张氏的年龄结构及生长特性

Age structure and growth characteristics of Hemiculter tchangi Fang

以鳞片作为年龄鉴定材料,对长江上游特有鱼类张氏（Hemiculter tchangi Fang）种群的年龄结构和生长特性进行了研究。结果表明：张氏鳞片的年轮结构呈疏密切割型,2-3月是年轮形成最多的月份。其渔获物由1-4龄组成,其中857尾为1-2龄,占总数的83.84%;雌∶雄性比为1.07∶1,符合1∶1理论比值（X^2=0.754,P〉0.05,n=1001）,随着年龄的增长呈雌鱼多于雄鱼的趋势。体长主要分布在81-180 mm（94.9%）,体重主要分布在2.9-50.0 g（67.69%）。体长和鳞径呈直线关系,体长和体重呈幂函数关系且幂指数接近3,属于匀速生长类型,生长方程为Lt=196.05（1-e^-0.36（t＋1.26）;Wt=97.195（1-e^-0.36（t＋1.26）^3.145,拐点年龄为1.92龄,相应的体长体重分别为133.5 mm、29.13 g。

Hemiculter tchangi Fang is an endemic fish in the upper Yangtze River.The age structure and growth were investigated during the present study.Individuals were collected monthly from November 2005 to February 2009 in the estuary of the Chishui River,the first-order tributary of the Yangtze River,locating at Hejiang county of Sichuan Province.Scales were removed from 1023 individuals to determine individual age.Analysis of margins suggested that new annual rings on scales were formed mainly in February and March.The age of individuals ranged from 1 and 4 years.The preponderant age classe was 1~2 year old,making up 83.84% of the total.The total sex-ratio（♀∶♂） of the population is 1.07∶1,in accordance with the hypothesis of 1∶1.With the advance of age,the number of females was more and more than males.The body length of the samples mostly ranged from 81 to 180 mm（94.9%）.The body weight mostly ranged from 2.9 to 50.0 g（67.69%）.The radius of scale（from focus to the flank） took on linear relationship with body length,which can be used for body length back calculation.Back calculated lengths were similar to those predicted by the growth models.Growth of H.tchangi showed a constant speed style,which can be described with von Bertalanffy equation.Growth parameters estimated from the back calculated lengths and weight at age were：L∞=508 mm,W∞=97.195,k=0.197/year,t0=-1.26 years.The body weight growth inflexion point was 1.92,with the corresponding body length of 133.5mm and body weight of 29.13 g.