A crucial question to understand the fish diversity of floodplain lakes is related with the effects of environmental factors, which could act in several scales. Besides a broad geomorphologic unit can exhibit differences related with available habitats and distance to colonizers sources. This question is running to be more and more important due the climatic changes that are changing the intensity of events of drought and flood. In this decade, the Amazon basin was impacted by two most severe droughts of the last one hundred years. We analyze environmental data and measures of fish species richness and evenness of twelve floodplain lakes of Solimões River, at the Central Amazon. Six lakes are located inside a floodplain island and the other six are placed in the banks of Solimões River. We did four samplings in each lake, synchronized with hydrological cycle, aiming to collect data of rising, flood, receding and drought seasons. We employed two Discriminant Analysis (DA) assuming units composed by lake and season as grouping variable and physical-chemical parameters of water(dissolved oxygen, temperature, deep and transparency) and fish diversity estimates (species richness and evenness) as independent variables.
In the first DA (l = 0.07849, p < 0.000), the variables dissolved oxygen, temperature and, deep were significative. In the second DA (l = 0.56542, p < 0.000) both variables (species richness and evenness) were significative, showing a pattern of higher richness and lower evenness in the floodplain lakes placed at the banks and an opposite pattern in the lakes located in the island.