Brachymystax lenok(Pallas

Brachymystax lenok (Pallas,) is a relic species that migrated from the north to the south during the Ice Age and is a cold-water foothill fish.

Brachymystax lenok feeds actively all year round. It mainly feeds on invertebrates, small fish, etc., and also preys on frogs and small rodents. It is extremely voracious, and the food in its stomach can account for about 10% of its own body weight. It can even prey on fish that are 1/2 the size of its own body. The time of the day when its appetite is strongest is in the morning and evening, and the rest of the time it hides in the shaded water bottom on both sides of the stream. The appetite is particularly strong after spawning. It usually hibernates in the deep water areas of rivers. The feeding time is mostly concentrated around morning and evening, and the feeding activities are frequent on cloudy days and can be seen all day long.

The initial sexual maturity age of the fine-scaled fish is 3+~5+ years old. Sexually mature individuals spawn in February-March, and the spawning grounds are mostly in shallow water with gravel bottoms. The spawning water temperature is below 10℃. The absolute egg carrying capacity is 2670-4510 eggs. The eggs sink and are discharged at one time. Females mature at 4 to 6 years old, while males mature earlier. They spawn once a year. They migrate upstream to spawn when the ice thaws in early spring. The spawning grounds are generally located in rapids with a depth of 1 to 1.2 meters and a gravel bottom. The spawning period is in late spring and early summer, with a water temperature of 8 to 12°C. The absolute fecundity is 1,629 to 7,420 eggs. Parents build spawning beds during spawning, and a large number of them die after reproduction, especially males. The eggs are sinking, light yellow, and about 4 mm in diameter. They develop more slowly under low water temperatures. It takes 50 days for the embryo to develop at 3.5°C, 45 days at 5°C, and 20.5 days at 11°C. The fry can only eat 12 to 15 days after hatching.

Common individuals of fine-scaled fish are mostly around 150 mm, and the largest can reach 450 mm. Due to the extremely backward fishery production in the production area, the phenomenon of poisoning, electrocution and blasting is very serious, resulting in a sharp decrease in the amount of resources in the densely populated areas below 1,200 meters above sea level. Most of the immature individuals that can be seen are 2-3 years old. There are still a certain number of them in the sparsely populated areas above 1,200 meters above sea level. Due to the dual influence of natural and human factors, the ecological environment of wild fish such as Qinling salmon in Zhangxian, Minxian and Weiyuan counties is deteriorating day by day, and the situation they face is worrying. On the one hand, with global warming and indiscriminate reclamation and logging, the grassland and forest vegetation have suffered serious damage, water resources have been sharply reduced, many streams and mountain springs in the territory have dried up, the water volume of rivers has decreased, the spawning sites of fish such as Qinling salmon have been destroyed, natural reproduction has been affected, and the number of survivors has been significantly reduced. On the other hand, driven by economic interests, there has been indiscriminate fishing and over-utilization of resources. Some farmers have used electric fishing devices to search for fish, and foreign merchants have purchased them at high prices, which has seriously damaged the wild fish resources such as Qinling salmon. The population is shrinking, and the reproductive parents are showing a trend of degeneration, developing in the direction of miniaturization and younger age.

In 2004, with the approval of relevant departments, the Qinling Salmon Nature Reserve in Zhang County was established. It is the first municipal nature reserve in Dingxi City. The reserve belongs to the nature reserve of wild animals. The reserve covers an area of 2,164.4 square kilometers, with a core area of 900 hectares, a buffer zone of 2,240 hectares, and an experimental area of 150 hectares. The reserve has a management station, which is under the management of the Zhang County People's Government. Zhang County has established a unique "Qinling Salmon Domestication Field" in the reserve.

The fine-scaled fish is a national second-level protected aquatic wild animal, and has important academic research value in ichthyology and zoogeography. Qinling fine-scaled salmon grows fast, has tender meat, no intramuscular spines, tastes delicious, has the function of preventing blood clots and accelerating wound healing, and is also called brain gold, with high nutritional value. It was a tribute to the court in the Song Dynasty. It is better than the "rainbow trout" produced in California, USA, and was listed as one of the precious resources in Dingxi in 1981.

There were no significant differences in the moisture (81.27%, 79.54%), crude protein content (13.08%, 13.76%), crude fat content (3.73%, 4.09%), and ash content (1.29%, 1.61%) of the muscles of male and female mullets (P>0.05); there were no significant differences in the total amino acid content (TAA), the total essential amino acid (EAA), and the total flavor amino acid (DAA) content (P>0.05); there were significant differences in the methionine content (P<0.05). The EAAI score of female fish (80.69) was slightly lower than that of male fish (82.47). The amino acid scores (AAS) and some chemical scores (CS) of most essential amino acids of male and female slender-scaled fish were greater than 1. The AAS of tryptophan and valine, and the CS of tryptophan and methionine + cystine of male and female slender-scaled fish were the lowest, becoming their respective limiting amino acids. The saturated fatty acid (SFA) content and monounsaturated fatty acid (MUFA) content of female fish were slightly lower than those of male fish, while the polyunsaturated fatty acid (PUFA) content was slightly higher than that of male fish (P>0.05); there was a significant difference in the C17:1n-9 content of male and female slender-scaled fish (P<0.05). This shows that slender-scaled fish is rich in nutrition.

        Listed in the second level of the List of Wild Animals Under National Key Protection in China.

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Qinling Slender-scaled Salmon is unique to China and is only distributed in the upper reaches of the Weihe River and its tributaries and the upper reaches of the Hanshui River and Ziwu River, which are tributaries on the north side of the Han River.
It lives in mountain streams at an altitude of 900-2300 meters in the Qinling area. The water is fast-flowing, clear, and the bottom of the water is mostly large gravel, rich in dissolved oxygen, and the water temperature does not exceed 20℃ all year round. In late autumn, it hibernates in deep pools or deep troughs of rivers. Except during flood season, it is rarely seen in the main stream of the plain.

The body is long and fusiform, slightly flattened laterally. The head is blunt, the back of the head is broad and flat, and the center is slightly convex. The snout is not protruding or slightly protruding. The mouth is terminal, the lower jaw is slightly shorter than the upper jaw, and the rear end of the upper jaw reaches below the center of the eye. There is a row of sharp teeth on each of the upper and lower jaws, the vomer and the palatine bones. The tongue is thick and free. The gill openings are large, lateral, and reach forward to below the center of the eye. The body is covered with fine scales, and the head is scaleless. The lateral line is complete and relatively straight. The dorsal fin is short, with a slightly concave outer edge; the adipose fin is opposite to the anal fin; the pelvic fin starts from below the middle of the dorsal fin base, extends backwards but does not reach the anus, and has a long axillary scale at its base; the caudal fin is forked. There are 65-75 p