Abstract: Takif ugu obscur us , popula rly named o bscure puf fer, is a f ish o f river-to-sea mig rat ion. No rma l se xual ident if icat ion metho d f ails w hen in repro ductio n per iod, because of no rema rkable dif ference between indiv idual in se co ndar y chara cters. A comprehensive .. 2.. 14.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 水.. 产.. 学.. 报.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 20 卷..  se xual ident if icat ionmetho d based on fe ature and posture wa s applied to 1 038 ind. o f puf fer, w hich w ere caught f rom March 15 to May 30 in 1995 in the lower a reach o f Yanqt ze Riv er f rom Yizheng to Taizho u, w ith in a dista nce of six ty kilometer s. The accurate percentage reaches 95. 4%. This metho d do es no t injure the sample, and it is so simple that it co uld do ev en when the puf fer is in a state o f f ree sw imming in po o l. The method, i. e. the f ish behav iour pattern metho d, o f f ish sex-ident if icat io n is reported fo r the f irst t ime. The study of fers a new method on the sexual ident if icat ion o f f ish, a nd it has certain co nt r ibut io n to the art if icial propag at ion a nd pro duction o f f ish.