The age of a fish can be determined by the number of concentric rings on its scales. A. Levenguk (1684) was the first to draw attention to the correspondence of the number of rings on the scales to the number of years the fish has lived. The ring counting technique is quite simple. Scales from the area at the base of the first dorsal fin are usually used to determine age.

The scales are washed in a solution of ammonia, wiped, clamped between two glass slides and viewed under a magnifying glass or at low magnification of a microscope. (It is advisable to lubricate small scales with glycerin before viewing.) Often, additional rings are visible between the annual rings, the origin of which is associated with spawning (salmon, herring) or a change in feeding intensity (cyprinid fish). Additional rings are not expressed along the entire length, but only on one side of the scales.

It should be recognized that not all fish species have scales with clearly visible annual rings. Therefore, to clarify the result of counting the number of annual rings, annual bone rings are used. Various bones are suitable for this purpose: in perches - the operculum, in sturgeon - the rays of the pectoral fins, in pike perch and catfish - the rays of the dorsal or anal fin (Fig. 1). It is more convenient to determine the age of many marine fish by the annual rings on the otoliths (flounder, notothenia, cod). In these cases, cross-cuts of the bones are made or sections are made. Annual rings are examined under a magnifying glass (ray sections are examined under a microscope); if necessary, for greater clarity, the preparations are lubricated with glycerin or moistened with water.
Interpretation of the results obtained may be difficult or ambiguous.

Rice. 1. Annual rings on the cut of the ray of fish, the pectoral fin of stellate sturgeon in water bodies of middle and high latitudes, certain terminology and special designations have been adopted to characterize the age of fish by annual rings.

The number of rings on the scales (bones, rays, otoliths) and the calendar age of fish are linked as follows:

Movement should be considered as the most important property of all living things. At the subcellular level, along with cell irritability, it is a hallmark of life. However, movement in the microcosm is characteristic of both plants and animals. The movement of multicellular structures with the help of specialized cells and tissues (muscle) is a distinctive feature of animal organisms. The emergence of the ability to move marked a new stage in evolution. The emergence of striated muscles in animals allowed them to conquer the entire biosphere.

In evolutionary terms, it was movement that gave rise to the emergence of the nervous system in the animal world. As the motor activity of animals became more complex, their nervous system became more complex. Within any class of both invertebrates and vertebrates, the level of development of the nervous system reflects the degree of complexity of motor activity. In vertebrates, the level of development of the musculoskeletal system correlates with the complexity of the structure of the nervous system and determines the complexity of behavioral reactions that ensure nutrition, settlement, reproduction, development of new territories, intra- and interspecific relationships.

Movement allows animals to effectively adapt to changes in the external environment, i.e., maintain their vitality, preserve the population and the species as a whole. The body's adaptability is based on two motor processes: evasion (protection) from an unfavorable factor or changing oneself. In the first case, the animal uses the musculoskeletal system (avoids danger, finds food, builds a shelter). In the second case, the animal adapts its body: increases blood circulation, increases the breathing rate, increases (reduces) heat transfer, etc. However, in both cases, the executive organs are structures that include contractile elements.

Calculating the age of fish is similar to the method when determining the growth rings of trees. This is how experts calculate the age of mollusks, mammals and reptiles. For land animals, a different principle applies - their age is determined by their teeth and bones. Foresters, farmers and entrepreneurs can use the data received to calculate how many years an animal has lived. Fishermen who have caught a large specimen are interested in how to determine the age of the fish.

Growth of annual rings

Scientists can easily learn almost all the information about a fish from its scales. Sclerite rings are winter and summer circles on the plate of a fish, from which the ability to reproduce, age, normalization of growth, and much more are calculated. Therefore, scientific research allows analysis of any population. Scientists, determining the age of fish by scales, will always be aware of all environmental statistics.

To accurately determine the age of a fish by its scales, a person must have certain information. If you take a caught individual and carefully examine it, then there will be rings on its scales - narrow and wide. The color of the rings varies from very light to dark. Wide and light rings indicate good nutrition and vigorous growth. Such a favorable period can be in autumn, summer or spring.

Significant appearance of ring formations occurs in April. In the absence of food, dark narrow rings appear. This is explained by the winter period, since it is difficult for fish to find food. Sometimes winter annual circles are so narrow that experts have difficulty detecting them.

After completing a one-year cycle, sclerite rings appear on the bones and scales of the fish. These circles alternate and overlap each other. Not all species have such lines, since the scale cover can only form a month after the larva emerges from the egg. Sometimes it happens that the scales begin to grow much later.

In the first year, a transparent scale forms. In the second annual cycle, a second, thicker one appears under it, in the third year also - and so on in the future. For example, a fish that has lived for 6 years has 6 rings, and they all differ in size. The first line is the oldest, it is also the smallest, and the largest is the youngest.

Sclerite formation

Over the years, the fish grows and has more scales. If the individual’s diet is poor and living conditions are harsh, sclerite circles begin to grow unevenly. Their width becomes different: in summer they are wide, and in winter they are narrow or completely absent. Poor and good living conditions can bring the rings closer or further away from each other. In any case, even if the dark arches are poorly visible, there will be wide and light arches - summer ones, which determine the age of the fish. Their number will accurately indicate the age of the individual.

Determining age from bones

Often wounds can be seen on the covering of an individual, which makes it difficult to read information from the rings. Fish farmers with extensive experience do this without difficulty; they are not afraid of such difficulties. They will say that the scales are simply wonderful and will tell the whole story about the fish. Fishermen without experience cannot boast of such skills. If the scale cover has been damaged, then the age of the fish can be determined by:

These are the main types that indicate age, height and other information if the scales are small or difficult to “read.” There are other bone formations, but for a beginner they will be difficult to view: they are mainly used by scientists.

From theory to practice

When a novice researcher gains experience, he will be able to determine the age of a caught individual up to two months. In addition, he will be able to read the story of the individual’s infancy, determine the history of diseases, with what intensity it grew, what were the living conditions in the reservoir.

If you come across a migratory species, for example, the salmon family, then from the bones you can determine how much time they spent at sea and in the river. To do this, just arm yourself with a calculator, pen and notepad. How can you determine the age of a fish:

If the researcher was unable to find out how old the fish is, then skull bones, otoliths, gill covers and vertebrae can be used. They are placed in water and boiled for at least 5 minutes. It is advisable to treat these fragments with salicylic alcohol. Then they are wiped with a rag until dry. A cut is made on the bones, but only neat and thin. The growth rings are visible under a microscope; the principle of study is the same as with scales.

Calculating the age of aquarium fish

Anyone who keeps aquarium fish at home should know about the method for calculating their age. This is useful information if a fishkeeper decides to go to a pet store and buy rare fish, since sellers sometimes provide inaccurate information. This activity is very difficult, but there are factors by which experts determine age:

In principle, these are the main ways in which a beginner can guess the age of the fish. Sometimes their color and slow movement indicate disease and poor nutrition, poor water quality and temperature changes. Therefore, you should not buy such aquarium fish. There are two disadvantages here:

1. The fish is old and how long it has left to live is unknown.
2. The fish is sick and it is unclear whether it will recover after purchase or not.

Therefore, aquarium fish should have a bright color coating and swim quickly.

Record long-livers

It is known that the lifespan of fish is sometimes longer than that of humans. For example, a beluga under normal living conditions can live about 100 years. The Kaluga sturgeon lives on average 58 years. The Far Eastern sturgeon is 66 years old, and the paddlefish is 23 years old. Scientists have recorded that one paddlefish was able to live for more than 50 years.

Atlantic sturgeon can live 155 years in favorable conditions. The category of long-livers includes eel, catfish, pike, taimen (up to 90 years). Lungfish live 88 years. In the United States, fishermen caught an 83-year-old sturgeon from the Winnebago Reservoir. The whale shark lives to be 70 years old. The mirror carp, which was caught in Japan, breaks all records. Surprisingly, this female was able to live 228 years.

In third place after the Atlantic sturgeon, the northern perch from Kamchatka set a record for life expectancy. The large fish was caught by local fishermen; it was 120 cm long and lived for approximately 140 years.

There are species of fish that are predisposed to rapid aging - these are Far Eastern salmon. For example, in pink salmon, spawning begins after one and a half years. At this age, she becomes an adult and begins to age early.

Other fish species live somewhat shorter lives: loaches, bream, ide, roach and perch (average 13 years). Muksun, crucian carp and nelma reach the age of 30 years. Minnows, catfish, minnows, tuguns (6 years). However, this life expectancy was calculated for fish that lived in the wild, and those that live in an aquarium live much longer.

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The age of a fish is reflected not only on its scales, but also on all its bones - “documents” that are stronger than scales. After all, there are fish without scales. Many catfish do not have scales. Some gobies also have no scales. In sharks, rays and other lower fish, instead of ordinary scales, the body is covered with plates with teeth (such plates are called placoid scales). In sturgeon fish, scales are replaced by five longitudinal rows of strong cone-shaped spines - bugs.

They have not yet learned to determine the age of fish from shark plates and sturgeon bugs, since the annual rings are not visible on them. But sturgeon fish have bones in their heads (as strong as those of bony fish), on which annual rings or planes are visible, which make it possible to determine the age of the fish.

Ichthyologists have found that the cuts in the rays of the fins also have annual stripes, and from them the age of the fish can be determined.

If the fish has a bony spine, then the age can be easily determined by the vertebrae.

Finally, the age of fish is also determined by otoliths - calcareous stones located in the auditory capsule of fish.

A long time ago it was noticed that there are stripes on the bones of fish. These stripes were sketched and reproduced in ancient books, but for a long time no one thought of linking these stripes with the age of fish. Only at the beginning of this century did they begin to study the age of fish from bones. The bones of flounder, cod and other commercial fish of the North and Baltic seas were studied, as a result of which they came to the conclusion that it is more convenient to determine age by flat bones similar to plates. Russian scientists E.K. Suvorov, V.K. Soldatov, V.O. Kler and others worked a lot in this direction.

If you remove the skin or muscles from the gill bones, slightly cook the bones and clean them with a toothbrush, then the annual stripes will be visible even with the naked eye. When viewed through a magnifying glass (5-10 times magnification), they are visible even more clearly. The picture shows two gill bones of a roach: on the left - the subopercular, on the right - the operculum. Both have 8 growth stripes and one narrow strip along the outer edge of the bones. Age - ninth year. The lower end of the gill operculum is thick and the first annual ring is difficult to find. The bones of the shoulder girdle and collarbone are removed through the gill openings, but this operation must be done carefully so that they remain intact. On bones, annual stripes are usually clearly visible, but in large fish older than 10 years, the first annual stripes (one or two) are often barely noticeable.

To determine age, vertebrae are ground vertically.

Ichthyologists have learned to determine the age of fish not only by flat thin bones, but also by bones that have a compact structure. A strong, thick ray of the pectoral fin of sturgeon or catfish is taken and an incision is made at its base. Then a plate is cut out, on which, after grinding, the annual planes can be found. The figure shows such a plate from a cut of the ray of the pectoral fin of a sterlet. 10 stripes are clearly visible - the sterlet was 10 years old.

Annual stripes are visible on sections of the rays of many, probably all fish. The age of cod can be easily determined by the rays of the dorsal fin; the age of catfish, whitefish, asp and other fish - by the rays of the pectoral fin.

However, it is not yet known how to determine the age of lampreys. This animal is very special: it has neither gill covers nor vertebrae, and the rays of its fins are completely soft. However, over time, ichthyologists will learn to determine the age of such fish. Ichthyological science is penetrating deeper and deeper into the secrets of the life of fish. If it is impossible to determine the age of a lamprey by its body structure, then direct observations of it in nature and in an aquarium must be used for this purpose.

Every fisherman should know how to determine the age of a fish. By age, you can detect all diseases and developmental disorders of any individual. Therefore, different specialists are engaged in research and breeding of fish. In 1684, A. Leeuwenhoek established that the years lived by each individual can be recognized by the concentric lines of the scales. Several centuries later, the German ichthyologist S. Hoffbauer described the structure of carp scales. According to his research, he determined that the annual rings formed on the scale plates show the exact age.

Experts involved in fishing activities know how to determine the age of a fish. The age of the caught fish is also determined by its size and weight. But these data will be inaccurate, because its development is influenced by the general conditions of the reservoir and the amount of food in it. Scientists determine the age of fish as follows:

• by scales;
• bones;
• gills;
• external coloring.

How to determine age by scales

Scales help determine how long an individual has grown over the previous year, how old the fish is and how intensively it has grown. The scales are examined under a microscope, magnifying it several dozen times. This is the most universal method by which the age of fish is determined. The plate of scales is covered with small rings that are similar to the annual rings of trees. They are used to determine the age of various mammals, as well as mollusks. Each ring is located along the entire perimeter of the scale and is equal to 1 year of life.

Unlike aquatic life, the age of land animals is determined by bones and teeth. The formation of annual rings on fish scales occurs in winter, but sometimes they appear in summer and spring. How to properly research them:

1. Damaged scales should not be used. They must be whole and large in size.
2. The scales are washed with alcohol.
3. If you look at the plates under a microscope, you can see not only rings, but also various depressions and ridges.

Gill covers can be used instead of scales. They have markings from which age is calculated. It is much more convenient to work with them, since their size is several times larger than scales.

How do annual rings appear in fish?

Age, reproductive capacity, and growth rate are all calculated from the rings. Studying the plates allows scientists to conduct appropriate analyzes and monitor the population of each individual, monitoring the environmental situation. If you carefully examine each ring, you will see that it has a wide light ring and a dark narrow one. What do they mean:

1. Light rings indicate that the individual was rapidly developing and growing. This growth rate occurs in April.
2. If conditions for development were unfavorable, then dark, narrow rings appear. This happens in winter.

All favorable and unfavorable development conditions are displayed on the bones and scales of fish in the form of layers. These formations are their peculiarity, which representatives of this fauna possess. A separate plate grown over the course of a year shows the conditions in which the individual lived throughout this period. It appears under last year's scales. If you count them, you can determine the age of the fish.

In some species, rings do not appear. This is due to the fact that the formation of a cover of scales does not begin to occur immediately, but 30-40 days after the larva leaves the egg. Transparent scales appear first. A second layer of thicker plates is formed in the second year of life. It appears under transparent scales. The third layer grows in the third year. An individual that reaches 7 years of age will have 7 rings.

Calculating age using rings

To calculate the age of a fish, you need to prepare everything you need. For research you will need a notepad, pen and calculator:

1. To enlarge the picture 20 times, use a magnifying glass or binoculars. It is often used by professional fishermen.
2. The work is carried out on a table, having previously covered it with a white cloth. Tools used include a knife and tweezers.
3. The carcass is inspected and a suitable area for research is selected. It is better to choose otolith or spine.
4. The selected area is thoroughly cleaned. Remove all blood and mucus. The fish can be placed in a container filled with diluted alcohol. After 5 minutes, the carcass is removed from the solution, and the area under study is wiped with a dry cloth.
5. A visual line is drawn from the central point of the carcass to the fin. 15 records are taken from this area.
6. The scales located in the fin area are not used, as they are difficult to see. Choose only solid plates with an even shape.
7. If a microscope is used for research, then the width of each sclerite is calculated using a scaled eyepiece.
8. All numbers are written down in a notebook and then calculated. The final numbers are her age.

The external state of the scales shows what happened to the fish throughout its life. The fish spawn when the scales break off. Therefore, the broken plates are used to determine how often an individual produced offspring.

Determining age from bones

What to do and how to find out the age of a fish if its scales are damaged or completely missing. Professional fishermen will be able to tell the entire life story of the fish, even if the material is damaged. But beginners will not be able to do this. Therefore, it is worth conducting a study of gill covers, ear stones, skulls, pectoral fins or bones, which will tell how the fish lived throughout the year. Determination process:

1. Gill covers, vertebrae or skull bones are placed in a container of water. The contents are boiled for 5 minutes.
2. Then all elements are treated with salicylic alcohol and wiped dry.
3. A thin, even cut is made on each bone.

Then the fragments are placed under a microscope and the growth rings are calculated. You can learn to determine the age of caught fish up to 2 months if you practice and gain enough experience.

What are sclerites

Sclerites (ridges) are formations that appear on the outer layer of scales. The formation of rings in some individuals occurs in the spring. But for bream living in the Aral Sea, this period falls in the fall, and for pike perch from the Azov Sea - at the end of July. Formation of sclerites:

1. An increase in the size of scales occurs along with the growth of the fish. And since the individual develops differently, the size of the scales also becomes different. This difference manifests itself in the form of sclerites and various scars. They have an arcuate or circular arrangement.
2. The gap between the sclerites and their width can be narrow or wide. Thin zones are formed during slow development (in cold climates), and wide zones (in warm climates) during intensive development.
3. The annual ring is determined by the outer line of nearby sclerites (narrowed growth area).
4. The additional formations that appear show how the life cycle of an individual has changed over the year. Sclerites occur due to temperature changes in water, feeding method, spawning and the frequency of migration. In the area of ​​the first year's ring, one can often see the manifestation of a fry ring.

Different types of fish have their own shape and size of scales.

Calculating the age of aquarium fish

When purchasing aquarium fish at a pet store, you may receive false information about their age. Therefore, you need to learn to determine their age yourself. But doing this with aquarium fish is much more difficult than with river fish. Main signs of old age:

• poor appetite;
• dull shade;
• lethargy;
• the fish moves weakly in the water.

Housekeeping conditions greatly affect the size of the fish and its color, and the scales are too small to determine age. Therefore, all these indicators sometimes mean that the fish is sick. Its mobility and bright coloring can return at any time.

This is a very interesting question that worries many anglers. Although, on the other hand, this is not entirely important if there are no restrictions on fishing. Some of them determine the approximate age of the fish by size. But the size and weight of the fish may depend on a number of factors, including the availability of food in the reservoir. Therefore, this approach gives only approximate results, although quite satisfactory.

If you look at the scales with a microscope, you can see peculiar rings on it, very similar to those observed on a cut of a tree. Each ring is a witness to another year lived. Based on the scales, it is possible to determine both the age of the fish and its length by which it has grown over the previous year.

Specimens up to 1 meter long have scales with a radius of up to 1 centimeter. The distance from the annual ring (initial) to the central part of the scale is about 6 mm. Using this information, it can be determined that the fish has grown by 60 cm over the year.

If you look at the scales under a microscope, you will notice another, but very important feature - the unevenness of the surface. On the scales you can see ridges and depressions, which are also called sclerites. Over the course of one year of life, 2 layers of sclerites appear - large and small. A large sclerite indicates a period of active growth of the fish, and a small one indicates that the fish has experienced the autumn-winter period.

If you accurately determine the number of double sclerites, you can simply determine the age of the fish. But, even in this case, you need to have certain skills.

But this is not a problem if the fish has large scales. At the same time, there are species of fish that have rather small scales and this method is not suitable, since it is not possible to calculate how long the fish lived. That is, it is possible to calculate it, but this will require special equipment. In this case, to calculate the age of the fish, the skeleton is taken as a basis. Based on this, we can conclude that it is not at all easy for an ordinary person to cope with this task, since the process requires special tools.

How do annual rings appear in fish?

To correctly and accurately determine the age of a fish, it is necessary to know the physiology of growth of annual rings.

If you look closely, you will notice that the rings are distributed in certain stages: after the wide and light rings there are narrow and dark rings. A wide ring indicates moments when the fish was actively growing and developing. As a rule, this is spring, summer and autumn. The dark ring forms when the fish is in cold water and with little to no food. Sometimes it is difficult to identify dark rings on fish, which indicates difficult wintering conditions.

Such rings are formed because the bones of the fish and its scales are endowed with such a feature as the appearance of layers, depending on living conditions. On the other hand, uniform development of scales or skeleton is only possible if the fish is in ideal conditions, which never happens.