基于地统计学的南沙海域鸢乌贼渔场分析

Analysis of Sthenoteuthis oualaniens fishing grounds in Nansha sea area based on geostatistics

根据2013年南沙海域4个季度渔业资源声学走航调查数据,以声学探测生物量作为表征渔场分布的指标,对南沙海域鸢乌贼渔场进行分析。结果表明:4个季度鸢乌贼渔场均具有极强的空间相关性,其变异函数的块金效应C0值均小于0.25;通过变异函数,对不同季节分别采用不同理论模型进行拟合,夏季和秋季指数模型为最优拟合模型,春季和冬季分别为球型模型和高斯模型,夏季和冬季模型拟合较好,空间相关性较春秋季强烈;采用克里格法分季度对鸢乌贼渔场进行空间插值分析,各季度渔场生物量较高的区域大部分集中于靠近陆地的区域,表现出明显的斑块状和片状分布特点,且鸢乌贼渔场随时间变化,有逐渐向南转移的趋势。根据变异函数的理论模型和空间插值分析,对插值结果的理论值和实际值进行交叉验证发现,各季度的模型选择恰当。

Based on data of underway survey with Nansha sea area collected by acoustic method in four seasons of 2013, we analyzed fishing grounds of Sthenoteuthis oualaniens in Nansha sea area. Acoustic detection of biomass was used as indicator of fishing grounds after normal transformation. The results showed that there was very strong spatial correlation of S. oualaniens fishing grounds in four seasons, and the nugget effect values of variation function were all less than 0.25. Using the variable function, different theoretical models were fitted respectively by different seasons. Exponential model was the best fitting model in summer and autumn, while spherical model in spring and Gaussian model in winter. The models fitted better for summer and winter than for the other two seasons, which also had stronger spatial correlation. The results of Kriging spatial interpolation analysis of different seasons showed that the higher biomass of fishing grounds was most centralized in the region near the island, which had obvious characteristics of patchy distribution. The fishing grounds of S. oualaniens had a tendency to move south gradually over time. According to the result of cross validation of theoretical value and observed value, the theoretical models and Kriging interpolation of different seasons are appropriate.