As the second largest lake in Tibet, why not develop it?

As the highest plateau in the world, the Qinghai-Tibet Plateau is called the "roof of the world". Most of the Qinghai-Tibet Plateau is located in Tibet, especially in the Ali area of Tibet, where the Himalayas, Gangdise Mountains and Karakorum Mountains meet, and it is called the "ancestor of thousands of mountains". Its average elevation is also the highest in Tibet, so it is also called the "roof of the world".

In addition to numerous high-altitude mountains, Tibet is also very rich in water resources, with about 3,700 freshwater lakes with a total area of 3,700 square kilometers and 3 15 saltwater lakes with a total area of about 1.68 million square kilometers. Among so many saltwater lakes, Selinchuo Lake has the largest area, the second largest in China and the largest in Tibet, with an area of 239 1 square kilometer, and the Namtso we are going to talk about today is second only to Selinchuo Lake. Namtso is located in the middle of Tibet. The whole lake is an irregular rectangle, 70 kilometers long from east to west and 30 kilometers wide from north to south, with a total area of 65,438+.

The storage capacity of Namtso is as high as 76.8 billion cubic meters, and the deepest part of the lake can reach 1.20 meters. The lake is clear, and large schools of fish can often be seen swimming in it. According to the estimation of Tibet Fisheries Bureau, the annual sustainable fish production in Namtso can reach 2,000 tons. However, despite this, the fish in the lake are still "indigenous fish" and no fishery culture has been developed so far. Why?

Fish resources in Namtso

Namtso Tibetan means Tianhu, and together with Yang Zhuo Yongcuo and Mabian Yongcuo, it is called the "three holy lakes" in Tibet. The reason why Namtso can become a saltwater lake is closely related to the characteristics of its closed lake. Its water source mainly comes from precipitation and melting glaciers and snow-capped mountains.

However, because the dry season here lasts for half a year (165438+ 10 to May of the following year), and the annual illumination time exceeds 65%, the wind is strong all year round, so the research institute

Although the fish resources in Namco should be rich in terms of annual sustainable catch, there are actually very few fish species in this great lake, only two kinds of fish: naked carp in Namco and plateau loach with different tails. Among these two kinds of fish, Naked Carp Namtso has the largest catch, accounting for 9 1.46%, while Misgurnus heterocaudatus only accounts for less than 9%.

Among them, the naked carp Namtso is a subordinate fish of Cyprinidae, and it is also a unique fish in China. Only distributed in Namtso, Tibet. It is a medium-sized Cyprinidae fish, with an average body length of about 28 cm and a maximum length of 38 cm. It is the most important economic fish in Namtso.

Alpine loach belongs to the genus Alpine Loach, which is the main dominant fish in many water bodies in plateau area. But in comparison, they are relatively small, with an average body length of about 7 cm, belonging to benthic fish. Because of their small area and low economic value, they account for a relatively small proportion in Namtso fishing.

So, why can the annual catch of two kinds of fish reach 2000 tons? In fact, this has little to do with human interference. First of all, Namtso's location itself is far away from residential areas. Secondly, Namtso belongs to a holy lake in Tibet, but few locals go fishing in it. The most crucial point is that Tibet is mainly nomadic, and there is less demand for fish. Therefore, combining these three factors, Namtso has only two kinds of fish, but it has also achieved the effect that fish can be seen everywhere.

Why doesn't such a big lake develop fishing?

When it comes to winter fishing, the first thing people think of is winter fishing in Chagan Lake. Every winter, there are more than 3 million Jin of fish caught in Chagan Lake alone, which is almost the same as the annual catch of Namtso estimated by Tibet Fisheries Bureau. However, the area of Chagan Lake is only 345 square kilometers, with a storage capacity of about 600 million cubic meters, compared with the area of 1, 966,5438+0 square kilometers and 76.8 billion.

It can be seen that Namtso has the potential to develop fisheries, but it has not been developed so far. Why? Let's talk about it from the following five aspects.

First: resource constraints. As a lake at high altitude, Namtso has clear water quality, but the resources in the lake are also very limited. The resources that fish depend on are mainly plankton (plants and animals), but there are only 26 species of phytoplankton in Namtso, and the density is relatively small, with only a few species. In some areas, there are not even zooplankton in the lake samples collected.

It is precisely because of the limitation of resources that the fish species here are very rare, and the fish are not big, and these resources are only enough for these two native fish to survive. Other fish will face food shortage when they enter.

Second: environmental factors. Namtso is the largest lake with the highest altitude in the world. The higher altitude makes the temperature here relatively low, especially in winter, and the ambient temperature is lower than 10 degrees Celsius, which makes most economic fish flinch. After all, these farmed fish have poor adaptability to environmental changes.

Third: pollution. Lack of food resources is not a problem for aquaculture because feed can be fed. However, feeding feed pollutes the water body to a certain extent, and fishery farming will inevitably use drugs, which will cause great pollution to the lake in Namtso, plus the status of the sacred lake.

Fourth: Threatening native fish. It is very cautious to introduce fish into wild water bodies, because this may lead to the reduction or even extinction of local fish. As two protozoan species that survive in extreme environment, the fish in Namtso are likely to be affected when introducing new economic fish. After all, they are not superior to most economic fish in size.

Moreover, at present, the fish in Namtso are also under protection and have entered the fishing ban period. As early as April this year, two men were arrested for illegally fishing naked carp in Namtso, and were finally sentenced and compensated for ecological restoration costs.

Because of the lack of aquatic resources, how do two kinds of fish survive in Namtso?

Fish can't live without aquatic life, especially ephemera. Bottom fish feed on plankton. Only when there are a certain number, some predatory fish can survive, because Namco actually has no predatory fish, only two kinds of bottom fish, alpine loach and naked carp, feed on plankton. However, the lack of aquatic organisms also makes their survival more difficult. Fortunately, both kinds of fish are.

The first is to lengthen the growth cycle. Less biomass means less food, so both kinds of fish grow slowly. Take naked carp as an example, they will not mature sexually until at least 5 years old, and during this period, their body length grows very slowly. For example, the average body length of 5-year-old naked carp is only about 17 cm, and after 5 years, the average body length of 10 naked carp is only 30 cm, and the body length of 5-year-old naked carp is less than 17 cm.

The second is reproduction. In order to survive this food test, the survival of the fittest is essential, so it challenges the reproductive ability of fish. Let's take naked carp for example. The average number of pregnant eggs of 5th instar females is 6500. With so many eggs in a closed water body and no predators, their hatching rate is very high.

In this way, there will be enough offspring to survive the fittest, so that the population can continue.

Although there are a certain number of fish in Namtso Lake, the species are very rare, which is caused by its relatively harsh environment at high altitude. At the same time, this environment also makes the biomass in the water body very low, which is not enough to feed more fish. Therefore, although Namtso Lake is large, it has not been developed so far.