【作者】 茹辉军；

【导师】 宁应之； 王洪铸；

【作者基本信息】 西北师范大学 ， 生态学， 2008， 硕士

【摘要】 河流-泛滥平原生态系统形成于长期的周期性的水文动态过程,具有复杂的生境异质性,是生物多样性最为丰富区域之一。长江中下游泛滥平原是我国生物多样性极其丰富的地区。然而,近50年以来,其水文连通受到江湖筑坝建闸的严重阻碍,加上围湖造田、环境污染以及酷渔乱捕等原因,长江水系鱼类多样性面临极大威胁,鱼类资源严重衰退。因此,对泛滥区水体鱼类物群落结构时空格局和洄游性鱼类洄游规律的研究,有助于了解江湖水文自然连通的生态功能,从而为鱼类资源保护和湖泊渔业科学管理提供科学依据。然而,目前我国在这方面的研究仍为空白。有鉴于此,本研究以长江中下游大型通江湖泊-洞庭湖的鱼类为研究对象,于2004年3-12月在洞庭湖出口城陵矶、东洞庭湖、南洞庭湖三个区域进行逐月调查采集,系统开展了鱼类群落多样性研究,探讨了江湖洄游性鱼类江湖洄游规律,主要研究结果与结论如下:1.共鉴定鱼类69种,隶属于6目14科44属。三个区域均以鲤形目种类数最多,占总种类数的63.8-65.5%。其中鲤科鱼类为最大类群,有41种,占总数的59.4%。按生态类型,洞庭湖鱼类分为江湖洄游性、江河山溪性和湖泊定居性3个生态类群。全湖月出现的鱼类种数为35±2,不同区域和不同季节间有一定差异。总体来看,湖区与长江干流的距离越近,种类数达到峰值的时间就越早,这暗示夏秋季鱼类由江入湖从而对洞庭湖鱼类资源进行补充。2.以优势度大于5000为标准对洞庭湖优势种鱼类进行了测度。结果显示,洞庭湖优势种有鲤、鲫、短颌鲚等17种,且80%以上的优势种为湖泊定居性种类。各区域鱼类优势种组成差异较大。优势种分析表明,洞庭湖鱼类有向小型定居性种类发展的趋势。3.对洞庭湖鱼类多样性指数进行了分析计算,结果显示鱼类多样性较高,且在不同区域和季节有差异。Shannon-Weaver指数HI、Wilhm指数HB和Simpson指数D变动范围分别在1.85-2.99、1.96-2.98和0.52-0.80。Pielou均匀性指数E亦较高,EI和EB分别为0.41-0.69和0.45-0.68。与1974年调查结果相比,洞庭湖鱼类物种多样性明显下降,种类组成发生了改变,洄游性鱼类种类明显减少。生境丧失、江湖水文连通受阻是导致这种现象的主要原因。4.对不同水位时期的渔获物进行了分析。总体上看,不同水位时期的渔获物在组成上存在较大差异。渔获鱼类在丰水期最多,枯水期最少。从重量和数量相对丰度上看,丰水期主要经济鱼类有草鱼、黄颡鱼、铜鱼、鲤、鲫和蛇鮈;枯水期在重量丰度上以鲤为主,在数量丰度上则以短颌鲚、鱊和餐等小型鱼类为主。渔产量也表现出大体一致的规律,即在水位较高的月份产量较高。这一规律揭示泛滥区水体鱼类受周期性水位波动极大,这种水文扰动对丰富鱼类资源量有着积极作用。5.采用生物学法对江湖洄游性鱼类中四大家鱼和铜鱼的种群动态作出分析,对幼鱼入湖时间作出了推断,但尚难估计成鱼的出湖时间。总体来看,四大家鱼在洞庭湖出现时间为7-11月。四大家鱼主要分布于城陵矶和东洞庭湖,已不能到达离干流较远的南洞庭湖。根据草鱼和鲢鱼的种群动态,推测它们幼鱼的入湖时间分别为7和8月。铜鱼分2批进入洞庭湖。第一批为4-6月组,个体较大;第二批为7-11组,个体较第一批小。对江湖洄游鱼类入湖的关键时期研究表明,保持水文自然连通对补充湖泊鱼类资源、维持鱼类自然种群有着重要意义。更多还原

【Abstract】 Formed by long periodically fluvial dynamics, river-floodplain ecosystem hold high habitat heterogeneity and is one of the richest biodiversity areas on the earth. The mid-lower reaches of the Yangtze River basin in China has a high biological diversity. However, in the past fifty years, the natural hydrological connectivity has impaired strongly by the construction of dams and sluices as well as reclaiming of lake to cultivated land, water pollution and overfishing. Fish resources in the Yangtze River and associated water bodies have declined seriously. Many fishes are endangered. Therefore, the studies on spatial-temporal pattern of fish assemblage and fish migration rhythms are essential to enhance our understanding of the ecological functions of hydrological connectivity gradients. Unfortunately, to date there is little work conducted on this. In the present study, a large river-connected lake, Dongting Lake, was selected as target water, a monthly investigation on fish diversity was carried out, also preliminary studies on the rhythms of fish migration were conducted in March-December, 2004.Three sampling areas were located along a transect from the Yangtze mainstream to the lake center, i.e. Chenglinji, East Dongting Lake and South Dongting Lake. The main results are given as follows:1. Totally 69 fish species belonging to 6 orders, 14 families and 44 genera were recorded. In terms of species number, cypriniformes was the richest in each region accounting for 63.8-65.5% of the total. Among them, Cyprinids were the largest group, accounting for 59.4% of the total. As regards the habitat and flow preference of fishes, three ecological categories were divided as river-lake migratory, potamophilus and limnicolous. Monthly changes of species number were 35±2, with great spatial and temporal variations. Generally, with regard to species numbers, the smaller the distance between sampling area and Yangtze mainstream is, the earlier the peak is reached. This indicates that the fish population of lakes can be recruited when fish migrated from river to lakes at summer and autumn.2. We measured the value of dominance, and dominant species were determined as species with the value of dominance over 5000. The results showed that there were 17 species, including Cyprinus carpio, Carassius auratus, Coilia brachygnathus, et al. Over 80% dominant species were limnicolous. The composition of dominant species changed greatly spatially and temporally. Analysis indicates that small-sized fishes and limnicolous groups trend to dominate the fish assemblage.3. The diversity indices were calculated. The results showed that fish diversity of the lake was high. The diversity indices were HI 1.85-2.99, HB1.96-2.98 and D 0.52-0.80, while evenness indices were EI 0.41-0.69 and EB 0.45-0.68. Compared with investigation carried out in 1974, the species diversity of Dongting Lake declined greatly, supraspecific categories are all less than before. The composition of species changed significantly, the migratory fishes decreased dramatically. These phenomenon revealed that habitat loss and hydrological connectivity impeded are main factors caused it.4. Main catch of sampling areas in terms of different water flow period. Generally, the composition of catch was different in relation to water level fluctuation. The highest catch occurred in high-water flow period, while the lowest in low-water flow period. With regard to relative richness, there are some difference in the main catch, i.e. Ctenopharyngodon idellus,Pseudobagrus fulvidraco,Coreius heterodon,Cyprinus carpio, Carassius auratus and Saurogobio dabryi were present in high water level period, while Cyprinus carpio in low water level period. As regards fish yield, it also has the similar pattern, i.e. the higher the water level was, the larger yield occurred. The results show that the fishes in the floodplains are affected strongly by the seasonal fluctuation of water level, which have positive effects for fish population reinforcement.5. The fish biology method is applied to study population dynamics of migratory fishes including four major Chinese carps and brass gudgeon (Coreius heterodon). The key time period of young fish migrating from river into the lake is inferred. Four major Chinese carps occur during July-November in Dongting Lake. They mainly appear in Chenglingji and east Dongting Lake, and rarely be found in south Dongting Lake where is far from the mainstream of the river. Analyses show that the key times of grass carp (Ctenopharyngodon idellus) and silver carp (Hypophthalmichthys molitrix) migrating into the lake are July and august respectively. As to brass gudgeon, two groups were found while migrating into the lake. Group I occurs in Apr-Jun, which has larger individuals; group II occurs in July-November, which has smaller ones. The study of fish migration suggests that the interactions between the Yangtze River and its linking water bodies result directly habitat complexity and complement, therefore, natural hydrological connectivity favors the exchanges of fish resources and plays an important role in maintaining its natural population size.更多还原