The life history of eels

Eels are commonly known as white eels and green eels. A migratory fish that descends into rivers. The distant journey it undertakes to reproduce is a miracle in the history of animal life.

In early spring every year, large numbers of young eels emerge from the sea, pass through the estuaries, and flock into the rivers. They are nocturnal, like running water, low light, and live in caves. They are extremely capable of tracing water and have a strong ability to escape. Usually, after male eels enter fresh water, they settle in ancillary water bodies downstream. Female eels continue to move up the river, swimming to the middle and upper reaches of the river and ancillary water bodies to find suitable water bodies to live in. Eels live in fresh water for 5-8 years and reach sexual maturity, but their gonads never mature. At this time, in autumn, they use the moisture of dew on the grass at night to crawl across the wilderness from various water bodies, enter the rivers near their habitats, and then flow into the river and then into the sea. Male and female fish meet at the mouth of the river, and the group begins a long journey across the ocean. The destination is their birthplace. Eels from eastern Asia travel more than 2,000 kilometers after entering the sea, and then reach the 400-meter-deep waters near the Central Mariana Islands east of the Philippines and south of Guam in the Western Pacific for breeding activities. After breeding, all the parent fish die, and the fertilized eggs float on the upper layer of the ocean and hatch into transparent willow leaf-shaped larvae, which become leaf eels. Leaf eels drift and develop with the tides, following the direction their parents came from. Two years later, it reaches the estuary area where its parents went to sea. At this time, the leaf eel has grown to 50-70 mm. Metamorphoses into transparent cylindrical young eels in the estuary. During metamorphosis, the larvae stop feeding and shorten their body length. After metamorphosis, the body length is only 40-50 mm, and they are called larvae. The young eels that have completed their metamorphosis enter fresh water, and pigment appears on their bodies. At this time, the young eels have developed into black eels. After entering the river, the male and female separate and each find their own destination to live in. When they grow up, they repeat the reproductive migration of their parents into the sea.

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