Recently some of the world’s leading ecologists have claimed that the key to a sustainable biosphere is research on a long list of standard research topics in ecology. Such a claim that basic research will (in an unspecified way) lead to sustainable use of resources in the face of a growing human population may lead to a false complacency: instead of addressing the problems of population growth and excessive use of resources, we may avoid such difficult issues by spending money on basic ecological research. The long-term changes in fish community composition in the lake were associated with introduction and invasion of fishes; changes in fishing intensity; modifications of the littoral, and changes of the lake ecological regime. Water level fluctuations beyond natural have modified the littoral habitats, which are of specific importance during different life stages of fish. Water level has an immense impact on fish reproduction, survival, recruitment, population dynamics, and eventually determines the catches of commercially important species. See also chapter: "Fisheries Management" Within this Chapter: Fish Biology Effect of Water Level Fluctuation on Fish Spatial Variability and Abundance of Pelagic Fish. This information can be published in our peer reviewed journal with impact factors and are calculated using citations not only from research articles but also review articles (which tend to receive more citations), editorials, letters, meeting abstracts, short communications, and case reports. The inclusion of these publications provides the opportunity for editors and publishers to manipulate the ratio used to calculate the impact factor and try to increase their number rapidly.