper slopes of the dams of the head and feeding ponds. Reinforced concrete slabs are laid on the slopes of dams and dams, as a rule, during the construction or reconstruction of ponds. Reeds and reeds growing in the coastal part of the ponds well protect dams and dams from waves and erosion. The upper part of the upper slope and the lower slope are usually sown with grasses (Privezentsev Yu. A., Vlasov V. A., 2004).

The dam has two slopes - wet, facing the water, and opposite to it - dry. The slope of the slopes depends on the height of the dam and the quality of the soil from which the dam is built. A wet slope is arranged double, and for large dams of head ponds even triple (i.e., the base of the slope is 2-3 times its height). For summer categories of ponds, it is better to build a wet slope more gently, since it creates a shallow zone rich in food organisms for fish, and in wintering ponds this slope should, on the contrary, be steeper in order to avoid reducing the area of ​​the wintering pond. To protect against erosion, the slopes are covered with turf, grass is sown on them, and in large ponds the wet slope is covered with stone, strengthened with wattle mats, wattle walls, etc. Planting trees on dams is unacceptable, since the roots destroy the dam, the crown obscures the surface of the water and the leaves pollute the pond. In addition, trees attract birds and other fish enemies to the ponds.

The service life of hydraulic structures increases significantly with proper and systematic care of them (moyaribka.ru).

In case of strong wave breakers, the slope of the dam from the side of the prevailing winds is additionally protected by special fasteners. Reinforced concrete slabs and brushwood fastenings are used to fasten the upper slopes of the dams of the feeding and head ponds (Grishchenko L.I., 1999).

The best soil for the construction of dams and dams is loam with a significant admixture of sand. If you use only clay, then when it freezes and then thaws, it cracks and swells. In addition, it is easily washed out from heavy rains or spring floods. A dam made of only one sand filters the water. Silty soils and chernozems are not suitable, as they are easily eroded and poorly compacted.

The site for a dam or dam must be prepared in advance. To do this, remove the entire plant layer (sod), remove stumps, shrubs, trees and their roots. If the soil in this place strongly filters the water, then they dig a trench along the axis of the future dam, deepening to a harder soil. The trench is filled with liquid clay and carefully rammed (Fig. 3).

Figure 3 - The device of the dam with a lock:1 - dam;2 - lock

Soil settlement of earth dams and dams is usually 10-15% of the total volume of the embankment, but can be more - up to 50% if peat is used. This must be taken into account when planning the height of the structure. The dam should rise above the water level by 0.7-1.0 m, dams - by 0.3-0.5 m. The crest of the dam should be at least 0.5 m wide. So that earth dams and dams do not collapse during operation , it is desirable to strengthen them (Privezentsev Yu. A., 2000).

Question number 49.

CHARACTERISTICS OF COMPOUND FEED.

compound feed is a multi-component mixture of various feed products, compiled according to scientifically based recipes to ensure complete feeding of animals.

The use of granulated feed, improving their quality and water resistance are the most important source of reducing feed costs when growing fish and increasing the cost of production.

Feed is made for various kinds fish reared in aquaculture, taking into account their age, weight and rearing method. When creating compound feed recipes, the norms of the physiological need of fish for energy, nutrients and biologically active substances are used (Privezentsev Yu. A., Vlasov V. A., 2004).

Currently, the following standards have been adopted for the nutritional value and quality of feed for fish (Table 1).

Table 1 - Quantity of main nutrients and indicators of feed quality for pond fish, %

Nutrients			Rainbow trout
	fingerlings	commercial fish	fingerlings	commercial fish
Crude protein
crude fat
Nitrogen-free extractives (NES)
Cellulose
Energy value, thousand kJ/kg
Iodine number, % iodine, no more
Acid number, mg KOH, no more

In accordance with these requirements, compound feed recipes have been developed for different age groups of carp, rainbow trout, channel catfish, bester. According to their purpose, they are divided into starting (for larvae and fry) and production (for older age groups).

Table 2 - Characteristics of compound feed (Privezentsev Yu. A., Vlasov V. A., 2004).

Mass fraction of moisture, %, no more
Mass fraction of crude protein, %, not less than: starter feed (carp grown in industrial conditions, salmon, channel catfish) for sturgeon compound feeds used in pond cultivation: underyearlings, repair material and carp spawners commercial two-year-olds, three-year-old carp feed for the industrial method of growing carp feed for growing valuable fish species
Mass fraction of raw fat for carp and other valuable fish species with the industrial method of cultivation,% no added fat with added fat
Mass fraction of carbohydrates, %, not more than: starter feed for carp grown in industrial conditions starter feed for salmon starter feed for sturgeons
Mass fraction of fiber, %, not more than: fish day starter feeds feed for fish production compound feeds for underyearlings, replacement young animals and producers production feed for commercial two-year-olds and three-year-olds
Mass fraction of calcium for all types of fish, %, not more than: starter feed production feed
Mass fraction of phosphorus, %, not more than: starter feed for valuable fish species production feed for valuable fish species starter feed for carp
Water resistance of granules, min. at least
Acid number of compound feed, mg KOH, no more
Shelf life, months, no more: Compound feed for carp grown in ponds: with an antioxidant without antioxidant compound feed for growing fish in industrial conditions: no added fat with added fat

The requirements for starter feeds differ from the requirements for production ones with an increased content of protein (at least 45%), fat, energy value, as well as a greater balance in amino acid composition, vitamins, microelements and other additives (Table 2). Higher requirements are imposed in feed for fish grown in cages and pools, since fish in them are practically devoid of natural food (Grishchenko L.I., 1999).

Each compound feed recipe is assigned a number. According to the Instructions for the preparation of compound feed for fish, numbers from 110 to 119 are set. However, there are modifications of temporary formulations.

Recently, special attention has been paid to the production of prophylactic (therapeutic) feed containing natural enterosorbent and new effective domestic probiotics, which, on the one hand, neutralize toxicants, and on the other hand, colonize the body of fish with bacteria - antagonists of pathogenic microorganisms, causative agents of many infectious diseases of fish ( Privezentsev Yu. A., Vlasov V. A., 2004).

The main feeds that are used in the preparation of feed for carp are presented in Table 3.

Table 3 - The ratio of ingredients in feed for carp grown in ponds,% (Vlasov, V.A., Skvortsova, E.G., 2010).

Ingredients	For underyearlings and manufacturers	For two year olds
1) Cakes and meals (at least 2 types)
2) Cereals: cereals
3) Bran
4) Yeast
5) Feed of animal origin
6) Herbal flour
7) Mineral supplements
8) Growth stimulants

Fish feed is prepared in the form semolina(starting), granules different diameters according to the age of the fish, as well as pasty. Granulated feed is mainly produced centrally at feed mills, while pasty feed is produced directly at fish farms. For cyprinids, sinking foods are used, and for salmon fish, floating foods are used (their water resistance is about 10-20 minutes). Best Recipes domestic and foreign fish feeds contain up to 9-12 different components, not counting the addition of vitamins, mineral salts, etc. They include animal feed, feed of plant origin, products of microbiological synthesis, premixes, enzyme preparations, antioxidants, antibiotics (Grishchenko L.I. ., 1999).

Granulated feed is divided into starting and production. They are produced in the form of grains and granules. Grits are intended for feeding fish from larvae to fingerlings weighing 5 g, granules - for fingerlings, yearlings, two-year-olds, three-year-olds, repair material and spawners. Depending on the size, grains and granules are divided into 10 groups (Table 4).

Table 4 - Characteristics of feed for fish

	Diameter, mm	Weight of fish, g
			salmon	sturgeons
	Up to 0.2 (semolina)
	0.2–0.4 (semolina)
	0.4–0.6 (semolina)
	0.6–1.0 (semolina)
	1.0–1.5 (semolina)
	1.5–2.5 (semolina)
	3.2 (granules)
	4.5 (granules)
	6.0 (granules)
	8.0 (granules)

Do all fish have a swim bladder?

Bottom, as well as deep-sea fish, do not have a swim bladder. Firstly, they do not need to emerge, and secondly, the swim bladder at great depths is simply useless - with the high water pressure that exists at depth, the gas from it would immediately be squeezed out.

How do these fish ensure buoyancy? Due to fat. Firstly, it provides a decrease in body density. Secondly, fat is incompressible. In conditions of enormous pressure at depth, this is a very important property.

Fish with a swim bladder cannot quickly move from the surface layers of the water to the deep and vice versa. Therefore, fish that make rapid vertical movements (tuna, mackerel) also lack a swim bladder.

Sharks don't have a swim bladder either. Therefore, they are forced to constantly be in motion, so as not to drown. As soon as they slow down, they immediately begin to sink. Therefore, sharks living in the water column are constantly moving even during rest. Sand sharks have a substitute for the bony fish swim bladder: they swallow bubbles of air and hold it in a special air pocket in their stomach.

To the question Which fish do not have a swim bladder? Why don't they drown? given by the author Kirill Leshchenko the best answer is In most fish that make rapid vertical movements, the swim bladder is reduced or completely absent. Of the Yenisei fish, these include loach and Siberian char, which live mainly near the bottom. Retention in the water column is carried out by them due to muscular movements. There is no swim bladder in marine fish that live at great depths. In deep-sea fish, buoyancy is provided mainly by fat, the main property of which is incompressibility. In conditions of enormous pressure at depth, this is a boon, since the gas from the swim bladder would be squeezed out immediately.
Sailfish (Istiophorus Lacepède, 1801) is a genus of the Sailfish family of the Perciformes order, including two species of fish. It lives in the tropical waters of the Indian Ocean (Istiophorus platypterus) and in the central and western parts of the Pacific Ocean (Istiophorus albicans). Sailboats and related species of the Istiophoridae and swordfish families do not have a swim bladder: at such a speed of movement and movement in the vertical direction, all gas exchange systems cannot ensure that the pressure in it is maintained at an optimal level, so it could only be a hindrance - these fish have negative buoyancy, compensating for this due to the asymmetry of the body relative to the horizontal plane (lift force, like an airplane wing) and muscle efforts, or due to the inclined planes of the pectoral and ventral fins during slow movement. All these features of anatomy and morphology allow these fish to be the fastest aquatic animals.
Bubbleless perch at a depth of seven hundred meters. These fish live in the deep waters of the Atlantic and do not have a swim bladder. They move on the ground with the help of their fins.
The flounder fish has a body strongly compressed from the sides, it is wide and short. The flounder does not have a swim bladder. The flounder differs from other fish in that it spends its entire life on its side, so it swims and lies on the bottom, only if it is in danger, the flounder can turn on its edge and swim quickly.
Sharks belong to the vertebrate phylum cartilaginous fish, a subclass of elasmobranchs (elasmobranchs - elasmobranchh), shark order. The stingrays also belong to the subclass of elasmobranchia. This subclass, which includes all types of sharks, rays and intermediate forms, is sometimes called selachia. Currently, about 360 species of sharks are known. And without a doubt, scientists have to discover many more new ones.
A characteristic feature of all sharks is a cartilaginous, not a bony skeleton, 5-7 gill slits on the sides of the head, the absence of a gill cover, skin covered with placoid scales, an upper jaw connected to the skull only by connective tissue ligaments or articulations of cartilage, the absence of a swim bladder and uneven caudal fin.

Living in water inevitably leaves an imprint on the structure of the body of fish. Not only the general plan of the structure, but also many organ systems designed to ensure the vital activity of fish in the aquatic environment, in their structure, and sometimes in the principles of functioning, differ from those in terrestrial animals. There are also those that are unique, that is, not found in representatives of other groups of vertebrates.

Among the problems facing aquatic organisms in general and fish in particular, one of the first in importance is the problem of retention in the water column. Simply put, the fish are faced with the question "how not to drown?" Really, the body density of fish, like most vertebrates, exceeds the density of water, varying for different types within 1.07 - 1.12. Thus, they would have to be negatively buoyant, and therefore sink in water, but we know that this does not happen. In the process of evolution, different groups of fish have developed a number of adaptations that allow them to compensate for negative buoyancy. Some groups of fish took the path of reducing the overall body density by increasing the volume of low-density tissues, such as adipose tissue, while others acquired a specialized organ - a swimming or gas bladder. Its structure and functioning will be discussed in this post.

The location of the swim bladder in the body of fish

So the classic definition of a swim bladder is:

The swim bladder is a gas-filled outgrowth of the anterior part of the intestine, the main function of which is to provide buoyancy to fish.

There are two points to note in this definition. Firstly, it does not say anything about the position of the outgrowth - despite the fact that in the vast majority of species it is dorsal, that is, it is laid on the dorsal side of the body (which is sometimes noted in the definition of the swim bladder). However, this does not happen in all groups of fish; in a small number of taxa, this is a ventral outgrowth. Secondly, to the phrase "main function" with a semantic emphasis on "main" - the swim bladder can perform many different functions, and hydrostatic in different groups of fish is not the only one, and sometimes the main one. I will talk more about this below.

Swim bladder in different groups of fish

First of all, let me remind you that we have determined that fish are a combined group of aquatic vertebrates that have gills throughout their lives, and use fin-type limbs for movement. As you can see, nothing is said about the swim bladder as an integral characteristic of fish in this definition. Why did this happen, because the swim bladder is not found in other groups of animals and is typical only for fish? The answer is simple - the fact is that, firstly, not all groups of fish have this organ, and, secondly, even in those groups for which it is characteristic, there are species that have lost it in the process of evolution as a more unnecessary organ.

The main modern large taxa of fish in relation to the presence / absence of the swim bladder and the functions it performs are characterized as follows:

Cyclostomes (lampreys and hagfishes)- no swim bladder
Cartilaginous (sharks, rays, chimeras) - no swim bladder
Coelocantate (coelacanths)- swim bladder reduced
Lungfish - available, respiratory organ
Multifeather - available, respiratory organ
Cartilaginous ganoids (sturgeons)- available, hydrostatic body
Bone ganoids - available, respiratory organ
Bony fish - there is, in some it is reduced, a hydrostatic organ, in a small number of species a respiratory organ

Swim bladder and lungs of terrestrial vertebrates

An interesting trend can be found from the above review - in evolutionarily older groups of fish, the swim bladder is a respiratory organ, and only in more contemporary bands it acquires the function of a hydrostatic organ. To understand the logic of these transformations, it is necessary to turn to the biology of living representatives of ancient fish groups and their fossil ancestors. Currently living species inhabit, as a rule, weakly flowing, stagnant or even drying up water bodies, in which the problem of a lack of oxygen dissolved in water is not uncommon. Similar conditions existed in the reservoirs of the Devonian period (about years ago), when their ancestors evolved. Such conditions forced the fish to look for other sources of oxygen. The only such source was atmospheric air, which these forms could swallow from the surface of the water and then "assimilate" in the anterior part of the intestine. As we know, the efficiency of this assimilation is the higher, the larger the area it goes - it was this that directed evolution along the path of increasing the volume of the anterior part of the intestine, which led to the appearance of a separate outgrowth, and then to an increase in its surface area. The end result of these processes was the appearance of the lung of terrestrial animals, the origin of which, according to modern concepts, is associated with the evolution of the swim bladder when it landed. Thus, the answer to the question "what was primary in functional terms, the lung or the swim bladder" is "lung" - apparently, it was the respiratory (respiratory) function that preceded the hydrostatic one.

common carp

Interestingly, the acquisition of a swim bladder, which performs the function of respiration, occurred independently in different groups of fish. Such a conclusion can be drawn by comparing its position relative to the digestive tube, for example, in multi-feathered and bone ganoids, which demonstrates to us two different ways of formation of the swim bladder. In polyfins, the swim bladder is a ventral (located to the belly from the digestive tract) outgrowth, while in bony ganoids (armored pike, amia), whose ancestors probably evolved in the same era as the ancestors of multifins, this outgrowth is located dorsally. In both groups, the connection of the swim bladder with the intestine is preserved through a special canal, which has the same location as the outgrowth - in the polypere it is ventral, in the bone ganoids it is dorsal. Otherwise, these structures are similar. The swim bladder of the polyfin resembles the lung of land animals and is considered the most primitive. This is a bilobed outgrowth, inner surface which has an almost smooth structure with a small number of folds. In bony ganoids, the swim bladder is also bilobed, but its inner surface has many ridges to increase the surface through which oxygen can penetrate. In another ancient group of fish - the fossil Myastolobate and in their living descendant of the Latimeria - the swim bladder formed as a ventral outgrowth of the intestine. It is also necessary to note the similarity of the position of the swim bladder of the fleshy-lobed and lung of terrestrial vertebrates, which is also located ventrally. This similarity is not a coincidence - it was the fleshy-lobed ones that made a revolution in the animal world, coming to land and giving rise to all terrestrial vertebrate life.

Early evolution of the swim bladder

Gradually, with the change in the ancient climate and the development of the ocean by fish, the respiratory function of the swim bladder was lost and the hydrostatic function came to the fore. As we remember, in all modern groups of bony fish, with a few exceptions, the swim bladder is a dorsal unpaired outgrowth. This position compares favorably with the ventral one, because in the first case of the dorsal location, the center of gravity of the body is shifted downward, which makes the position of the body in the aquatic environment more stable. There is no doubt that in most modern fish, the swim bladder evolved from a dorsal outgrowth that their ancestors had. However, the hypothesis that in a number of groups the swim bladder could "crawl" from the ventral side to the dorsal one also does not find significant contradictions. The most remarkable thing is that we can observe this process in some modern species, in which the structure of the swim bladder is intermediate between the dorsal and ventral location. So in fish of the genus Erythrinus, the bladder, although located dorsally, is connected by a duct extending from the lateral part of the intestine. We observe an even more interesting structure in the lungfish Neoceratodus, in which the swim bladder is also located dorsally, but the canal connecting it with the intestine departs from the ventral part of the digestive tube and wraps up, skirting the intestine. At the same time, the "wrapping" of the entire system is also observed - the blood supplying vessels and nerves go first down, then under the intestines, and only after that they go up again to the swim bladder.

clearly various options the positions of the swim bladder of fish are shown in the figure below.

Very often, when fish lose the ability to swim normally, for example, they are in an unnatural position at the surface of the water or at the very day, aquarists and other people who often watch this pass the death sentence on the fish, without even trying to figure out the reasons. How justified is such a decision and is it worth it to flush the fish immediately into the "toilet" to "facilitate their" fate?

In fact, not everything is so simple, first you need to have an idea of ​​\u200b\u200bwhat the problem is, many aquarists immediately begin to look for "witches" and few people think about problems with the swim bladder and, accordingly, few actually try to figure out why it happened. Not in all cases, such a phenomenon, when fish swim at the very bottom or at the surface, means imminent death. Now, if you wave your hand or flush it down the toilet, then definitely.

Full text of the news:

One of the most common cases of health problems for fish in an aquarium is buoyancy problems where fish don't seem to have the strength to lift themselves off the bottom or, on the contrary, go down and not swim close to the surface. Most often, aquarists are mistaken in making their conclusion about the impending imminent death of fish, often these erroneous decisions come from the lack of our knowledge about the structure of the body of fish, in this case about the swim bladder.

Many believe that swim bladders in fish are a constant thing, but in fact this is not so, their volume is changeable and moreover, the bladders (there are two of them in most fish) have slightly different functions, at least they have serious differences. In order to make a diagnosis and make decisions about the fate of the fish, you must first get acquainted with the principles of the bubbles, because often problems with the buoyancy of fish are fixable if you understand the situation. The first or anterior bladder has denser walls, it is practically not subject to changes, in addition, this bladder has a strong connection with the spine of the fish, due to which it is rigidly fixed. The second or rear bubble is located closer to the tail, it has less dense walls, and it can vary significantly in the density of the gas inside, in addition, its position can change. Despite the fact that the bubbles are connected to each other, this connection can be called conditional.

Types of swim bladders

Fish can be conditionally divided into two types, in which the work with filling the swim bladders with gas is built differently. Some fish are of the so-called open-bladder type, i.e. they have a channel that directly connects the bladders and the food system, much like in humans. They use the esophagus to deflate or inflate the bladder with gas. This group includes goldfish, catfish and so on.

Another group of fish such as cichlids and perches have bladder-type closures, with the help of the complex structure of the circulatory system or gas glands, for example, they inflate or deflate their bladders.

There is another type of fish that may lack a swim bladder, or have some combination of the two types mentioned above.

Problems with buoyancy of fish

It should be noted that Western experts are cautious about the term "swim bladder disease", since it is rather difficult to determine the true causes, most often such problems in fish occur in the second turn, and are a consequence. It is generally accepted that there is a positive and a negative swim bladder disorder. With a positive diagnosis, a situation is considered when the fish swim near the surface of the aquarium, while the protective mucus on the side that is located on top dries quickly and leads to the emergence of new diseases through the appearance of open wounds that are not protected by mucus. Negative swim bladder disorders are fixed when the fish sink to the bottom of the aquarium, in this case, the problem occurs with the mucus due to the fact that the fish constantly rubs against the bottom, thereby breaking the layer of protective mucus and damaging the skin.

Diagnosis

In order to make a correct diagnosis of a fish, it is necessary to carefully study its habitat, perhaps the answer will be if you carefully remember your actions when buying fish, perhaps even then strange behavior of fish was noted. It is very important to check the condition of the water and its parameters, the temperature and the level of acidity of the water, to check the presence of ammonia, the levels of nitrites and nitrates. Another parameter is also important - the overpopulation of fish in the aquarium, this condition is often forgotten and completely in vain, it is very important to look at the water indicators through the "prism", the number of fish in the aquarium. The more parameters and conditions you get from the aquarium, the easier it will be for you to actually determine the cause of the fish disease.

Also, a common cause of problems with buoyancy of fish is poor feeding of fish. For fish, food plays an important role, poor-quality feeding can lead to many health problems for fish.

Positive buoyancy disorder

Displacement of the posterior bladder in most cases results in a positive buoyancy disorder of the fish, but at the same time, problems with the displacement of the swim bladder do not often lead to abnormal behavior or swimming in fish. But there is a more serious reason for the violation of buoyancy of fish - diseases of the gastrointestinal system of fish.

A third, less common cause of bladder deformity and positive buoyancy disorder is foreign object entry, potentially resulting. Despite all this positive buoyancy disorder, it does not often lead to the death of fish, and if proper medical care occurs in time, fish quite often survive and recover well.

Negative buoyancy disorder

Unlike a positive buoyancy disorder, a negative one has a more negative prognosis, and besides, aquarists do not make any attempts to understand the situation for quite a long time. The main cause of buoyancy problems in this case is the accumulation of fluid in the bladders of the fish. The ingress of liquid occurs due to the intake of food, since in many fish the esophagus has a direct connection with the bubbles. Water displaces air and it becomes much more difficult for fish to swim and maintain their body position in the water. Another common cause of a negative disorder is bacterial infection, the infection of the blisters again leads to the formation of fluid. The third most unlikely cause is a bladder rupture due to injury or illness, which can lead to a complete loss of gas.

Treatment

If there are signs of illness and problems with the buoyancy of the fish, you must first of all carefully consider the water, you must bring all the indicators back to normal and ensure that the water in the aquarium is filtered. Some experts recommend adding salt to the water, but this is a very controversial decision, since the wrong dosage will lead to other problems and is not sure to solve the problem with the buoyancy of the fish. In addition, salt can cause problems in the operation of devices and can lead to serious damage to them.

plays an important role in this matter proper nutrition fish, in particular sometimes cichlids, are fed meat products at a time when many of them need plant foods. Another problem with feeding fish is associated with the constant feeding of dry food, which by the way most often leads to a positive buoyancy disorder. Some types of food are difficult for fish to process, because these products are not natural for them, many probably fed fish with dry food intended for other species and often thought, well, what's the difference? The difference is that dry food has a different structure and feeding with the wrong type of food leads to increased gas formation in the intestines of fish. Chopped fresh green peas help to solve the problem of excess gases.

To combat positive or negative buoyancy disorders, surgeons often use a special needle, which is used to gently pierce the bladder of fish and release excess air or suck out excess liquid. Another thing is if the problem is in the displacement of the swim bladder, then the fish cannot be saved without serious surgical intervention. Everything is much more complicated with a negative diagnosis, only ultrasound can diagnose the exact problem, which means that the chances of fish surviving are small, do you know many aquarists who are willing to pay for this procedure for their fish, not to mention how ineffective good specialists are? But only an ultrasound makes it clear exactly what causes and if it is an infection, then which bacteria and which antibiotics should be given to the fish for treatment.

To reduce the risk lethal outcome it is necessary to give the fish an opportunity to break away from the bottom; for this, floats are attached to the fish with high level buoyancy, which make the fish swim in the water, and not lie limply on the bottom.

As you can see, in reality, fish buoyancy problems are much more complicated in every sense, and this does not mean at all that fish have no chance of survival. It also means, at least it can, that you are clearly doing something wrong for your pets. Poor buoyancy syndrome is a complex phenomenon and it is almost impossible for aquarists to determine the exact cause, unless of course the aquarist is an experienced veterinarian with diagnostic equipment.