Climate change causes reductions in fish habitat suitability in Loktak Lake, India

• Labeo Rohita's habitat in Loktak Lake spans 9 km 2 (very high), 51.2 km 2 (high), 80.7 km 2 (medium) and 14.9 km 2 (low) suitability. • Habitat suitability is expected to decline under SSP1-2.6 and SSP5-8.5 climate scenarios in both the near and far future. • The fuzzy-logic habitat model in this study, driven by expert knowledge, is a versatile tool for data-scarce regions. Climate change affects ecological processes that govern species distribution patterns at different spatio-temporal scales. To aid in habitat restoration aimed at increasing biodiversity, numerous habitat models were developed and employed in the past. In this study, a fuzzy logic-based habitat model, coupling a fuzzy inference system and a hydrological-hydrodynamic model, is proposed to identify the baseline conditions of suitable habitat for juvenile fish. The main objective is to map and predict the current and future habitat suitability for Labeo Rohita in the data-scarce Loktak Lake, India. To predict future habitat suitability, climate change scenarios defined by the Intergovernmental Panel for Climate Change (IPCC) were used for the years 2041–2060 and 2081–2100 under two different scenarios of Shared Socio-Economic Pathways (SSP) SSP1-2.6 and SSP5-8.5. These future scenarios were used as input data for a model chain, containing a hydrological SWAT model, a hydrodynamic Delft3D model and the fuzzy-logic habitat model. This model chain considers consequences of climate change and explores the combined effects of changes in water temperature, dissolved oxygen and water depth on the habitat suitability. The model results show current habitat suitability with 9.0 km 2 of the lake surface with very high suitability, 51.2 km 2 with high suitability, 80.7 km 2 with medium suitability, and 14.9 km 2 with low suitability. In the SSP1-2.6 and SSP5-8.5 scenarios, it is predicted that the habitat suitability decreases. Specifically, medium habitat areas of 26.7 km 2 and 79.5 km 2 will be transformed in to low-suitability areas by 2100, for SSP1-2.6 and SSP5-8.5, respectively. These results show the impact of climate change, in combination with economic development, including future land use changes. Hence, pathways for ecologically sustainable management of fish habitat in lakes are necessary to steer habitat quality in the future.