Research Journal of Life Science APRIL-2021 Volume 8 NO. 1 (7-14) journal homepage: www.rjls.ub.ac.id How to cite this article : Rahman, M. A., Iranawati, F., Sambah, A. B. (2021). Design and Effect of Escape Vent in a Trap on the Catch of Blue Swimming Crab (Portunus Pelagicus): A Preliminary Study. Research Journal of Life Science, 8(1), 7-14. https://doi.org/10.21776/ub.rjls.2021.008.01.2 Design and Effect of Escape Vent in a Trap on the Catch of Blue Swimming Crab (Portunus Pelagicus): A Preliminary Study Muhammad Arif Rahman 1*) , Feni Iranawati 2) and Abu Bakar Sambah 3) Faculty of Fisheries and Marine Science, University of Brawijaya Email Address : arifelzain@ub.ac.id Abstract Blue Swimming Crab (Portunus pelagicus, BSC) is one of the Indonesian important fisheries commodities often captured by traps. Under Decree No. 56/2016, the Ministry of Marine Affairs and Fisheries managed the BSC, with the standard size of BSC is >10cm of Carapace Width (CW) or >60 g of Weight (W), and non-berried or carried eggs for female. This study aims to determine BSC's crawling pattern toward the trap, design an escape vent on the trap, and assess catch of BSC using vented trap and non-vented trap. The video footage was used to examine crawling pattern of 30 BSCs on the laboratory. The study also includes field experiment by deploying twenty traps (10 vented traps and 10 non-vented traps) on the sea. The study obtained two crawling patterns of BSC, crawling forward and sideways with the most BSC crawled sideways. Design of escape vent was 4.6 cm length x 2.6 cm height. The BSCs captured in the vented traps have >10cm of CW, while 14% of BSCs in the non-vented traps have <10 cm of CW. The use of escape vent did not affect the catch (weight) of BSC in the trap. Introduction Blue Swimming Crab (Portunus pelagicus, BSC) is one of the most importance crustacean species in Indonesia and, together with crabs, accounted for 9.11% of total export value of fisheries product in 2017 (MMAF, 2018). Java Sea, South Sulawesi, East Sumatera, and Malaka strait are the importance areas for BSC's fishery (IMACS, 2015). The BSC was exported to various country in the form of frozen meat or canned meat. The biggest market for Indonesian BSC was the United State of America, followed by Japan, Malaysia, Singapore, France, England, and Thailand (APRI, 2019). In addition, increase in market demand and high economic viability were likely to increase fishing pressure of BCS (Nugraheni et al., 2015) and therefore, decreased Catch per Unit Effort (CpUE) and caused over fishing state of BSC fishery in some area of fisheries management (Wilayah Pengelolaan Perikanan, WPP) in Indonesia, such as WPP 712 (i.e. Java Sea) (Muhsoni et al., 2009; Budiarto et al., 2015; Tama et al., 2017).Since 2015, the Ministry of Marine Affairs and Fisheries (MMAF) (2018) has implemented the Ministerial Decree of Marine Affairs and Fisheries number 1/2015, which then been revised in 2016 by decree number 56/2016, to regulate and ensure the sustainability of lobster (Panulirus spp.) and crabs (Portunus spp. and Scylla spp.). The decree stated that legal size of BSC is >10 cm of carapace width (CW) or >60 g of weight (W), and also the BSC sould not carrying eggs. However, several studies stated that BSCs were captured in the various size of CW, ranged from 4.02 to 17.12 cm, in several Indonesian waters (Apriliyanto et al., 2014; Nugraheni et al., 2015; Kurniasih et al., 2016; Murni et al., 2018; Rahman et al., 2019). Collapsible trap or pot is one of the fishing gears that is used to catch the BSC in Indonesia (IMACS, 2015). Trap is categorised as passive KEYWORDS Crustacea; Escape gap; Passive gears; Size; WPP 712