Study on main catch composition and fishing ground change of light purse seine in Northwest Pacific

The light purse seine fishery in the high seas of the Northwest Pacific has been a new kind of pelagic fishery developed in China in recent years, with certain development potential. Understanding the catch composition and fishery change of light purse seine is important for the fishery management and development in the Northwest Pacific. Based on the statistical data from 2014 to 2019, we made a statistical analysis on the catch, investigating the catch per unit effort (CPUE) and the main catch composition of light purse seine in Northwest Pacific. Besides, we analyzed the seasonal variation of the distribution of the fishing ground had gravity center by the method of gravity center of catch and cluster analysis. The results show that: 1) There was a big difference in the annual catch yield and catch per unit effort (CPUE). Generally, the yield increased first and then decreased, and CPUE decreased year after year. 2) A total of eight species had been found, among which Scomber japonicus was the main catch species with a frequency of 100%, followed by Sardinops sagax with a frequency of 87.5%, and the catch of other species was relatively small. 3) The center of gravity of the fishing ground had gradually moved to the northeast since April, and turned back to the Southwest after reaching the northeast from August to October, showing a certain anticlockwise variation. The center of gravity of the fishing ground gradually moved to the northeast, and the center of gravity moved 0.92° east in longitude and 1.57° north in latitude from 2014 to 2019. 4) The clustering results show that the monthly yield barycenters could be divided into four categories (July, August, September and October, May and November, April, June). The annual yield barycenters could also be divided into four categories (2016, 2017 and 2018, 2019, 2014, 2015), indicating that there were certain inter-annual and seasonal changes in the light purse seine fishing grounds in the Northwest Pacific.