Cut and paste work… Sorry tis hot..
The life cycle of the eel
The eel is a so-called catadromous fish that grows up in fresh or brackish water and propagates in the Sargassozee at great depths.
The larvae draw aided by the Gulf Stream to Europe. The genus of eel is determined by the conditions in which the fish grows up.
If the eel has stored a certain amount of fat in its flesh, it is called silver eels.The animals become fat, the eyes become larger and they get a light grey color with a white belly, the fins become larger and the skin becomes thicker. When the return journey begins to the spawning area in the Sargasso Sea, through the upper water layers, the Eels are not yet completely sexually ripe. Further sex development takes place during the journey.
Research at Leiden University has shown that Eels are able to complete 6,000 kilometers.Also here is discovered that Eels use very little energy for swimming. In total, they burn only a very small amount of energy to move around. For the journey of 6,000 kilometers thus only about 60 grams per kilogram of body weight, similar to 5 small bags of chips. This is remarkable in comparison with other trekfish such as salmon; It uses more than 50% of its body weight to reach the spawning grounds.
Adult eels probably lay their eggs in the Sargasso Sea, where the wilgenblad-shaped larvae (lat.: Leptocephali) grow up.This was discovered in 1923 by the Danish researcher Johannes Schmidt, who found the smallest larvae in the Sargasso Sea. However, the spawning process itself has never been seen by humans. The spawning place is well known from the Japanese eel and other eel species.
The flattened shape of the larvae is functional because they are not visible in the ocean area between 15 and 200 meters in which the animals pull up.In This part of the ocean, the photozone that forms the largest habitat in the world is not a single shelter and all organisms are almost invisible. More and more leptocephali is discovered, which can be up to 180 cm long. These include aalvormigen and spine (Notacanthidae), which all use the extremely flattened form, to survive in this environment.
The glass eel
After two years, the larvae are actively swimming and moving with the Gulf Stream the continental shelf and slowly getting the round shape of the eel, while the length decreases slightly.The translucent glass eels that enter the fresh water after three years have a length of 65 mm. The glass eels do not have a specific direction seeking instinct, but the direction of the trek is still roughly fixed. American and European eels are two related species and both spawn in the Sargassozee. American Eels attract to the northwest, European Alen attract to the northeast. It is striking that relatively many hybrids are found in Iceland. The very long trek route of the Sargassozee is explained by the Continent shift through which the Atlantic Ocean in the millions of years that the species exists has become increasingly broader. The species has been able to adapt very gradually to the increasingly long migratory route.
This journey takes about three years, after which the glass nemaltjes with millions try to attract the European waters (including the Netherlands and Belgium).In The fresh water, the transparency disappears rather quickly through pigmentation. Some glass nemanks remain under the coast to grow up and look for mussel banks, channels and wrecks. Waterworks (15,000 units) including dams, dikes and hydropower plants have ensured that in recent decades the original Migration routes of the glass eel are massively blocked. This ensures that the glass eel can almost impossible to enter and the mature eel can almost impossible to pull out.
I would also like to know that.I once read the story that it was just reversed as with salmon. Eels are born in the sea then go to fresh water and later return to salt water. Ointmen are born in fresh water then go to salt water and later go back to fresh water. I also don’t know what is true of these stories.