The rich freshwater biodiversity of northeast India is threatened by human-induced climate change. Vulnerability assessments are needed to help understand potential effects and guide management for specific species and rivers. This project aims to develop capacity to conduct such assessments by training current and future scientists through workshops and hands-on exercises. We began by circulating an online questionnaire and used the responses of 20 participants to understand baseline knowledge and skills, identify potential species, and identify individuals interested in further training activities. We then held an initial planning meeting in the region with 18 scientists, managers, and project staff to select a small subset of species and to plan further work. During an in-person, three-day training workshop, we covered the theory and practical skills needed to conduct climate vulnerability analysis of freshwater fish species. Over 30 scientists and students from throughout northeast India received training through this workshop. Following this training workshop, we conducted an in-person, five-day workshop with 11 dedicated participants focused on the hands-on assessment of three fish species important to the region. The assessments conducted during this workshop were then refined by the authors through subsequent analyses and report writing. The project was thus able to develop capacity in the region while assessing the vulnerability of three fish species as detailed in this report. Three fish species with contrasting habitat needs & sufficient available data were selected for climate vulnerability assessment: zig-zag eel (Mastacembulus armatus Lacepède 1800), snow trout (Schizothorax sp. Heckel 1838), & golden mahseer (Tor putitora Hamilton 1822). We used correlation-based species distribution modeling to predict current & future habitat suitability & thereby assessed vulnerability as predicted climate-change induced losses & gains of suitable habitat. Following best practices for this approach, we assessed vulnerability within northeast India plus a much larger region that included all of India plus the entire Brahmaputra, Indus, and Irrawaddy River basins. We describe models & results for this entire region, while also summarizing results for the project region in northeast India. We found that climate change was likely to result in substantial loss of currently suitable habitat for all three species, but predicted gains in habitat were able to offset losses to varying degrees (Figure 1). M. armatus is predicted to be highly vulnerable, as all three climate models agreed that this species would lose 49.2% of currently suitable habitat under the high emissions scenario while gaining relatively little. Our results suggest that M. armatus is suited for a warm, moist tropical climate characterized by a narrow range of winter temperatures and relatively low annual temperature variation, which are likely to be altered by warming winters and increasing annual temperature range. However, losses were lower in northeast India and substantial portions of Meghalaya, Nagaland and Manipur were predicted to provide suitable habitat regardless of climate change scenario or model. These areas may represent important core habitats where river, fisheries, and watershed management could help to reduce other threats and conserve suitable habitat. Climate Vulnerability Assessments of Freshwater Fish Species in Northeast India Schizothorax is predicted to be less vulnerable to climate change, with all three models agreeing that the 19.1% predicted losses of current habitat would be largely offset by habitat gains. This means that the amount of suitable habitat could remain stable if these fish are able to access and establish populations in newly suitable areas. Our models suggested that suitable habitat for Schizothorax is near headwater areas with maximum air temperatures around 20°C, annual precipitation around 2500 mm & dry season precipitation below 100 mm. Substantial warming of maximum temperatures was the primary driver of climate change effects, resulting in suitable habitat shifting to colder, higher elevations in the Himalaya proper. A relatively small amount of habitat was predicted to be suitable under current climate conditions in northeast India, & most of this is predicted to be lost due to climate change. Thus, Schizothorax is much more vulnerable to climate change in northeast India due to the lack of colder, higher elevation areas available for habitat gains. Two keys, closely-related actions that could reduce climate vulnerability are reducing erosion & restoring forest cover throughout watersheds. Tor putitora is predicted to be moderately vulnerable to climate change, with all three climate models agreeing 28.6% of current habitat could be lost with lower predicted gains of only 10.8%. Our models predicted suitable habitat for Tor putitora in larger rivers relatively far upstream with maximum air temperatures around 20 and 35°C, annual precipitation between 1000 and 3000 mm, and dry season precipitation below 100 mm. Warming maximum temperatures are the primary clear driver of climate change effects, resulting in suitable habitat predicted to shift somewhat upstream. Within northeast India, the species was predicted to lose substantial amounts of habitat in Assam and southern Manipur. However, large swathes were predicted to remain suitable even under the warmest projections in higher elevations of Nagaland and central Manipur. We suspect that T. putitora will be able to partially adapt to changing conditions due to a demonstrated ability to feed on diverse items, migrate large distances, use non-preferred reservoirs, and acclimate to warming temperatures. Nevertheless, T. putitora populations have been greatly reduced by other stressors in recent years and a further pressure by climate change will not improve this situation. Important actions for reducing the vulnerability of T. putitora include reducing cropland cover in the watershed and its negative effects on rivers through remedial actions, sustainable fisheries management, and ensuring movement by restricting dam development and constructing fish passage structures at existing barriers. Our project demonstrates the potential for developing expertise & studying the ecology & climate vulnerability of freshwater fish species in Northeast India. Monitoring through scientific & community data collection programs are urgently needed to track potential losses of these & other species, as ceremonial uses, fisheries opportunities, & angling based ecotourism opportunities could be lost. Further studies are desperately needed for the other approximately 400 species which were not addressed here, many of which are poorly studied & have limited occurrence records. Past efforts & expertise of fish scientists have primarily focused on the description of new species, which has been & still is vastly important for documenting the rich biodiversity of fish. These expertise needs to be broadened to enable ecological studies & the inclusion of traditional ecological knowledge. These studies are urgently needed to map the distribution of biodiversity in the region, understand habitat needs, & predict the effects of climate change & other stressors. Without this knowledge, it will not be possible to develop robust conservation plans or simply to track what has & will likely be lost in the future.
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