## 1 Introduction  
Due to the convergence of the Kuroshio and Oyashio currents (Figure 1), the North Pacific has become a significant fishing ground, especially renowned for its long-standing tradition of light-based fisheries [1, 2]. Despite a noted decline in recent years, the lit fishing industry continues to make a substantial contribution to the distant-water fishery [3]. The lit fisheries of the North Pacific are primarily concentrated in two regions: the west stock and the central-east stock (Figure 1). Approximately 600 fishing vessels using lights operate in the North Pacific. These vessels can be categorized into three main types: around 280 using stick-held dip nets to catch Pacific saury, 260 employing jiggers to catch squid, and 60 purse seiners primarily targeting club mackerel, spotted mackerel, and Japanese sardines. In the western stock, all three types of gear are utilized, whereas fishing in the central-east stock is predominantly conducted by squid vessels from China and Japan. These vessels operate from mid-May to early August, with peak activity occurring in June and July, during which nearly all vessels are actively engaged in fishing [3, 4, 5]. Although the fishing industry in the North Pacific has generally shown a downward trend, the central-east stock has experienced growth [4]. Comprehensive and efficient monitoring of these vessels is instrumental for the effective management of distant-water fisheries. Additionally, with the recent drastic climate changes, the precise dynamics of fishing movements combined with ecological environments could also aid in understanding the factors influencing the dynamics of fishing grounds, thereby providing a scientific basis for forecasting distant-water fishery conditions [6; 7; 8]. However, monitoring efforts for such lit fisheries in the high seas have been hindered by the lack of effective vessel monitoring data. Precise monitoring methods and long-term surveillance data for such fisheries remain insufficient. In recent years, nighttime remote sensing technology has been widely used for monitoring fishing vessels using lights and analyzing dynamic changes [9; 10; 11; 12]. Among the most prominent sources of nighttime remote sensing imagery are the Defense Meteorological Satellite Program's Operational Linescan System (DMSP-OLS) and the Visible Infrared Imaging Radiometer Suite's Day/Night Band (VIIRS-DNB), which are valued for their global coverage and long time series [13; 14]. Lit fishing vessels typically appear as small bright spikes in nighttime imagery, and traditional detection methods have primarily relied on visual interpretation, followed by the application of various threshold-based methods [15; 16; 17]. [PERSON] et al. [9] analyzed the spike features in VIIRS DNB data collected during moonless and cloudless nights and developed an algorithm that detected vessels by evaluating the sharpness of the light spikes. They also established a comprehensive process for filtering out land-based and gas flare sources. The results of the detection process were validated through vessel position data, confirming the algorithm's effectiveness. Building on this workflow, the Earth Observation Group (EOG) has further developed and refined the automated fishing vessel extraction process. They have designed an adaptive threshold method to accommodate varying weather conditions and released the corresponding  
Figure 1: Study region of the lit fishing grounds in the North Pacific (central-east stock, 176E–165W, 35N–48N), overlaid with the average sea surface temperature from the summer fishing season of 2020. The top global map shows the location of the study area, overlaid with the average cloud fraction from the summer fishing season of 2020. The cloud fraction data are sourced from GlobColour ([[http://globcolour.info](http://globcolour.info)]([http://globcolour.info](http://globcolour.info))), which has been developed, validated, and distributed by ACRI-ST, France.