Above 2ºC global warming, the proportion of freshwater fish species vulnerable to climate change increases substantially  .At 2°C, 36.4% of fish species are projected to be vulnerable to local or global extinction by 2100, increasing to 56.4% under 4℃ warming  . Global warming reduces available habitat for freshwater species due to reduced precipitation and increased drought leading to increasing water temperatures above optimal physiological limits in floodplains, estuaries, wetlands, ephemeral pools, rivers and lakes . Along the Zambezi River, projected flow reductions could cause a 22% reduction in annual spawning habitat and depletion of food resources for fry and juvenile fish that could impede fish migration and reduce stocks . More aquatic species will have the capacity to cope with 2℃ compared to 4℃ global warming, with more negative effects on physiological performance at 4°C . Endemic, specialised fish species will have a lower capacity to adjust to elevated water temperatures compared to hardier generalist fishes . More work is needed to understand the risk for invertebrates , and to understand the potential effects of reduced mixing of water and other climate risks on freshwater biodiversity.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report