基于GIS的虾夷扇贝养殖适宜性综合评价——以北黄海大小长山岛为例

Abstract

由于水产养殖缺乏科学空间规划，近年来中国最大的虾夷扇贝（<em>Patinopecten yessoensis</em>）养殖基地长山群岛发生了扇贝大规模死亡现象。当地渔业主管部门急需水产养殖空间格局优化的技术手段和科学依据。采用叶绿素a浓度、海水表面温度、水深、透明度以及评价单元到渔港、城镇、旅游区和自然保护区的距离等指标，构建了虾夷扇贝养殖适宜性评价模型，并以大小长山岛海域为示范区，对该海域的虾夷扇贝的养殖适宜性进行了空间分析。结果表明：大小长山岛海域虾夷扇贝养殖适宜性较高且具有较大的空间变异，在不考虑海域使用冲突情形下，养殖适宜性指数在6.0-7.0以及7.0以上的海域占示范区的面积比例分别为26.04%（167.75 km²）和4.73%（44.06 km²），且高适宜性（SSI > 7.0）区主要分布在大长山岛西北和西南海域；而由于航道和水产养殖存在海域使用冲突，高适宜区面积大幅下降为19.56 km²。在此基础上对大小长山岛海域虾夷扇贝养殖空间格局优化提出了建议。利用一些简单的距离指标反映了陆地基础设施因素对水产养殖选址的影响，体现了海陆统筹的理念并可为海陆统筹技术方法研究提供重要借鉴。;Changshan archipelago in North Yellow Sea, the biggest base for Japanese scallop aquaculture in China, has recently experienced a series of problems including large-scale scallop death, environmental degradation and sea use conflicts. Most of them are attributed to the shortage of scientific spatial planning for Japanese scallop aquaculture and the subsequent over-density issue to great extent. The local government and farmers are in urgent need of the technology and scientific foundation for spatial adjustment and optimization of current scallop aquaculture. It is widely accepted that the definition and characterization of suitable aquaculture zones is pivotal for the success and sustainable development of aquaculture, GIS based suitability studies for aquaculture site selection, however, are surprisingly very rare in China. With the islands of Dachangshan and Xiaochangshan (IDX) as a case, a GIS-based aquaculture site suitability index (SSI) model was used in the spatial suitability analysis of Japanese scallop aquaculture. The distances to towns, biological conservation zones, island tourism zones, fishery harbors and navigation lines in addition to SST, bathymetry, water transparency, Chl a were used as criteria or parameters for site selection, which were selected according to the current sea uses and ecological issues of concern in IDX and the requirements of Japanese scallop for environments as well. Field surveyed data were used to obtain the parameters for Chl a and water transparency whereas the other parameters were extracted from basic geospatial vector data or raster data(only ocean color SST here) for the study area to produce thematic layers in the form of raster by means of distance tool or interpolation tool in ArcGIS 10. All data were re-sampled or interpolated to the same resolution of 250 meters and a suitability score for each criterion was established using a scoring system from 1 to 8, with 8 being the most suitable and 1 being the least suitable for developing scallop culture. To make full use of the expertise and research results of foreign scientists in this field, the weights and scoring system for these parameters were mainly determined according to relevant references and slightly adjusted based on the opinions of local aquaculture experts and farmers. After that, a site suitability index model based on a liner weighted combination of suitability score for each parameter was used to calculate the site suitability index (SSI) for each assessment unit(pixel here). Due to the sea use conflicts between scallop aquaculture and navigation, biological conservation and island recreation, some water areas cannot be used as scallop aquaculture sites and form spatial constraints. Given that the issue of sea use conflicts is a big concern in marine aquaculture site selection, the spatial and areal distribution of SSI for IDX were analyzed both in the scenarios of no spatial constraints and spatial constraints, on which basis aquaculture structure optimization plan for IDX was proposed in this paper. The results showed that IDX were fairly suitable for Japanese scallop aquaculture and of big spatial variation. 32.06% of the potential water area (211.81 km²) had suitability index bigger than 6.0 in the scenario of no spatial constraints. The highly suitable sites with SSI above 7 (accounting for 4.73% of the potential water area) were mainly distributed to the northwest and southwest of Dachangshan Island with an area of 44.06 km². In addition, it was found that the spatial constrains mainly resulted from the sea use conflict between aquaculture and marine navigation, which made the area of highly suitable level (SSI > 7.0) drop from 44.06 km² to 19.56 km². The adjustment of navigation line can improve the potential of scallop aquaculture potential greatly. In this paper, the impact of scallop aquaculture on nature reserve of wild fishery species was considered in the scallop site suitability model, highlighting the concern of biodiversity conservation. Besides, the role of land based social-infrastructure resources such as fishery harbors and towns in site selection reflected the thought of land-ocean overall planning. In the end, advice on the spatial pattern adjustment of Japanese scallop aquaculture in IDX was given based on the aquaculture site suitability analysis. The results are expected to provide an important scientific foundation for spatial structure optimization of Japanese scallop aquaculture in IDX whereas the methodology can be used as an important reference for the spatial pattern adjustment of marine aquaculture in China.