Analysis of the fishing intensity and management status of Anguilla japonica fry in the north coast of the Yangtze River Estuary- based on BeiDou VMS data and licenses data

The Japanese eel (Anguilla japonica) is one of the Red List of Threatened Species as an “endangered” species in the International Union for Conservation of Nature (IUCN). This study focused on analysing the fishing characteristics of fishing vessels targeting Japanese eel fry (glass eels) within Chinese waters and examining current management practices for this species. We analyzed the fishing behavior of 497 vessels along the north coast of the Yangtze River Estuary using data from the BeiDou Vessel Monitoring System (VMS). Key study insights included the following. (1) The correspondence between vessels' actual fishing range and licensed-designated fishing zones was approximately 48.6 %. (2) The observed fleets mainly fell into two operational categories: Single-vessel (a single vessel fishing independently, SV), representing 15.1 % of the fleets, and Primary-secondary-vessel (where a primary-vessel carries one to three secondary-vessels to the fishing area, anchors, and releases the secondary-vessels to fish independently, PSV), representing 84.9 %. (3) For SVs, fishing areas are categorised into one, two, and more than three areas. (4) Fishing areas varied by vessel size: vessels under 12 m primarily operated in offshore waters at 0–20 m depths, and those over 24 m operated in deeper offshore waters at depths of 20–40 m. In comparison, vessels between 12 and 24 m were located in intermediate areas. (5) Fishing intensity varied significantly across regions, with the highest concentration observed in coastal waters at 0–20 m depth off Rudong waters and Dongtai waters, where fishing density reached 13–18 vessels/100 km². (6) Since the implementation of the Yangtze River Estuary Fishing Ban Zone in 2021, the core fishing grounds of eel fry fishing has shifted from the Haimen at the Yangtze River Estuary to the Rudong and the Dongtai sea waters. Based on the aforementioned research outcomes, the following recommendations are proposed: 1) For PSVs, fishery management authorities should mandate the standardised installation of BeiDou VMS on secondary-vessels. 2) It is advisable to enact regulations stipulating the permissible quantity of fishing nets carried by vessels based on their specifications.