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Abstract
The fishing industry of Hai Phong round-pillar crab trap is a highly selective fishery, the object of which is valuable for export and domestic consumption. However, in recent years, the number of crab trap boats has tended to decrease. The results of the research and investigation show that the length of the boat for trapping crabs in Hai Phong is small, with an average length of 9.9 - 15.8m. All fishing gears have the same structure and specifications, with a bottom diameter of 550 mm, a cage height of 200 mm, a mesh size of 2a = 30mm and smaller than the size of the cage net of round cylindrical crab traps specified in TCVN 10466: 2021 (2a = 50mm). The exploitation capacity of the vessels engaged in the trapping industry from 46.2-80.5kg/day and tends to increase by group of vessel lengths. The composition of catches is mainly the following groups: crabs, surface fish, octopus, fish species (melon fish, grouper, stretch fish, trout). The percentage of crabs that are not allowed to be exploited accounted for an average of 56.1% and the rate of crabs that were allowed to be exploited only accounted for 43.9%. Profit tends to increase by group of ship lengths, reaching an average of 205.9 - 313.1 million VND/vessel/year.