沱江宽体华鳅的年龄与生长

Age and Growth of Sinibotia reevesae in the Tuojiang River

2010年4～11月，在沱江的资中．隆昌段采集宽体华鳅（Sinibotiareevesae）573尾，研究了其年龄结构和生长特性。结果表明，微耳石厚度适中，易于磨片，且磨片后轮纹清晰，能准确反映宽体华鳅的年龄情况。收集到的沱江宽体华鳅体长主要分布在80～100mm，占总数的67．54％；体重主要分布在8～20g，占总数的69．11％；年龄由2～6龄组成，以3～4龄为主，占85．91％；种群雌雄性比为1：1．11。体长（L,单位mm）和体重（W，单位g）关系，雌雄群体间无明显差异（P〉0．05），其表达式为W=5×10-6L3.2868（n=573，R2=0．8202），为近等速生长类型。vonBertalanffy生长方程为Lt=128．72[1-e.-0.1974（t＋1.66]和Wt=42．95[1-e-0.1974（t＋1.66]-3.2868。体长生长速度和加速度方程为dL／dt=25．4133e-0.1974（t＋1.66和d2L／dt2=-5．0158e-0.1974（t＋1.66）[1-e-0.1974（t＋1.66），体重生长速度和加速度方程为dW／dt=27．8666e-0.1974（t＋0.66）[1-e—0.1974（t＋1.66）]2.2868和d2W／dt2=5．5009e-0.1974（t＋1.66[1-e-0.1974（t＋0.66）]1.2868×[3．2868e-0．1974（t＋0.66）-1]。生长拐点年龄为4．37，此时的体长和体重分别为89．46mm和12．99g。分析显示，沱江资中-隆昌段宽体华鳅自然种群资源未遭到严重破坏，但合理开发水电资源和选择合适的渔具、渔法是进行其资源保护的最有效措施。

Sinibotia reevesae is an endemic fish which lives only in the upper reaches of the Yangtze River.The purpose of this study is to determine age structure and growth characteristics of S. reevesae, and to propose effective measures to protect this species. A total of 573 specimens were monthly collected from April to November 2010 in Zizhong-Longchang section of the Tuojiang River, a tributary river of the Yangtze River. Standard length and body weight of each specimen were measured. Calculation of increment rate and growth indexes of body length and body weight of S. reevesae by YIN Min-Chen＇s methods （1995）. The growth of S. reevesae was fitted by the equation of Von Bertalanffy. Statistic analysis of all data were taken using Microsoft excel 2003 and SPSS 19.0. Lapillus moderate thick and there were clear rings or annuli on it which was the most accurate structure for age determination （Fig. 1）. The standard length of the samples mainly ranged from 80 to 100 mm, accounting for 67.54% of the total （Fig. 2）; total weight mostly ranged from 8 to 20 g and accounting for 69.11% of the total （Fig. 3）. Age of the fishes was identified to five age classes （2 - 6 years old） and individuals of 3 - 4 years old were dominated with frequency of 85.91% （Fig. 4）. Sex ratio （♀ ： ♀） was 1 ： 1.11. There was a linear correlation between standard body length and otolith radius, and the regression equation was L = 125.25Ro - 11.706 （n = 362, R2 = 0.802 3, P 〈 0.01） （Fig. 5）. The increment rate and growth index were analysised by back-calculated body length. The results showed significant difference between 2 - 3 years old and 4 - 5 years old, among them 2 years old was the highest （Table 1）. The relationship between standard length （L, unit mm） and total weight （W, unit g） showed no significant difference between males and females, which could be expressed as： W= 5 × 10-6L3.286 8 （n = 573, R2 = 0.820 2） （Fig. 6）. The body length has increased rapidly before 4 years old and the increment rate of body weight was the hightest between 3 and 4 years old （Table 2）. The growth of S. reevesae was in a constant speed which can be described with von Bertalanffy equation： Lt = 128.7211 - e-0.197 4（t＋ 1.66）], Wt = 42.95[ 1 - e-0.197 4（t ＋ 1.66）]3.186 8. Growth rate and acceleration growth rate equation of body length were dL/dt = 25.413 3 e-0.1974（t＋ 166）and dZL/dt2 =- 5.015 8 e-0.1974（t＋ 1.66）, respectively. Meanwhile, the growth rate and acceleration growth rate equation of weight were dW/dt = 27.866 6 e- 0.1974 （t ＋ 1.66） [1 - e- 0.1974 （t ＋ 1.66）]2.2868 and d2W/dt2 = 5.500 9 e-0.1974（t＋ 1.66） [1 - e-0.1974（t＋ 1.66）]1.2868 × [3.286 8 e-0.1974（t＋ 1.66） _ 1], respectively. The growth inflexion points was 4.37 years with the corresponding standard body lengths 89.46 mm and body weights of 12.99 g （Fig. 7）. Our data suggest that the resource ofS. reevesae had already been fished properly in Zizhong-Longchang section of the Tuojiang River. However, in order to better protect the resource of S. reevesae, measures such as strict ban to unreasonable catching and exploring the hydropower resources should be enhanced.