Chinese Sturgeon (Acipenser sinensis) in the Yangtze River: a hydroacoustic assessment of fish location and abundance on the last spawning ground

摘要: Chinese sturgeon ( Acipenser sinensis), was once widely dispersed in almost all watersheds draining towards the western coasts of Pacific Ocean. Today, species is one highly endangered fish China and can be found only Yangtze Pearl rivers their adjacent coastal marine areas. Due to construction Gezhouba Dam, spawning grounds for were drastically restricted but fortunately remained River at a small-scale site located just downstream along short reach river closely dam. Since 1998 we have undertaken annual investigations this area using hydroacoustic methods, order estimate size cohort selection habitats. Based on strength sizes echo signals, mature individuals discriminated from other then numerated. Most detected close bottom preferred distribute themselves areas with water depths less than 15 meters. Because different structures homogeneous granular material, distribution mainly influenced by perhaps current patterns. Total amount sturgeons entire estimated simply summing up numbers according identified densities depths. Usually, there about two separate activities which took place annually during observation period, scale activity being much larger first time following events. Estimations cohorts ground before wave upstream migrants appeared, 400 200 periods 1998-1999 2002, respectively. It demonstrated that: a) space not sufficient accommodate simultaneously, b) serious decline stocks investigational period seems indicated when comparing counts between 2002. The 50% alarming figure.