CATDOLL : CATDOLL: What is the nutritional value of fish? How is the nutritional value of fish ranked?

1. What is the nutritional value of fish?

1. Protein: The protein content of fish muscle is generally 15%-25%, the muscle fibers are thin and short, the water content in the tissue is high, the taste is tender, and it is easier to digest and absorb by the gastrointestinal tract than poultry and livestock protein;

2. Fat: The average fat content of fish is 1%-3%. The specific content depends on the species. For example, eel and tuna have a higher fat content, while cod has a lower fat content. Fish fat contains a large amount of unsaturated fatty acids, which is an important source of essential fatty acids for the human body. It has a certain effect of lowering blood lipids and preventing atherosclerosis.

3. Vitamins: The liver of marine fish contains a large amount of vitamin A and vitamin D, which is an important source of vitamin A and vitamin D for the body. It can promote the body's absorption of calcium, contribute to bone health, protect eyesight, etc.

4. Minerals: The mineral content of fish is 1%-2%, including iron, calcium, potassium, sodium, zinc and other minerals, and is rich in nutrients.

2. What is the nutritional value ranking of fish?

The ranking of freshwater fish is bighead carp (fathead fish), crucian carp, carp, etc. The ranking of marine fish is black cod, silver cod, salmon, etc.

3. What are the characteristics of fish?

The shape, body temperature, bones and skin of fish are different from those of other animals. In addition, fish have an organ that other animals do not have - the swim bladder. The existence of the swim bladder is also the reason why fish can float in the water.

1. Shape Fish have various shapes, sometimes with big differences, but in general most fish are slender and streamlined. Generally speaking, fish that swim fast in the water have slender bodies, while fish that swim slowly or live at the bottom of the water are relatively flat. However, some fish have very strange shapes, such as seahorses. The smallest fish is less than 1 cm, and the largest fish (whale shark) can reach 18 meters.

2. Body temperature. Fish are cold-blooded animals. The body temperature of some tunas and sharks (especially sharks of the family Carcharhinidae) is higher than the temperature of the surrounding environment. Bluefin tuna is the only fish with constant body temperature.

3. Skeletal fish skeletons are made of cartilage (cartilaginous fish) or bone (bony fish). There are four to seven gills on both sides of the skull, of which the front one has evolved into the zygomatic bone. The spine of fish is connected to the skull, the ribs in the chest are connected to the spine, and there are long spines extending from the spine on the back, tail and abdomen.

4. Skin fish have two layers of skin. The surface layer contains glands that can secrete mucus, and the inner layer has many connective tissues, scales and pigment cells. The outer layer of mucus helps fish reduce resistance when swimming. Cartilaginous fish do not have mucus, but the tiny, tooth-like protrusions on their skin have a similar function.

5. Swim bladder The swim bladder is an inflatable sac-like organ in the fish's body. Its main function is not breathing. Fish rely on the swim bladder to adjust their specific gravity. The fish can slowly rise or descend without moving. Most bony fish have a swim bladder, an organ for regulating buoyancy.

4. What are the characteristics of the ancestors of fish?

The ancestor of fish is lancelets. The origin of this animal is very early. Incomplete fossils were found 400 million years ago. In the Devonian period, many modern fish had already appeared. Ancient fish can be divided into four categories, namely, armored skins, jawless fish, cartilaginous fish and bony fish. Among them, armored skins have become extinct, and only a few jawless fish remain. Cartilaginous fish and bony fish are the main branches of fish.

5. What are the reproductive characteristics of fish?

Most fish are dioecious, and chase, lay eggs, ejaculate, and hatch when they reach sexual maturity. The feeding habits of fry are different from those of adult fish, and gradually become the same as they grow up. Some fish are fertilized and develop in vivo, and female fish give birth to small fish directly, which is ovoviviparous or pseudoviviparous.

The eggs of some cartilaginous fish and a few bony fish are not only fertilized in vivo, but also develop in the oviduct or ovarian cavity. The embryos are well protected by the mother, and the reproduction of these fish is generally not restricted to a specific breeding site. The oviparous female must expel the eggs from the mother's body, and they can only meet the sperm expelled by the male in the water to complete fertilization and embryonic development.

6. What are the characteristics of ancient fish specimens?

They are all fossils, and most of the fish species are small fish.

7. What are the characteristics of fish’s living environment?

Water is the only living environment for fish; fish cannot survive without water. On the other hand, generally speaking, wherever there is water, there are fish, so fish are widely distributed: (1) from the poles to the equator; (2) from mountain streams at an altitude of 6,000 meters to the deep sea at 10,000 meters; (3) from quiet lakes to rapids with a flow rate of up to 2 meters; (4) from snakehead fish (Dallia pectoralis) that survive in -2°C ice to medaka (Cyprinodon macularins) that inhabits 52°C mountain hot springs; (5) from fresh water, brackish water, to sea water, fish are distributed in all kinds of water environments.

Water environment characteristics:

(1) Water contains a large amount of inorganic salts and other substances.

(2) The density and specific gravity of water are greater than those of air. The density of water is 800 times that of air, and the specific gravity of water is 1 at 4°C.

(3) Water has a large heat capacity and small changes in water temperature.

(4) Dissolved oxygen in water: 3-9 mL/L. Fresh water contains 10.23 mL/L of oxygen at 0 degrees Celsius, and the oxygen content decreases as the temperature rises.

(5) For every 10m increase in water depth, the pressure increases by one atmosphere.

8. What are the characteristics of various fish?

There are many main characteristics of various fish, such as breathing with gills, living in water, and relying on fins to move. First of all, all fish live in water. Some can leave the water for a short period of time and hibernate with trace amounts of water until water comes back. Secondly, one of the reasons why fish live in water is that they mainly breathe with gills and live in water. Fins are the helpers of fish swimming.

9. What are the main nutrients contained in fish?

1. The nutrients in fish mainly include polyunsaturated fatty acids, protein, vitamins, minerals (potassium, phosphorus, sulfur) and other nutrients.

2. The protein content in fish soup is relatively high, and the protein in fish is easy to digest and absorb, which can effectively supplement the body with rich protein and improve the body's immunity. Secondly, fish are rich in vitamin A and vitamin D, especially in the liver of marine fish, which contains more vitamin A and vitamin D. Eating them can play a greater role in bone metabolism and vision.

3. Nutritional rankings of different fish: crucian carp, black carp, bluefin tuna, hairtail, carp, grass carp, silver carp, sea bass, grouper, black carp, etc.

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10. What are the breathing characteristics of amphibious fish?

Amphibians: Juveniles breathe with gills, while adults breathe with lungs and skin; Juveniles grow at the bottom of water, while adults grow between water and land.

Fish: breathe with gills, live at the bottom of water, and lay eggs. The questioner has the wrong concept, amphibians and fish are two different concepts.