Measures to improve the Survival rate of Rana chensinensis in overwintering period

There are mainly Chinese forest frog (Ranachensinensis) and Heilongjiang forest frog (R.amurensis) in China, which are widely distributed in the three provinces of northeast China. Because of the unique nutritional and medicinal value of forest frog, especially frog oil is popular in domestic and foreign markets, there is a wide gap between supply and demand. Zhao Zhenhuan of Shanghai Fisheries University first put forward the idea of southward breeding of Rana chensinensis in the 1950s, and carried out growth and reproduction experiments in the natural environment of 31 ^ 0 north latitude and 122 east longitude in the suburbs of Shanghai. Over the years, many people have carried out basic research in this area. Wang Shoubing of Fudan University studied the effect of temperature change on the embryonic development of Rana chensinensis. The results showed that Rana chensinensis had a strong tolerance to temperature change during embryonic development, and the change of temperature in spring in southern China would not seriously affect its embryonic development. Jiang Chaoguang of Fudan University studied the nutritional requirements of Rana chensinensis in tadpole stage and preliminarily determined the feed ratio in tadpole stage of artificial culture of Rana chensinensis. The above results provide a theoretical basis for the artificial culture of Rana chensinensis in the south.

L medicinal value

Oviductus Ranae, the fallopian tube of female forest frog, is a valuable traditional Chinese medicine, especially Chinese forest frog and Heilongjiang forest frog. The protein content of Oviductus Ranae is 76%, which contains more than 20 kinds of amino acids, followed by fat and sugar. In addition, there are a variety of minerals: calcium 5.75%, phosphorus 0.O52%, iron 1.465%, potassium 16.52%, sodium 3.56%; rich in vitamin A, B, C and a variety of hormones, containing 347 calories / 100g. The main active ingredient of Oviductus Ranae is frog alcohol, which has the effect of tonifying kidney and nourishing essence, moistening lung and nourishing yin. It specializes in the treatment of kidney deficiency and qi weakness, energy depletion, memory loss, women producing blood, postpartum lack of milk and neurasthenia. According to traditional Chinese medicine, it can treat "infantile red qi, swelling and umbilical injury, pain relief, qi deficiency, poor labor, detoxification, diuresis and detumescence, and fatigue cough." it has the special effect of nourishing the lung and kidney.

two。 nutritive value

Forest frog can be called a delicacy, and it is actually an animal resource with high economic value for both medicine and food. Its products are very popular in the international market, especially in Hong Kong and Southeast Asia, enjoy a high reputation, high sales price, is one of the important commodities in the export of medicinal animals in China. The main product of forest frog is Oviductus Ranae. At present, the domestic market is 2000 RMB3000 / kg. Frog meat and seeds, the by-products of forest frogs, are delicacies on the table, and their internal organs and bones can be used as feed.

3. Ecological benefit

According to statistics, one forest frog can prey on more than 30,000 various pests a year. It feeds exclusively on active insects or worms. Through gastric examination, it is found that there are 6 classes, 13 orders and nearly 60 kinds of food in the stomach of forest frogs, mainly insects. The main species are Coleoptera, Orthoptera, Homoptera, Diptera and Hemiptera, followed by Araneae, Araneae and snails. Forest frogs mainly live in coniferous and broad-leaved mixed forests, and forest pests can meet a large amount of food for their growth. The forest frog is insatiably greedy and almost indiscriminately catches all the insects it can, so the forest frog is also known as the "forest guardian", especially for the control of larch caterpillars in forest areas, which has important ecological significance.

How to improve the Survival rate of Forest Frog in overwintering period

The northern winter is long and cold. Under harsh environmental conditions, the overwintering of Chinese forest frog in the northern mountain area is mainly in the water area. During the overwintering period, the physiological changes such as the decrease of metabolic intensity, the number of respiration, the slowing of heart rhythm and the contraction of blood vessels and microvessels make the oxygen consumption of forest frogs decrease month by month, which is beneficial for forest frogs to spend the severe winter in water. However, there are many unfavorable factors that affect the safety of forest frog to survive the winter. under the condition of being frozen for a long time, the internal changes of the water body must be completely different from those before freezing. With the decrease of air temperature and the thickening of ice sheet, the water temperature gradually dropped to 0 ℃, and the amount of water decreased due to freezing and infiltration. Due to the decomposition of organic matter and the respiration of frogs, fish and other organisms, the oxygen content in the water continues to decline, while the carbon dioxide content continues to rise. The changes of these environmental conditions pose a serious threat to the forest frog overwintering. Therefore, efforts must be made to improve the survival rate of forest frogs during overwintering.

First of all, it is necessary to make preparations for the forest frog before overwintering. For example, if the newly built overwintering ponds make use of the original dams and puddles to survive the winter, the dams should be deepened and silt and weeds should be removed as far as possible so as to reduce organic oxygen consumption and prevent harmful gases from occurring.

Secondly, it is necessary to meet the need of dissolved oxygen in the overwintering period of forest frog. There are two sources of dissolved oxygen in water: one is that the oxygen in the air is dissolved in water, and the other is that the photosynthesis of aquatic plants produces oxygen. However, after the water surface is frozen, the contact between water and air is cut off by ice, the oxygen in the air cannot be dissolved in water, and the source of dissolved oxygen replenished by air is cut off. Many overwintering ponds have no aquatic plants. Even if there are aquatic plants, due to the thickness of mountain ice and black ice, directly affect the photosynthesis of aquatic plants, it is impossible to rely on the photosynthesis of aquatic plants to produce oxygen. Therefore, the main cause of death of overwintering forest frog is asphyxiation due to hypoxia.

According to many years' observation, the problem of living water overwintering pool is not big, because the natural running water is continuous, the dissolved oxygen in the water is replenished in time. Therefore, the phenomenon of mass death of frogs will not occur in winter.

At present, most of the overwintering ponds for raising frogs are stagnant (also known as stagnant) overwintering ponds. In winter, the water source dries up, there is no living water flowing through the overwintering pool, the dissolved oxygen can not be replenished, and the decreasing rate of oxygen content in the water increases month by month. By January, the oxygen content in the water is only 4 mg / L water (the normal overwintering requirement of forest frog is 6 mg / L water). Especially the frog overwinters at the bottom of the water, and the anoxia in the pool water often starts from the bottom, and the amount of dissolved oxygen in the water is more and less, which is a great threat to the frog during the overwintering period.

To solve the problem of insufficient dissolved oxygen in the overwintering pond, the following three methods can be adopted: first, the water storage capacity of the overwintering pond should be sufficient, the Autumn Equinox should be full of water before and after, and the water depth is not less than 2.5m. According to the requirement of 150 overwintering frogs per square meter, the water surface area should not be too small. The size of the water surface can be 1000 eggs per year, and the water surface area of the overwintering pond is about 1 mu. Second, when frogs and fish are overwintering in a pond, because frogs and fish compete for oxygen, the amount of overwintering fish should be controlled at 0.2 kilograms of 1 cubic meter of water, which is half lower than the normal amount. And try to get rid of wild miscellaneous fish in order to reduce oxygen consumption. Third, the whole overwintering period should be carefully managed and the overwintering situation of frogs should be observed regularly. Because aquatic animals are very sensitive to hypoxia, aquatic insects such as Cyclops, pine algae, water axes and aphids can be seen near ice eyes during severe hypoxia (such as dissolved oxygen falling below 3 mg / L of water). Therefore, when opening the ice eye, observing whether the aquatic insects are upstream can be used as a sign to infer the amount of dissolved oxygen in the water.

In case of severe hypoxia, the following measures can be taken:

One is to inject water to replenish oxygen. Draw nearby water sources (wells, rivers, reservoirs, springs) and inject them into the overwintering pool. The second is to use ice holes to replenish oxygen. The ice eye is in deep water, and an ice hole with a width of 1.5 meters and a length of 3 meters is made on one mu of water. Discharge along the main wind direction, through the role of the wind to form water waves, accelerate the dissolution of oxygen into the water, in order to improve the effect of oxygen supplement. In order to prevent the ice eye from freezing again, grass curtains can be used to cover it at night.