| Changhai County is an important aquaculture area in the northern Yellow Sea of China,and the large proportion of raft culture has led to changes in the hydrodynamic structure of the culture area,which has a significant impact on the growth of organisms in the culture area.The seawater temperature is the most important factor in the mariculture environment,which directly affects the growth and health of the cultured organisms.Therefore,a prediction model for the mariculture dynamic environment in the aquaculture area of Changhai County was constructed.This model can provide prediction and early warning of the dynamic environment for mariculture in Changhai County and provide guarantee for healthy aquaculture,which has important practical significance and application value.In this paper,a three-dimensional hydrodynamic model of the aquaculture area in Changhai County under the action of tide,wind,temperature and salt was constructed by using the FVCOM model,the model was verified by using the actual measurement data,and the tide,tidal current,temperature and salinity simulation results of the sea area were analyzed.Secondly,based on the numerical model,the effect of the floating raft resistance was introduced,and a three-dimensional hydrodynamic model of the aquaculture area was constructed,in which the floating raft resistance was taken into account.The hydrodynamics of the aquaculture area in Changhai County were numerically simulated.The results showed that the presence of the aquaculture rafts significantly weakened the hydrodynamic field of the aquaculture area,with surface flow rates decreasing by30%-50%,middle water layers decreasing by 15%-25%,and bottom water layers decreasing by10%-20%.In narrow waterways between islands,the bottom water layer experienced an increase in flow rate of 25%-30%.At the same time,the existence of culturing floating raft resistance changes the size and direction of the residual flow field in the sea area near the culture area to varying degrees.Based on the constructed mariculture dynamic environment prediction model,the seawater temperature in the culture area of Changhai County was simulated and predicted from 2018 to2020,and the suitable time and area for culturing were analyzed based on the biological characteristics of the cultured shellfish in this culture area with reference to their suitable growth temperature intervals.The results show that: in the vertical distribution,there is a seasonal thermocline of seawater temperature in summer,while the seawater is mixed evenly in winter;in the horizontal direction,the seawater temperature in the study area in summer shows an obvious distribution feature of low in the southeast and high in the northwest,and the horizontal temperature distribution in winter is opposite to that in summer.For the two main species of Crassostrea gigas and Yesso scallop in Changhai County,the water temperature data from the numerical simulation were used to select the suitable zone and adaptation time for their culture.The suitable growth time for Crassostrea gigas is from April to December.The low temperature from January to March is not suitable for its culture.The suitable growth time for Yesso scallop is from April to July,from October to December.The high temperature from August and September is not suitable for its culture.But it can be placed under the thermocline by using lifting and lowering floating raft to get low temperature seawater.Based on the data of shellfish growth temperature,the total time of the suitable situation for shellfish culture was calculated,and it was found that the change of seawater temperature has a great influence on the cultured shellfish.Therefore,the model can be used to predict the water temperature in the cultured sea area to provide reference for farmers and achieve healthy development of mariculture. |
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