CATDOLL : CATDOLL: What is the reason for the good quality of fish? What is the reason for the growth and reproduction of fish?

1. What is the reason for the good quality of fish?

Fish is an important part of people's daily diet. It has high nutritional value and is therefore loved by people. There are many varieties of fish farming in my country, and the farming area is also very large. As we all know, good quality fish sells for a high price, so what factors affect the quality of fish? Today, let's take a look at the four major factors that affect the quality of fish.

fish

1. Fish species

1. Different species of fish have different protein and fat content in their muscles, different meat structures, and large differences in price.

2. Different species of fish have different contents of amino acids that make up the protein in the fish meat, such as lysine, arginine, glutamic acid, aspartic acid, alanine, etc., and the taste is also different.

3. The types and proportions of fatty acids in fish fat, especially the proportion of docosahexaenoic acid (DHA), also vary, resulting in different tastes of fish.

4. DHA is a natural melatonin and an essential nutrient for the human body. Fish with high DHA content include tuna, bonito, salmon, mackerel, etc.

5. The content of the above-mentioned amino acids and DHA in the muscles of marine fish is higher than that of freshwater fish, so marine fish tastes better than freshwater fish.

6. In aquaculture, the selection of breeding species must meet the following conditions: choose suitable breeding species based on the local breeding environment and climatic conditions; examine whether they have market development prospects; the selected breeding species must not have any difficulties in terms of seedlings, feed, etc.; be able to master the feeding and management techniques of the breeding species, and invite breeding experts for regular guidance, etc.

2. Aquaculture water environment

1. Aquaculture requires sufficient water resources, fresh water quality and no pollution.

2. First, establish a farm in a place with sufficient water resources, up-to-standard water quality, convenient irrigation and drainage, and convenient transportation. Secondly, cultivate good water quality. During the breeding process, pay close attention to changes in water temperature, transparency, dissolved oxygen, pH value, etc. to ensure that the water quality always remains rich, active, tender and refreshing.

3. Feeding

1. Feed is the material basis for farmed fish to survive. The balance between protein, fat, carbohydrates and vitamins in the feed is crucial. Fish eating high-quality and fresh feed can improve their physiological state and immunity, and increase their survival rate. Fish farmed in this way have good color, normal body shape, strong vitality, firm fish meat and good taste.

fish

2. Feed feeding: select palatable, high-quality, fresh feed according to the physiological characteristics of fish, and strictly follow the four principles for scientific feeding; adjust the feeding amount in time according to weather conditions and fish feeding conditions; make full use of the breeding space of the water body, adopt a mixed breeding method of multiple varieties, rationally use the natural bait and artificial feed in the water body, improve the breeding water environment, and improve the breeding efficiency.

4. Use of fishery drugs

1. In the process of aquaculture, when cleaning ponds and disinfecting, seedlings and feeding tools, and adjusting water quality, the selection of fishery drugs should be scientific and reasonable, and special attention should be paid to the usage and dosage to prevent the quality of farmed fish from being affected by improper use of drugs.

2. The use of fishery drugs should be based on different aquaculture species and different pathogenic factors. Appropriate national standard fishery drugs should be selected, and treatment should be carried out according to the prescribed dosage, usage method, and course of treatment, and the regulations on drug withdrawal periods should be strictly implemented.

3. In breeding, we should start from the nutritional needs of animal growth, feed hygiene, breeding management and other aspects to reduce the occurrence of diseases and ensure human food safety.

The above are the four major factors that affect the quality of fish. Different species of fish have different nutrition, taste and market demand. Before breeding, we must consider our actual situation and choose a suitable species. During the breeding process, we must ensure that the feed and water sources are clean and hygienic, and do a good job of disinfection and disease prevention to improve the quality of fish.

2. What are the reasons for fish growth and reproduction?

1. Oviparous. This is the reproduction method of most fish. The fish expel the eggs from the body, and the embryos develop completely outside the body. The nutrients are provided by the eggs and have nothing to do with the mother's nutrition.

2. Ovoviviparity: The fertilized egg develops in the mother's reproductive tract, and its nutrition is provided by the yolk, which has nothing to do with the mother's nutrition.

3. Viviparity. The fertilized eggs of some fish develop in the mother's reproductive tract, and the embryos are connected to the mother's blood circulation. The development of these embryos is not only nourished by the yolk, but also related to the mother's nutrition.

Extended information: In order to breed excellent fry, you must choose healthy broodstock with excellent color, fins and size for breeding. Special care, close attention to water quality changes, live bait, or occasional feeding of fish grass can breed the best fry. Some fish have special requirements for water quality conditions when breeding. Be careful to prevent broodstock from swallowing their own eggs or fry. Fish lovers can estimate the number of fry based on the smooth spawning situation and provide enough food for the fry.

3. Why is there so much fish species?

“The sea is wide enough for fish to leap, and the sky is high enough for birds to fly.” The sky is the territory of birds, and the water is the world of fish. Why can fish dominate and thrive in the vast ocean and lakes? Because nature has endowed them with the ability to live in water.

Due to the influence of various environmental conditions in the water, fish have various appearances. But the fish that live the best and have the largest number have a spindle-shaped body. The streamlined spindle shape can greatly reduce the resistance when swimming in the water. The surface of a good body shape often has a layer of slippery liquid, which is the mucus secreted by the fish skin. This mucus is evenly applied to the fish scales, making the streamlined surface like a lubricant, reducing the friction between the fish body and the water during movement. There are multiple fins on the trunk of the fish, which are the fish's movement organs. There are paired pectoral fins and pelvic fins, as well as unpaired dorsal fins, anal fins and caudal fins. These fins are combined with muscle contraction and keep paddling, just like a propeller installed on the fish body, pushing the fish body forward continuously. Each fin has a division of labor. The pectoral fins and pelvic fins are responsible for the balance of the fish body and changing the direction of movement, while the caudal fin, anal fin and dorsal fin control the direction of movement and prevent the fish body from swaying left and right. The underwater world is not a peaceful world. Sometimes there are strong winds and surging waves; sometimes the temperature rises and falls, and the temperature is uncertain; sometimes there are "sneak attacks" and "robberies" from other species. Fish have their own instincts to deal with these. There is a special sensory organ on both sides of the fish's body. The sensory organ communicates with the outside world through the small holes on the scales. Many small holes on the scales are distributed along the sensory organ on both sides of the fish's body, arranged in a line. This line composed of the arrangement of scale holes is called the lateral line. Through this lateral line, fish can feel the direction of the water flow, the fluctuation of the water, the high and low water temperature and the sound waves in the water. Once the wind blows and the "water" moves, the lateral line immediately notifies the fish body, and the fish immediately prepares for emergencies.

Nature has given fish "18 martial arts", so it is no wonder that fish can be found in almost all waters around the world and grow and expand their ranks, making fish the largest family among vertebrates.

4. What is the reason for the decrease in wild fish in Hainan?

1. Overfishing. For the fish in lakes and rivers, people think that if they are all caught, they will appear again next year, and there is no such thing as leaving any small fish fry. However, this "root-out" fishing method is one of the main culprits that has caused the disappearance of many wild fish.

2. Invasion of alien species. China is one of the countries that suffers the most serious problem of alien species invasion. Many people think that alien species can be eaten, but in fact, many of them are unusable, and it is difficult to deal with them with conventional methods, so they have been causing continuous damage to my country's ecological environment. The reduction of wild fish is one example. These alien species have greatly invaded the territory that originally belonged to native fish, and some of them even feed on native fish. Therefore, it is understandable that the number of wild fish is decreasing.

3. Excessive use of pesticides. In the past, using pesticides on farms was a luxury, but now choosing not to use pesticides on farms is considered an outlier, which shows how popular pesticides are now. However, this popularity is not a good thing for wild fish. In the past, without pesticides, fish in ponds could live without worries. Now people use pesticides on a large scale. Once it rains, the pesticides in the soil will flow into rivers or lakes with rainwater, causing a fatal blow to the survival of wild fish.

5. What are the reasons for fish migration?

Reproductive migration

Most fish migrations are reproductive migrations, and the purpose is naturally to lay eggs. The directions of migration vary, some are from the open sea to the coastal areas, some are from streams and rivers to the estuaries, and some are from the lower reaches of rivers to the upper reaches. Some are shorter and swim from the center of the lake to the edge of the lake. The reason for this migration is that the destination is often a good place for hatching young fish, and there are a lot of plankton for them to eat.

6. What is the reason for the lack of fish in Namtso Lake?

There are a lot of fish resources in Namtso, and there are two main reasons behind this.

First, the unique climate and geographical environment of Nam Co have created a unique natural environment in the Nam Co area;

Second, there are many Tibetan people living in the Namtso River Basin. These factors have a significant impact on the ecological environment of the region.

First, the area around the lake is sparsely populated, and the local population relies mainly on traditional fishing, which is not the main mode of production and operation;

Second, plateau fish grow slowly and have low fat content, so Tibetans regard them as low-quality food. They can choose their own beef or mutton, which has led to a long-standing tradition of not eating fish.

7. Why are fish resources so abundant?

First of all, fish must have a certain amount of space to survive, and the size of the space directly determines the number of fish resources.

Secondly, bait is the most critical factor. The factors affecting the amount of bait mainly include: light and heat conditions, the confluence of cold and warm currents, upwelling compensatory currents, nutrients brought by river injection, and the upwelling of sea water in temperate sea areas in winter.

Again, light, water temperature, water quality, the number of natural enemies, human activities, etc. will all have an impact on fish.

8. Why are there so few fish in Lake Urmia?

Lake Urmír is located in the northwest of Iran, in the East Azerbaijan Province, close to Turkey, and belongs to the arid zone of the northern hemisphere. It is the second largest saltwater lake on earth, with an area of ​​about 5,200 square kilometers. The lake was about 140 kilometers long and 55 kilometers wide, but now only 5% of its area remains. Due to years of drought and numerous water conservancy projects, the salt content in the water has increased, the fungi are unbalanced, and now it is drying up. The continuous drought has caused the lake surface to shrink significantly, and the lake water has changed from beautiful blue-green to blood red. This is why there are few fish in Lake Urmír.

9. What causes stress in fish?

Causes of fish stress: Stress is a phenomenon of non-specific, physiological tension in fish caused by certain stress factors. Stress reaction is an abnormal state of fish when their tolerance to adverse environmental factors reaches or approaches the limit, rather than an independent disease. A series of abnormal symptoms of fish caused by stress factors are collectively referred to as stress syndrome. Adverse stimuli that deviate from the normal living range of fish are stressors.

For fish, the main stress factors include physical factors such as low temperature, high temperature, vibration, chemical factors such as low dissolved oxygen and water pollution, biological factors such as pathogenic microorganisms and parasites, as well as social and mental factors such as high density, netting, pond separation, and transportation.

Stress factors can cause excitement of the sympathetic nerves of fish, increase the concentration of catecholamines epinephrine and norepinephrine in the blood, and then increase the cortisol hormone in the blood.

Therefore, stressed fish will show abnormal behavior, decreased appetite, inhibited growth, reduced fertility, increased skin permeability, decreased resistance to disease, and even death.

10. What is the reason for the decline in fish population in the Rhine River?

Mainly water pollution.

50 years ago, the Rhine River was the river with the largest salmon production in Europe, but salmon completely disappeared in 1958. In the early 1950s, the Rhine River was still clear and people could swim and fish in the river.

By the end of the 1950s, the countries in the basin began large-scale post-war reconstruction. A large number of energy, chemical and smelting companies simultaneously demanded industrial water from the Rhine and discharged large amounts of wastewater into the river. The water quality of the Rhine deteriorated sharply. In the 1970s, when the pollution was the most serious, the dissolved oxygen in the river water near the city was almost zero, and the fish completely disappeared. It was called the "sewer of Western Europe."