The Biology Of Coreius Guichenoti (Sauvage Et Dabry) In The Upper Reaches Of The Yangtze River

Coreius guichenoti(Sauvage et Dabry),endemic to the upper section of the Yangtze River,belongs to Cypriniformes,Cyprinidae,Rhinogobio.It is one of the main commercial fishes in the upper section of the Yangtze River and weighs most in the catches of the upper section of the Yangtze River.C.guichenoti is a migratory fish,and lives through its whole life history in the river.However,C.guichenoti has a tendency of shrinking in habitat and declining in resource due to the environmental change and overfishing.This study mainly deals with the following two aspects of C.guichenoti:the age and growth and reproduction.The study also investigates the environment of the major survey stations in the upper section of the Yangtze River.The main results are as follows:7476 specimens were collected from 2005 to 2007 in Panzhihua,Yibin,Hejiang, Wanzhou,Yichang and Yidu,mainly from fishermen,fishmongers and the markets.The fishing gears include gill nets,crotchets and electro fisher.Partial data obtained during 2004 were adopted and 1470 specimens in total were used for the reproductive biology study,which were collected from Panzhihua,Yibin,Hejiang,Fuling,Mudong,Wanzhou and Yichang.The C.guichenoti stock had a relatively complex age structure which was composed of seven age groups from one to seven.The preponderant age groups in catch were 1-4 accounting for 91.88%in total and the number of individuals from age 5 upwards declined sharply.The body length in catch ranged from 22.0 to 485.0mm,mainly 60-220mm(81.97%) and the body weight ranged from 0.1-2100.0g,mainly 0.1-150.0g (78.40%).The growth of C.guichenoti belongs to isometric pattern,which could be described by von Bertalanffy equation.The growth equations of body-length and body-weight were as follows:L_t=720.4[1-e^{-0.1096(t+0.7788)}]W_t=4587.7[1-e^{-0.1096(t+0.7788)}]^3.0311The body-weight growth inflexion point is 9.34,with corresponding body-length of 482.73mm,and the body-weight of 1363.26g.The study also calculates the limited age of C.guichenoti(Tmax) which is 26 years old.C.guichenoti matured at the age of 4 years old and the spawning season was from late April to middle July,with May and June as the reproduction peak period.The GSI of female attained highest during May and then during June.Male have two reproductive peaks:May and July.The spawned eggs of C.guichenoti first occurred on April 22 in 2007 when the average of water temperature was 19.5 to 20.3℃and the average Secchi water transparency was 14.0 to 15.6cm.The gonads at stage IV were first found on April 29 in 2007.All the spawned eggs and mature females were found in Panzhihua.The absolute fecundity of C.guichenoti is from 4464 to 131920 per fish,with an average of 46386±51589.28.The relative fecundity of C.guichenoti is from 5 to 73 eggs/g body weight,with an average of 36.60±27.65.The diameters of 158 oocytes sampled from a mature female of C.guichenoti were measured It ranges from 0.74 to 2.20mm,with an average of 1.59±0.31mm and 33.54%of oocytes ranged between 1.5 to 1.7mm.It was inferred from the egg-diameter distribution that C.guichenoti might be batch spawners.