Modelling the distribution of fish habitat type and habitat diversity in natural rivers.

• Effective river management requires analysis of spatial distribution and habitat diversity. • Under normal flow the distribution of fish habitat is along the river channel while under flood flow is on the banks. • Two-dimensional habitat diversity construction model accurately simulates habitat diversity regardless of flow magnitude. Analyzing the spatial distribution and habitat diversity of river habitats not only helps us understand river ecology and guides effective management, but also informs efforts to create suitable habitats for fish and restore environmental diversity. Henceforth, we developed a Two-Dimensional Habitat Diversity Construction Model to predict and analyze the variation and spatial distribution of fish habitat types under the normal (for both dry and wet seasons) and flood flows (for different return periods). Shannon and Simpson Index, and Habitat Diversity Index (HDI) were used to assess the habitat diversity under normal and flood flow conditions. The simulation results showed that under normal flow, fish habitat distribution is along the channel while under flood flow it is more on the banks. Under average annual flow and high flow during the rainy season, 4.4 % and 20.51 % of water-covered areas, respectively, lack suitable habitats. For flood flows with return periods of 2 years and 100 years, 55.6 % and 73.36 % of water-covered areas do not support any habitat types. Regardless of the flow type, the model can reasonably evaluate the spatial distribution and habitat diversity of various habitat types in the river. Findings from this study will assist in conserving existing fish habitats, and in introducing missing/lacking habitats. In addition, it could provide a reference for creating ecological habitats for fish in rivers and restoring habitat diversity. [ABSTRACT FROM AUTHOR]