The ult rasonic telemet ry sy stem co nsisted of a so nic r eceiv er, a hy dro phone and sonic t ransmitters ( tags) , all of w hich w ere made by Sono tr onics, I nc. , U SA. U ltr aso nic tags ( tw o ty pes: 78kHz a nd 40kHz) w ere teste d in the Y ichang reach be low Gezhouba Dam and fo und that the so nic signal could be detected an est imated 1500m r ange. The receiver-hy dr ophone sy stem w as mounted on a gla ssf iber bo at ( 6. 3 meter lo ng, 63. 4 kW outboa rd mo to r ) , using t riangulat ion, enabled accur ate lo cat ing o f f ish w ith GPS assistance. Ta gged individuals could be identif ied by the sig nals f rom the so nic-coded tags. 15 of f inal sexua l mature stur geon wer e tagged below Gezho uba Dam at the Y ichang reach o f Yangt ze Riv er in Octo ber 1995 and 1996. The scanned area w as f r om the dam to the reach at Yidu City, cover ing abo ut 50 km in length. All o f 10 f ish tagg ed w ere located in 1996, and mo nitored their mo vement s o f each f ish during their pre-spaw ning, po st-spaw ning and spaw ning. The reach wa s survey ed 4 t imes each da y. 10 of the tagg ed f ish were located totally 573 t imes. Each of them w as successiv ely lo cate d f or 6~ 48 days respectiv ely, averaging 19. 8 day s. The telemetr y technique used in Yangt ze R iver could be used to studies on mig rat ion, lo cat ing breeding sites a nd spaw ning r equirement s of o ther f ishe s o r aquat ic an-i mals in the Yangtze and other rivers.