Preliminary Studies On Otolith Daily Increment And Growth Of Taihu Icefish In Three Gorge

Taihu icefish(Neosalanx taihuensis) is one of the most famous species in Taihu Lake. Based on the observation of microstructure and daily increment on otolith of Taihu icefish sampled from Jiangjin of Yangtze river in 2006, the growth and the spawning date of Taihu icefish were studied.The main results were as follows:1. The primordium, growth core and daily increment on the otolith of Taihu icefish could be observed clearly under microscope. Only one growth core could being found on the otolith,its long radius range was 20.0～82.5μm,,the average was 43.2μm;and there was only one black primordium in the core,its long radius range was 7.5～32.5μm, the average was 20.8μm.There were high denstity areas and optically low dense areas alternately on the otoliths.The trans check was easily distinguished on most of the otoliths.2. Short radius and long radius of otolith was correlated. The relationship between long radius of otolith and body length was linear, the equation was: SR=15.553＋0.6866LR, n=90, R²=0.7412; and the relationship between long radius of otolith and body length was linear too,the equation was: BI＝16.986＋0.1099LR, R²=0.7626,n=90; whereas no relationship between long radius of otolith and body weight.3. The growth model of body length fitted into exponential functions, the equation was: BL=7.833D^0.3997, R²=0.8069, n=90; and the weight fitted into logarithm formula, the equation was: W=0.0446e(0.244D), R²=0.8104, n=90; the relationship between body length and weight fitted into W_t=aL_t^b function, the equation was W_t=0.1×10^-5L_t^3.3529,R²=0.9163.4. In 2006, the date of spawning seemed to occur on February 11,and the last date appeared to be May 27.The spawning date of Taihu icefish in Yangtze river were maily in March and April, these were ahead of the spawning date in Taihu.