A huge number of fishermen and scientists from all over the world have long been wondering how to determine the age of a fish. The process of determining the age of a fish is somewhat similar to determining how old a tree is, only instead of studying the age rings of the cut, in the case of underwater inhabitants, they study the scales.

It is easiest to determine the age of a fish by the scales, as this is one of the most prominent and simple indicators. Some determine this indicator by the gills and bones, but this is a complex operation that only experienced fishermen or qualified scientists can handle.

When using various magnifying instruments, such as a microscope, you can see on the fish scales something similar to the age rings of trees. Underwater inhabitants have some similarities - each ring on the scales means one year of life lived. Scales help not only to determine the age of the fish, but also provides an opportunity to obtain information about the change in length over the past year.

As a rule, the diameter of the scales of fish that reach a length of up to 100 centimeters is about 10 millimeters. For example, if the distance between the initial ring and the center of the scale is about 5 millimeters, then we can safely say that in a year the fish has added about 50 centimeters to its length.

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Under magnifying devices, you can see another important feature of the structure of the scales - its surface is not entirely uniform. There are sclerites on the scales - these are peculiar depressions and ridges that are present on the scaly plate of each fish. Every year, the scales are overgrown with a large and small layer of sclerites, that is, there are two of them. The formation of a small layer indicates that the fish survived the autumn-winter period, and a large layer indicates the past year of life.

In order to understand how to determine the age of a fish by sclerites, you need to have certain skills. But, this method is the most accurate. When determining the number of sclerites on the scales, it is impossible to make a mistake, but it is necessary to have special equipment.

This method is suitable for fish that have large scales. But, some underwater inhabitants were not at all overgrown with scales, or overgrown, but covered with scales of small diameter. You can count age rings, but you will need magnifying equipment and certain skills.

If the fish does not have scales at all, or it is very small, then you can examine the gill cover. Thanks to such studies, scientists have completely refuted all the legends about centennial carps, pikes and catfish. But, in order to understand how to determine the age of a fish with small scales, you need to have certain skills, so it is better to use the simple table above.

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Detained poachers told the secret of their success for a good bite. The fish inspectors were so surprised by the lack of poaching equipment...

Database

Everyone knows that it is possible to accurately determine the age of a tree by the annual layers (rings), which are clearly visible on the transverse cut. But only by sawing the root end of the trunk it is possible to find out the true age of the tree. Using this, the foresters learn both the age of individual trees and the average age of a whole group of trees. In mollusks, reptiles and other groups of animals, everything is spelled out in exactly the same way. In mammals - on the teeth and bones, in birds - on the bones, etc. In addition to the number of years lived, bones, teeth, trunks and other organs also carry more detailed information about many vital parameters and even collisions (hungry and feeding periods, spawning, diseases, etc.). In livestock and crop production, foresters and livestock breeders actively use all these data when calculating plantings, planning the number of herds, and ro in many other cases.

It's the same with fish. By the scales, it is possible to find out in detail the past of a given individual and even predict the near future. By sclerite rings (summer and winter rings on the scales of cyprinids), a scientist can determine at what age a given fish becomes capable of breeding, whether it grows well, what age groups are found in the catch and what should be expected in the future. This is important, as fish of a certain age are not allowed to be caught. From a scientific research standpoint, this is the easiest way to conduct an ecological analysis of any population.

Physiology of the occurrence of annual rings in fish

In order to correctly determine how old the fish is and what has happened to it over the years, it is necessary to understand the principle of the formation of annual rings. If you look closely at the rings, you can see their alternation: wide light ones are replaced by narrow dark ones, and so on. A wide light ring means that during the formation of this sclerite, the fish fed well and grew actively. That is, it happened in spring, summer or early autumn. Moreover, the most significant growth of the annual ring in all fish of our reservoirs begins precisely in April. A narrow and dark ring is formed during the cold period, when there is no food. In some fish, winter rings are not visible at all in some years.

Sclerite rings arise in fish as a result of the fact that their scales and bones are able to form layers in the form of alternating rings, belts, planes, and sclerite ridges (or scallops). Each year of a fish's life corresponds to a certain ring on the scales or on the bone. Far from all fish, the exact time of the appearance of a scale cover on the body has been established. In some, the first scales are noticeable 30-40 days after the larvae hatch from the eggs, in others it is much later. At first, the scale has a tweed of a thin transparent plate. Approximately a year later, under the scale of the first year, a second, larger one grows, the outer edge of which protrudes beyond the edge of the first plate. In the third year, a third appears, and so on. In an adult fish that is, for example, five years old, each scale consists of five plates (scales). This is somewhat reminiscent of a children's pyramid: on top is the smallest scale, which is also the oldest plate, below is the largest, which is also the youngest.

How are sclerites formed?

As the fish grows, so does the size of the scales. And since the fish, depending on the living conditions and physical condition, grows unevenly, the growth of scales also occurs unevenly, which then slows down, then accelerates. This unevenness is reflected on the scales in the form of scars of various thicknesses, ridges called sclerites (obviously from the Greek word "scleros" - hard, hard), which are arranged in circles or arches. The width of the sclerites is not the same, and the intervals between them are also not the same. With the rapid growth of the fish (in summer), more sclerites grow and the distance between them is wider. With slow growth of the fish, the sclerites are brought together. This is seen in autumn. It is believed that in winter sclerites do not form at all. Bands of wide and narrow sclerites formed during one year make up the annual growth ring. How many such annual rings are on the scales, the same number of years the fish.

In addition to annual rings, there are additional rings on the scales that reflect periods of changes in fish growth during the year, depending on the nature of the diet, water temperature, and spawning time. There is also a fry ring, which is often noticeable in the zone of the first annual ring.

The shape and pattern of the scales vary from fish to fish, so the recognition of growth rings requires good observation and research skills. Of practical importance is the determination of the growth of fish for each year of its life, that is, the determination of the growth rate of fish. The age and annual increments of the length and weight of the fish can be determined quite accurately.

Where exactly do fish "write" their age

It would be ideal to take large scales from the fish, get it wet, bring it to the light and after a couple of seconds proudly announce that this pike is already seven years old, that it has grown evenly, has not had time to spawn yet, and now it will not have time. And also to find out that she was not sick with anything, did not starve, and easily endured her six winters, so you can fearlessly eat her. But this is ideal. When you try to reproduce this on a pond, it turns out that all the scales are damaged, or small, or unreadable. An experienced fish farmer, of course, will say that the scales are simply wonderful and will quickly describe the features of the life of this individual. But what about less experienced anglers? To begin with, all fish have different scales and are divided into several main types.

But how to determine the age of a fish if it does not have scales or if it is, but small and damaged? In this case, the so-called flat bones come to the rescue. First of all - auditory otoliths, gill covers, bones of the jaw, shoulder girdle, skull or bone skeleton of the pectoral fins, slices of fin rays and other bone formations.

How can you see the annual rings in fish

Now let's move on to practice. After acquiring a stable skill, you can determine the age of the fish with an accuracy of several months. Then, armed with some equipment, a pen, paper and a calculator, it is possible to calculate many other vital parameters of the trophy. Find out how he grew up, ate, wintered, spawned, and also got sick, whether he was stressed, how his infancy, childhood and youth went. If the fish is migratory, then you can find out how much time it spent in the river and how much in the sea.

If you are going to conduct research on a pond, you need to take a magnifying glass with 8, 10, and even better with a 20x magnification. Although any scientist will advise you to take a portable binocular with you, and not a magnifying glass. You will also need a flat white surface, tweezers, a scalpel or a thin knife, ammonia or ordinary ethyl alcohol and a thick napkin. The part of the fish chosen for research: scales, otolith or vertebrae, must first be thoroughly cleaned of dirt, mucus, and blood. If the scales and vertebrae are heavily soiled, then put them in alcohol for five minutes, then rub them, but it is better to get wet and dry. It is best to remove 10-15 scales from the middle of the body of each fish, in the area from the lateral line to the base of the dorsal or adipose fin. It is not recommended to take scales from the lateral line and bases of the fins, as they are difficult to see. Scales choose a whole, ideal shape and characteristic of this species. If you are doing this at home, it is better to use a microscope, if you have one. The so-called scaled eyepiece with divisions will help to calculate different parameters using the formula, with which you can calculate the absolute and relative widths of different sclerites, and then use these numbers to obtain the necessary information about the age of the caught fish.

Selected for inspection vertebrae, flat bones of the skull, auditory otolith stones, gill covers, dip in boiling water for 3-5 minutes or rinse in diluted alcohol (gasoline, ammonia). Then wipe with a flannel cloth or soft brush, dry and make a thin cut. If one doesn't work, make another. For such cases, always leave enough material for study. Annual rings are considered according to the same principle as on the scales.

How is age calculated?

Scientists rarely say: "This carp is seven years old." Having examined the scales or bone, they notice that there was still an increase of this year and deduce a more accurate figure; 7+, that is, seven full years, and plus is the increase in the last year. If you caught carp in winter or spring, you will get an integer. And to call it correctly - a seven-year-old (or a two-year-old, a three-year-old, etc.). And if you caught the same carp in the summer or autumn, then a plus is added, and correctly this carp is called the “seven-year-old”. And other fish caught during this period will be underyearlings, one-year-olds, two-year-olds, three-year-olds, etc. Be careful, because a fish that has survived long-term hunger and cold has another small ring, so you can miscalculate. If the scale is clear, and there is a device and the necessary tools at hand, you will be able to learn a lot of interesting things about the trophy. Using simple formulas, you can calculate what size a three-year-old pike perch was last winter or the summer before last. The Scandinavian scientist Einar Lea, who proposed one of these formulas, studied the age and growth rate of the Norwegian herring and came to the conclusion that the growth of the scales is proportional to the growth of the fish, that is, the annual increase in scales is related to the length of the scales in the same way as the annual increase in body length is to the total length. body. For example, if it is found that the scales for a certain year have grown by 1/10 of the entire length of the taken scales, then it can be assumed that in the same year the growth of the fish in length was also 1/10 of the body length. That is, by determining the ratio of annual scale growth for each year, it is possible to determine the body length of the fish in each year it lives. By the scales, one can also determine what happened with spawning in this individual. In many fish, during spawning, the edges of the scales break off, deform, and an uneven ring is obtained. By counting the crooked rings, it becomes clear how many times in the life of this fish there was spawning.

Next, we examine the favorable and unfavorable periods in the life of the trophy. The fish grows throughout its life, but unevenly. In winter, it almost does not grow, but even in spring and summer its growth can be uneven. In feeding and warm years, it grows intensively, so its sclerite is wide and light. And in the hungry spring, the sclerite is already darker.

Sometimes you can see several light rings in a row. This most often occurs if the dark ring is so narrow that it cannot be fixed with the eye. By the exact size of these rings, using simple formulas, you can calculate what sizes (height and weight) the fish had in the summer of the year before last or in the winter five years ago.

The scales of bony fish consist of a fibrillar (collagen) plate having. a protein base on which a mineralized gealodentine layer is located on top. In the process of growth, one plate is formed, then the 2nd, and so on.

The gealodentin layer is deposited on the scales in the form of ridges or sclerites. During the period of rapid growth, wide sclerites are deposited, while during the period of slow growth, narrow sclerites are deposited. Extended and contiguous (wide and narrow) form an annual growth zone.

The annual ring is the boundary between narrow (winter) and wide (summer) sclerites.

Fry (fry passes into adulthood)

Sloping (special case of fry) is typical for migratory fish

Spawning (during spawning (after spawning))

Salmon have a broken ring

The size of the scale, or its length, is measured by the average radius from the center to the edge of the back of the scales in some fish, and in others 1 to the edge of the front. If the edge is wavy, with rounded teeth, then to obtain the length, the distance from the center to the top of the middle tooth is measured.

Fish of high and temperate latitudes, where abiotic conditions change significantly during the year, as a rule, have quite distinct annual rings on their scales. At the same time, individuals caught in the period from March to August in most cases have a dark (winter) part of the annual ring along the edge of the scales. Such age groups are usually called "year-olds" (two-year-olds, three-year-olds, etc.) and the age is denoted by an integer (1,2, 3, etc.).

In fish during the period of intensive growth, a light part of the annual ring (“growth”) is observed along the edge of the scales. The age groups of fish caught in the autumn-winter period - before the completion of the laying of the winter part of the ring - (from September to February) are usually called “letka” and add the sign “+” to the digital designation of the whole number of years (year-olds - 0+; two-year-olds - 1+; three-year plans - 2+, etc.).

10. Method for determining the age of fish by bones, rays of fins and otoliths.

Bones: use toads. covers, jaw bones, some integumentary bones of the head, vertebral bodies, urostyle.

Advantages: annual rings are viewed without the preparation of devices and without additional rings.

Disadvantages: the complexity of the release of bones from tissues; Large amounts of space occupied; Difficulties in identification.

Perch - w/ lid

Sturgeons, catfish - saw cuts of the rays of the pectoral fins

Cod, pollock, sea bass, catfish - by the vertebrae

Otoliths - cod, ruff, burbot, smelt, herring

Definition principles:

In the process of growth, an opaque zone appears - not transparent, with slow growth - transparent.

Methods: mechanical - grinding, cutting; chemical - aging in 30% ammonia solution, calcination (for cod)

The age reading is made from the central part of the otolith, called the nucleus. The otolith nucleus plus the first hyaline zone - the first year of life, the next opaque and hyaline zones - the second year of life, etc.

The use of otoliths for age determination is generally more reliable than the use of scales. However, it should be borne in mind that in a number of cases, especially in fish of older age groups, the first annual ring is poorly defined, vague, and it can be mistaken for the otolith nucleus.

In addition to annual rings, additional rings are also visible on otoliths, but they are less sharp and for the most part not closed.

Chapter VII

FISH AGE DETERMINATION

Significance of fish age studies

In the Amur, there is a large kaluga (Huso daurikus), reaching a weight of 1 ton or more. The excellent studies mentioned by V.K. Soldatov (1915) showed that the Amur kaluga spawns for the first time at the age of 18-20 years, having a weight of almost a centner. This means that Kaluga, which has a significant weight at the age of 10, is still a young fish that has not reached puberty. On the basis of these data, business owners should consider kaluga fish to be late-ripening and, taking care of maintaining the kaluga fishery, should not intensively catch kaluga younger than 18 years old.

Sterlet reaches sexual maturity at 3-4 years. And the puberty of the smelt comes early: the one-year-old smelt is already able to spawn. Similar information is also necessary for fisheries, just as for a cattle breeder it is necessary to know the age of the animals he breeds.

Depending on the age of the fish, some features that distinguish one species of fish from another also change.

About the importance of studying the age of fish, K. A. Kiselevich (1927) says the following: “taking several hundred or thousands of fish from a running school and studying the scales of each of them, we find out not only the age of each of them, but the total number of fish 2, - 3 -, 4-year-old, etc. age. To complete the picture, it is always necessary to know not only the age of the fish, but also its size, and then calculate the average size of each age. By taking from year to year in the same places in the same places, in a permanently established way, several hundred or thousands of fish and determining their age and size, we can compare the age composition of the fish caught and the average size of each age from year to year and trace how much they improve or worsen. fish stocks. Elsewhere, he speaks even more expressively about the importance of studying the age of fish: “By constantly studying the age composition and growth rate of fish, we can judge whether the fishery uses the natural resources of the reservoir sufficiently and whether it (the fishery) should be reduced or expanded. Based on these studies, a rational fish economy is being built, that is, the most complete use of the fish products of the reservoir. In short, without knowing the age of the fish, we cannot judge the fish stocks of this or that reservoir.

The determination of the age grouping of fish is necessary where the issue of underfishing or overfishing and, in general, fish stocks is being decided. Average samples with a predominance of older fish (overgrown fish) can to a certain extent confirm the underexploitation of these fish species. Catches consisting of juvenile fish indicate overfishing of the respective fish species (if fished under the same conditions).

Knowing the rate of fish growth, we establish the annual (or even monthly) growth of the body of fish, and this makes it possible to determine the age at which it is most profitable, most profitable to catch this type of fish. It is known that old fish gives poor growth.

Every ichthyologist needs to know the "Collection of Articles on the Method of Determining the Age and Growth of Fish" (1926), which contains a number of articles (translated and original) of high methodological value. An article from this collection by N. L. Chugunov “Determining the age and growth rate of fish from bones” is useful. The author, in addition to theoretical justifications, gives practical advice, describes and develops the method indicated by V. O. Kler for calculating the growth of fish from bones. In addition to this collection, books and articles have been published outlining the study of growth. Especially needed are the works of G. N. Monastyrsky (1930 and others), N. I. Chugunova (1959), G. G. Galkin (1958).

Determination of age by scales

Annual rings on fish scales are usually counted at a magnification of 10-20 times, and sometimes more. In the first case, it is convenient to use a desktop magnifier.

Growth rings are not clearly visible on every scale. Therefore, it is necessary to select good scales, save them sensibly and prepare them for detailed viewing. In this case, the following collection rules must be followed.

Write down the name of the fish, the place and time of collection, the size and weight of the fish. Specify the entire length of the fish (ab), body length to the end of the tail notch (ac), body length without caudal fin (ad) and length of the body or carcass (od). These measurements are shown in Fig. 39. Show the weight of the fish in grams or kilograms.

Rice. 39. Measurements in studies of the growth and age of fish.

The dotted line shows the places where scales should be taken from (according to Pravdin, 1939).

It is very important to determine the sex and degree of maturity of the reproductive products.

Based on such definitions, one can judge in what year males and females become sexually mature, as well as the timing of their spawning.

In most fish, scales for determining age are taken from the middle of the side of the fish (within the boundaries of dotted ovals, Fig. 39), above or below the lateral line. The age of scaleless fish is determined by the bones, and the scales from fish that do not have a lateral line are taken from the middle of the side of the fish.

5-10 scales are taken from each fish and placed in envelopes or in a special booklet (5-10 cm in size) made of writing paper.

The collected scales are stored in a dry place. When determining the age, the scales are washed in diluted ammonia or in plain water (raw) and cleaned with a soft brush (or between the fingers) from the mucus covering them.

Age is usually determined by the front of the scales.

Before starting to determine the age, it is recommended to carefully familiarize yourself with the numerous forms of scales of different ages of fish depicted in the Atlas of G. G. Galkin (1958).

The article by A. I. Rabinerson (1927) refers to the structure of the scales of the Norwegian herring (Fig. 40): “The entire surface of the scales is furrowed with parallel rows of thin lines slightly curving along the edges; these lines give the impression: as if they were arcs of circles described by very large radii, in any case many times greater than the dimensions of the scale.

Such formations, called sclerites, are located in a rather monotonous row in herring and do not give any indication of the age of the individual. In addition, four concentric dark rings are striking on the scales. These four arc rings are nothing more than the boundaries of annual scale rings.

The first (from the center) ring corresponds to the complete first year of the fish's life, the second - to the second year, etc. Annual rings on the herring scales are expressed on the front of the scales. On the back, they are invisible. On fig. 41 shows the scales of a three-year-old herring. Annual rings are limited by white (light) lines.

For greater clarity, in Fig. Figure 42 shows the layout of the sclerites of the Amur pink salmon taken in 1928. In the center of the scale there is a small ring a 1 with sclerites not strongly separated. Next comes a ring with sparsely located sclerites. A 2 . Both rings (A 1 +a 2) we count as one ring A, the first light ring. Behind this ring is a belt of closely spaced sclerites, a dark ring B. Finally, the last belt of sparsely seated sclerites, the light belt IN, bordering the edge of the scales.

Thus, the pink salmon taken in 1928 had an age (I mentioned this above) of about one and a half years, i.e., it was the generation that emerged from the eggs laid in the autumn of 1926. In the autumn of 1926, pink salmon entered the river and laid there caviar. By the spring of 1927, pink salmon fry hatched from the eggs, which lived for some time in the river (ring a 1) and then rolled into the sea (ring a 2 ). Between rings a 1 And A 2 , i.e., between the life of a fry in river water and in sea water, there is a small belt of contiguous sclerites. This convergence of sclerites can be noticed if one carefully counts the sclerites of the first ring. A from center of scale to its upper and lower edges (7th, 8th, and 9th sclerites close together). Obviously, when moving from fresh water to salt water, the growth of sclerites slowed down (while the fish got used to the new habitat). With this interpretation, the formation of the entire first ring (A) refers to the period March-September 1927, the formation of the second ring (B) - by October-December 1927 and January-March 1928, and the last (unfinished) ring (VC April-July 1928. Therefore, we set the age of the taken pink salmon that came to the Amur for spawning at one and a half years.

Fig.42. Schematic drawing of the scales of pink salmon. Age one and a half years (according to Pravdin, 1939)

On fig. 43 is a photograph of pink salmon scales. So, when counting annual rings, two rings are taken for an annual ring: one is light with large sclerites and one (neighboring) is dark with small sclerites.

In Atlantic salmon Salmo salar and S. trutta, river and sea growth rings are clearly distinguishable, and since these salmon can spawn several times (usually no more than 3 - 4), they also have a so-called spawning ring on their scales and
whether a spawning mark. Before studying the age of salmon by scales, microphotographs of their scales should be viewed; there are many such drawings in both Soviet and foreign publications (Fig. 44).

On fig. 45 shows a greatly enlarged segment of the rear part of the scales of a whitefish. On a piece of scales there are seven annual rings. The first annual ring is located in the center of the scale and consists of several (10-12) circles of strips, sufficiently separated from each other. The circles are the sclerites discussed above. The first ring is separated from the second annual ring

Rice. 44. Salmon scales after the first spawning (according to Suvorov from Chugunova, 1952).

(here we are talking about annual rings, consisting of a number of sclerite rings, and not about rings of individual sclerites) with a dark stripe, on both sides several rows of very close, narrowly spaced sclerites are visible. The following rings are separated by the same dark stripes: the second from the third, the third from the fourth, etc. It is easy to notice in the figure that the annual rings are not equally wide: the first (we count from the center) three annual rings are wider than the next four, moreover, the last ring, the seventh, is the narrowest. Consequently, in the first three years, the scales grew rapidly, and starting from the fourth

years, the growth of the scales, obviously, began to slow down. The ring of the seventh year is probably not finished, but it is still certain that the width of the seventh ring will be less than any of the first three annual rings. The observed unevenness of annual rings is explained by the fact that whitefish grew rapidly in the first three years; in the fourth year, he obviously spawned, as a result of which his growth was slowed down; slowly in comparison with the first three years, the growth of other, older ages (5, 6 and 7 years) also proceeds. We will return to this issue when we talk about the growth rate of fish.

Rice. 46 is borrowed from the book of the Finnish researcher T. N. Jarvi (Jarvi, 1928). In this book there are many similar drawings (drawn even more clearly), and on each of them one can count the annual rings. In the works of Soviet authors (especially of recent years) there are also many drawings of the scales of whitefish and other fish.

Consider also the scales of fish from the carp family. On fig. 46 shows the scales of a three-year-old roach, on the scales there are three annual rings (Chugunova, 1959). The nature of the sclerites is also clearly expressed here, and their location is clearly visible.

We already know that on the scales of herring, the sclerites are located in the form of very gentle arcs, while on the scales of salmon and whitefish, they are in the form of fairly regular ovals or even circles. In circles they are also expressed on the scales of carp.

Rice. 46. ​​Scheme of the scales of a three-year-old fish (according to Chugunova, 1952).

On the scales are expressed, in addition to annual rings (a, c and e), additional rings (b, d And e).

Light rings are considered summer rings, which determine the summer growth of fish, and dark rings are slow growth zones, often called winter rings. Therefore, in each annual ring, these two parts must be distinguished. The posterior margin of the annual ring is considered to be the posterior margin of the ring of closely spaced sclerites. Previously, a ring of closely spaced sclerites was mistaken for a winter ring; now this term is more consistent with an autumn ring (Chugunova, 1959), but it is no less arbitrary than the term winter ring.

Look again at the scale drawings shown here. On the scales of the Norwegian herring, winter concentric rings do not coincide with either the location or size of the sclerites. On the scales of pink salmon, winter rings are difficult to separate from summer rings; here we consider a group of closely spaced sclerites to be winter rings. Approximately the same pattern has winter rings of scales and many other (but not all) fish of the salmon family. On the scales of cyprinids, the winter rings, coinciding with those of the sclerites, are at the same time sharply separated from the summer rings and, like those of salmonids, consist of a series of closely spaced narrow sclerites. It should be noted that the name "winter ring" can not always be used, because the growth of many fish stops in winter.

From each studied fish, it is necessary to look at several (in any case, at least 5-7, and in doubtful cases, much more) scales. The scales of young flounders are very convenient for age determination (Fig. 47).

Rice. 47. Scales of a four-year-old flounder (according to Pravdin, 1939).

In addition to scale ambiguities arising from damage to the scales or deviations from the normal appearance (there are scales where no rings can be noticed), very often (in some fish it is quite natural) the spawning rings mentioned above can be noticed.

Using pink salmon scales as an example, it was indicated that in the first summer ring of pink salmon there is a small additional ring, the appearance of which we explained by the slowdown in the growth of the scales (and all young fish) due to the temporary unfavorable state of the fish when it passes from river water to sea water. But in the life of fish there may be other reasons that also contribute to a temporary slowdown in growth. These reasons include fish spawning. During the maturation of reproductive products and in the process of their laying, which is sometimes preceded by very long journeys to spawning grounds, accompanied by starvation in many fish, the fish loses weight, and its growth and the growth of scales slow down. The sclerites of the last fish during the spawning period (from the moment of preparation for spawning) are narrow and give dark rings that cannot be considered annual. Such additional rings make it difficult and sometimes very confusing to count the annual rings on the scales. An inexperienced observer can make a mistake and exaggerate the number of years. But if you understand them, then the additional rings make it possible to explain many phenomena in the life of fish.

Spawning rings or spawning marks are seen on the scales of many fish. From spawning marks on the scales of herring D. F. Zamakhaev (1940) and N. I. Chugunova (1940 a.). D.F. Zamakhaev noted that a spawning mark is deposited on the scales of several species of Caspian herring, characterized by the following features: 1) the presence of a break ring, not parallel to the edges of the scales, 2) a sharp intersection of rows of striae (thin non-concentric folds on the front of the scale) by the break ring; the posterior edge of the scales does not have striae); 3) absence of striae in the proximal part of the new growth zone; 4) violation of the direction of new striae in some areas of new growth; and 5) a sharp thinning of the zone of new growth. Spawning marks in herring are most noticeable on the scales located under the dorsal fin in the middle of the body.

Spawning rings on salmon scales are even better expressed. For some rings, conclusions are made about the year of the first spawning of fish and about repeated spawning.

Thus, not only the age of the fish, but also other life phenomena are determined by the scales, and N. I. Chugunova’s proposal to use the term “reading the scales” is justified.

The laying of the annual ring does not always begin in early spring (depending on temperature). In this regard, the work of N. S. Solovieva (1938) on the study of the time of laying of winter rings and the beginning of growth on herring scales in various regions of the Barents Sea is of interest. The author came to the conclusion that “the annual ring on the scales of the Murmansk herring begins to form at the height of the hydrological summer (August). Thus, there is no connection between the cessation of fish growth and a decrease in temperature in this case; obviously, the main influence on the establishment of the winter ring is the cessation of feeding, which occurs due to the high degree of fatness of the herring. The growth of the scales, and consequently, of the herring itself, begins in May, when, having used up the reserves of fat over the winter, it receives a huge amount of food and intensively fattens.

Recognition of winter rings is a very difficult job: the researcher is always faced with numerous transitional forms of these rings, but the principle underlying such differences is of undoubted interest. Similar studies of winter herring rings were carried out by P. A. Murashkintseva (1938).

In each species of fish, annual and additional rings have their own characteristics, which can be clarified by looking at the mass amount of scales.

N. I. Chugunova (1959) gives instructions on distinguishing rings on the scales of roach.

The annual rings are closed, run parallel to the circumference of the scales, and they are formed at the border of closely spaced sclerites of autumn-winter growth and parted sclerites of spring-summer growth. Spawning rings are usually seen by the rupture of sclerites and their irregular arrangement: fragments of sclerites go in different directions. A thickened dark sclerite often forms on the back of the scale, which is usually divided into horseshoe-shaped segments.

Additional rings are formed under the influence of various environmental factors (a sharp change in the physical conditions of the environment, nutrition, etc.). Accessory rings are very similar, but less distinct than annual rings, and are of several types (fry, random delay rings, or vice versa, growth enhancement, etc.). Fry or sloping rings are formed near the center of the scale (inside the first annual ring). Probably, such a ring appears when the fry moves from the river to the sea. The boundaries of the fry ring are less pronounced than those of the first annual ring.

The fry ring is not necessary for all fish, but its establishment is necessary in order to accurately determine the ring of the first year of a fish's life: often a fry ring is mistaken for an annual one. N. I. Chugunova (1959) gives the following answer: “When the scales of some kind of fish are examined for the first time, the age and growth of which is unknown, it is necessary to compare the length of underyearlings collected in a reservoir in autumn, or yearlings collected in early spring, with those calculated by scales length of fish at the age of one year. In this way, it is possible to establish the difference between the annual and fry rings. This method can be accepted rather conditionally. And the author himself admits that the first annual ring should be recognizable by its structure, and not by the corresponding calculated length of the fish, since if the length of the fish at the age of the first year is found by recalculating the lengths of large fish, then, as a rule, it will be less than normal .

When growing underyearlings of carp in the Volga floodplain, we (me and F. E. Karantonis) noticed that on the scales of carp 4-5 months old there were several well-demarcated rings, which, if the true age of carp were unknown, should be recognized as annual rings.

F. E. Karantonis (1945) gave exhaustive explanations of these additional rings. The scales of carp, which lived only one summer, had 6 rings, and each ring corresponded to the characteristics of the living conditions of juveniles. The first ring of the post-larval period (age about 10 days after hatching, body length 10 mm). The second ring of the hollow period, when the fish grew intensively, taking advantage of the expanses of flooded meadows; for 12 days of full life, the fish receives an increase of 42 mm. The third ring-sclerites are very close together - in juveniles, carp, remaining in drying lakes, where the living conditions for carp juveniles were extremely poor. The fourth ring arose in the fish that we planted in the pond, where they received abundant food. For 39 days in the pond, the fry grew by 107.5 mm. The fifth ring indicates a new growth inhibition due to poor nutrition (the fish were deprived of artificial feeding). The sixth ring is a ring of the usual autumn growth depression, characteristic of all fish in our climate.

If the visibility of annual rings on the scales is unclear, then one of. ways to improve their visibility is the so-called differentiated coloration of the scales, which was proposed by P. V. Trempovich (1932). Scales wrapped in gauze are kept for 17-20 h in a solution (37.5%) of iron sulfate. Before the study, the scales are well washed with ordinary (tap) water, dried with filter paper and transferred to a drop of a solution (3%) of tannin.

From the action of ferrous sulfate and tannin, the scales turn black. Annual rings become more visible. However, not all fish have such staining of the scales gives the desired results. For example, in bleak (Milinsky, 1946), in which the winter rings are very narrow (they consist of only two rows of narrow sclerites), such staining does not improve the visibility of annual rings.

The age of the fish is indicated either by Roman or Arabic numerals without a plus or with a plus (8.8+). The first eight indicates that the fish is 8 years old (for example, a perch taken in May-June has a full year), the second eight (8+) indicates that the fish is more than eight years old, but less than nine (for example, a perch taken in December). The age of salmon is indicated differently: the number of years spent by salmon in the river is put in front, and then the number of years spent in the sea (or in the lake) is indicated. For example, 3+1 means that the salmon (young) lived in the river for three years, then it lived in the sea for one year. Sometimes this formula is denoted differently: 3 + 1 + SM + 1, i.e. salmon spent three years in the river, then one year in the sea, then spawned in the river (sign SM) and again spent one year in the sea. Maybe such an entry is 5z, 64, etc. The lowercase numbers indicate the total number of years of salmon, the lowercase numbers indicate the number of years spent in 1 river. Meet in the ichthyological literature and other methods for designating the years of life of salmon.

Determination of age by bones and otoliths

On many fish bones, as well as on scales, stripes alternate correctly. Some of these stripes appear (even when viewed without a magnifying glass) as light, while others appear as dark. Light stripes are wide, dark stripes are narrow, i.e., a pattern is observed that repeats the pattern of the scales.

IN as a result of studying the age of the bones, it was found that the best material for this is flat bones, similar to plates. Such bones in fish are the four bones of the gill cover - the preoperculum, the operculum, the operculum, and the interoperculum; the jaw bones that border the mouth; the bones of the so-called shoulder girdle, which separate the gill slit of the fish from the body;

The method of determining the age of fish from bones quickly entered the practice of fish researchers: more and more new data have been cited and are cited, indicating that there is a strictly defined number of stripes on the bones of each fish, coinciding with the annual rings of the scales, and that these strips accurately determine the number years of fish life. In addition to the above bones, when determining the age of fish, vertebrae and bones from the auditory apparatus of fish, known as otoliths, or auditory ossicles, as well as hard rays of fins, are taken.

I. N. Arnold (1911) cited data on determining the age of beluga, sturgeon, stellate sturgeon, pike, perch, pike perch, burbot, carp, bream, roach, roach, tench, ide, syrt or fish, and whitefish. To count the years of sturgeons, I. N. Arnold recommends taking the bones of the shoulder girdle and gill cover, and the latter must be thinned and polished; The age of pikes can also be well determined by polished vertebrae; in perch, annual rings should be counted by the lid claws and by the bone of the upper jaw, the rear edge of which in perch ends in a significant expansion; in burbot, along the vertebrae and otoliths; in carp, along the gill cover and vertebrae; in bream and roach, along the bones of the shoulder girdle; in a fish, by the vertebrae; in whitefishes, along the gill cover and vertebrae.

The instructions of I. N. Arnold are still mainly used by everyone who is engaged in the study of the age of fish by their flat bones. A. G. Smirnov (1929) noted that the annual bands on the bones of the gill covers of the Aral shemai are far from being clearly expressed. Therefore, the author conducted a special study of shemai gill covers. He stained bones with hematoxylin, methyleneblau, picrocarmine and boric carmine and exposed them to 25% ammonia, 5-10% sodium hydroxide and caustic potash, benzene, gasoline, sulfuric ether, ethyl alcohol and glycerin. Only treatment with glycerin gave a noticeable benefit. Peeled gill bones for 10-15 min were kept in glycerin, then they were heated in it to 290 ° C (i.e., to boiling). In boiling glycerin, the bone turns from transparent to milky white, and against this background, annual rings begin to stand out clearly. With further boiling, the object turns yellow and, in connection with this, the pattern of annual layers is somewhat darkened.

V.K. Soldatov (1915), who performed the most difficult work on determining the age of a very large number of sturgeon fish of the Amur, writes: “When processing bones, we did this: carefully cutting out the bones that we needed from fresh fish, we did not only the muscles and other soft parts easily separated, they were lowered into boiling water with a key; separating all unnecessary parts from the bones, washing the bones with water and wiping with a brush, we usually dried them and kept them dry until the moment when they needed to be examined. Usually, well-boiled and pre-cleaned bones could have been immediately examined, since the layering on them was very prominent: for other bones, they required further treatment - with alcohol of various concentrations and gasoline or ether to remove moisture and fat from them. The viewing itself was carried out as follows: the bones were slightly moistened with alcohol and examined in the light or against a dark background, depending on the thickness and greater or lesser clarity in the alternation of layers.

Based on the determination of the age of the Amur sturgeon, V.K. Soldatov came to interesting conclusions of great economic importance. “Kaluga becomes an adult fish capable of reproduction only 17 years after leaving the caviar, having reached by this time at least 5 pounds (about a centner) in weight and about 230 centimeters of full length or 165 centimeters of commercial, and the Amur sturgeon becomes capable of reproducing their own kind in the 9-10th year after leaving the caviar, reaching by this time an average of about 14 pounds (about 6 kg) weight with an absolute length of an average of about 108-116 centimeters of full length and about 73.4-78.8 centimeters of fishing length.

T The same conclusions gave V.K. Soldatov grounds for resolutely saying that the fishery that existed at that time on the Amur caught kaluga and sturgeons, mainly juveniles, that is, those that had not reached puberty. About 91% of the more than 2000 Kaluga sturgeons examined by V.K. The irrationality of such a fishery is obvious and was the reason for the sharp reduction in the stocks of Amur sturgeon. To restore stocks, the Soviet authorities carried out a complete ban on Amur sturgeon fishing.

A. N. Probatov (1936), based on a study of the age and growth of the Amur sturgeons on the bones (according to transverse sections of the first ray of the pectoral fin), came to the conclusion that in the Amur there are separate biological groups of kaluga and sturgeons.

On fig. 49-53 show the cleaned bones of fish with noticeable annual growths on them.

W

The method of determining the age of fish from otoliths is widely used. Fish do not have an external and middle ear, i.e., there is neither an auricle, nor an auditory opening, nor a tympanic membrane, but there is only the so-called inner ear with an auditory nerve. Inside the auditory apparatus are also otoliths, which have different shapes in different fish.

Rice. 52. Bone of the shoulder girdle of a twelve-year-old

bream (according to Arnold, 1911),

Finding otoliths in the head of a fish without skill is not so easy, but acquiring the right skill for everyone is quite affordable. Take two or three dried heads of smelt or ruff, in which the bones of the head are small and easily crumble. Among the crushed bones, you will quickly see two large white grains of an oblong shape; one side of these grains is convex, the other is depressed, grooves go to the outer edges of the grains. These grains are the otoliths. Looking closely at the otoliths, one can easily find their place and location among the head bones and on fresh fish.

Rice. 53. Interopercular bone of a twenty-five-year-old flounder (according to Arnold, 1911).

Annual rings are clearly expressed on the otoliths, by which the age of the fish is determined (Fig. 54). A careful study of the otoliths of the flounder by the German scientist Immermann showed that the otolith of the flounder consists of a gelatinous-fibrous substance, which contains crystals of carbonic lime. Otolith fibers have the ability to solder into concentric plates, and in spring and summer white rings grow, in autumn they are dark. The white ring, together with the dark one, is considered one annual ring. The rings are well distinguished on the otoliths of young fish, worse on the otoliths of old fish.

Many modern works relating to the determination of the age of fish contain many new indications of how and what kind of bones should be used in the study of the age of fish. But usually they do not look at any one bone, but take different bones and scales, which is how the control of the correctness of the definition is achieved. Therefore, it is also necessary to select and view otoliths.

P. F. Fedorov (1931) subjected the otoliths of the White Sea smelt to chemical treatment and described his findings as follows: “First of all, the otolith is placed in 25% ammonia (known as ammonia), which contributes to its degreasing. In ammonia, the otolith is kept from 30 minutes to 24 hours, but in most cases 4-5 hours. After such treatment, the otolith is washed in hot water and then examined under a magnifying glass in a drop of glycerin. However, such an operation does not always give good results: there were cases when the otolith was kept in ammonia for more than a day and its annual rings still did not become clearer.

Rice. 54. Otoliths (from top to bottom):

polished otolith of a five-year-old

burbot; otolith of six-year-old burbot;

otolith of a six-year-old flounder.

Such otoliths after keeping in ammonia and washing with hot water were placed for 3-5 minutes in a boiling solution of sodium chloride (for 6 G salt was taken 100 cm 3 water) and washed again in hot water. The visibility of annual rings from this improved.

If the described method of processing did not give the annual rings of the otolith the required distinctness, then P. F. Fedorov made thin sections. Along a line running perpendicular to the longitudinal axis of the otolith, a cut was made with a jigsaw through the center (longitudinal sawing of the otolith) or simply the otolith was ground down with a file, and then carefully polished on a whetstone. After such polishing, the otolith was poured into rosin on a glass slide so that the polished plane was facing the glass. When the rosin hardened, the second part of the otolith was filed off with a file until its remaining plate on the glass became close to being translucent. Then the otolith plate was polished on a whetstone until it was completely translucent. When the section was ready, a drop of xylene was introduced onto the glass slide, which dissolved the rosin. The object was then covered with Canadian balsam and covered with a coverslip.

A. Ya. Bazikalova, T. N. Kallinikova, V. S. Mikhin, and D. N. Taliev (1937) determined the age of Baikal gobies from otolith sections. The otoliths were polished on both sides on a piece of pressed pumice. Good results are obtained by grinding on white fine-grained artificial pumice of good quality; Coarse-grained coarse pumice is unsuitable for grinding, since on it the section, not being thin enough, breaks easily.

Sections of otoliths of gobies were viewed in glycerin on a glass slide at a low magnification of the microscope and under transmitted light.

Otoliths are used as a material for determining not only the age, but also the growth of cod. D.F. Zamakhaev (1941) described a method for calculating the growth of cod by otoliths, recognizing that when determining the age and growth of old fish, otoliths have a great advantage over scales: annual rings are better visible and processing can be carried out faster (in 6 h you can prepare 40 preparations of scales, and otoliths for the same time - about 200 pieces). The author describes this method as follows.

The otolith was previously covered with black lacquer, broken by hand and polished on a grindstone. Particular attention was paid to the fact that, if possible, the fracture occurred in the middle of the otolith, on the evenness of the section and on the perpendicularity of the plane of the section to the longitudinal axis of the otolith.

Rings on the otolith were measured with an eyepiece micrometer under binocular in reflected light.

Annual rings on the thin section of the otolith can be measured in two directions - along the short and long axes.

In the direction of the short axis, measurements were made on the concave side of the otolith, along the long axis, on its narrowed part. In the first case, the point from which measurements were made often did not coincide with the center of the first annual ring; in the second case, measurements were made from this center. It should be noted that the center of the first annual ring does not always coincide with the center of the otolith. It is difficult to make such a preparation, in relation to which there would be full confidence that the center of the initial growth of the otolith fell into the plane of the section.

The measurement of growth rings along the long axis of the section is less convenient due to their vagueness and the large number of cracks that form mainly in this direction during the breaking and grinding of the otolith. On the contrary, measurements along the short axis present no difficulty.

It turned out that the difference in growth calculations for both dimensions is very small. D. F. Zamakhaev came to the conclusion that otoliths are quite suitable for determining the growth of cod from 30 to 100 ohm.

V. O. Kler (1916) proposed a completely new method for determining the age of fish, a method that has now become very common. He established that “it is more convenient to read the age of fish not on flat solid bones, as is usually the case, but on bones that have a compact structure, which in turn is possible only when studying bones through thin sections.”

Rice. 55. The first ray of the pectoral fin of the sterlet (according to Clair, 1916). Beam cuts along lines a, b, And V gave the correct definition of age.

These words express the whole essence of Clair's method of determining the age of fish. This method makes it possible to take such bones as the first ray of the pectoral fin or bones lying at the upper lobe of the caudal fin, the so-called fulcra, to determine the age of sturgeons. These bones are easy to cut out, and the fish (goods) does not deteriorate at all from such an operation.

On fig. 55 shows the first ray of the pectoral fin of a large sterlet. Letters a B C D And d indicate the places where the cross cuts were made. Cuts along the lines a, b and c gave the correct definition of the age of the sterlet; on cuts G And d the age was less, because the cut did not capture the old, first annual layers. On fig. 56 shows a section of a plate from the same beam; 10 annual rings are clearly visible on the thin section.

V. O. Kler (1927a), while investigating the structure of the bones of various animals, also did much for the method of determining the age of fish.

If in sturgeon fish annual rings are clearly visible on the section of the first ray of the pectoral fin, then in nelma (from salmon fish) the age can be easily determined on the section of the maxillary bone. On fig. 57 shows the maxillary bones of nelma (a straight line indicates the place of cutting). On fig. 58, annual rings are clearly visible on a thin section of a segment of the maxillary bone of nelma.

C
V. O. Kler also gave detailed instructions on the technique of making thin sections. He considers crushed pumice to be the best grinding powder.

Rice. 56. Polished plate of the first pectoral fin of a ten-year-old sterlet (according to Clair, 1916). Numbers indicate annual rings.

Bone plates should be polished in vaseline or other liquid mineral oil. For the final finishing of the section when sticking to glass, V. O. Kler recommends using Canadian balsam. “For this, Canadian balsam is taken, dried to such a hardness that at room temperature, when pressed with a fingernail, only a small trace remains on it. For gluing, the glass is heated so that when a piece of balm is applied to it, the latter melts. The operation is performed on a copper plate heated with an alcohol lamp.

Rice. 57. Maxillary bones of nelma (according to Clair, 1916). A straight line through the necks of the bones indicates where the cut should be made.

D. N. Taliev (1931) was the first to use the method of determining the age of cod (fish with soft rays) by the first ray of the dorsal fin. The author took the beam together with the articular head (in cod it consists of two ridges). The slide was made like this. Starting from the articular head, the beam was polished on a semi-velvet file, holding it by the upper part; when the articular head and almost the entire interception were polished on the file, they finished grinding on frosted glass in emery or on a fine-grained bar, while observing that the beam was always perpendicular to the grinding surface.

On a polished surface, through a magnifying glass, it is easy to count annual rings. To obtain a bilateral section, D.N. Taliev attached a beam with a polished surface using rosin melted on an alcohol lamp; when the rosin cooled, in order not to grind the entire beam, it was broken off at the bottom of the rosin. For the manufacture of one section, 3-10 min. The age on such sections is determined under a microscope at low magnifications. The fin ray preparation is shown in Fig. 59.

Rice. 58. Cross section of a cut of the maxillary bone of nelma (according to Clair, 1916). Annual rings are clearly visible.

The age of catfish by the first ray of the pectoral fin is determined in the same way as the age of sturgeons. “From each beam at the head, in the place where the recess ends, a plate with a thickness of up to 1 mm and polished on a small file, ”A. N. Probatov (1929) describes the preparation of catfish rays to determine its age.

Rice. 59. Sections of the first and second rays of the first dorsal fin of a four-year-old cod (according to Taliev, 1931).

Rice. 60 shows a cross-section of the ray of the pectoral fin of an eight-year-old whitefish, fig. 61-year-old asp.

N. L. Chugunov (1926) contributed a lot to the method of determining the age of sturgeon fish from bones. The transverse cut of the beam is made with an ordinary jigsaw, in which two thin files are fixed strictly parallel, separated in the clamps of the jigsaw by a thin copper plate. With the help of saw blades installed in this way, a cut of the appropriate thickness is easily cut, which, if the saw blades are properly installed, does not require subsequent grinding.

Rice. 60. Transverse section of the ray of the pectoral fin of an eight-year-old whitefish according to Probatov, 1929).

Rice. 61. Transverse section of a fin ray of an eight-year-old whitefish of the pectoral fin of an asp (according to Probatov, 1929). Asp is 5 years old.

For greater clarity in the calculation of the annual planes, the ray plates should be immersed in xylene before viewing.

The cut thickness should be about 0.5 mm. N. L. Chugunov advises cutting a cut near the articular head of the ray and no further than 1-1.5 cm from her. The calculation of annual rings is carried out under a magnifying glass or under a microscope. The thinnest metal files are most suitable for sawing.

Instead of a jigsaw with two files inserted in parallel, they began to use a special device. The device for making sections of sturgeon rays was described by N. I. Chugunova (1959).

It is a platform on which two parallel (at a distance of 0.5 cm) disc-shaped fine-toothed saw blades made of tool steel. These files are driven by hand or electricity. The fin beam is placed in a clamp mounted on the table in front of the files, which, with the help of a spring located under the table, moves the beam to the files (Fig. 62).

The cut is made at the very head in order to preserve the first year on the cut. The first cut is made no further than 1 cm from the anterior edge of the head. The age on such sections (polished in the same device) is determined at a magnification of 20-25 times. Slices | for enlightenment moistened with toluene or xylene.

Rice. 62. Device for making sections of sturgeon rays, front view (according to Chugunov, 1926):

a-disc file; b-grinding wheel; in-clamps; g - transmission from the electric motor: d - protective cover; e - table; and - screw.

L.P. Astanin (1947) described a new method for preparing sections of non-decalcified bones. The bones soften under the influence of boiling in water or under the influence of steam. Then such bones are easily cut with a razor.

P. A. Dryagin (1936), having encountered difficulties in determining the age of the carp from the river. Chu, used thin sections of sections of the third hard ray of the dorsal fin.

VV Petrov (1927) used a more convenient method of collecting sturgeon rays. He wrapped the cut beam in strips of paper, on which he wrote down the measurements and the sex of the fish, and then laid the bones in the sun without any digestion. The bones dried out and the paper stuck. In this form, the bones were wrapped in a common package and placed in a box for shipment.

D. A. Belchuk (1938) was engaged in determining the age of the one-finned greenling. For this purpose, the bones of the gill cover operculum and suboperculum, scales, bone of the shoulder girdle-cleithrum, vertebrae and otoliths were taken. Better visibility and a more accurate number of years had scales taken under the pectoral fins and from the middle part of the body. The otoliths were too fragile and did not give the desired results. On the suboperculuni, the annual layers are better visible than on the operculum, but the cleithrum bone turned out to be more convenient for determining the age. Calculating years by vertebrae is very difficult. The author comes to the conclusion that scales and cleithrum are the best elements for determining the age of greenlings.

The work of the Dono-Kuban Research Fishery Station introduced changes to the methodology for determining the age of fish from fin cuts (Boiko, 1951). The possibility of obtaining transverse sections of fin rays of various fish (and not only sturgeon, catfish and cod) has been proved. The cuts were prepared from the whole fin, and not just from the first simple beam). E. G. Boyko describes the technique for making saw cuts of fin rays in this way.

The entire fin or several rays of the fin are separated and dried. When dried, the rays are tightly fastened to each other by fin membranes and do not crumble when sawing. Fins with thin rays (in small fish) are poured into celluloid for compaction. Cross cut is done using a jigsaw with a thin file. Instead of grinding saw cuts, they are enlightened with transformer and burdock oils or xylene. Saw thickness 0.4-0.5 mm. Annual rings are visible on both simple and branched rays. Fin cuts of asp, bream, pike perch, cod, carp, crucian carp, sabrefish, ram, silver bream, fish, carp, ide, chum salmon, salmon, ivasi, Caspian shad, Volga and Don herring, mullet and striped mullet have good visibility. Annual rings on the rays were not found in the bonito. The author writes that for 7-8 h you can prepare 200-250 cuts or pour 200-300 fins into celluloid, or view up to 300-500 cuts.

Fin rays from small fish, before making cuts from them, can be thickened by lowering them several times into a solution of photographic film in acetone. The film is pre-washed in warm water to remove the emulsion.

The technique of using fin rays for determining the age of fish is more suitable than using scales and bones, and can be done quickly and without much preparation. However, the question of the possibility of using such saw cuts to calculate the growth rate of fish is unclear.

It is impossible not to note the attempt by S. M. Kaganovskaya (1933) to determine the age of the shark Squalus acanthias by the spines of the dorsal fins; these spines have stripes corresponding to annual rings.

The described methods for determining the age of fish by scales and bones are the most reliable, but they are by no means final: research thought should not calm down, but should check, criticize these methods, deepen the essential of them, and obsolete or not corresponding to the modern state ichthyological science should be discarded and replaced with a new, more justified one.

However, there is still a need to use simpler methods. Among such methods are the so-called Petersen curves, which are used for a quick, although far from accurate) grouping of a fish catch according to its (age composition (Fig. 63).

The method proposed by the Norwegian researcher Petersen first entered the practice of scientific and commercial fisheries research more than 50 years ago and consists in the following.

Rice. 63. Petersen curve.

A portion (if possible large) of fish is taken from the catch. Each fish is measured, then the lengths are grouped into classes, for example, through 1-2-5-7, etc. cm , and it is calculated how many fish are in which class. For example, you might end up with a line like this:

Length 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

body, cm

Number 10 | 53 | 100 |120 ​​| 70| 5 | 0 | 0 | 5 | 50 | 80 | 70 | 90 | 20 | 5

individuals

Considering the above series, one can notice that in the sample taken there are no fish whose length would be from 60 to 80 cm. There are small and large fish in the sample, i.e. the sample taken includes young and old fish (meaning that the sample belongs to the same systematic group). The resulting series can be more visually represented graphically (see Fig. 63). The graph shows the same as the series, but the simplicity and clarity on the graph is incomparably greater. It is clearly seen that the fish catch is divided into two groups: the first has a body length from 10 to 60 cm, the second is from 80 to 150 cm. The first group is young fish, the second is adult fish. The same rows can be made according to the weight of the fish.

By grouping the fish in this way according to their body length, we are approaching conclusions about the age of the fish, but we are only getting closer, because the exact age of the fish taken remains undetermined; the growth rate of these fish has not been determined either.

There is a common expression: silent as a fish. However, with a smart approach and knowledge of some theoretical foundations, you can “talk” even a freshly caught pike. In particular, you can get fairly accurate information about the number of years she lived. It is necessary for ichthyologists to determine the age of fish for scientific research as part of their professional activities, environmentalists are concerned with this issue in terms of the impact of the environment on the population of a particular fish, employees of the fishing fleet are concerned about the economic benefits of the catch.

An amateur fisherman is rarely occupied with such global problems: usually his interests lie in the field of practice. For example, it is unreasonable to fry or dry an old pike, but to stuff a “veteran” or use it in the form of cutlets is the very thing. Yes, the number of lives can be roughly estimated by the size of the fish, but this method is very inaccurate. A well-fed fish and an individual on a half-starvation ration, with the same number of years lived, will be very different in size. Fortunately, there are much more accurate ways to study age. Ideally, they require the use of a microscope, but when fishing, only approximate data can be obtained by eye.

Determination of age by scales

The study of scales is the most common and reliable method of research in this direction. It applies to most. Its essence lies in the study of scales for the number of annual rings. The fact is that, ideally, every year of a fish's life is marked by the appearance of a new ring, according to the tree principle.

For research in the laboratory, a microscope is used: a fresh or specially prepared flake is washed with a weak solution of ammonia and placed between glass slides under the eyepiece. A significant increase is not necessary - it even blurs the picture. To obtain approximate data, the sharp eye of an experienced angler or his own, armed with a magnifying glass, is sufficient.

The disadvantage of the method lies in its dependence on a number of conditions. The number of rings on the scale is not always ideal for age. Additional, less pronounced rings may appear due to changes in the lifestyle or diet of the fish. For example, this is typical for the transition from fry to regular food, fasting periods and. In addition, the annual rings may be less than the years actually lived by the fish: for example, eel scales appear at 3-4 years of age.

Examination of bones and otoliths

To study the age of some fish species, the “scaly” research method is either uninformative or in principle inapplicable. For example, to determine the exact age of the river perch, ichthyologists use an integrated approach: the method of studying the scales described above is combined with the analysis of flat bones. To obtain objective data, the results of all studies are taken into account.

Usually for this purpose gill covers are used: the growth rings on them are no less pronounced than on the scales. Examination under a microscope is not carried out: the gill bones are large enough for an ordinary visual inspection (you can use a magnifying glass). The material for analysis is prepared simply: the bone is separated from the carcass, cleaned of soft tissues and dried. A prerequisite: the fish must be fresh - lying in formalin or rotten is not good.

In cod fish and flounder, the scales are very small and delicate, therefore, in addition to studying it, the age of individuals of these species is determined by otoliths(colloquially - ear stones). They are removed from the labyrinth, carefully degreased, and sometimes sanded to give maximum transparency. Large specimens are broken, fixed on a glass slide with a plastic mass, clarified and scrupulously examined visually. It is clear that this method is applicable only in laboratory conditions.

How to find out the age by the ray of the fin?

Another purely scientific technique used in the laboratory is the study of the ray of the fin. Ichthyologists and oceanologists widely use it when analyzing the age of sharks: the scales of marine predators resemble large sandpaper and are unsuitable for research. In the case of sharks, the ray of the unpaired fin is taken as material.

Among freshwater fish, this research method is the most informative for all breeds of sturgeons, as well as catfish. If in the case of sharks, annual rings are immediately visible, it is enough to remove and clean the beam, then for the above freshwater fish, this method of determining age is much more labor- and science-intensive. Preparation of a preparation for examination under a microscope is impossible without the use of a special machine and reagents: it is necessary to make the thinnest section of the pectoral fin ray, process it and fix it on a glass slide. The technique is very informative and accurate, but, unfortunately, unrealizable at home.

And in general, the main thing is not the number of years lived by the fish and not even its size: it is important that you caught it yourself. And after receiving a fishing zen, you can ask about the age of the catch - purely for the purpose of self-development!