| Eriocheir sinensis is a highly sought after aquatic crustacean economic animal on the market.It is not only delicious,but also rich in a variety of nutrients,as well as medicinal value.Since the 21st century,with the improvement and popularization of the ecological breeding technology of Eriocheir sinensis,the production cost of seedlings has gradually decreased,the output of seedlings has increased year by year,and the production capacity has been continuously improved.In 2016,the production of Chinese mitten crab Eriocheir sinensis The seedlings produced by the earthen pond ecological nursery account for more than 95% of the total demand for breeding seedlings.The whole life cycle of Eriocheir sinensis is divided into three stages:pre-embryo,embryo and post-embryonic stage.The post-embryonic development stage includes four stages:larvae,crab,juvenile crab and adult crab,and larval stage(including stage IV).The larval and M-stage large-eyed larvae are the initiation of post-embryonic development of Eriocheir sinensis and play a decisive role in the healthy development of the entire post-embryonic stage.In the research of nursery temperature,the effective accumulated temperature and developmental starting temperature of the post-embryonic development stage of Eriocheir sinensis seedlings should be studied.The effective accumulated temperature rule is a direct reflection of the relationship between temperature and development.Biological zero and effective accumulated temperature are important biological indicators of crustaceans.They can not only measure the response of aquatic animals to environmental temperature changes,but also regulate temperature and development for artificial breeding of aquatic animals.The calendar provides an important reference.In this study,the combination of indoor aquarium cultivation and outdoor temperature monitoring was used to observe and record the temperature and developmental period data regularly.The data were processed by statistical methods to explore the biological zeroness and effectiveness of the Chinese mitten crab Eriocheir sinensis.Accumulated temperature.The experiment was conducted on the larvae of the Yangtze River water system of the Chinese mitten crab,the"Jianghai 21"cultivar,which was cultivated in Sheyang area.The indoor single-factor three-treatment and three-repetition constant temperature test were designed.The three treatment groups were set at a constant temperature of 20°C,22°C,24°C.),regularly monitor development temperature and duration.Statistical analysis was performed using one-way variance method for experimental data and local five-year historical monitoring data.The results showed that:(1)There was no significant difference between the statistical data of biological zero degree and effective accumulated temperature test data and historical data(p>0.05),and the biological zero degree of post-embryonic development stage of Eriocheir sinensis was6.91°C.The effective accumulated temperature is 274.18°C·d.(2)Within the test temperature range,the developmental stage of the larvae of Eriocheir sinensis was shortened with increasing temperature.At present,the trials and reports on the cultivation stage of the Chinese mitten crab larvae are focused on the research of production technology flow and indoor planting water quality control.There are few studies on ecological nursery in outdoor soil pools,and most of them are the effects of single factors on seedlings.So far,we have not seen a comprehensive systematic report on the detection and analysis of various factors in the ecological breeding ponds of Eriocheir sinensis,and a comprehensive systematic report on the multi-year changes in the water quality of the larvae.In order to study the change characteristics of water environmental factors in natural sea water and soil pond of Eriocheir sinensis,the water quality of Eriocheir sinensis seedlings was monitored every four days from April to May in2015 to 2016,and the data were recorded and the water quality changes were analyzed.Testing items include water temperature T,salinity S,DO,nitrogen nutrients,phosphorus nutrients,chemical oxygen demand,etc.At the same time,the historical water quality monitoring data of our laboratory during the seedling-raising period from 2013 to 2014 were collected to analyze the variation regularity of water quality factors in four years.The monitoring results of this experiment showed that the average water temperature in the nursery pond was lower at 17.0°C in 2014,17.4°C in 2015,and above 18°C in 2013 and 2016.The water depth of the nursery pond is maintained at 2.0m,which can effectively maintain the water temperature stability.The temperature and stability of the temperature affect the time of seedling raising.In the year when the average temperature is low,it takes 2-3 days to develop into the big eye larvae,but it has little effect on the seedling yield.The dissolved oxygen in the nursery pond is always higher than 5mg/L.The pH ranged from 8.34 to 8.68,and the variation range of the nursery pond during the whole monitoring period was about 0.3,and the change was very stable.The salinity is basically stable,ranging from 23.2 to 26.5,which is in line with the water quality standards of Eriocheir sinensis.The salinity of the nursery pond was always slightly higher than that of the reservoir,but the difference was not significant(p>0.05).The ammonia nitrogen in the nursery ponds increased with the prolonging of the nursery time,but it was still far lower than the water quality requirements of the technical regulations for artificial breeding of Eriocheir sinensis.The content of nitrite nitrogen increased slightly with the increase of seedling time,but it was much lower than the content specified in the technical regulations of artificial mitten seedlings of Eriocheir sinensis.The range of nitrate nitrogen in the reservoir and nursery ponds ranged from 0.020 to 0.110 mg/L.Nitrate nitrogen is the final product of nitrification reaction.Combined with the previous indicators,the nitrification reaction of water is better.During the nursery period from 2013 to 2016,the total nitrogen in the reservoir and nursery ponds ranged from 0.209 to 0.273 mg/L and 0.218-0.514 mg/L;0.220-0.280 mg/L and0.224-0.564 mg/L;0.260-0.345 Mg/L and 0.261-0.750 mg/L;0.278-0.387 mg/L and 0.280-0.860 mg/L.Total nitrogen showed an upward trend,with the highest monitored value and the highest average occurring in 2016,reaching 0.860 mg/L and 0.554 mg/L,but still at a low level.The total nitrogen showed a gradual increase trend.However,the monitoring values of ammonia nitrogen,nitrogen nitrate and nitrite nitrogen were lower,indicating that the total nitrogen in the nursery pond was mainly soluble organic nitrogen.The concentration of inorganic phosphorus in the nursery ponds increased in 2013 and 2014 compared with the inorganic phosphorus in 2015 and 2016.Four years increased with the increase of nursery time.The trend of COD changes in the four years was consistent,which increased with the increase of nursery time(Figure 11).The mid-term COD of the four-year nursery ponds met the water quality standard of seawater(COD<2mg/L),and the highest in the late 2016 was 2.793 mg/L,but still met the water quality standard of seawater(COD<3 mg/L).The trend of total phosphorus is similar to that of inorganic phosphorus.Through four years of monitoring results analysis,the natural seawater pH value,salinity and water temperature of Sheyang Chinese mitten crab breeding base are suitable,and the nitrogen,phosphorus nutrient and COD indicators have a certain upward trend,but the 2013-2016 test monitoring pool The average production and output per unit area increased year by year.In 2016,the test monitoring pool reached 47.80 kg per 667 m~2.From our survey of production records of nursery bases,the two nursery ponds with the highest output in 2016reached 84 kg and 104.5 kg per 667 m~2 respectively.It is proved that the shooting sun nursery base has the potential to increase the yield of the nursery pond under the existing production mode.The results of this study can provide a reference for the improvement of river crab ecological breeding technology and the protection of offshore wetland,and promote the rational and healthy development of ecological breeding of river crab soil pool. |
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