基于Voronoi图与空间自相关的西北太平洋柔鱼资源空间聚集特征分析

以西北太平洋柔鱼Ommastrephes bartramii为例,基于2007—2010年中国鱿钓船的生产统计原始点位数据,利用Voronoi图和空间自相关方法,评估柔鱼资源的全局空间模式、局部空间聚集特征,并以空间可视化方式呈现。在渔业资源及空间分析中,高产值聚集的海域称为空间热点,而低产值聚集的海域称为空间冷点。研究表明,全局自相关统计量Morans I和General G均指示了西北太平洋柔鱼资源的聚集分布状态。局部空间自相关显示,2007和2009年均具有2个热点和1个冷点区域,2008年具有1个热点和1个冷点区域,2010年具有1个热点和2个冷点区域,这些热冷点呈南北向或东西向分布态势。热冷点格局的叠加图显示,研究区内存在1个强热点、1个弱热点和1个强冷点,其中弱热点覆盖的区域在4年间表现为热点和冷点的交互变动。对7—11月平均海表温度和叶绿素a浓度的分析显示,热点和冷点均为中心渔场,热冷点形成的温度条件无显著差异;热冷点形成的叶绿素a浓度范围为0.2~1.1mg/m3,其中冷点区域的浓度相对较高。

Aanlyzing spatial aggregation of Ommastrephes bartramii in the Northwest Pacific Ocean based on Voronoi diagram and spatial autocorrelation

An integrated method of Voronoi diagram and spatial autocorrelation was used to explore global spatial pattern, local spatial hot spot and its variation of fishery resources abundance of Ommastrephes bartramii in the Northwest Pacific Ocean. The O. bartramii within the boundaries from 38°N to 45°N and 150°E to 160°E from 2007 to 2010 in the Northwest Pacific Ocean was selected as the research subjects, based on the original fishing data of each fishing boat of China. Using an ArcGIS environment, the spatial aggregation patterns of O. bartramii were revealed by using the global spatial autocorrelation statistics of both Moran's I and General G, as well as mapped both spatially and visually. In the fields of fisheries resources and spatial analysis, sea areas with clustered high productivity are hot spots, whereas sea areas with clustered low productivity are cold spots. The local spatial autocorrelation statistics show that, there were 2 hot spots and 1 cold spot in both 2007 and 2009, and there were 1 hot spot and 1 cold spot in 2008, while there were 1 hot spot and 2 cold spot in 2010. These hot or cold spots were distributed along either a north-south or an east-west axis. An overlay map of the four years of hot/cold spots demonstrates that there was 1 strong hot spot, 1 weak hot spot and 1 strong cold spot across the study area. The strong hot/cold spots were always the same spots for each year, while the weak hot spot was changed its state between a hot spot and a cold spot. An analysis of the variation of spatial hot spots based on monthly mean (July to November) sea surface temperature (SST) and monthly mean (July to November) chlorophyll-a concentration (Chl a) demonstrated that, both hot spots and cold spots are central fishing grounds. There is not obvious difference of SST between the hot and cold spots, while the hot and cold spots were observed in the areas with 0.2 to 1.1 mg/m³ Chl a concentration but the Chl a concentration of a cold spot is larger than that of a hot spot.