松嫩湖群鱼类群落相似性

根据2008年5月至2011年1月对松嫩湖群20个主要渔业湖泊的鱼类资源调查,分析了该湖群鱼类区系特征和群落相似性状况。松嫩湖群的鱼类区系由4目9科34属46种和亚种构成,其中土著鱼类3目8科27属39种和亚种,包括中国特有种3种,中国易危种1种,冷水种5种;由5个区系复合体构成,以东部江河平原区系复合体为主体;鲤形目31种,鲤科26种,分别占优势;鱼类区系具有南北方物种相互渗透、古北界与东洋界交汇过渡的混色类群特征。目前松嫩湖群鱼类群落种类组成的相似度总体较低,群落数量结构的相似度总体较高,鱼类群落相似性面临的主要问题是自然与人为因素导致湖泊生态环境的变化和放养、移殖与过度捕捞导致鱼类资源的减少与小型化,二者的叠加效应使鱼类群落长期处于受损状态,群落结构及其相似性处在动态变化中,群落内种间关系的协调性、种群结构的合理性和群落结构的稳定性均在下降。针对这些情况和群落相似性现状,提出未来松嫩湖群湖泊渔业的发展方向是优化调整群落结构,发展多种群湖泊渔业,合理利用土著鱼类资源。

Similarity of fish communities in groups of lakes on the Songnen Plain, China

Low plain lake groups of the Songnen Plain are located in the northern part of the Northeast Plain in Heilongjiang and Jilin Provinces, China in a region with a temperate semi-humid climate. The lake groups cover a combined area of about 2,570 km². These lakes cover small areas with shallow basins, are spaced densely, and include various types of lakes, forming an important freshwater fishery in northeastern China. The lake groups were once part of a large paleolake in the Songnen Plain and are now drained by the Songhua, Nen and Huolin rivers. As a result, the lake groups and the rivers support closely-related fish fauna and have similar levels of species diversity. However, recent economic expansion and the resulting frequent interference from human activities are degrading the natural environment as well as the climate. The combined effects of these human-induced changes have attracted considerable interest to the study of the fishery resources of the lake groups; the lakes cover an area with high levels of biodiversity and are sensitive to environmental change. During May 2008 and January 2011, a survey of fishery resources was conducted at 20 lakes in the region to analyze the composition of the fish populations and gain an understanding of the characteristics of the fish fauna and the community diversity of the lake groups, to determine which species are dominant and to study the similarities of the fish communities. A total of 74,307 fish individuals and 7,907.6 kg of fish were collected in 20 lakes by gill net, trawl net and pull net. These included 46 species and subspecies, belonging to 34 genera, 9 families, and 4 orders, which included 392 surveys using one of the three types of nets. Most were endemic freshwater fishes of Asia, although Mylopharyngodon piceus, Ctenopharyngodon idella, Protosalanx hyalocranius, Megalobrama amblycephala, Hypophthalmichthys molitrix, Aristichthys nobilis, and Siniperca scherzeri were stocked and introduced species. Eight native and seven introduced/stocked species were dominant. Most of the native species belonged to Cypriniformes, including 31 species and subspecies or 79.49% of all fishes found; of those, 31 species were in the order Cypriniformes and 26 were members of the family Cyprinidae. The Cypriniformes and Siluriformes of the superorder Ostariophysi included 87.18% of the total fishes, representing a remarkably larger proportion of the total fish population than that of any other region in eastern China. The ichthyofauna of the lake groups consisted of 39 native species, belonging to 27 genera, eight families, and three orders, of which three are endemic to China, one is listed as vulnerable in China, and five are cold water fishes. Five faunal complexes make up the ichthyofauna of the lake groups and the eastern plain faunal complexes were dominant; 61.54% of the species were common species from the North and South of China, and 38.46% were northern endemic species. That is, there was an overlap and transition between the Palaearctic and Oriental realms. When the 190 pairs of lakes selected from the 20 lakes studied here were analyzed, 75.79%, 78.95%, and51.05% of the pairs were low or extremely low in the degree of similarity in species composition based on the Jaccard''s, Sorenson''s, and Morisita-Horn''s indices, respectively. For the same 190 pairs of lakes, 58.95% of the pairs were low and extremely low in the degree of similarity in biomass based on Morisita-Horn''s Index. For these 190 pairs 3.68% were low and extremely low in the degree of similarity in three ways: species composition, individuals present, and biomass. Overall, the species composition of the fish communities varied widely, weak relationships were found in the lakes based on the spatial distribution of fish species, the fish fauna of the individual lakes were not very diverse, and the structures of the populations appear stable. The degree of community similarity between the lakes was quite small based on the quantity of fish present in each lake. The relationships between the lakes are more similar when one considers the spatial distribution of the population, species diversity, and the stability of the populations. These findings suggest that natural and manmade factors are causing negative environmental changes that are resulting in a loss of fishery resources in terms of both biodiversity and biomass; anthropogenic factors include overfishing and the stocking of introduced species are causing a lack of similarity between the fish communities of the lake groups. A brief discussion of the future path for developing the fishery resources in this region is also provided.