Growth characteristics and morphological features of Pseudobrama simoni in Changshu section of Yangtze River

The age,growth and morphological features were investigated in 362 samples of Pseudobrama simoni collected in Changshu section of Yangtze River from August to December of 2009 in order to reveal the population and growth status. It was found that the population of Pseudobrama simoni was comprised of 3 age classes ranging from dominantl 1 year old individuals(accounting for 51. 3%) to 3 year old individuals. The population of Pseudobrama simoni was changed from 62. 33 mm to 133. 65 mm in body length,primarily between 75 mm to 110 mm,representing 75. 41% of the samples. The Pseudobrama simoni had body weight from 3. 70 g to 46. 10 g,mostly between3. 70 g to 18. 70 g accounting for 80. 11%,with significant differences in body length and body weight and without significant differences in condition factor,body depth,head length and other 28 morphological features between female and male. The regression equation between scale radius( R) and body length( L) was expressed as L♀=391. 67R4- 2211. 8R3+ 4609. 7R2- 4171. 4R + 1463. 2(n = 156,P 0. 001,r2= 0. 6973),and L♂= 171. 22R4-895. 44R3+ 1719. 8R2- 1406. 4R + 486. 47( n = 178,P 0. 001,r2= 0. 7821),while the regression equation between body length and body weight(W) was described as W♀= 4. 52 × 10- 6L3. 2901(n =156,r2= 0. 94),W♂= 1. 09× 10- 5L3. 0915(n =178,r2= 0. 98). The growth characteristics of the fish were described by the Von Bertalanffy growth equation Lt♀= 142. 31 × [1- e- 0. 1125(t + 8. 3442)],and Lt♂= 153. 73 × [1- e- 0. 1024(t + 6. 8309)]. The growth inflexion point was found to be t = 2. 24 year old in the female,and t = 3. 96 year old in the male,young tendency in the lower reaches of Yangtze River.