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.