How old are you eating grass?

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How old are you eating grass?

2018-09-13 00:25:41 180 ℃

When you eat boiled fish, pickled fish, steamed fish, braised fish, have you thought about it?

Every day, the aunts who buy food will pick good chicken, duck and fish and make delicious meals for their families. I often see how much they ask each other about the vegetables in the vegetable basket, and buy a few pounds of ribs to compare which dish is affordable today. I almost never see the aunts ask: "Hey! How old are you buying this grass fish?" It sounds horrible.

However, sometimes the problem of not adjusting is scientifically meaningful. The high life of the squid can reach a hundred years, short as silver fish but only a few months. Studying the age of fish not only provides an understanding of the physiological characteristics of the fish itself, but also provides a data base for the rational development of fishery resources.

In fact, as early as the 18th century, the scientific community identified the age of the fish's bone structure. Through the efforts of many researchers, many methods of identification have been developed. Now let's see these "fish age identification".

First, the scales of the fish scale

The traces of the years are carved on the scales. Look at the fish scales, the surface texture is sparse and sparse. This is because the body of the fish is uneven in the whole year, the spring and summer are strong, and the autumn and winter are gradually slow. Reflected on the scales, it causes periodic changes in the texture. For example, the scale texture of small yellow croakers is loose in the spring and summer seasons, and the belts are tight in autumn and winter. In the second year of spring and summer, the belts become loose, so the boundaries between the loose and tight cycles are obvious. Annual rings. Sometimes, the fish scales are transmitted under strong light, and you can see the obvious annual ring, just like the Supreme Lord of the Rings will show the devil's spell in the flame. Recording the number of annual rings, you can guess the age of the fish. If there are two annual rings, it can be regarded as 3 fish age (virtual age), and can also be classified as 2 fish age (real age). Different fish species have different shapes of scales. The more representative types are sparse (small yellow croaker) and cut (salmon, squid).

A(Sparse)

B(cutting type)

2, otolith calendar

the so-called otolith, It is a tiny crystal of calcium carbonate in the fish ear, which can be divided into approximately circular micro-ear stones according to shape and position; arrow-shaped arrow ear stones; star-shaped star ear stones. Although the otoliths are small, they cannot be ignored. They help the fish balance the body and perceive the sound.

Left: Yellow-lipped fish star otolith, right: large yellow croaker star ear stone

People are deeply interested in the otolith also quietly recorded the age information of the fish. Since the discovery of the annual rings on the otoliths in 1899, otoliths have been used as important materials for identifying the age of fish. Take out the otolith of the fish, select the appropriate type of otolith, and after treatment, observe and record the number of annual rings on the otolith from an optimal angle, and estimate the age of the fish. The number of annual rings in the figure below is 8, which can be regarded as 8 fish age.

Squid Star Otoliths (white dots indicate annual wheel position)

In 1971, It has also been found that the otolith has a daily round - a daily round - whereby one can establish a fish growth equation and use mathematical methods to calculate the growth and development of the fish. However, reading the day information is a more delicate job.

Echinococcosis otoliths day round

In addition to the above two identified fish ages In addition to the method, the researchers have established a number of identification methods, such as the age of the otolith to identify the age; the length of the body to estimate the age, and so on.

Despite the development of many methods of identification, there are still some regrets. In general, the accuracy of these methods is not high, and the operation is cumbersome. Here, we expect scientists to develop more accurate and simple identification methods. Perhaps, one day in the future, when the aunts buy vegetables, they will also include the age of the fish in the reference range, while the fishmongers’ stalls are written with “wild grass fish three years, seven months, six days, ten pounds”.

References:

Zhang Xuejian, Cheng Jiayu. Overview of fish age identification research. Marine Fisheries. 2009.31(1): 92-99

Li Chenglin. Fishology. Beijing: China Agricultural Press, 2002: 194-200

District Youjun, Liao Rui, Li Jiaer, et al. 4 species Comparison of Morphological Characteristics of Otoliths in Shishou Fish. Journal of South China Agricultural University. 2012.33(2):203-210

Shen Jianzhong, Cao Wenxuan, Cui Yibo, et al. The relationship between the weight of Otolith and age and its The role of age identification. Journal of Hydrobiology. 2002.26(6): 662-667

District Youjun, Liao Rui, Li Jiaer, et al. Using the ear stone to study the Pearl River mouth fish spawning and growth of the Taiwan Strait .2012.31 (1):. 87-88

author: Huang Xiaodong