How do fish swim in the water?

All kinds of animals have their own way of life, which is obviously manifested in the way of exercise. Fast movement can avoid the enemy's pursuit and catch food, while slow movement is easy to be destroyed by the enemy and it is difficult to get food. So how do fish that live in water swim? Do different fish swim at the same speed? (1) The motivation of fish swimming mainly comes from three aspects: First, the contraction of trunk and tail muscles makes the body twist left and right repeatedly, and the water is pressed backwards to make the body move forward; The second is to move forward by swinging the fin; The third is to make the body move forward by using the impulse of spraying water backwards through the gill holes. Among them, 1 is the main one, and the latter two generally play an auxiliary role. However, different fish have different preferences for these three forces, and the same species applies these three forces differently in different situations. But in any case, the three ways are used alternately in the whole movement process, and when necessary, the three actions are carried out at the same time. (2) The way fish swim is 1. Wave motion is produced by muscle contraction on the side of the body, which is more obvious in long fish such as eel and eel. Monopterus albus and Monopterus albus are both cylindrical, and the muscles on both sides are uniformly distributed. Therefore, the whole body is a device that uses strength in sports. At the beginning of exercise, the muscles at the front end of the body contract first, then gradually increase to the tail end, and then the muscles at the other side contract in the same way. In this way, the muscles on both sides alternately move, the whole body forms a wave-like swing, and the horizontal moving distance of the fish is also increasing. Because the muscle contraction force increases from front to back along one side of the body, the contraction force is greater when it reaches the body. The longer the body is, the more obvious the wave-like movement is, the more stable the head is, and it rarely swings from side to side during the exercise. Monopterus albus has a long body, and its caudal fin has degenerated into several skin folds. The first half of the sea eel's body is round and the second half is flat, which is helpful for swimming. Hairtail is almost completely flat, so it has strong swimming ability; Sharks and Spanish mackerel also use the muscle contraction force on both sides of their bodies for wave-like movement, but their bodies are different from eels and eels, but they are similar to spindles. The wave-like movement mainly comes from the back half or 1/3 of the body, while the lateral movement in the middle of the body becomes very small, even close to zero, which greatly strengthens the role of the tail fin. When the shark's tail swings from side to side, the odd fins and side fins of the fish play a role in stabilizing the body and avoiding tumbling and bumping back and forth in swimming. The movement force of eel moves to the tail more obviously. It has a slender tail handle, and its height in the vertical plane has dropped very low. Crescent-shaped tail fin, even the raised back on the horizontal plane of tail handle, is suitable for reducing energy consumption caused by tail flick and improving efficiency. However, after the force moves to the tail, the fish easily loses its lateral balance, causing its head to swing from side to side as soon as it swings its tail. This weakness has been overcome by raising the vertical plane in the middle of the body to increase the resistance to swinging from side to side. At the same time, it is also beneficial to the inertia of the head and prevents the head from leaning to one side when swimming. 2. The motion produced by fin swing is the motion produced by fin swing, and its power also comes from muscles, but it is limited to the local muscles at the root of fin. The function of fin movement has been well proved in the box bream: because its body is wrapped in a bone box, it can no longer be pushed by the flexion of the body, so the movement can only be completed by the fin exposed outside the bone box. Many fish have developed pectoral fins and ventral fins, but they are mainly used to stabilize the body and master the direction, and are rarely used for high-speed sports. Special cases were found in rays and flat rays. Their pectoral fins are combined with their body plates. When the pectoral fin is fanned up and down in a wave shape, the body can move forward. The dorsal fin and anal fin are also mainly used for balance, but in some long fish, such as the dorsal fin of hairtail, the anal fin of electric eel, and the dorsal fin and anal fin of sea eel are all very long. When they move forward quickly, they push the fish body in line with the fluctuation of the whole body. When moving slowly, the body is propelled by separate waves. Some short fish, such as flounder, also help fish move slowly through long dorsal fin and gluteal fin, while hippocampus has a special shape and weak sports ability, mainly with tiny dorsal fin. 3. Spray water through gill holes to make the fish move. Spraying water through gill holes is also a driving force for fish to move forward, which mainly depends on the position of gill holes. Water spraying has different effects on different fish. Among fast-moving fish, gill holes are most conducive to spraying water backwards, and spraying water is between the moment when the fish bends and the moment when the trunk moves forward, so the maximum moving speed can be achieved when spraying water. 4. Jumping or flying fish In addition to swimming, another prominent movement mode is jumping or flying, such as sudden change of water temperature, stimulation, avoiding enemies, chasing food, jumping over obstacles, etc. , often cause jumping off a building. Crawling is also one of the ways of fish movement, but it is rare. Generally occurs in benthic fish, such as Ankang, ricochet clothes and other utensils. The pectoral fin with meat handle crawls, and the independent finger fin under the pectoral fin also has crawling function. (3) The speed and distance of fish's movement are different because of different fish's body shape and movement mode. Among marine fish, swordfish is the swimming champion. Because the body is streamlined and muscular, the caudal fin is crescent-shaped, and the resistance during exercise is small, the swimming speed can reach 1 10km, followed by swordfish 104km, salmon 40km, tuna 2 1km, perch 16 km, and shark. As for flat rays, spherical rays and stingrays, the speed is even slower. The "marathon champion" with the longest parade distance among fish is European eel, which can parade 1. 1 000 km, eel catfish can swim 2400km and yellow snapper can swim 2,000 km. However, this is only the measured distance of the marker release. Under natural conditions, this figure may be conservative. As for swimming posture, some fish are as good at "treading water" as swimmers, such as turtles and seahorses, and some fish are good at "backstroke", such as African abalone, tuna and swordfish, and then make a semi-arc movement in the air, and then dive into the water again with their heads forward. Some people can glide, which is a further development of jumping. For example, flying fish must speed up as much as possible before coming out of the water, jump out of the water, and then spread their enlarged pectoral fins to glide in the air, with a gliding distance of about 300m·m m. Salmon is an excellent fish jumper. When they migrate from the ocean to fresh water, they must repeatedly jump over various obstacles and spawn upstream.