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salmon breeding migration

22/12/2023 09:05:07

Salmon, like most other fish, go through a series of growth stages from the time the eggs hatch. Because of its high commercial value and the large scale of aquaculture, special industrial terms are used in academic circles to describe the various growth stages of salmon: Funny larvae: billige Sexpuppen   The life of salmon begins in the spawning period, and the female salmon will The eggs are laid between gravels on the bottom of stagnant areas of rivers and streams and then fertilized externally by male salmon. The fertilized eggs hatch into larvae after 2 to 6 months.

Alevin: also called "sac fry", is a newly hatched early larvae with a yolk sac. It has no ability to move yet and can only drift with the tide. It has no foraging ability to absorb external nutrients, so it relies on storage. The nutrients in the yolk sac can continue to survive and grow;
Juvenile fish (fry): commonly known as "fry". Kleine Brüste Sexpuppen   When the larvae continue to grow for a period of time, the yolk sac becomes depleted of nutrients and shrinks, but at the same time the tail also develops and gains limited swimming ability. At this time, the larvae become juvenile fish that can swim short distances between gravels and feed mainly on plankton;
Juvenile fish (parr): When the juvenile fish grows to a size about the same length as a human finger, it has begun to have fish scales to protect itself and fins that can be extended to assist swimming. Schlanke Sexpuppen   The shape also begins to resemble ordinary fish, so it is also Commonly known as "fingerling". Because these juvenile fish have acquired the ability to swim freely, they can actively patrol an area in search of food, and their diet has become more carnivorous, changing from plankton to mainly invertebrates (such as shrimps and aquatic insects). Body mass also begins to increase rapidly over the next three years of growth. Although the young salmon at this stage have a certain ability to survive on their own, they still need to avoid other predators because they are still small. They usually live in groups using underwater plants and rocks as shelters, and show a strong sense of territory. Dark oval or striped vertical spots called "parr marks" may also be displayed as protective color. Larger juvenile salmon will also prey on other small fish and amphibian larvae (tadpoles), and will steal the eggs of other fish (even the same kind);
Smolt: When a young salmon grows to about two to four years old, it is no longer necessary (or unable) to continue to rely on the shelter of a bunker. Lebensechte Sexpuppen   The young spots on the side of the body will gradually disappear, and the body will also undergo physiological changes. to cope with the impending long-distance migration. In order for these second/third/fourth-year-old fish to cope with the saltwater/brackish water environment of the ocean and estuaries, the euryhaline nature of the salmon body will increase to maintain the homeostasis of osmotic pressure in the body, and the body color will change to a lighter silver. Gray with reflective camouflage to survive in open water, this color change is also called "smoltification". Some silver-aged fish have even begun to mature sexually and can fertilize eggs laid by other migratory salmon before they migrate;
Adult: Also called "post-smolt" salmon. When the silvered salmon reaches a length of about 15-20 centimeters (5.9-7.9 inches), they begin to leave freshwater rivers and migrate to the sea, where they begin to fully transform into adult fish. The adult fish that enter the sea remain in schools and feed exclusively on other forage fish, such as herring and mackerel, and continue to grow in size over the next four years. Lebensgroße Sexpuppen   When these adult fish are fully sexually mature, they will migrate upstream in the autumn back to the freshwater waters where they were born to breed. A large proportion of the salmon will die during the migration, and a considerable number of salmon will quickly decline after spawning. die.

Salmon are anadromous fish that usually spawn in freshwater areas with sufficient water and oxygen upstream of the river. The eggs hatch between the gravels on the bottom of the water and grow into young salmon. The young salmon will quickly grow vertical spots to provide them with protective color, and they will live in the river for the next 6 months to 3 years (depending on the species). Salmon feed on the surface of the water. Almost the vast majority of salmon return to the exact river where they were born. Salmon are very good swimmers and can jump out of the water and climb upstream of waterfalls. Young salmon will continue to live in fresh water until they have silver scales, and their bodies will also undergo changes to survive in sea water. However, only 10% of salmon eggs can grow to this stage.

After migrating to the ocean, salmon spend one to five years (depending on the species) at sea, where they gradually become sexually mature. The recreational activities of salmon are greatly affected by the tide. They are very familiar with the conditions of the sea water. They swim to the sea when the tide is low and to the rivers when the tide is high. During the breeding season, most salmon will return to their birthplace to spawn based on their olfactory memory.  


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