Habitat response of adult fish species under the influence of ecological flow and hydrodynamic regime in perennial river system

The escalating anthropogenic activities in recent decades are constantly affecting the aquatic ecology and posing a threat to freshwater species. In this study, a two-dimensional ecohydraulic model and multiple criteria decision analysis (MCDA) coupled framework is employed in the Dikhow River, India, to investigate the favourable habitat condition for the nearly threatened Notopterus chitala fish locally known as Chital fish. The habitat residence suitability and habitat suitability indices are calculated at the observed and ecological flows. The ecological flow rates are computed from flow duration curve shifting and flow duration curve analysis methods. The hydrodynamic computations are carried out using a 1D-2D coupled MIKE FLOOD model. The habitat assessment of the targeted species is carried out by constructing the suitability curves from the computed hydraulic parameters at different environmental management conditions. Results from the habitat assessment curves indicate that the maximum habitat suitability index is found for the targeted fish species at average annual flow. Based on the MCDA analysis, the outer banks of the meander zones are identified as not suitable residence regions for the target species. This study revealed that the coupled approach could be useful to regulate the stream restoration strategies and identify potential habitat preference locations in the domain.