Analysis of Hauling Net Hours for Gazami Crab (Portunus trituberculatus) Gillnets Based on the Beidou Vessel Monitoring System (BDVMS)

Abstract

Zhang, S.; Tang, F.; Fan, W.; Yang, S.; Zhu, W.; Zhang, H., and Cui, X., 2023. Analysis of hauling net hours for Gazami crab (Portunus trituberculatus) gillnets based on the Beidou vessel monitoring system (BDVMS). Journal of Coastal Research, 39(4), 663–674. Charlotte (North Carolina), ISSN 0749-0208.Gillnets are among the most widely used fishing gear in the world, and there are nearly 97 thousand gillnetters in China's offshore. With the decline of resource fisheries, the fishing quota has remained a topic of concern for the world's fishing nations. At the beginning of 2017, the Ministry of Agriculture and Rural Affairs of the People's Republic of China implemented the total management of marine fishery resources and began to launch the quota fishing experiment. The vessel monitoring system (VMS) provides a new data source for fisheries research. It is a new attempt to estimate fishing yield from VMS. Refined fishing intensity can be obtained through calculation of hauling time or net length. In China, the shipboard Beidou satellite navigation system terminal was installed on well-equipped fishing vessels. It sends vessel identification and location information at three minute intervals and with 10 m spatial resolution. In this paper, the speed threshold was used to consider the hauling duration of the net. The hauling nets' hours were calculated to estimate the catch rate with the hours. The speed thresholds of the 56 vessels were from 1.7 to 2.4 m/s. The hauling duration in hour of the vessels were distributed throughout eight fishing grounds in 2017. Hauling duration was divided into 0.01° × 0.01° grids based on coordinate locations. The average hauling duration of the nets was 1.7 h, and the maximum value was 41.5 h. There were approximately 514 thousand net hauling points, and the catch weight of the swimming crab (Portunus trituberculatus) was calculated to be approximately 4.7 million kg in 2017 based on the hauling duration data.