【作者】 田辉伍；

【导师】 陈大庆；

【作者基本信息】 西南大学 ， 水产养殖， 2013， 博士

【摘要】 长薄鳅和红唇薄鳅隶属鲤形目(Cypriniformes)鳅科(Cobitidae)沙鳅亚科(Botiinae)薄鳅属(Leptobotia),主要分布于长江上游及其支流,均属长江上游特有鱼类,其中长薄鳅己被列入《中国物种红色名录》。近年来由于过度捕捞,水电梯级开发等原因致使两种鱼类的生境不断破碎、萎缩,资源恢复和物种保护面临着巨大挑战。本研究基于2010年10月至2012年12月调查数据对长薄鳅和红唇薄鳅的资源现状、个体生物学特征、种群动态、鱼类早期资源和种群遗传结构进行了研究。论文主要研究结果如下：1、研究区域共调查到鱼类102种,隶属于7目17科,物种数目与沱江的相似度最高,与金沙江的相似度最低,102种鱼类中20种为长江上游特有鱼类。研究区域物种数目与历史资料相比下降较多(38种),长薄鳅和红唇薄鳅的分布区域也已发生改变,长薄鳅分布于长江上游除沱江外的其它各水域；红唇薄鳅已难在金沙江、沱江和嘉陵江采集到样本。2、长薄鳅和红唇薄鳅耳石、脊椎骨和鳃盖骨均具有较为明显的年轮特征,年龄的可判读率依次为耳石>脊椎骨>鳃盖骨,鳃盖骨相对较差,因此综合选择耳石作为两种鱼类的年龄鉴定材料。透射光下,两种鱼类的耳石横截面由明带和暗带相间组成,其中红唇薄鳅耳石存在普遍的原基分离现象。长薄鳅和红唇薄鳅的耳石年轮形成时间主要为3-6月。1525尾长薄鳅样本由1-9龄9个年龄组组成,体长59-461mm(100-250mm占72.76%),体重3.1-1333.7g(<250g占90.43%)；1658尾红唇薄鳅样本由2-7龄6个年龄组组成,体长70-166mm(90-130mm占3.12%),体重4.4-60.9g(10-30g占78.71%)。两种鱼类的生长参数如下：长薄鳅-k=0.133／年、L一654.99mm、t0=-0.049、,t1=8.42年；红唇薄鳅k﹦0.232／L=220.17mm、t0=一0.053、t1=4.67年。拟合的生长方程分别为：长薄鳅L1一654.99(1一e),红唇薄鳅厶=220.17(1一e)两种鱼类的生长特征差异较大,表现为长薄鳅生长速度较慢、L。值相对较大、拐点年龄较高；红唇薄鳅生长速度较快、L。值相对较小、拐点年龄较低。长薄鳅胃含物共检出8类21种(属),红唇薄鳅共检出7类15种(属),两种鱼类均以小型鱼类、甲壳类、软体类和昆虫类为食,其中甲壳类和小型鱼类为长薄鳅的主要食物来源(重量百分比>75%),钩虾和蜓科幼虫为红唇薄鳅的主要食物来源(重量百分比>65%)。两种鱼类的食物组成多样性指数和均匀度指数属中等水平,优势种集中性较高,因此可初步判定长薄鳅为偏食较大型底栖动物的肉食性鱼类,红唇薄鳅为偏食较小型底栖动物的肉食性鱼类。长薄鳅和红唇薄鳅雌雄性比分别为1.238：1和1.222：1,初次性成熟年龄分别为2.3龄和3.5龄,相应体长分别为175.40mm和123.04mm。成熟个体平均卵径分别为1433.40±236.20um和1361.40±214.40u.m,均属一次性产卵类型鱼类。长薄鳅绝对怀卵量和相对怀卵量分别为22484±6422粒和58.74±15.64粒/g,红唇薄鳅分别为4513±1411粒和161.6±26.2粒／g,长薄鳅和红唇薄鳅的繁殖时间集中在6-7月。3、长薄鳅总死亡系数(Z)、自然死亡系数(M)、开发率(E)和开捕体长(L。)分别为0.810、0.208、0.740和103.96mm,红唇薄鳅分别为1.580、0.393、0.750和91.75mm。根据体长股分析模型,2011年和2012年长薄鳅年均资源量(B)为8.00吨和8.09吨,最大可持续产量(MSY)为4.08吨和4.79吨,红唇薄鳅年均资源量(B)为2.63吨和2.39吨,最大可持续产量(MSY)为1.10吨和1.01吨。根据B-H动态综合模型,长薄鳅和红唇薄鳅当前开发率(0.740和0.750)均高于最佳渔业开发率(0.430和0.636),显示两种鱼类均已处于过度捕捞状态。4、2010-2012年江津江段长薄鳅和红唇薄鳅年平均产卵量为0.62x108ind和0.52×108ind。根据鱼卵发育时期和流速推算,长薄鳅核心产卵场主要为弥沱(弥沱镇一黄市坝)、榕山(铜车湾—楼坊头村)、合江下(茶息亭一赤水河口)和朱杨(朱杨溪一大堂河)4个：红唇薄鳅核心产卵场主要为泸州(桓子树一泸州城南)、上白沙(石鼻子村一鹿角树)、朱沱(龟剑滩一幺店子)和朱杨下(罗林村一二溪)4个。相关分析结果显示,两种鱼类产卵行为与水温和水位的变化存在显著相关关系(P<0.05)。5、采用线粒体DNA序列分析了长薄鳅8个群体176尾样本、红唇薄鳅4个群体146尾样本的遗传结构,长薄鳅和红唇薄鳅Cyt b基因序列分别检出变异位点25和36个、单倍型25和39个,单倍型多样性(凰)为0.60852和0.87008,核苷酸多样性(n)为0.00089和0.00337。控制区基因序列共检出变异位点50和56个、单倍型44和55个,单倍型多样性(凰)为0.90709和0.97253,核苷酸多样性(n)为0.00315和0.00689,结果显示红唇薄鳅的遗传多样性较长薄鳅高。长薄鳅和红唇薄鳅单倍型网络结构图和N J树均未显示与地理种群相关的信息。长薄鳅和红唇薄鳅群体间和群体内的分子变异方差分析结果表明：两种鱼类种群内的变异均大于种群间的变异,变异主要来自种群内部,群体遗传分化不显著(F<0.05),种群基因交流十分频繁(Nm>1)。中性检验值Tajima’s D. Fu and Li’s D*、Fu and Li’s F*和单错配分布结果显示长薄鳅经历了最近的种群扩张事件,红唇薄鳅难以确定是否经历了最近的种群扩张事件。更多还原

【Abstract】 Elongate loach (Leptobotia elongata) and Redlip loach (Leptobotia rubrilabris), belong to Leptobotia of Cobitidae, Cypriniformes, are native species of the Yangtze River. These two species mainly distributed in the upper reaches and branches, due to over fishing and development of hydropower, the habitat of these fish species has been in serious danger. Elongate loach is listed in "China Species Red List". This study aims to provide a data record and comprehensive analysis of Elongate loach and Redlip loach population in the Yangtze River. The field inventory was conducted in September2010to December2012,1025specimens of elongate loach and1658specimens of redlip loach were collected from the upper reaches of the Yangtze River, Based on the inventory data, the analysis of the biological characteristics of individual fish, population dynamics, genetic structure and variation of elongate loach and redlip loach are carried out, the findings of this study are:1. Although there were140fish species distributed in the study area. However, only102species were collected which belong to7orders and17families in this study. Among the collected species,20species were endemic of the upper reaches of the Yangtze River. The species similarity is highest between the study area and the Tuo River, while the lowest species similarity is between the study area and the Jinsha River. Comparison with the historical data indicates that the distribution area of elongate loach and redlip loach changed. Elongate loach can be collected in all section in the upper reaches of the Yangtze River except the Tuo River, whereas redlip loach substantially disappeared in the Jinsha River, the Tuo River and the Jialing River, and samples were merely collected in mainstream and the Minjiang River recently. The average annual catches of elongate loach have been dramatically decreased more than5tonnes from the last decade. Reflecting field survey, redlip loach also experiences significant fishing pressure in the study area.2. Both Elongate loach and redlip loach have clear annulus differences on otolith, vertebrae and opercular. The ability of discriminating elongate loach and redlip loach decrease as the order as: otolith, vertebrae and opercular decrease. The average error between otolith and vertebrae is higher than that of otolith and opercular. Otolith was selected as verification for identifying age of elongate loach and redlip loach. Observed in transmitted light, translucent band and opaque band arranged in circles on the cross-section of otolith, and the separation phenomenon widespread in the otolith primordial of redlip loach. Results of marginal growth increment showed that new ring of otolith formed mainly from March to June both in elongate loach and redlip loach.The relationship between otolith radius and body length of elongate loach and redlip loach were linear correlation. Results of age identification showed that the collected elongate loach samples are in9age groups from1to9ages, the range of body length is from59to461mm, and the weight is from3.1to1333.7g. While the redlip loach samples are in6age groups from2to7ages, the body length is from70to166mm, and the weight is from4.4to60.9g. Because of no significant difference of growth parameters obtained from back-calculation body length and Shepherd method, the average value of the parameters estimated from two methods were taken advantage of as the basic data for the following analysis. In terms of elongate loach, b=3.085, k=0.133/year,L∞=654.99mm, t0=-0.049year and ti=8.42years; for redlip loach, b=2.988, k=0.232/year, L∞=220.17mm, t0=-0.053year and ti=4.67years. Growth equation of elongate loach is Lt=654.99(1-e-0.133(t+0.049),and that of redlip,oach was Lt=220.17(1-e-0.232(t+0.053)). growth characteristics of the two species were significant different: elongate loach grows more slowly with relative large L∞and high inflection point of the weight growth. But the redlip loach grows faster with relative small L∞and lower inflection point of the weight growth.The diet of elongate loach consisted of21prey items from a widely array of biological groups which belong to8categories, while the diet of redlip loach consisted of15prey items which belong to7categories. Elongate loach mainly feeded by fish, crustaceans, molluscs, insects and so on, its main food source were gammarid and small fish (weight percentage%W>75%). Redlip loach mainly feeded by crustaceans, molluscs and insects, and the major food were gammarus and the larvae of Aeshnidae (weight percentage%W>65%). Prey diversity and prey evenness in a medium level in both loaches, which indicated the high concentration of dominant species in diets. It can be concluded that elongate loach mainly feeded by larger benthic fauna, and redlip loach mainly feeded by smaller benthic fauna.Sex ratio of elongate loach and redlip loach were1.238:1and1.222:1.The minimum ages of individuals at first maturity were2.29year and3.48year, with corresponding body length of175.40mm and123.04mm, respectively. Average egg diameters of mature individuals were1433.40±236.20μm and1361.40±214.40μm, respectively, and the style of spawning of them were one-off. Absolute fecundity and relative fecundity were22484±6422egg,7224±2972egg and58.74±15.64egg/g,251.1±23.7egg/g, respectively. Survey on the early age fish population and coefficient of maturation analysis showed that the spawning activity of both elongate loach and redlip loach took place from June to July.3Population parameters estimated from length-converted catch curve and other empirical formulas were derived:For elongate loach:Z=0.810, M=0.208, E=0.740and LC=103.96mm. For redlip loach:Z=1.580, M=0.393, E=0.750and LC=91.75mm. According to length-based cohort analysis (LCA) model, the average annual stock biomass (B) of elongate loach were8.00tonnes and8.09tonnes, the maximum sustainable yield (MSY) were4.08tonnes and4.79tonnes, respectively in2011and2012. The average annual stock biomass (B) of redlip loach was2.63tonnes and2.39tonnes, the maximum sustainable yield (MSY) was1.10tonnes and1.01tonnes, respectively in2011and2012. According to Beverton-Holt dynamic model, the current exploitation ratios (0.740and0.750) were higher than the maximum exploitation ratio (0.430and0.636). These results suggested that both elongate loach and redlip loach had been over-exploited.4According to the survey results from2010to2012, the average fecundity of elongate loach and redlip loach were0.62×108ind and0.52×10ind at jiangjin section in the upper reaches of the Yangtze River. The results of spawning ground showed that18sections and10sections were suitable for elongate loach and redlip loach to spawn. The major spawning ground for elongate loach were Mituo town to Huangshiba village, Tongchewan village to Loufangtou village, Chaxiting village to Chishui estuaries and Zhuyangxi town to Datanghe village. The main spawning ground for redlip loach were Huanzishu village to Luzhou south, Shibizi village to Lujiaoshu village, Guijiantan village to Yaodianzi village and Luolin Village to Erxi Village. The spawning behavior was significantly correlated with water temperature and water level. While the water flows velocity does not have significant impact on the spawning.5In this study,176specimens of elongate loach were collected from8sample sites and146specimens of redlip loach collected from4sample sites for the genetic structure analysis. With the utilization of mitochondrial DNA analysis,25and36variable sites,25and39haplotypes of elongate loach and redlip loach were detected by Cyt b gene sequences, and haplotype diversity(Hd) were0.60852and0.87008, nucleotide diversity (π) were0.00089and0.00337, respectively.50and 56variable sites,44and55haplotypes of elongate loach and redlip loach were detected from control region gene sequences, and haplotype diversity (Ha) were0.90709and0.97253, nucleotide diversity (π) were0.00315and0.00689, respectively. The results showed that the genetic diversity of redlip loach was higher than elongate loach. Haplotype network structure and NJ molecular phylogenetic tree of both two fishes were not sharp branch or geographic populations. Hierarchical analysis of molecular variance (AMOVA) of Cyt b and control region gene sequence among and within populations revealed no significant genetic structuring among populations and variation were mainly within the population. Also, there was no significant population structure (Fst<0.05), and estimates of gene flows among groups were relatively high(Nm>1). Significant values of Tajima’s D, Fu and Li’s D*and Fu and Li’s F*, together with uni-modal mismatch distribution indicated that elongate loach had experienced recent demographic expansion, but the redlip loach had not clear experienced recent demographic expansion.更多还原