The eel spawns near the mouth of its burrow, spitting foam before spawning into a pile of nests, fertilized eggs in the foam with the help of the buoyancy of the foam, the development of the surface of the water, both male and female fish have the habit of nest protection. Spawning adult fish spit foam, in the hole accumulated into a mass, the amount of eggs is small, not spawned in the foam, spawned in the nest, about 7-8 days can be hatched out of the young fish.
Eel is hermaphrodite, heterozygous insemination
Eel reproductive situation is more special, the young for female, reproduction of a time, the transformation into male, this female, male transformation phenomenon known as the sex reversal phenomenon.
The reproductive season of eel is about May to August, in its individual development, with the characteristics of male and female sex reversal, that is, from the embryonic stage to the first sexual maturity are female (i.e., body length of 35 centimeters below the body of the individual's gonads all ovaries); spawning ovaries gradually become spermatic ovaries; body length of 36 to 48 centimeters, part of the sex reversal, the male and female individuals are almost equal to belong to the hermaphrodite animals; growth to 53 centimeters or more is mostly spermatic. 53 centimeters or more are mostly spermathecae. When the juvenile fish can only grow to 20 centimeters, 2 winter age of the female fish to reach maturity, the body length of at least 34 centimeters. The largest individual can reach 70 cm and weigh 1.5 kg. In May 2013, a 3-6 kg, 1.5 m long eel was caught in Huzhou. Eels spawn near the mouth of their burrow, spitting foam piles into nests before spawning, fertilized eggs in the foam with the help of the buoyancy of the foam, developing on the surface of the water, both male and female fish have the habit of nest protection.
1. Breeding and environmental conditions The eel reproduces only once a year, in April and August each year, with a peak season in May and June. Its spawning cycle is long. Before the breeding season of eels, the parent eels first hit the breeding hole. Generally, the holes are made at the edge of the ridge, and the holes are usually opened at the hidden part of the ridge, with the lower edge of the holes 2/3 submerged in water, divided into the front hole and the back hole. The front hole is wider at 10 centimeters in length, about 5 centimeters in height and 10 centimeters in width. The posterior hole is elongated and serves as a sheltered habitat. In larger bodies of water or in waters where it is inconvenient to make holes, eels look for dense water plants, roots, rubble, rock crevices, and other objects that can be hidden to make nests.
2. The natural sex ratio and mate composition of the reproductive group of eels throughout the reproductive period is more female than male. In February female eels accounted for 91.3%, from June to August female eels laid eggs after the gonads gradually reversed, to September female eels gradually reduced to 38.3%, October to December female eels gradually reduced to 38.3%, October to December female eels gradually reduced to 38.3%. In September, females gradually decrease to 38.3%, and in October and December, females and males each account for about 50% of the total. In the fall and winter, people catch eels to catch big and leave small, so after the spring is still more female and less male. Reproduction of eels, most of them belong to the offspring and the parent generation, but also with the first two generations of male eels. But in the absence of male eels, there are a small number of female eels in the same batch of eels reversed to male eels, and then with the same batch of female eels to breed offspring, which is the eel is different from the special features of other animals.
3. Natural spawning and hatching Sexually mature female eels have a light orange-red abdomen (also grayish-yellow), and some of the parent eels have a red horizontal line. Before spawning, female and male eels spit foam to build a nest, and then spawn in the top of the hole fell on top of the grass roots, fertilized eggs and foam floating in the mouth of the hole. Fertilized eggs are yellow or orange, semi-transparent, and the diameter of the eggs (after absorbing water) is generally 2 to 4 millimeters. Parent eels, especially male parent eels have the habit of protecting the eggs, generally to guard the yolk sac of the eel fry until the disappearance. Parent eels spit foam for the nest generally have the following roles: one is to make the fertilized eggs are not easy to be detected by the enemy, to protect the eel eggs; two is to make the fertilized eggs to float on the surface of the water, and the surface of the water is generally high in dissolved oxygen, the water temperature is high (eel egg incubation suitable water temperature of 21 28 ℃), conducive to improving the hatch rate; three is a parent eel spit foam, there are eel eggs hatch plays an important role in the material, has not yet been recognized what kind of material.
From the fertilization of eel eggs to the hatching of young eels, it generally takes 5 to 7 days in water temperature around 30 ℃ and 9 to 11 days in water temperature around 25 ℃. The fertilization and hatching rate of eels in nature can reach 95% to 100%.