Every fisherman should know how to determine the age of a fish. By age, you can detect all diseases and developmental disorders of any individual. Therefore, different specialists are engaged in research and breeding of fish. In 1684, A. Leeuwenhoek established that the years lived by each individual can be recognized by the concentric lines of the scales. Several centuries later, the German ichthyologist S. Hoffbauer described the structure of carp scales. According to his research, he determined that the annual rings formed on the scale plates show the exact age.
How to determine age by scales
Scales help determine how long an individual has grown over the previous year, how old the fish is and how intensively it has grown. The scales are examined under a microscope, magnifying it several dozen times. This is the most universal method by which the age of fish is determined. The plate of scales is covered with small rings that are similar to the annual rings of trees. They are used to determine the age of various mammals, as well as mollusks. Each ring is located along the entire perimeter of the scale and is equal to 1 year of life.
Unlike aquatic life, the age of land animals is determined by bones and teeth. The formation of annual rings on fish scales occurs in winter, but sometimes they appear in summer and spring. How to properly research them:
- Damaged scales should not be used. They must be whole and large in size.
- The scales are washed with alcohol.
- If you look at the plates under a microscope, you can see not only rings, but also various depressions and ridges.
Gill covers can be used instead of scales. They have markings from which age is calculated. It is much more convenient to work with them, since their size is several times larger than scales.
How do annual rings appear in fish?
Age, reproductive capacity, and growth rate are all calculated from the rings. Studying the plates allows scientists to conduct appropriate analyzes and monitor the population of each individual, monitoring the environmental situation. If you carefully examine each ring, you will see that it has a wide light ring and a dark narrow one. What do they mean:
- Light rings indicate that the individual was rapidly developing and growing. This growth rate occurs in April.
- If conditions for development were unfavorable, then dark, narrow rings appear. This happens in winter.
All favorable and unfavorable development conditions are displayed on the bones and scales of fish in the form of layers. These formations are their peculiarity, which representatives of this fauna possess. A separate plate grown over the course of a year shows the conditions in which the individual lived throughout this period. It appears under last year's scales. If you count them, you can determine the age of the fish.
In some species, rings do not appear. This is due to the fact that the formation of a cover of scales does not begin to occur immediately, but 30-40 days after the larva leaves the egg. Transparent scales appear first. A second layer of thicker plates is formed in the second year of life. It appears under transparent scales. The third layer grows in the third year. An individual that reaches 7 years of age will have 7 rings.
Calculating age using rings
To calculate the age of a fish, you need to prepare everything you need. For research you will need a notepad, pen and calculator:
- To enlarge the picture 20 times, use a magnifying glass or binoculars. It is often used by professional fishermen.
- The work is carried out on a table, having previously covered it with a white cloth. Tools used include a knife and tweezers.
- The carcass is inspected and a suitable area for research is selected. It is better to choose otolith or spine.
- The selected area is thoroughly cleaned. Remove all blood and mucus. The fish can be placed in a container filled with diluted alcohol. After 5 minutes, the carcass is removed from the solution, and the area under study is wiped with a dry cloth.
- A visual line is drawn from the central point of the carcass to the fin. 15 records are taken from this area.
- The scales located in the fin area are not used, as they are difficult to see. Choose only solid plates with an even shape.
- If a microscope is used for research, then the width of each sclerite is calculated using a scaled eyepiece.
- All numbers are written down in a notebook and then calculated. The final numbers are her age.
The external state of the scales shows what happened to the fish throughout its life. The fish spawn when the scales break off. Therefore, the broken plates are used to determine how often an individual produced offspring.
Determining the age of fish of various species
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 absolutely 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
06.02.2018
Determining age from bones
What to do and how to find out the age of a fish if its scales are damaged or completely missing. Professional fishermen will be able to tell the entire life story of the fish, even if the material is damaged. But beginners will not be able to do this. Therefore, it is worth conducting a study of gill covers, ear stones, skulls, pectoral fins or bones, which will tell how the fish lived throughout the year. Determination process:
- Gill covers, vertebrae or skull bones are placed in a container of water. The contents are boiled for 5 minutes.
- Then all elements are treated with salicylic alcohol and wiped dry.
- A thin, even cut is made on each bone.
Then the fragments are placed under a microscope and the growth rings are calculated. You can learn to determine the age of caught fish up to 2 months if you practice and gain enough experience.
Ways to calculate how old a fish is
There are several ways to do this:
- Examine scales
- Examine the bones
- Study external signs (color, etc.)
How to determine age by examining scales
Perhaps the most universal way to determine the age of a fish is to analyze its scales. To do this, you will need a microscope or magnifying glass that provides tenfold magnification.
Such an analysis can be compared to determining the age of a tree by its growth rings, but when examining fish, it is not necessary to saw it. When looking at the scales, you can notice small rings. Each of them is equal to one year. Very often they are called winter, despite the fact that they can appear at other times of the year, for example, in spring or summer. The habitat does not affect their appearance, so the age of any individual, be it river or sea, can be determined in this way.
With the help of magnifying devices, it is possible to determine the size of an individual in different years of its life. Let's imagine a fish one meter long with a scale radius of one centimeter. Let's say the segment running from the first ring to the center of the scales is six millimeters. Thus, it can be understood that at the age of one year the length of the fish was sixty centimeters.
Thanks to this, you can also see the growth rate. If the rings are close to each other, the fish grew slowly during this period of time. This also allows you to determine the presence of any diseases that have affected growth. Growth rates can also indicate how well the individual ate.
Identification by bones and cartilage
Thanks to the rapid development of ichthyology, scientists have managed to dispel many legends about giant, long-lived fish. For example, one of the most popular tales among scientists and fishermen was the story of a pike that allegedly lived for more than two hundred years and weighed about one hundred and thirty kilograms. Her skeleton was even displayed at scientific exhibitions. A more detailed study showed that in fact the skeleton was assembled from the bones of two representatives of the pike species. The purpose of the deception was to make a profit.
This is why it is necessary to have other options in stock for determining the life length of a fish. In a situation where determining age by scales is impossible, several other methods can serve as a solution. For example, conduct a study of auditory pebbles and gill cover.
Even if only bones remain, the number of years she lived can still be known. For each year that the fish swims, a stripe appears on its gill covers. Cartilaginous species also have their own annual rings. They are located on the rays at the base of the pectoral fins.
The lifespan of some species can be determined by cutting the otoliths. They are durable formations that appear at places experiencing mechanical irritation. At the cut site, all the rings are very clearly visible.
How to determine the age of an aquarium fish
A farmer who personally breeds fish is unlikely to encounter problems when determining age. In the end, it is he who must monitor their birth. As for aquarium fish, the situation is much more complicated. It is impossible to determine the age by eye - the scales are too small. Coloring and size are also not very suitable, since they are greatly influenced by environmental conditions such as temperature, food and much more. The following signs are characteristic of old fish:
- Dull scales;
- Lethargy;
- Weak appetite
- Reduced movement speed.
However, even these signs may indicate a completely different cause - illness. Over time, the color may become bright again, and the fish itself will return to its former prowess and appetite.
Long-lived fish
It is extremely important for ichthyologists to know the exact answer to the question “how to find out the age of a fish.” Knowing it, you can make many different predictions
For example, when to expect a population increase (many species reproduce every few years). For particularly interesting specimens, for example, those listed in the Red Book, scientists observe for years to accurately say when the fish will lay eggs.
It is especially difficult to say something about the age of long-lived species, of which there are many in nature. For example, the above-mentioned pike can live up to ninety years. Another good example is Kamchatka perch. The life record of this giant reached one hundred and forty years. There are also many rumors about catfish. It is rumored that they can live more than a hundred years, but in fact there has never been an individual who has lived more than forty.
What are sclerites
Sclerites (ridges) are formations that appear on the outer layer of scales. The formation of rings in some individuals occurs in the spring. But for bream living in the Aral Sea, this period falls in the fall, and for pike perch from the Azov Sea - at the end of July. Formation of sclerites:
- An increase in the size of scales occurs along with the growth of the fish. And since the individual develops differently, the size of the scales also becomes different. This difference manifests itself in the form of sclerites and various scars. They have an arcuate or circular arrangement.
- The gap between the sclerites and their width can be narrow or wide. Thin zones are formed during slow development (in cold climates), and wide zones (in warm climates) during intensive development.
- The annual ring is determined by the outer line of nearby sclerites (narrowed growth area).
- The additional formations that appear show how the life cycle of an individual has changed over the year. Sclerites occur due to temperature changes in water, feeding method, spawning and the frequency of migration. In the area of the first year's ring, one can often see the manifestation of a fry ring.
Different types of fish have their own shape and size of scales.
Determining the age of fish of different species
It is easier to find out the age of a fish at any time if it has narrow but long scales. Thus, it is much easier to find out 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. Under such conditions, you will need to take flat bones as an example. The age of sturgeon is determined by the huge rays of the dorsal fins. To do this, take the largest beam and cut it at its widest point. After this, the cut area is polished until transparent, after which it will be possible to notice the annual rings. Then, the age is calculated using the generally accepted method that is used for scales. This approach is used to determine the age of other fish species, for example, such as catfish.
In addition to these methods, there is another method that is based on the study of gills. Marks similar to those on the scales remain on the gill covers at the end of each year. Scientists have determined that, in addition, fish that do not have a skeleton have their own annual rings. Such rings are formed on the thick rays of the pectoral fins.
In order to find out the abundance of a particular species of fish, you need to understand how dynamically a particular type of fish begins. There are species that spawn quite late. If you take Amur salmon, they only begin to spawn at the age of 20. Even without that, if you take a walk through individual species, you can understand that any species begins absolutely independently of one another and any species lives for a certain period of time
For science, it is extremely important 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, the approximate age of the fish does not mean anything significant for them.
Calculating the age of aquarium fish
When purchasing aquarium fish at a pet store, you may receive false information about their age. Therefore, you need to learn to determine their age yourself. But doing this with aquarium fish is much more difficult than with river fish. Main signs of old age:
- poor appetite;
- dull shade;
- lethargy;
- the fish moves weakly in the water.
Housekeeping conditions greatly affect the size of the fish and its color, and the scales are too small to determine age. Therefore, all these indicators sometimes mean that the fish is sick. Its mobility and bright coloring can return at any time.
Ecological forms of perch
Any body of water more or less varied in bottom topography and size will be inhabited by two types of perches. The first ones, who from birth to old age will live near the coastline. The second group will be located in deep holes and dumps. At the same time, their food supply will differ significantly.
The diet of the coastal group includes mainly all invertebrates and seasonally young fish. The second group will start hunting for their fellow fish and other fish species early on. The calorie content of the feed will be different in both cases. And that means the growth rate. It may happen that a 15-centimeter perch and a one-kilogram humpback caught on the same day will turn out to be fry of the same season. And visually you can’t even tell that the age of the perch will be the same.
If the characteristics of the reservoir allow, then coastal and deep perch will be found. Even participate in reproduction. When a thermocline occurs in a reservoir, group meetings usually do not occur. Each lives its own life and reproduces in its own conditions. Races can meet during feeding. However, if the thermocline allows.
So it turns out that it is simply not possible to determine the age of a perch by size in centimeters and weight in grams. A fish weighing 200 grams may turn out to be 5-6 years old, or maybe one and a half years old.
