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. That's why scientific research allow 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 food and intensive 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 in winter, because 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, the sclerite circles begin to grow unevenly. Their width becomes different: in summer they are wide, and in winter they are narrow or completely absent. Bad and good conditions habitats 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 of 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 useful information, if a fish farmer decides to go to a pet store and buy rare fish, since sellers sometimes provide false 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:
- The fish is old and how long it has left to live is unknown.
- 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. Big fish caught by local fishermen, it was 120 cm long and lived for about 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 work of Russian scientists played a significant role in the development of methods for studying the age of fish. Works by V.K. Soldatov on studying the age composition of Amur sturgeons based on bones, studies by I.N. Arnold, N.L. Chugunov, E.K. Suvorov, G.N. Monastyrsky, N.I. Chugunova and others. They gave a lot both for the theoretical development of the issue and in the direct application of the method to solve practical problems.
The great importance of determining the age of fish for resolving fishery issues has led to the fact that recently a lot of material has accumulated in this area, both in foreign and Soviet literature, and there are many methodologically interesting studies (review of methods for determining age and rate fish growth is given in the book by N.I. Chugunova, 1959).
The main object for age determination Most fish have scales.
Collecting scales is simple. The scales are easily processed and in many species of fish - almost all salmon, herring, carp, cod and others - allow one to reliably determine age. Scales used for age determination fish, is usually taken under the base of the first dorsal fin and placed between sheets of notepad made of unglued paper; on the page on which the scales were placed, data is recorded about the fish specimen from which the scales were taken (length, weight, sex, place of capture, fishing gear, etc.). To determine the age, the scales, previously washed in a weak solution of ammonia, are placed between two glass slides and viewed under a magnifying glass or microscope, depending on their size. Delicate scales, such as those of cod, are sometimes best placed in glycerin-gelatin. It is not recommended to put scales into Canada balsam to determine age, because it becomes very bright and the annual rings become difficult to see.
In perch, burbot and some other fish, a good object for determining age is flat bones, such as the operculum and cleithrum. The visibility of the growth layers on bones is often no less distinct than on scales. The most reliable is to determine the age of the same fish, simultaneously carried out using both scales and bones, which serve as good control material. The method of preparing bones to determine age is very simple: the bone is cleared of meat, degreased and dried. As a rule, it is impossible to determine age based on bones collected from rotten fish or those lying in formaldehyde, since such bones usually become cloudy.
In cod and flounder, age determination is often made by otoliths - ear stones (Fig. 88), which are removed from the skull by opening the labyrinth. To determine age, otoliths must be degreased and, in some cases, slightly polished to make them more transparent. Relatively large otoliths (at least 0.5) are usually broken transversely, the otolith is inserted with its pointed end into a piece of wax or black plasticine with the break facing up and, moistened with an antireflective liquid (xylene, transformer oil, etc.), examined with the necessary magnification.
In sturgeons, catfish and some sharks (Acanthias), age is determined by the fin ray: in sharks - gypsy, in sturgeons and catfish - pectoral. Moreover, in sharks, rings are visible on the fin ray immediately after cleaning the ray; in sturgeon and catfish, it is first necessary to prepare a cross section of this ray, which is polished until transparent, and then glued to a glass slide with Canadian balsam, and in this form can be used to determine age. To prepare sections, a special machine was designed, consisting of two parallel machines; fixed round files driven by an electric motor. By adjusting the distance between the files, you can make cuts of varying thickness. Beam cuts can also be made using a regular jigsaw with metal files or an electric jigsaw.
Since the formation of the annual mark occurs as a result of changes in the growth rate, the question naturally arises whether “annual rings” could form several times a year, not only as a result of cessation of nutrition in winter, but also as a result, for example, of a hunger strike in winter. the time of spawning, transition from one type of food to another, more nutritious, etc. The main method of determining whether the number of rings on the scales corresponds to the age of the fish is to study the scales of fish whose age is known, or fish that have lived a certain time after their the first time scales were taken. As shown by the study of fish living for a certain number of years in ponds and aquariums, as well as the capture of fish previously tagged in open water bodies (salmon, cod, roach), the number of rings on the scales and layers on the bones corresponds, as a rule, to the number of years lived by the fish . True, sometimes additional rings do appear on scales and bones, the appearance of which is often natural and associated with a certain moment in the life of the fish. So, for example, some fish (dace, roach, etc.) have a so-called fry ring inside the first year ring, which is associated with the moment of transition of the juveniles from feeding on plankton to feeding on bottom organisms.
Often the accessory rings are not expressed in a circle, but only on one side of the scales, which makes them easy to distinguish from annual ones.
Many fish have spawning rings and marks on their scales, which are the result of cessation of feeding and exhaustion during spawning.
Spawning marks are of two types: Type I is observed in Atlantic and Caspian herring and salmon. It is formed by destruction of mainly the lateral sides of the scales and their subsequent restoration. Type II is observed in roach, bream and some other fish. It is formed in those species in which spawning weight loss is less pronounced. Destruction of the scales does not occur during spawning, only a slight change in the structure of the sclerites is observed, a “dark” sclerite or omission of sclerite is formed, and in its place a white shiny strip appears. Spawning marks in males are more clearly expressed than in females (especially salmon). Quite often they coincide with annual rings. For example, during spawning, the scales of Caspian herring begin to deteriorate, which leads to the formation of a certain deep mark on it. In salmonids, spawning marks are also clearly visible on the scales, having the shape of rings, but of a slightly different nature than annual ones. Moreover, in male salmon S"almo salar L. spawning marks are usually more clearly expressed than in females.
In the Cassius roach, by studying the scales of marked and re-caught fish, in addition to spawning and fry, three more types of additional spots were established, namely the 1st type, which appears when the growth of the fish is accidentally delayed, the 2nd type, which appears in case of change the nature of scale growth, and the 3rd type, formed along the break line on scales regenerating after mechanical damage.
The formation of annual and additional rings, as well as spawning marks, on the scales of fish is an adaptation that makes it possible to maintain the correspondence of the scale cover with the body shape that changes as a result of weight loss; Since the scales usually overlap each other in a tiled manner, the correspondence between changes in the shape of the body and the scale cover is achieved to a large extent due to the sliding of one scale over another. The rings and markings on the anterior and posterior edges of the scales are less clearly defined than on the sides, where the scales are adjacent to each other without overlapping and where, for example, during spawning, the greatest destruction of the scales takes place.
Naturally, the question arises whether the presence of additional rings on the scales, bones and otoliths of fish does not make the entire method of determining age using annual marks generally flawed, and what are the methods for distinguishing annual rings from additional ones?
Rice. 89. Scales of a three-year-old carp, treated with chloral hydrate and divided into plates corresponding to individual years of growth
nykh. A lot of work has been done to resolve this issue. In particular, V.V. Petrov and G.K. Petrushevsky (1929) tried to macerate carp scales and divide them into separate plates, each corresponding to a specific year of growth (Fig. 89). O. Vinge (1915) measured the width of individual sclerites on cod scales and plotted these values on graphs. From the number of apexes corresponding to the size of the widest sclerites, he obtained the number of annual rings; Although the additional rings gave some change in the size of the sclerites, it was less significant than the annual ones. Usually, to check the correctness of age determination, they use not just one object, but several, for example, if the determination is made by scales, then from some control specimens, in addition to scales, the bones of the gill cover are taken.
Along with the study of rings on scales and bones, it is also absolutely necessary to study the lifestyle of fish to identify patterns of its growth that could affect the growth of scales.
Knowing the moments in the life of a fish that can affect the growth of scales will allow, if there are corresponding rings on the scales, to treat them with great caution and it will be easier to identify their nature. The greatest difficulty is in recognizing the fry ring. Usually, in order not to confuse the fry ring with the first annual, in the fall several samples of fry of the species under study are taken, analysis of the size of which makes it possible to establish with certainty which ring we were dealing with - an annual or a fry. In general, as a rule, additional rings and marks of all types are less pronounced than annual ones, and with some skill they can usually be identified without much difficulty.
We examined cases when the number of zones on scales and bones is greater than the number years, lived by the fish, but it may also be that the number of rings on the scales and marks on the bones, on the contrary, is less than the number of years lived by the fish. This question is of particular importance when determining age by scales. Regenerated scales have fewer annual rings than normal scales. In addition, in some fish, such as the eel, scales are formed only in the third or fourth year of life, and, naturally, the number of annual rings on the scales is obviously less than the number of years the fish has lived and the number of marks on the bones.
As can be seen from the above, the listed deviations from the norm in no way reduce the overall value of the method of determining the age of fish by scales and bones. When using this method, all that is required is a careful analysis of the nature of the rings and an individual approach to each object being studied, and most importantly, taking into account the specific features of the ecology of the fish.
Question "How to determine the age of fish?" has long been of interest to scientists and, as it turned out, it is not so difficult to do.
If you examine the scales of a fish under a microscope or even under the most ordinary magnifying glass with tenfold magnification, you can easily see rings similar to the rings on a piece of wood. Each of the rings corresponds to 1 year of the fish’s life and is called “winter”, although in some cases it may appear in spring or summer. It is curious that these annual rings are also formed on the scales of fish in equatorial waters, as well as in fish living at great depths, although it would seem that they constantly live in unchanging climatic conditions. Therefore, the answer to the question “How to determine age and age is the same - the habitat has no influence on this.
fish in different years her life?
By the scales you can determine not only the age of the fish, but also the length that it reached annually. Let's say a meter has a radius of one centimeter. The distance from the first annual ring to the center of the scales is 6 millimeters. Consequently, at one year of age the fish was 60 centimeters long.
If, for example, you look at the scales of a salmon, you can easily notice that the fish grew very slowly during the first two years of its life. The inner growth rings are located very close to each other. Then growth accelerated noticeably. This means that the young fish went to sea from the river, where there was much less food. On the surface of the scales there may be traces of fish participation in spawning and transferred diseases. As a result, for a knowledgeable ichthyologist, a fish scale serves as a genuine passport, making it possible to find out the age, annual size, time spent in the sea, river and the number of spawns.
How to determine the age of fish that have no scales or are very small?
In this case, the necessary analysis can be done on the operculum, cross-section of the vertebra and auditory pebbles. Thanks to modern methods for determining the age of fish, many misconceptions about the extraordinary longevity of carp, pike and catfish have been dispelled. Although to this day, popular and educational literature mentions a pike that supposedly lived 267 years and reached a weight of nine pounds. The portrait and skeleton of this pike were shown in German museums for a long time. Later, a count of the vertebrae in the skeleton showed that it was assembled from the bones of two (or more) large pike and is the fruit of the creation of the enterprising ancestors of the well-known Ostap Bender.
And if we operate only with reliable data, then the maximum age of pike, catfish and halibut is 80 years, cod - more than thirty, beluga - about one hundred, oceanic herring - 25, carp - 20, pink salmon - 2, and Azov anchovy - 3. However, , cod at the age of 30 are rarer than 100-year-old people. Sea bass grows much slower than cod. The predominant specimens in the catches, about 40 centimeters long, are of a respectable age (up to 17 years!). As a rule, all fish grow very slowly. The increase in length of fish slows down over the years, and weight gain usually accelerates.
How to determine age sea fish by other signs?
He's good
determined by the bones: each year lived by the fish is indicated by a stripe on the gill covers. Ichthyologists have found that they even have annual rings. They are formed on thick rays that are located at the base of the pectoral fins. And in certain species of fish, age is determined by otoliths. When cutting it, the annual rings are clearly visible. Scientists are thinking very seriously about the question of how to determine the age of fish as accurately as possible, since this is of purely practical importance. To predict the abundance of a particular species, you need to understand the dynamics of that species. Large quantity fish reach sexual maturity quite late. Thus, Amur salmon spawns for the first time at twenty years of age. During this time, they are closely monitored, since even minor changes in their habitat can cause the death of the entire species.
So how to determine the age of fish?
It turns out that there is nothing complicated here, and there are many ways to do this. There are more complicated methods, and there are very simple ones that are accessible to any of us. You just need to arm yourself with a magnifying glass.
This is very interesting question, which 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.
There is another way by which you can find out a more accurate age of a fish, just as you can calculate the age of a tree from a cut using its annual rings. You can find out about this by the scales, if you examine them carefully, by the bones and gills. Specialists involved in this field know almost everything about fish: what age they are, how intensively they grew, how many times they spawned, etc. In other words, fish scales are like a business card, or more precisely, like a passport.
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. A dark ring forms when the fish is in cold water and practically 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.
Each year of a fish's life does not remain unmarked on the scales or fish bones. At first, the scale consists of a transparent plate. A year later, a second plate forms under it, which extends beyond the edge of the first. Then the third, then the fourth, etc. If the fish is about 5 years old, then its scales consist of 5 plates, one after the other. This arrangement is reminiscent of a layer cake, when the smallest but oldest plate is on top, and the largest but youngest plate is below.
How can you see the annual rings of fish?
It is very problematic to count or detect annual rings in fish, especially with the naked eye. Therefore, you need to have a magnifying glass or binoculars if everything happens on a pond. If you decide to deal with this problem at home, then it is better to arm yourself with a microscope. Before the process itself you need:
- Prepare the scales for inspection and, if necessary, wash them with alcohol.
- For inspection, it is better to take the largest scales, which are located on the sides.
- The scale should not have mechanical damage.
For more accurate calculations, it is necessary to take into account the absolute and relative size of sclerites. Under a microscope, annual rings, ridges and depressions will be visible. After several such approaches, it is possible to determine the age of the fish realistically and with great accuracy.
How is the age of a fish calculated?
Using scales and bones, you can determine with some accuracy the age of the fish or its growth a year earlier. To do this you will need a microscope and some tools. Based on the state of the scales, it is possible to determine what happened to the fish during spawning periods, for example. In some species of fish, when they go to spawn, their scales break off. Based on this factor, you can determine how many times the fish has already spawned in its life.
It is always easier to determine the age of a fish if it has thin but long scales. Thus, it is much easier to determine the age of pike, taimen, grayling, herring and many other species of fish.
It is much more difficult to determine the age of perch, burbot or eel. In this case, you will have to take flat bones as a sample. The age of sturgeon is determined by the large rays of the dorsal fins. To do this, take the largest beam and cut it at its widest point. Then the cut area is polished until transparent, after which the annual rings can be seen. After this, the age is calculated using the generally accepted method, which is applied to scales. This approach is used to determine the age of other fish species, such as catfish.
In addition to these methods, there is another method, which is based on the study of gills. Marks similar to those on the scales remain on the gill covers after each year. Scientists have determined that even fish that do not have a skeleton have their own annual rings. Such rings are formed on the thick rays of the pectoral fins.
To determine the abundance of a particular fish species, it is necessary to understand how dynamically a particular fish species develops. There are species that spawn quite late. If you take Amur salmon, they only begin to spawn at the age of 20. And so, if you go through individual species, you can understand that each species develops completely independently of one another and each species lives for a certain period of time. It is very important for science to know how long a particular species of fish can live in order to control the populations of certain species of fish. As for fishermen, for them the approximate age of the fish does not mean anything significant.
The scales of bony fishes consist of a fibrillar (collagen) plate having. a protein base on which a mineralized hyalodentine layer is located on top. During the growth process, one plate is formed, then a 2nd one, etc.
The healodentine layer is deposited on the scales in the form of ridges or sclerites. During the period of rapid growth, wide sclerites are deposited, and during the period of slow growth, narrow sclerites are deposited. Moved and brought together (wide and narrow) form the annual growth zone.
The annual ring is the boundary between narrow (winter) and wide (summer) sclerites.
Fry (fry become adults)
Downstream (a special case of fry) is typical for migrating fish
Spawning (during spawning (after spawning))
Salmon have a broken ring
The size of the scales, or its length, is measured along 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, measure the distance from the center to the top of the middle tooth.
Fishes of high and temperate latitudes, where abiotic conditions vary significantly throughout the year, as a rule, have fairly clear annual rings on their scales. Moreover, individuals caught between March and August in most cases have a dark (winter) part of the annual ring along the edge of their scales. Such age groups are usually called “year-olds” (two-year-olds, three-year-olds, etc.) and age is denoted by an integer (1,2, 3, etc.).
In fish during periods of intensive growth, a light part of the annual ring (“growth”) is observed along the edge of the scales. Age groups of fish caught in the autumn-winter period - until the completion of the establishment of the winter part of the ring - (from September to February) are usually called “letka” and the sign “+” is added to the digital designation of the whole number of years (young yearlings - 0+; two-year-olds - 1+; three-year-olds - 2+, etc.).
10. Methodology for determining the age of fish from bones, fin rays and otoliths.
Bones: Used by toads. covers, jaw bones, some integumentary bones of the head, vertebral bodies, urostyle.
Advantages: annual rings are viewed without preparing apparatus and without additional rings.
Disadvantages: laboriousness of freeing bones from tissues; Large amounts of space occupied; Difficulties in identification.
Perch – w/lid
Sturgeon, catfish – cuts of rays of pectoral fins
Cod, pollock, sea bass, catfish - by vertebrae
Otoliths – cod, ruffe, burbot, smelt, herring
Determination principles:
During the growth process, an opaque zone appears - not transparent, but with slow growth - transparent.
Methods: mechanical – grinding, cutting; chemical – soaking in 30% ammonia solution, calcination (for cod)
The age reading is made from the central part of the otolith, called the nucleus. The otolith core plus the first hyaline zone - the first year of life, the following opaque and hyaline zones - the second year of life, etc.
Using otoliths to determine age generally gives a more reliable result than using scales. However, it should be borne in mind that in some cases, especially in older fish age groups, the first annual ring is poorly defined, vague, and, by mistake, 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 mostly not closed.
