1. Loach is a fish that spawns multiple times. Under natural conditions, reproduction begins in early April, with the peak spawning period from May to June, and eggs can still be laid until September. The water temperature for breeding is 18-30℃, and the optimal water temperature is 22-28℃.

2. The sexual maturity of female loaches is later than that of male loaches. When the body length is 5 cm, the female loach has a pair of ovaries. When the body length is 8 cm, the two ovaries merge together to form one ovary. Extending from the front end to the back end, the entire ovary begins to mature.

3. The number of eggs a female loach carries varies greatly depending on the size of the individual. The smallest sexually mature individual is 8 cm long and can carry about 2,000 eggs. A 10 cm body can carry 7,000 to 10,000 eggs. A 12 cm body can carry 12,000 to 14,000 eggs. A 15 cm body can carry 12,000 to 14,000 eggs. The number of eggs ranges from 15,000 to 18,000. A 20 cm long egg can carry around 24,000 eggs. The largest number of eggs can exceed 65,000. Oval, with an egg diameter of about 0.8 to 1.0 mm, and expands to 1.3 to 1.5 mm after absorbing water. The egg is yellow, semi-viscous, and has weak adhesion. Due to the inconsistent maturity of eggs in the ovary, the amount of eggs ovulated each time is about 50% to 60% of the number of eggs conceived.

4. The smallest sexually mature individual of the male loach is more than 6 cm long, and matures earlier than the female loach. The male loach has a pair of testes, located on both sides of the abdominal cavity, which are belt-shaped and asymmetrical. The testes on the right side are The testis is longer and narrower than the one on the left, and is lighter in weight. When the male loach is 9 to 11 centimeters long, there are about 100 million sperm in the testis. Loach likes to lay eggs on sunny mornings after rain. Before laying eggs, the female loach swims in front. Several male loaches are chasing after them. During the estrus, male and female loaches mostly move on the water surface and around the fish nest. When the estrus reaches its climax, the heads and bodies of the male and female loaches rub against each other and swim out of the water one after another. The male loach chases and entangles the female loach and curls around the female's abdomen to stimulate the female to lay eggs. At the same time, the male loach also discharges sperm for in vitro fertilization. The frequency of this action varies depending on the size of the individual. Larger individuals can More than 10 times, the fertilized eggs first adhere to aquatic plants or other attachments. As the water fluctuates, they easily fall off the attachments and sink to the bottom of the water.