When cleaning the fish pond, it was found that there were many puddles of different sizes at the bottom of the pond, which were caused by tilapia spawning and reproduction. In the process of tilapia culture, the first sexual maturity age of tilapia is 4 ~ 6 months old. High temperature and good nutritional conditions make tilapia grow fast and mature early. On the contrary, it matures later. The first sexual maturity150 ~ 200g, the male fish matured earlier and the individual was larger. After overwintering, due to the long overwintering period, the mature age of fish species has generally reached or exceeded 6 months, so individuals weighing only about 50 grams can mature and lay eggs under the condition of suitable water temperature and sufficient bait. It can be seen that the development and maturity of gonads are not only related to the growth of individuals, but also play a decisive role in age. Before laying eggs, males usually dig holes to build nests. When there are mature females in the school, they will pair up to lay eggs. Therefore, in tilapia culture, if there are both female and male fish, they can generally lay eggs and breed naturally, and when cleaning the pond, many puddles of different sizes can be seen at the bottom of the pond (Figure 7).

Fig. 7 Small puddle at the bottom of the pond