||The purpose of this project is to survey and assess the crab resources in north of the Taiwan Strait. The main tasks include (1) to analyze the Taiwanese trawler fisheries’catch and effort statistics in north of the Taiwan Strait and to obtain the historic trend of abundance indices of the crabs resources, (2) to survey the amount and dynamics of fishing boats aimed at the crabs in north of the Taiwan Strait and to measure and obtain the size-frequency data, (3) to examine the main species composition of crabs from north of the Taiwan Strait, (4) to design the logbook and develop the retrieval channel of logbook.
According to the logbook data of Taiwanese pair (1970~1989) and otter(1970~2010) trawlers fisheries’ catch and effort statistics, there is more abundant crab resources in the center and north of Taiwan Strait, and it distributes between 24 degree and 26.5 degree north and between 121 degree and 123 degree east. The main fishing season is during winter (from Jan. to Dec.). The CPUE trend shows that the value decreases from 1970 to 2001 and CPUE increases after 2001.
According to the logbook data from the specimens of crab-trap fishing in 2013 (from Mar. to Oct.) showed that (1) the main fishing areas were between 25 degree and 27 degree north and between 121 degree and 123 degree; (2) the main fishing species were Charybdis feriatus, Portunus sanguinolentus and Charybdis natator in the northern waters of Taiwan Strait, and the most abundant species is Charybdis feriatus; (3) the crab width of is Portunus sanguinolentus between 88 and 180 mm, and the smaller crab was found from June to Aug; the crab width of is Charybdis feriatus between70 and 180 mm, and the smaller crab was found from June to Oct.; (4) the CPUE values of Charybdis feriatus were lower (beneath 20g/pot) from Mar. to Jul, and one increased from Aug; the CPUE values of Portunus sanguinolentus were lower (beneath 10g/pot) from Apr. to Jul, and one also increased from August.