浙江省帆张网捕捞强度分布的提取方法

捕捞强度是渔业资源管理和评估领域的重要参数之一。传统的计算方法无法满足实时、大范围、快速统计时空分布的需要。本文提出根据VMS数据对渔船生产活动划分作业阶段；结合帆张网渔船的作业特点，采用阈值划分和密度聚类算法提取网位，计算各航次的捕捞时长；划分地理格网并累加其范围内的捕捞时长，以各格网平均每平方公里累计捕捞时长(h/km2)作为帆张网捕捞强度的量化依据，并可视化捕捞强度空间分布。本研究以2017年浙江省所属帆张网渔船的北斗VMS船位数据为研究对象，共提取有效作业航次733个，网位6021个，累计捕捞时长736 761.78h。在121.6E~126.5E，27.6N~33.9N范围内划分0.1°×0.1°地理格网，2017年上半年帆张网捕捞相对分散，各格网平均捕捞强度11.26 h/km2；下半年相对集中，平均捕捞强度12.83 h/km2；全年平均14.76 h/km2。其中，在125.4E~126.1E，31.2N~32.1N范围内捕捞强度最大，平均28.51 h/km2。本文设计的网位提取、捕捞时长、捕捞强度空间分布，为分析帆张网渔船作业状态和捕捞强度量化提供新的研究思路。

Extraction method of stow net fishing intensity distribution in Zhejiang Province

Fishing intensity is one of the important parameters in the field of fishery resource management and assessment. The traditional calculation method cannot satisfy the needs of real-time, large-scale, fast statistical spatial-temporal distribution. This paper proposes to divide the operation stages of fishing vessel production trip based on VMS data; combined with the operating characteristics of stow net fishing vessels, use the threshold position and density clustering algorithm to extract the net position, and calculated the fishing duration of each trip; the geographical grid is divided and accumulated within its range. The average fishing duration per square kilometer (h/km2) of each grid was used as the quantitative basis for the fishing intensity of the stow net, and the spatial distribution of fishing intensity was visualized. In this research, the Beidou VMS position data of the stow net fishing vessel belonging to Zhejiang Province in 2017 was taken as the research object. A total of 733 effective operating trips and 6021 net positions were extracted, and the total fishing time was 736 761.78h. Geographic grids of 0.1° × 0.1° are divided in the range of 121.6E ~ 126.5E and 27.6N ~ 33.9N. The stow nets in the first half of 2017 were relatively scattered, and the average fishing intensity of each grid was 11.26 h/km2; relatively concentrated in the second half of the year, with an average fishing intensity of 12.83 h/km2; the annual average of 14.76 h/km2. Among them, in the range of 125.4E ~ 126.1E and 31.2N ~ 32.1N have the highest fishing intensity, with an average of 28.51 h/km2. The extraction net position, fishing duration and spatial distribution of fishing intensity were designed in this paper provides new research ideas for analyzing the operation status of fishing nets and the quantification of fishing intensity.