||一、The purpose of this project is to survey and assess the crab resources in north of the Taiwan Strait and off Penghu. The main tasks include (1) to survey the dynamics of fishing boats aimed at the crabs in north of the Taiwan Strait and off Penghu, (2) to examine the main species composition of crabs from north of the Taiwan Strait and to design the logbook and develop the retrieval channel of logbook for collecting and analyzing spatiotemporal distribution of fishing effort, catch and CPUE, (3) to measure the crab wide for obtaining the size-frequency data and to analyze the reproductive biology of main crab. 二、The results showed that (1) the main fishing areas were between 25 and 28 degrees north and between 121 and 125 degrees east; (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 Portunus sanguinolentus was between 70 and 180 mm, and the smaller crab was found from June to Aug and Dec.; the crab width of Charybdis feriatus was between70 and 180 mm, and the smaller crab was found all year around; (4) the CPUE values of Charybdis feriatus were lower (beneath 20g/pot) from Mar. to Jul, one increased from Aug. to Nov, and decreased from Dec. ; the CPUE values of Portunus sanguinolentus were lower (beneath 10g/pot) from Apr. to Jul, and one also increased from August; (5) no or rare complete mature individual was shown in Jan., Sep. and Oct. for Portunus sanguinolentus, but there are some ones was found in the other months., the most proportion of the immature stage and early-developing stage were found from Nov. to Oct., but the minor proportion of the ones was found in Jul. and Aug.; no or rare complete mature individual was shown in March and from Aug. to Dec. for Charybdis feriatus; the most proportion of the immature stage and early-developing stage were found March and from Aug. to Dec., but the minor proportion of the ones was found in Feb. and Jul. ; (6) the first maturity length (L50) for for Portunus sanguinolentus and Charybdis feriatus were 9.854 and 8.538 cm, respectively.