Carrying Capacity Assessment For Typical Bay

When the scale or stocking density of aquaculture exceeds the carrying capacity of one given waters used for aquaculture,the negative environmental impact of aquaculture is prominent,which is reflected as self-pollution.The impact affects the quality of cultured organisms,and even causes massive mortality of cultured organisms,and threatens the regional ecological security.Thus,the image of aquaculture,especially the bait breeding culture,is not good and faces the risk of being banned.Nevertheless,aquaculture is an important means for fishermen with a very low social opportunity cost,and it is an important starting point for rural revitalization.To avoid being banned,the scale of aquaculture should be kept below the carrying capacity,which urgently needs to be determined.Carrying capacity is the cornerstone of the industry management.Nevertheless,the accuracy of the existing carrying capacity assessment has not been actually verified in situ,which inevitably makes people doubt the assessment results.If the doubt is confirmed,it is especially important to establish more evaluation techniques.Moreover,mathematical models are the primary method for impact evaluation,yet constructing mathematical models describing one ecology system requires large amounts of timeseries data.Nevertheless,the areas in urgent need of evaluation often lack the necessary historical data,and it is difficult to form a large number of effective modeling data in a short period.These factors have also led to the necessity of establishing a carrying capacity evaluation system with less time series data.To confirm the conjecture that there were differences in the evaluation results determined by different methods,the present study compared assessment results of the carrying capacity for one system used for shellfish and macroalgae in the Sanggou Bay,Shandong Province.Taking Maniao Bay,Hainan Province,with less time series data as an example,the evaluation technology of the carrying capacity of the cage culture was established to enrich the technical system for the carrying capacity evaluation.The results are as follows:1)The carrying capacity for the Chinese scallop in Sanggou Bay assessed by Fang et al.(1996)was 7.78 ind.m-3,which was considered as the base line value.The difference extents in carrying capacity determined by Ge et al.(2008),the amended method based on Ge et al.(2008),and the Herman model was-48.70%,-25.84%and 172.24%,respectively.Thus,the evaluation results differ significantly among the evaluation models.2)Based on the similarity theory,the physical filed of Maniao Bay was simplified.Moreover,the pollution discharge pattern of cage culture in the bay was simplified according to the pollution source simplification theory.The setting fluxes of biodeposition produced by cage culture were simulated through the Ansys Fluent software.The residual errors and the Spearman correlation between the simulated and the measured fluxes,the simulated posterior difference ratio and the small error probability all reached the eligibility criteria.Thus,the simulation of the sedimentation flux of the biodeposition is plausible.3)The accumulation model for biodeposition was established,and the measured sediment data were verified and the parameter sensitivity was analyzed.The results showed that the constructed model was credible.4)The relationship between fish biomass and production of biodeposotion was established,which was coupled with the biodeposition accumulation model to determine the carrying capacity for cage culture under different culture conditions.and it is believed that the existing breeding scale in Manao Bay does not exceed the breeding capacity.Thus,the present work affirms that there are differences in the single evaluation techniques and understandable doubts about the results of the existing single model evaluation.To reduce the assessment risk,in addition to fully understanding the ecological process of the ecosystem or directly verifying the assessment results,a variety of assessment techniques should be used,and their average value is considered as the comprehensive carrying capacity of the assessed waters.Moreover,the simplified method for assessing the environmental carrying capacity of the Maniao Bay in the present study can be used as one of the methods for the carrying capacity evaluation in waters lacking long-term series data.It also provides a technique for the multimodal evaluation.Of course the method should be assessed under more conditions.