三峡库区鲢年龄结构与生长特征

Age structure and growth characteristics of silver carp(Hypophthalmichthys molitrix)in the Three Gorges Reservoir area

三峡库区为四大家鱼提供了广阔的肥育场所,在长江四大家鱼资源保护中具有非常重要的作用。目前关于库区四大家鱼种群结构和生长状况还不清楚,不利于其资源保护。2019年8月-2020年8月对三峡库区鲢(Hypophthalmichthys molitrix)的资源现状进行了调查,采集了388尾样本,分析了其年龄结构与生长特征。结果显示:采集到的鲢体长为100~805 mm,其中84.54%的鲢分布在100~400 mm;体质量为14.8~9166.3 g,其中82.22%的鲢分布在1.0 kg以下;年龄组成为1~7龄,其中90.98%的鲢为1~3龄。三峡库区鲢体长(L)与体重(W)呈显著的幂函数关系:W=8×10^(-6)L^(3.1389)(n=388,R^(2)=0.981),为匀速生长类型。体长与鳞径(R)呈显著的线性函数关系:R=0.0062L-0.0834(n=388,R^(2)=0.951)。体长、体重生长方程分别为:L_(t)=1014.50[1-e^(-0.1783(t+0.0455))];W_(t)=21848.11[1-e^(-0.1783(t+0.0455))]^(3.1389)。拐点年龄为t_(i)=6.4龄,对应的体长、体重分别是:L_(t)=693.03 mm,W_(t)=6605.67 g。与历史数据相比,三峡库区鲢种群表现出小型化趋势,主要体现在小个体鱼比例增加以及生长速度减慢。

The Three Gorges Reservoir area provides an extensive fattening place for the four major Chinese carp,which plays an essential role in the conservation of the four major Chinese carp resources in the Yangtze River.However,research are still lack on the population structures and growth characteristics of the four major Chinese carps in the Three Gorges Reservoir area,which is not conducive to conserving their resources in this area.A resource survey was conducted from August 2019 to August 2020 for the Hypophthalmichthys molitrix in the Three Gorges Reservoir area,and 388 samples were collected and analyzed for their age structure and growth characteristics.The results showed that the collected H.molitrix ranged from 100 to 805 mm in body length,mainly distributed between 100 to 400 mm,accounting for 84.54%of the total.The body weight ranged from 14.8 to 9166.3 g,mainly distributed below 1.0 kg,accounting for 82.22%of the total.The age ranged from 1 to 7 years,most of the individuals were 1~3 years,accounting for 90.98%of the total.A significant power function relationship existed between body length and body weight:W=8×10^(-6)L^(3.1389)(n=388,R^(2)=0.981),and exhibited a uniform growth pattern.A significant linear relationship existed between body length and scale diameter:R=0.0062 L-0.0834(n=388,R^(2)=0.951).The growth equations of body length and body weight were L_(t)=1014.50[1-e^(-0.1783(t+0.0455))]and W_(t)=21848.11[1-e^(-0.1783(t+0.0455))]^(3.1389),respectively.The growth inflection age was 6.4,and the body length and weight corresponding to the inflection age were L_(t)=693.03 mm and W_(t)=6605.67 g,respectively.The results indicated that the H.molitrix population in the Three Gorges Reservoir area showed a trend of miniaturization compared with historical data,which was mainly reflected in the increasein the proportion of small individual fish and the slowing of the growth rate.Overfishing before the ten-year fishing ban might be one of the main reasons for miniaturizing the H.molitrix population in the Three Gorges Reservoir area.