Aquaculture–biodiversity trade-offs in mountain freshwater ecosystems: insights from the North-Western Indian Himalaya

Abstract

Mountain freshwater ecosystems are valuable social–ecological systems that support specialised and, in many cases, endemic fish populations, in turn supporting capture fisheries and new aquaculture systems. Aquaculture is a food security strategy and a rural livelihood diversification solution increasingly promoted in the North-Western Indian Himalaya, though its expansion poses serious trade-offs with freshwater biodiversity conservation. This review synthesises existing knowledge of aquaculture–biodiversity interactions, using the North-Western Indian Himalaya as a focal case study to examine ecosystem-based management of aquatic living resources and develop context-specific insights for mountain freshwater systems. Regional data and the literature show that native cold-water fishes—namely, mahseer ( Tor spp.) and snow trout ( Schizothorax spp.)—occupy narrow ecological niches and have limited adaptive capacity. These species are vulnerable to habitat fragmentation, hydrological alteration, and warming temperatures. Conversely, exotic species, especially rainbow trout ( Oncorhynchus mykiss ) and common carp (Cyprinus carpio ), dominate aquaculture development in the region, exacerbating trade-offs between aquaculture and biodiversity across species, habitats, genetic, and temporal scales. The synthesis indicates that climate change and geomorphological instability may amplify these trade-offs by increasing environmental uncertainty for both wild stocks and culture systems. Aquaculture may provide an alternative source of fish production where capture fisheries decline, but poorly managed intensification could increase pressure on freshwater biodiversity and ecosystem functions. We propose management pathways to align production and conservation, centred on ecosystem-based basin planning, prioritising indigenous species, developing climate-resilient, low-input systems, and implementing inclusive governance frameworks. This synthesis shows that in mountain freshwater ecosystems, sustaining aquatic living resources amid accelerating environmental change requires deliberately managing trade-offs rather than maximising short-term production.