Ichthyologists quite often should determine the age of the fishes caught from natural reservoirs. Knowledge of exact age of fish is necessary to understand at what age the caught food fish receives ability to reproduction, how well it grows what fish of age meets in catches of fishermen most often.
Instruction
1. To learn age of fish, attentively consider rings on her scales, and if necessary for their more exact analysis use viewing by means of a magnifying glass or a microscope. As scales at fish appear at a whitebait stage, and then grow within a year rather unevenly, on them there are congestions of fabrics in the form of concentric grooves in the place where the scale "grows" into skin of the considered small fish. Attentively consider scales of the studied fish, and by the form you almost unmistakably determine her age. As a rule, at fishes coevals all scales are thin also translucent, and concentric rings appear only at the fishes who already endured winter.
2. Study concentric circles on scales, wishing to determine the age of fish and to understand how many years to the small fish considered by you. As in the winter of fish hide in benthonic sand, bury in clay and silt, at the basis of scales the raid which then is noticeable in the form of hardly noticeable concentric circle accumulates. Count quantity of such concentric circles, and you without effort learn age of fish, at the same time the lack of such circles demonstrates only the fact that the small fish studied by you is only a yesterday's whitebait which had not to winter in a reservoir yet.
3. Carry out determination of age fish not only the analysis of concentric circles on scales, but also consider density of scales. Annually at each small fish under old scales appear new, a little acting by the size from under them. So, at two-year-old fish you will see dual scales, at three-year-old fish – stroyenny scales. And the small fish studied by you is more senior, the more will be at her such scales. Study at a food fish – the size of otolit are firm formations which are responsible for orientation of a small fish in space. And the these formations are more dense, the studied fish is more senior.
4. Apply to exact determination of age of a food fish also other methods of the analysis, studying the received results in total. So compare the size of otolit directly proportional to age of a food fish, to the rigid consolidations located on a back fin of the studied fish. Count quantity of color rims on scales of fish to understand how many times to such small fish were necessary to winter in a reservoir, and the cumulative analysis taking into account all methods will help you to determine the age of fish most precisely.