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[Objectives] To explore the ecological aquaculture model in ponds in North China, several single techniques were assembled into the same culture system. [Methods] Three ponds were selected, the species and stocking rate were exactly the same, the water was not changed during the culture period, and the water loss due to evaporation and leakage was recovered. Since the middle of May, the hydrochemical indicators such as ammonia nitrogen, nitrite nitrogen, water temperature, dissolved oxygen and pH were monitored every 10 d. According to the monitoring results of ammonia nitrogen, carbon sources were added to the culture ponds to adjust the ratio of C to N, and carbon sources were added 9 times during the culture period. The stocking rate and yield per unit area were accurately measured at the beginning and end of the experiment, and no less than 30 fishes were randomly sampled to calculate the relevant growth indicators and feed coefficients. [Results] Except that the nonionic ammonia in pond 3# exceeded the standard by 10.3% on July 25, all other hydrochemical indicators met the Fisheries Water Quality Standard, and there was no significant difference in all hydrochemical indicators at the same time（P＞0.05). The survival rate in 3 ponds was more than 95.0%, the average body weight of individuals out of the pond had no difference（P＞0.05), and the feed coefficient was 1.41-1.43. There was no disease during the culture period, and the water was saved by 46.6% compared with the traditional culture model. [Conclusions] This study can provide a basis for the construction of a new model suitable for ecological aquaculture in ponds in North China. [ABSTRACT FROM AUTHOR]

The rice planting area in Northeast China has reached 5.6 million ha, but the utilization rate of comprehensive culture area in paddy field is only 2%. It is mainly dominated by fish culture in paddy field and crab culture in paddy field, which has broad development prospects. In recent years, the comprehensive planting and culture area of paddy fields in Liaoning Province has developed rapidly with a total of 80 000 ha. In accordance with the local environmental conditions, Heilongjiang and Jilin regions have introduced a new model and technology of comprehensive planting and culture in paddy fields, and developed a comprehensive planting and breeding model of paddy fields with characteristics. At present, the comprehensive planting and culture in paddy fields in Northeast China is still in the stage of rapid development, which needs to be further developed towards specialization, scale, industrialization, high quality and brand. [ABSTRACT FROM AUTHOR]

[Objectives] To study the effects of biological flocs on growth performance of Cyprinus carpio var. Furui No. 2 and aquaculture water quality. [Methods] The comparative experiment method was adopted. An experimental group and a control group were set up,with 3 replicates in each group. The experimental group used beet molasses as the carbon source which was added once a week. The breed,quantity,and specifications of stocked fish in each group were exactly the same. The experiment lasted for 60 d. Fish growth indicators were measured every 7 d. After one week of the experiment,ammonia nitrogen and nitrite were monitored once a week,and dissolved oxygen was monitored once a day. [Results] The survival rate of fish,the average weight of,the weight gain rate,and the specific growth rate of the experimental group were significantly higher than those of the control group（ P < 0.05）,and the feed conversion rate was significantly lower than that of the control group（ P < 0.05）. One week after adding the carbon source in the experimental group,the ammonia nitrogen was lower than the control group,and after three weeks it was significantly lower than the control group（ P < 0.05）; after adding the carbon source,the nitrite in the experimental group was lower than the control group,there was no significant difference in the first three weeks（ P > 0.05）,and there was a significant difference after three weeks（ P < 0.05）. The feed conversion rate of the experimental group was significantly lower than that of the control group（ P < 0.05）. [Conclusions]Adding a carbon source can significantly reduce ammonia nitrogen,nitrite and other toxic and harmful substances in the aquaculture water,promote the growth of aquaculture fish and increase the feed utilization rate. [ABSTRACT FROM AUTHOR]