Age, Grouth And Reproduction Of The Common Bream Abramis Brama In Ulungur Lake, Xinjiang, China

The common bream, Abramis brama (Linnaeus1758), belongs to Genus Abramis, subfamily Leuciscinae, family Cyprinidae. In the Ulungur Lake, common bream was served as an important species of local commercial fishery. From2007to2008,1844specimens of the common bream were collected from the Ulungur Lake and comparative research on their age, growth, reproduction and population structurewere conducted. The main objective of the study is to supplement fundamental biological data of the species and provide scientific information for local fisheries management. The main results are as follows:Lapillus, with distinctive bright and dark rings under transmitted light, was optimal age determination structure for common bream, especially the cross sectioned lapillus for estimating older ages. For lower age classes, scale, opercular bones and cleithrum were feasible for age determination but have possibilities to underestimate ages of the older individuals. Cross-sectioned lapillus had the highest agreement (90.5%) at values between two times age readings by the same reader, followed by plane sectioned lapillus (84.5%), cleithrum (83.7%), opercular bones (80.7%) and scales (74.2%) successively. Compared with basic age readings from cross-sectioned lapillus, agreement and CV (coefficient of variation) of other structures were as follows:plane sectioned lapillus (83.6%,1.5%), cleithrum (71.2%,5.1%), opercular bones (62.4%,4.3%) and scales (30.0%,13.8%). Fork length of all specimens ranged from28.0to474.0mm and weight varied between0.15to1750g with only11individuals with folk length longer than400mm. The results showed an allometric growth of common bream population in the Ulungur Lake, the fork length-weight relationship could be expressed as W=1.52х10-6FL3.4228(R2=0.9926, n=731), and no differences existed between sexes. The von Bertalanffy growth equation was fitted on the back-calculated fork length data for age classes ranged from1-11as FL=510.28(1-e-0.054(t+05903)). No significant differences in fork length at ages showed between males and females though females were slightly larger.The overall sex ratio (female to male) was1.17:1, which was variable with the age classes and fork length. Specimens in age groups1and2or with folk length ranged20-60mm were sex unidentifiable, age groups between3to8and60-180mm in fork length were male individuals dominated, while more females in groups older than9years and180-440mm in fork length. The first ages at maturity for female and males were6and5, while both sexes matured at fork length100mm. By age of6,50%males and by age of7,50%females were sexually mature, respectively, and fork length for both sexes were140mm. By age13for females and by age11for males with280mm in fork length for both sexes were100%sexually mature. Fork length, weight and age for males and females at first sexual maturity (FL50%) were179.10mm,79.9g,7.42years, and154.71mm,49.0g,6.10years, respectively. For individuals with fork length between154-426mm and weight between26.9-1330.0g, the absolute fecundity ranged from6186-420259eggs with a mean of104271; the relative fecundity for per folk length ranged from29.6-1045.4eggs/mm with a mean of337.2eggs/mm; the relative fecundity per unit of body weight ranged from40.8-391.1eggs/g and the mean was229.1eggs/g. The relationship between absolute fecundity and folk length was described as F=6.35x10-6FL4133(R2=0.8611), and relationship between absolute fecundity and body weight was F=289.2W-17547.0(R2=0.8774).