Aquaculture Suitability Assessment For Typical Bay In Northern China

With the development of economy,aquaculture gradually plays a more and more important role in satisfying the increasing human demand for food and nutrition.Presently,aquaculture is facing with many problems,such as conflicts with multi-sea use,low productivity and higher ecological and economic costs.Sanggou Bay and its surrounding waters(SBSW)are important aquaculture areas in China's coastal ocean.Focusing on large-scale cultivation of kelp and mollusks,and with a relatively stable combination of species over time,the aquaculture activity here is a typical representative of China mariculture.Preliminary investigation shows that the existing aquaculture areas in SBSW do not fully comply with the marine functional zoning,and the intensive sea usage by aquaculture has caused conflicts between sea usage of different sectors.To rearrange the spatial layout of aquaculture,rationally use the space resources in the region and deploy effectively the service value of SBSW,and to improve the efficiency and profits of aquaculture industry,research on aquaculture suitability assessment as a reference for layout tradeoff should be conducted to select the most suitable sites for aquaculture.The research progress and core techniques of aquaculture spatial planning and aquaculture suitability evaluation at home and abroad are reviewed in this paper,examples were given for the significant research achievements in the field of aquaculture suitability assessment,and the methodologies involved in the research were summarized,including spatial analysis based on GIS technology,criteria selection,weight calculation,and the GIS-based evaluation model establishment for SBSW.All of these are aiming to provide a guideline for ecosystem-based aquaculture spatial planning and sustainable aquaculture management.By suitability assessment for aquaculture,the contradiction associated with sea use activities can be effectively reduced,suggestions for cultivation site selection,suitable species selection and farming scale can be provided.This work can also provide references for decision makers and stakeholders,and also assist crucial decision-making process for multi-spatial scale planning of aquaculture.The main technical methods in the field of aquaculture spatial planning research are introduced in this paper,which is based on the technical function of ArcGIS spatial analysis,decision-making support and visual display,to build an aquaculture suitability evaluation system upon the assessment of policy suitability and environmental suitability.Firstly,following the Weihai Municipal Marine Functional Zoning,a total of19 blocks of different sea use were assigned to 7 functional zones in SBSW,including aquaculture zone,port-navigation zone,tourism-recreation zone,industrial and urban sea use zone,conservation zone,special sea use zone and reserved zone.Secondly,the7 functional zones were reclassified as three kinds of zones for aquaculture planning,including permitted aquaculture zone,restricted aquaculture zone,and prohibited aquaculture zone(policy suitability layer).The marine functional zone layer and policy suitability layer overlapped with existing aquaculture activities layer respectively was used to compare and analyze the sea use conflicts.Then,using kelp(Saccharina japonica),the main culture species in SBSW,as the object of aquaculture environmental suitability assessment.Indicators selected as evaluation criteria for this study include light intensity,water temperature,current velocity,inorganic nitrogen,salinity and depth.Remote sensing technology is employed to obtain the present layout of aquaculture sea use(the display of longlines).Data of environment parameters were collected mainly by field survey and supplemented by hydrodynamic model simulation.The Sensitivity Analysis results of Dynamic Energy Budget(DEB)model——STELLA model coupled with Analytic Hierarchy Process were used to calculate weight for the indicators,scoring curve obtained by the forcing function of environmental factors related to kelp growth was used as a basis for suitability evaluation.Linear weighted sum method was used to calculate gross score of suitability assessment for kelp aquaculture.The results of suitability assessment in policy and environment aspects are described as follows:(1)By comparing and analyzing the distribution of aquaculture activities and other sea use activities in the study area,a certain degree of conflict of sea use were revealed by the policy suitability assessment,in both temporal and spatial dimensions.According to the spatial plan,permitted aquaculture zone covers an area of 205.4km~2,slightly over 39%of the 522km~2 total sea area of SBSW.The existing aquaculture area covers 110.6km~2,accounting for 21%of the total area of SBSW,and 54%of the total area of permitted aquaculture zone.Although the current aquaculture area does not exceed the total area of permitted aquaculture zone,farming rafts actually occupy 45km~2 of the prohibited aquaculture zone,accounting for 9%of the total area of SBSW.The main conflict in sea usage is between aquaculture and port-navigation,with an overlap for at least 30km~2.On the contrary,the enhancement area in permitted aquaculture zone is treated as the waters with synergies,with an area about20km~2,accounting for 4%of SBSW area.(2)The result of environmental suitability in the duration of kelp growth shows that,the suitability score for kelp culture in SBSW is in the range of 0-6.7,and mainly distributed in 4-6,which is attributed to moderately suitable,accounting for 67%of the total study area;the most suitable and unsuitable area are 23%and 10%of total study area respectively.The water areas with higher scores are mostly located in the surrounding waters of Ailun Bay and eastern Chudao area,lower scores were mainly observed in the shallow inshore waters.These results have been verified by kelp farming practice.According to the results of aquaculture suitability evaluation,marine spatial planning and aquaculture activities planning can be carried out.Suitability evaluation may also provide reference for the government authorities to enforce aquaculture zoning and marine function zoning,put forward suggestions for aquaculture spatial planning and governance in SBSW,and help decision-making for future development and utilization of China coastal oceans.