Question "How to determine the age of fish?" scientists have been interested for a long time and, as it turned out, it is not so difficult to do this.
If you look at fish scales under a microscope or even under the most ordinary magnifying glass with a tenfold increase, you can easily see rings similar to those on a saw cut. Each of the rings corresponds to 1 year of life of the fish 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 the age of river fish and the age of marine fish?" the same - the habitat does not affect this.
How to determine the size of a fish in different years of its life?
The scales can be used to determine not only the age of the fish, but also the length that it reached annually. Suppose a meter-long fish has scales with a radius of one centimeter. The distance from the first annual ring to the center of the scale is 6 millimeters. Therefore, at the age of one year, the fish was 60 centimeters long.
If, toFor example, consider salmon scales, you can easily notice that the first two years of life, the fish grew very slowly. The inner growth rings are very close to each other. Then growth accelerated markedly. And this means that the young fish went out to sea from the river, where there was much less food. On the surface of the scales, traces of the participation of fish in spawning and past diseases may remain. As a result, for a knowledgeable ichthyologist, a fish scale serves as a genuine passport, making it possible to find out age, annual size, time spent in the sea, river, and the number of spawning.
How to determine the age of fish that lack or have very small scales?
In this case, the necessary analysis can be done on the gill cover, transverse cut of the vertebrae and auditory stones. Thanks to modern methods for determining the age of fish, many misconceptions about the extraordinary longevity of carps, pikes and catfish have been dispelled. Although to this day in popular and educational literature they mention a pike, which 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, the calculation of the vertebrae in the skeleton showed that it was assembled from the bones of two (or more) large pikes and was 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 age limit for pike, catfish and halibut is 80 years, cod - more than thirty, beluga - about a hundred, oceanic herring - 25, carp - 20, pink salmon -2, and the Azov anchovy - 3. However, cod at the age of 30 is less common than 100-year-old people. Sea bass grows much slower than cod. Specimens prevailing in the catches, about 40 centimeters long, have a respectable age (up to 17 years!). As a rule, all deep-sea fish grow very slowly. The growth of fish in length slows down over the years, and weight gain usually accelerates.
How to determine the age of marine fish by other signs?
is determined by the bones: each year lived by the fish is indicated by a stripe on the gill covers. Ichthyologists have found that even cartilaginous fish have annual rings. They form on thick rays that are located at the base of the pectoral fins. And in some species of fish, age is determined by otoliths. When sawing it, annual rings are clearly visible. Scientists are very seriously thinking 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 the development of this species. A large number of fish reach sexual maturity rather late. So, the Amur salmon spawns for the first time at the age of twenty. During this time, they are closely monitored, as 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 difficult methodsthere are very simple ones available to any of us. You just need to arm yourself with a magnifying glass.