北江间的年龄与生长特征

Age and Growth Characteristics of Hemibarbus medius in the Beijiang River

于2007年4月至2009年3月间,在广东北江中上游地区采集间[鱼骨]（Hemibarbus medius）样本640尾,以鳞片作为年龄鉴定材料,对其种群的年龄与生长特征进行了研究。结果表明,间[鱼骨]鳞片上年轮结构清晰,前区主要表现为疏密型,而侧区主要为切割型;鳞片的边缘生长率表明,间[鱼骨]年轮的形成期主要为3-4月份。样本由0^＋-6^＋龄7个龄组组成,其中,雌性由1^＋-6^＋龄6个龄组组成,主要为1^＋-4^＋龄;而雄性由1^＋-5^＋龄5个龄组组成,主要为1^＋-3^＋龄;在4^＋-6^＋龄个体中,雌性78尾,雄性27尾,雌性显著多于雄性。体长（L,cm）与体重（W,g）的关系为W=0.011L^3.149（♀）、W=0.011L^3.135（♂）,协方差分析表明,雌雄个体体长与体重关系的差异不显著,所有样本体长与体重的关系式为W=0.011L^3.148。体长与鳞长（R,mm）呈幂函数及直线关系,关系式分别为L=6.387R0.853、L=4.569R＋2.587。拟合的von Bertalanffy生长参数为L∞=29.855 0 cm,k=0.223 1,W∞=483.889 8 g,t0=﹣0.928 2龄。对理论体长与实测体长、理论体重与实测体重进行χ^2检验,两者的差异均不显著,表明von Bertalanffy生长方程能较好地拟合间[鱼骨]的生长。体重生长的拐点年龄为4.21龄,拐点体长约为20.37 cm,体重约为166.19 g。作为渔业保护对策,建议起捕年龄3龄以上或体长17 cm以上的个体。

Total of 640 specimens of fish Hemibarbus medius was collected from April 2007 to March 2009 in the Beijiang River, Guangdong province to simulate their age and growth. We made measurement on each specimen and determined their age by scales, calculated, the standard length and body weight. Annual rings were formed primarily by the pattern of sparseness-denseness and the cut of the scales. The cut pattern was present on the rear-side region whereas the pattern of sparseness-denseness was visible in the prezone region（Fig. 1）. The percentage of marginal increment showed that the annual rings of the scales mainly formed from March to April（Fig. 2）. The sex ratio of female to male was 1.23︰1. The age of female was from 1^＋ to 6^＋, mainly in age of 1^＋, 2^＋, 3^＋ and 4^＋, while the age of male was from 1^＋ to 5^＋, mainly in age of 1^＋, 2^＋ and 3^＋. The proportion of females in age 4^＋﹣6^＋（74.29%） were much higher than males（25.71%） in the samples. The standard length of specimens ranged from 8.4 to 24.3 cm, of 86.20% specimen was less than 20 cm. The body weight ranged from 10.06 to 318.80 g, but 87.82% of them was less than 150 g（Fig. 3, Table 1）. The relationship between standard length and body weight was W = 0.011L3.149 for females, and W = 0.011L^3.135 for males, and W = 0.011L^3.148 for the combined sexes（Fig. 4）. No significant difference was detected in the growth rate between females and males. The relationship between standard length and scale radius（R） was L = 6.387 R 0.853 and L = 4.569 R ＋ 2.587（Fig. 5）. The von Bertalanffy growth arameters by combined both female and male based on length-at-age data were L∞ = 29.855 0 cm, k = 0.223 1, W∞ = 483.889 8 g, and t0 =﹣0.928 2 year（Fig. 6）. No any significant differences were found between the measured values of standard length, body weight and the estimated values of standard length and body weight derived from the von Bertalanffy equations by of χ^2-test. Growth inflexion point were 4.21 years with the standard length 20.37 cm, and weight 166.19 g, respectively（Fig. 7）. The standard length growth rate in von Bertalanffy functions gradually decreased with age, and the accelerated rate was below zero at all times and inclined to zero. The body weight growth rate in von Bertalanffy functions gradually increased before the growth inflexion point and then decreased, and the accelerated rate was above zero and decreased before the growth inflexion point, and then below zero. Our data suggest that the Hemibarbus medius population in Beijiang River had been overexploited. To protect the population for sustainable utilization, we suggest only fish longer than 17 cm（age 3） should be harvested.