## 1 Introduction  
Direct resource surveys for fisheries research include trawl, ichthyoplankton, underwater acoustic, and sighting surveys, along with scientific evaluation. Resource quantity estimates of fishery resources based on these methods are of particular importance from the perspective of resource management of major commercial species [1, 2]. Trawl surveys quantify fishery catches primarily by using scientific research vessels and have been continuously conducted since 1930 to identify and evaluate the spatiotemporal distribution and resource quantity of major commercial fish species worldwide [3, 4]. In addition, given that the acoustic survey method using a scientific echosounder can estimate the spatiotemporal distribution and existing amounts of fishery organisms over large surveys area in a short period of time, research on major pelagic fish species such as North Pacific pollock and Atlantic mackerel has been widely conducted since the 1980s [5, 6, 7]. Acoustic surveys enhance the accuracy of acoustic estimations by identifying and determining the length distribution of major pelagic fish species alongside travel surveys [8]. Mid-water trawl surveys, which catch pelagic fish detected by scientific echosounders, have a significant advantage in species identification when a single species is caught. However, they are limited with respect to temporal and spatial analyses of biological resources, such as vertical distribution of specific fish species. Furthermore, such surveys based on body length analyses are limited if catches accumulate in the codend of trawl nets, in which multiple species are mixed and distributed according to the fluctuation of catch depth [9]. In addition, surveys using fishing gear can directly or indirectly affect the marine environment [10]. To minimize damage to biological resources, eco-friendly studies are increasingly being conducted to identify ecological characteristics, such as the depth distribution of organisms, by installing underwater cameras on trawl gear or using autonomous underwater vehicles (AUVs) or underwater drones [11, 12, 13, 14]. Unlike conventional research methods that involve the direct collection of target species, the recently developed and commercialized Deep Vision (Scantrol Deep Vision AS, Bergen, Norway) uses a stereo camera to identify and measure fish species passing through the device after being caught by mid-water trawls [15]. In addition, the system can determine the spatiotemporal distribution of fish species caught along the trawl path and measure the length to an accuracy of within less than 5% [15]. Therefore, Deep Vision is an eco-friendly research technology that can be used to facilitate species identification, distribution depth, and length measurements without catching organisms, as the codend can be opened during trawl surveys. Previous comparative studies using Deep Vision have verified the results of species identification and length measurements for major migratory pelagic fish such as Arctic cod (_Arctogadus glacialis_), haddock (_Melanogrammus aeglefinus_), and Atlantic mackerel (_Somber scombrus_), using an acoustic survey and a mid-water trawl with Deep Vision installed [16; 17; 18]. An earlier study described the accuracy of the length measurement of fish imaged using Deep Vision [15]. Although Deep Vision has been introduced for the third time globally and for the first time in Korea, major fish species in Korean waters have yet to be sufficiently studied. In addition, the development of technologies to facilitate the sustainable management of domestic fisheries and conservation of marine ecosystems is required. Consequently, it is necessary to devise eco-friendly survey methods with minimal negative impacts on fisheries resources.