Table of fish sizes and weights. Classification of fish: basics of taxonomy and examples
Fish reproduction.
Our freshwater fish reproduce almost exclusively by spawning - females spawn eggs, and males fertilize them with milk. Sexual maturity in most fish occurs in the third or fourth year of life, in smelt - in the first, in pike - in the second, in the eel - no earlier than the sixth, and sometimes in the twentieth, in beluga - in the twelfth to fifteenth.
The timing of puberty may vary depending on environmental conditions.
For example, the Chud whitefish, acclimatized in Lake Sevan, reaches sexual maturity two years earlier than in its native lake. Carp in the central zone of the USSR becomes sexually mature in the fourth or fifth year of life, and in the Caucasus - in the second or third. In some cases, under unfavorable external environmental conditions, fish reproductive products do not mature and their degeneration and resorption occur.
Typically, fish spawn several times during their lives, while eels and Far Eastern salmon spawn once, after which they die. A significant percentage of mortality after spawning is observed in northern and Baltic salmon. Long-living fish (for example, pike and carp) lose their ability to reproduce in old age.
The process of spawning, called spawning, also occurs in fish under certain environmental conditions. Most fish spawn in the spring, salmon, whitefish and trout in the fall, and burbot in the winter. Spawning of each species of fish begins at a certain water temperature. For example, burbot spawns at a water temperature of about 0°, whitefish 1-3°, salmon 3-8°, perch 7-8°, roach about 10°, bream 12-14°, carp at a water temperature of about 151° and above .
Spawning sites are varied.More often, fish choose shallow, well-warmed areas of reservoirs. Pike and carp spawn on the fields; perch, bream, and roach spawn on coastal aquatic vegetation. Some fish spawn on fast, often pebble rifts (trout, grayling, chub, barbel), less often - in the water column
(chekhon)
or at great depths (eel).
The choice of one or another spawning site for various fish is not accidental. This is due to the properties of the eggs and the lifestyle of the hatching larvae and growing fry. For example, asp, chub, and podust, which spawn in fast currents, have sticky eggs, which protects them from being carried away by the current. Their larvae are afraid of light, hide under stones and other shelters, and this saves them from enemies. Fish have the same sticky eggs, laying them in quiet backwaters on aquatic vegetation. Here, eggs develop better in the water column, since, having fallen to the bottom, they find themselves in unfavorable oxygen conditions (oxygen in such places is spent on rotting plants). The larvae of these fish have glands on their heads that secrete a sticky substance that allows them to stick to aquatic plants and develop in the most favorable conditions.
In most cases, after spawning, fish immediately leave the spawning grounds and do not care about the further fate of the offspring. In this respect, salmon differ sharply in that before spawning they drive away all fish from the spawning area.
Moreover, they lay their eggs in specially dug depressions in the pebble soil and cover them on top with pebbles and sand. Catfish also take care of the eggs, and the male even protects them until the fry hatch. Caring for the offspring of sticklebacks goes even further. The male stickleback builds a special nest from aquatic plants. The eggs are laid and fertilized in the nest, and the male, being at the entrance, guards the eggs and hatched fry.
Females of different fish lay unequal numbers of eggs. The largest numbers (sometimes over a million pieces) are thrown by carp, pike perch, and burbot; the smallest are salmon and whitefish. High fertility of fish is necessary for the preservation of the species, since during the development of eggs into adult fish, a very large percentage of eggs and fry die. The established percentage of commercial survival of bream ranges from 0.0006 to 0.014%, i.e., if we take the average fecundity of a female bream at the age of three equal to 100,000 eggs, then only two or three females survive to the first spawning.
The development of eggs in fish with spring spawning is short. Carp fry hatch after 6-8 days, ide - after 8-12, pike - after 14-20 days. The development of eggs in fish with autumn or winter spawning lasts 5-6 months, since otherwise the larvae and growing juveniles would not find food for themselves.
The hatched larvae at first cannot obtain food and feed on substances contained in the yolk sac attached to their abdomen, but soon the yolk sac dissolves and the larva turns into a fry, which switches to independent active feeding.
Growth rates and sizes of fish.
The growth rates and sizes that fish reach are not the same in different reservoirs and depend mainly on the hydrobiological conditions of the environment, which, in turn, are associated with the physicochemical, climatic and soil characteristics of the reservoir. According to the hydrobiological regime, reservoirs are divided into three main types: low-feed, forage and non-feed.
In feeding ponds, the water is less transparent and contains a sufficient amount of nutrient salts. The water reaction and oxygen regime are different, the bottom is mostly silty-sandy, with well-developed vegetation. Most slow-flowing rivers and lowland lakes belong to this type.
Non-feeding ponds have dark brown water. The reaction is in most cases acidic, oxygen saturation is moderate, the bottom is most often peaty, and the vegetation is monotonous. This type of reservoir mainly includes small forest lakes in the northern part of the USSR.
Each type of fish chooses a certain type of reservoir in accordance with its characteristics. Trout and whitefish prefer the first type of lakes and it is in them that they reach their largest sizes. Bream, ide and pike perch grow best in feeding ponds.
In nature, there are many bodies of water that occupy an intermediate position between the described types, and often it is impossible to predict the growth rate and maximum size of the fish found in them. An angler who starts fishing in an unfamiliar body of water first of all wants to know what size fish he can count on.
This does not require a detailed study of the reservoir. Growth rates can be determined by the age of the first fish caught in the reservoir. For example, a perch at a normal growth rate should weigh 20 g at the age of two years, 50-60 g at the age of three, 90-100 g at four years, 150-200 g at the age of five, etc. If it turns out that the specimen under study is at the age of five years old weighs 50 g, which means the regime of the reservoir is not favorable for the life of perch and the largest specimen is unlikely to weigh more than 150-200 g. On the contrary, if at the age of five the perch weighs 200 g, then very large perches can be found in this reservoir. The above considerations are equally valid for all types of fish. The growth rates of some fish in the most favorable water bodies are indicated in
table 2.
The age of a fish is determined by its scales. As the fish grows, the size of each scale also increases due to the appearance of new, young, large scales from below, i.e., as the age of the fish increases, the scales increase in thickness and consist, as it were, of a stack of plates superimposed on each other, of which the top one is the oldest and small, and the bottom one is the largest and youngest. If you examine the scales through a magnifying glass with 8-10x magnification, you can see a series of concentric rings corresponding to the edges of all the gradually formed plates.
But the growth of the fish, and with it the scales, is uneven throughout the year. In summer, fish grow quickly, and the distances between the edges of the plates appearing from below are greatest. In autumn, due to slower growth, these distances decrease, and by winter the edges come so close that one dark ring is formed. In winter, the fish does not grow, and in summer, new concentric circles appear on its scales, which by autumn merge and give a new dark ring.
The number of dark rings on the fish’s scales will correspond to the number of years of its life.
Instinct and experience.
Some fishermen attribute exceptional intelligence to fish, telling “hunting” stories about pikes and ides opening the lids of cages, about bream rising through the forest to the surface of the water so that, once convinced of the presence of an angler, they disappear into the depths, about “smart” carp, knocking down with their tail bait from the hook and only after that feast on it; about “cunning” perches driving away their less intelligent comrades from a hook with a nozzle, etc.
Of course, most of these stories are a figment of the imagination of those telling them, but there are examples that seem to confirm the presence of “smartness” in fish. Don’t the long journeys of salmon, whitefish, and eels in search of favorable spawning places seem smart? Or the protection of offspring observed in stickleback, catfish and some other fish? Or the method of obtaining food used by the tropical spray fish, which, releasing a stream of water from its mouth, knocks insects from the trees surrounding the pond and grabs them as they fall? The behavior of the fish, clearly wary of thick and rough forests, also seems intelligent.
Academician I.P. Pavlov believes that fish, like land animals, have two types of activity that seem to replace reason: based on individual experience and instinctive, passed on from generation to generation. These two types of activity explain the actions of fish that seem smart to us.
The role of skills in the actions of fish is clearly illustrated by the following example. The aquarium with the pike in it was partitioned with glass and a live fish was allowed into the fenced off part.
The pike immediately rushed towards the fish, but after hitting the glass several times, it stopped its unsuccessful attempts. When the glass was taken out, the pike, taught by “bitter” experience, no longer renewed attempts to grab the fish.
In the same way, a fish that has been hooked or grabbed an inedible spoon takes the bait much more carefully. Therefore, in remote reservoirs, where fish are unfamiliar with people and fishing rods, they are less careful than in reservoirs frequently visited by fishermen.
In order for a fish to become wary of rough tackle, it does not have to be hooked itself.
Sharp throws of one frightened, hooked fish can frighten and alert the entire flock for a long time, causing a suspicious attitude towards the proposed bait.
Sometimes fish use the experience acquired by their neighbor. In this regard, the behavior of a school of bream surrounded by a seine is characteristic. First, finding themselves in the tone, the bream rush in all directions; but as soon as one of them, taking advantage of the unevenness of the bottom, slips under the bowstring, the whole flock immediately rushes after him.
Since the caution of a fish is directly related to the experience it has acquired, the older the fish, the more suspicious it is of all kinds of unfamiliar objects. In different species of fish, caution is developed differently. The most cautious species include carp, bream, trout, and ide; the least cautious species include perch, burbot, and pike.
The gregarious lifestyle plays a big role. It is easier for a flock to escape from enemies, find food and places convenient for breeding.
Thus, the “wit,” “intelligence,” and “cunning” of fish are explained by the existence of innate instinct and acquired experience. Instinctively, the fish is afraid of swinging the rod, shaking the soil, splashing in the water, it avoids thick and rough fishing line, a hook that is not disguised by the bait, etc. This means that the fisherman must be able to disguise his tackle, be careful and observant.
Poorly fed reservoirs are characterized by cold, clear water, in which there is a high concentration of oxygen and a small admixture of salts. Their bottom is rocky or sandy, and aquatic vegetation is poorly developed. Typically, reservoirs of this type are located in the mountains.
Feeding ponds are characterized by less transparent water with a large amount of mineral salts dissolved in it. Their bottom is sandy and muddy, and aquatic vegetation is well developed. Typically, this type of reservoir is represented by flat lakes and slow-flowing rivers.
In non-feeding reservoirs, the water is almost opaque, brown or brown in color, moderately saturated with oxygen. The bottom is peat, the aquatic vegetation is monotonous. Typically, such reservoirs are represented by lakes located in the northern regions of Russia.
Each specific type of fish prefers to live in a certain type of reservoir. Thus, lakes with little food are most suitable for trout, where fish of this species reach their maximum sizes. Pike perch, ide and bream feel best in feeding ponds. Non-food reservoirs are distinguished by the fact that fish of any species grow there very slowly and only in rare cases reach the maximum size for their species.
In addition to reservoirs with clearly defined features of one type or another, there are a huge number of those where these features are smoothed out or include several features of different types. In order to determine in advance what size fish can be caught in a particular body of water, it is enough to learn how to correctly determine the age of the caught fish. So, for example, a perch living under normal conditions weighs about 20 g by the end of the second year of life, 60 g by the end of the third, at the age of four years its weight is about 100 g, and by the age of five it reaches 150 g. If the caught fish , whose age is estimated at five years, weighs less than 100 g, then the conditions of this reservoir are unfavorable for its habitat, and it is unlikely that normal specimens will be caught here. And vice versa, if at the age of five years a specimen of perch weighs about 200 g, it means that large and very large fish of this species can be caught in this reservoir.
Below is the table. 2, with which you can determine the approximate age of some fish by weight and length.
table 2
Relationship between age and size of fish
It should be remembered that, according to the law, every fish caught must be measured, and if it does not reach the required size, it must be released into the wild.
The following devices and items are suitable for measuring fish during fishing:
Measuring ruler, centimeter tape, tape measure, caliper;
The butt of the rod has special notches (if the manufacturer has not designated them, you can apply your own markings);
Any objects whose length is reliably known;
Matchbox (side length is 5 cm);
Plastic bank card (side length is 8.5 cm);
A pack of cigarettes (length about 9 cm).
To take measurements, the fish should be laid out on a smooth surface (a tarpaulin or oilcloth is suitable for this purpose). The measurement procedure itself must be carried out carefully, trying not to injure the fish. It is not recommended to lift fish by the gills or eye sockets.
Next, using a special measuring device or any object whose length is known for certain, measure the length of the fish’s body and head, then the girth and height. In this case, the length of the head is the distance from the top of the snout to the most distant posterior edge of the gill cover.
The age of a fish can be quite easily determined by the state of the growth zones on the scales, as well as by the otoliths - auditory stones that are located in the pits on the sides of the fish's head. It can also be recognized by sections of the vertebrae and fin rays.
Perhaps the easiest way to determine the age of a fish is by its scales. The fact is that as any individual grows, the size of its scales also increases. In this case, existing scales do not become larger, but new, larger ones are formed under them.
Thus, as the fish matures, its scales thicken. Each scale becomes like a pyramid consisting of plates. In this case, the top one is the smallest and the oldest, and the bottom one is the largest and the newest. Establishing the age of fish by scales is similar to a similar process for calculating the age of trees by annual rings. On the scales, the role of rings is played by growth zones - circles of bone matter that form as the fish grows. Upon careful examination, you will find that wide light rings on the scales alternate with thin dark ones.
Light stripes are formed during the period when the fish received a sufficient amount of food. This usually happens in spring, summer or early autumn. Active growth of rings on the scales of all fish begins in mid-April.
As for the narrow dark stripes, they appear during the cold period when there is a lack of food. In some years, in some fish, the rings that form on the scales are so thin that they are almost invisible.
When determining age from auditory pebbles and bones, the type of compaction of the bone substance is taken into account. Thus, bone tissue formed in winter is translucent, and in summer it is opaque and matte.
Using ear stones, you can determine the age of fish that do not have scales or have poorly developed scales (catfish, tench).
Before starting the examination, bones, otoliths, ridges and scales should be cleaned of dirt and mucus. In case of severe contamination, the material is placed in a weak solution of ammonia, then wiped and dried.
To determine the age of a fish, it is best to take 10–15 scales from the middle of the body, from the place under the dorsal fin. Scales taken from the lateral line should not be used for this purpose. In this case, the scales must be free of defects and of the correct shape inherent in a particular type of fish.
So, the number of rings on the scales corresponds to the age of the fish. If the specimen was caught in spring or winter, its age will be displayed as an integer.
Leaving fish for a long time without food often leads to the formation of another annual ring on the scales, which can ruin the entire experiment.
If the fish was caught in the fall or summer, some more time should be added to its age. Such specimens are called younglings or two-year-olds, three-year-olds and so on.
Now let's look at the life expectancy of freshwater fish. You should know that small species of fish (bleaks, etc.) rarely live more than 10 years. Carp, perch, bream and some other fish can live up to 20 years. The longest-living fish in our reservoirs are carp, catfish and pike, whose age often exceeds 70 years.
From the book In the beginning there was a word. Aphorisms author Dushenko Konstantin VasilievichMeter and Rhyme Poetry is a feeling clad in the armor of meter and rhyme. Henryk Elzenberg (1887–1967), Polish philosopher Caezura is the heartbeat of the creative spirit, it cannot be adopted from another, which is possible in euphony. Heinrich Heine (1797–1856), German poet Rhyme follows
From the book Great Soviet Encyclopedia (RA) by the author TSB From the book Criminals and Crimes. Camp painting, criminal jargon author Kuchinsky Alexander Vladimirovich From the book Pendulum Step [The art of dodging shots, high-speed shooting methods and disarming techniques] author Ivanov-Katansky Sergey Anatolievich From the book The Complete Encyclopedia of Our Misconceptions authorSize of tattoos The size (size) of tattoos on the surface of the body of convicts varies greatly. The size of tattoos is influenced by factors such as gender, fashion, body surface area (whether the format allows), etc. If in the 30s–50s in prison
From the book The Complete Illustrated Encyclopedia of Our Misconceptions [with illustrations] author Mazurkevich Sergei AlexandrovichChapter 3. New ways of snatching weapons and new ways of conducting dueling actions with movements of 1–6 steps, in which the defender wins... ... New methods of disarming by knocking weapons out of hands Lesson 491. Warm-up.2. Learn the technique of snatching a pistol from
From the book The Complete Illustrated Encyclopedia of Our Misconceptions [with transparent pictures] author Mazurkevich Sergei Alexandrovich From the book Exercises to enlarge the penis by Kemmer AaronPenis size A woman prefers an extra centimeter in a man's penis to anything this world can give. Arabic proverb Probably, the myth that the size of the penis does not matter was invented by experts to reassure men who did not meet their size. Still the size
From the book Digital Photography from A to Z author Gazarov Artur YurievichPenis size A woman prefers an extra centimeter in a man's penis to anything this world can give. Arabic proverb Probably, the myth that the size of the penis does not matter was invented by experts to reassure men who did not meet their size. Still the size
From the book How to understand housing and communal services and not overpay author Shefel Olga MikhailovnaYour size. Measuring An important part of penis exercises is tracking your own results. If the dimensions do not change, you will need to understand the reasons. Perhaps something needs to be changed in training. Measurements also allow you to judge at what stage
From the book Holidays without intermediaries author Romanovskaya Diana From the book Locksmith's Guide to Locks by Phillips Bill From the IFRS book. Crib author Schroeder Natalia G.Adjusting the size So, what do we need to organize a vacation? Understanding what we want from our vacation, free time and budget. We dealt with the first point in the previous chapter. With free time, everything is also clear. Now let's move on to the budget. We have two ways
From the book Survival Manual for Military Scouts [Combat Experience] author Ardashev Alexey NikolaevichFish are lower vertebrates that live in water. Fish and fish products have high nutritional value, are a source of complete animal protein, and are valued in medical and dietary nutrition. The physiological norm for consumption of fish products is about 24 kg per person. In our country, the actual consumption of fish products is much lower than the norm (29% of the recommended norm).
Fish is quickly digested and easily absorbed by the human body; For elderly, sick, overweight people, fish products are healthier than meat.
Fish is the most important supplier of minerals in the human diet.
The body of a fish can have a variety of shapes - flat, spindle-shaped, arrow-shaped. It depends on its living conditions.
The body of the fish consists of a head, body, tail and fins.
The skin of the fish has scales; in sturgeons, the body is covered with bone scales and grains. On the surface of the skin there are cells that secrete mucus, which helps the fish move and protects it from microorganisms and harmful substances.
All tissues and organs of fish are divided into:
- edible - meat, cod liver, milt, caviar;
- inedible - scales, fins, gills, bones, entrails.
The edible portion of the fish can range from 50 to 80%.
Diagram of the fish body structure: 1 - total length; 2—field length; 3 — carcass length; 4 — tail length; a - gill cover; b - dorsal fin; c - adipose fin; g - pectoral fin; d - ventral fin; e - anal fin; g - caudal fin.
Fish are divided according to their skeletal structure into cartilaginous and bony.
Cartilaginous fish include sturgeon and lampreys, and bony fish include all other types of fish.
According to their lifestyle, all fish are divided into freshwater, semi-anadromous, anadromous and marine.
Freshwater fish live and spawn in rivers, lakes, and ponds (pike, trout, carp, etc.).
Semi-anadromous fish live in river mouths and in desalinated areas of the sea, breeding in rivers.
Migratory fish live in the seas, and rise to spawn along the upper reaches of rivers (sturgeon, Far Eastern salmon, etc.), or live in rivers, and go to the sea to spawn (eel).
Marine fish live and breed in the seas and oceans (mackerel, mackerel, herring, flounder, etc.).
According to the standard, some types of fish are divided into large, medium and small according to weight or size. There are total and fishing lengths (Fig.).
In commercial practice, they use the fishing length (from the front point of the head to the beginning of the caudal fin (Fig. g).
Large fish are valued higher and are superior in taste to small ones.
Some types of fish (sprat, herring, smelt, etc.) are not divided by length or weight.
Fish is divided into groups according to fat content:
— especially fatty — more than 15%;
— fatty — up to 15%;
— medium fat — up to 8%;
— skinny — up to 2%.
The classification of fish has a complex structure. According to the degree of ossification of the main skeleton, fish are distinguished: cartilaginous (sharks, rays), cartilaginous (sturgeon) and bony (most commercial fish).
According to their lifestyle, fish are divided into marine, anadromous, semi-anadromous and freshwater. Marine fish live only in salty sea or ocean water (herring, mackerel, flounder, etc.). Migrants live in the sea, and for spawning they enter rivers and lakes (salmonids). Semi-anadromous live in estuaries and desalinated areas of seas (sturgeon). Freshwater animals live and breed in fresh waters.
The most advanced and recognized zoological classification of fish was created by Academician L. S. Berg. The basis of this classification and its lowest link is the species - a set of individuals living in a certain geographical area and possessing a number of inherited characteristics that distinguish this species from other species. The highest systematic grouping is a class. The classification of fish according to L. S. Berg can be presented in the form of a diagram:
species → genus → families → subfamilies suborders → orders → subclasses → classes
All fish belong to two very unequal classes in number and importance: the class of cyclostomes (lampreys) and the class of fish (all other fish).
Various factors are used to determine the scientific name of fish. Thus, the external characteristics of fish often determine the species name. For example, the scales of an adult living shemaya have a copper tint, hence the species name chalcoides (chalkos - copper, eidos - species). Often the species name determines the habitat of the fish: tag tsh - sea, caspikus - Caspian, tanaicus - Don, fluviatilis - river, etc. About 16,000 species of fish are known.
Domestic catches mainly consist of fish of the following families: carp, catfish, pike, salmon, sturgeon, herring, mackerel, horse mackerel, cod, flounder, scorpion fish, etc. However, this does not completely exhaust the species composition of domestic fish catches, which is enriched literally with every during the day.
And the signs underlying it will be discussed in our article.
general characteristics
It’s not for nothing that self-confident people are compared to these animals. They say about them: “Feels like a fish in water.” Indeed, fish have structural features that allowed them to master this habitat. These include a streamlined body shape, the presence of fins and scales, mucus-rich skin and gill breathing.
Basics of classification
These aquatic animals can be grouped according to different characteristics. First of all, the classification of fish according to structural features is considered. Depending on this, the classes Cartilaginous and Bone are distinguished. Representatives of the latter have more progressive structural features and numbers. Therefore, within this systematic unit, a number of orders are still distinguished.
According to the area of use, ornamental and commercial fish are distinguished. People breed the first ones in aquariums and ponds as decorative decorations. These are angelfish, catfish, neons, guppies, barbs and many others. Humans raise commercial fish for food consumption. Since ancient times, their meat and caviar have been a favorite delicacy, and their fat has been a valuable medicine.
There is also an ecological classification of fish. It takes into account their living conditions. These can be different types of reservoirs: fresh, ocean or sea.
Catch a big fish and...
The classification of commercial fish also takes into account size. The method of catching and subsequent storage of raw materials depends on this characteristic. Based on weight and size, fish are classified into small, medium and large fish. Each of these groups has its own valuable qualities. For example, sprats have excellent taste and are widely used in the food industry, despite their very small size.
For gastronomic properties are of particular importance. Therefore, they are distinguished by the amount of fat. For example, for cod, navaga and hake this figure does not exceed 4%. These types are considered lean, or skinny. The highest indicators for this trait are sprat, mackerel, herring, saury, sturgeon and stellate sturgeon. Their fat content significantly exceeds the 8% mark.
In commodity science, the concepts of “species” and “families” are used. Fish, the classification of fish is determined in trade practice most often on the basis of external characteristics. For example, it unites representatives whose body is laterally compressed and whose scales fall off freely. Such fish lack a lateral line. They have a single dorsal fin, and the tail fin has a characteristic notch. This family includes herring, sprat, sprat, and sprats.
Anatomical classification of fish: table
Features for comparison | Class Cartilaginous fish | Class Bony fish |
Skeletal structure | Completely formed by cartilage tissue | The skeleton contains bone tissue |
Presence of gill covers | Absent, gill slits open outward with independent openings | Present, protect gills and participate in respiratory movements |
swim bladder | Absent | Available |
Type of fertilization and development | Internal, direct | External, indirect |
Features of selection | The ducts of the digestive, reproductive and excretory systems secrete into the cloaca | There is no cloaca, each organ system opens with its own opening |
Habitat
The classification of fish by habitat also defines several groups. The first includes marine inhabitants. These are flounder, herring, halibut, mackerel, cod. Freshwater fish include silver carp, sterlet, carp, burbot, and crucian carp. They spend their entire lives in one habitat, where they spawn. The life activity of these ecological groups depends on the salinity of the water. So, if marine fish are transferred to fresh water, they will quickly die.
Migratory fish
The classification of fish according to habitat and lifestyle includes another group called anadromous. This includes representatives of the superclass that live in the seas, but go to fresh water bodies to spawn. These are sturgeons and such migratory fish are also called anadromous. But eels travel in the opposite direction during spawning - from rivers to seas. These are typical representatives of catadromous fish.
Making such a difficult path, the representatives of the passers lose a lot of strength. They have to swim against the current, overcome rapids and waterfalls. All this time they do not eat, but use up their own supply of fat and nutrients. Therefore, many migratory fish swim to the breeding site, spawn and die. Young individuals return to their permanent habitat. It is still a mystery how fish find their way home. Others are able to spawn several times during their life. During spawning, many fish undergo external metamorphoses. For example, pink salmon grow a hump on their back and their jaws become bent.
So, the classification of fish is based on several characteristics. These include features of the skeleton and internal structure, size, fat content, habitat, lifestyle, and area of use.