Freshwater river systems are valuable to the communities around the world as they provide food, water, livelihoods, and natural materials. Unfortunately, there has been a decline in these ecosystems and the fish species that inhabit them. They face threats from degradation and fragmentation to overharvesting, pollution, and climate change. This publication explains the methods of the conservation of these freshwater fish populations in protected areas. Fish Conservation Zones (FCZs) first appeared in Lao People’s Democratic Republic. Now, there are more than 1,300 in Southeast Asia. The text also gives details about the new developments of the Critical Ecosystem Partnership Fund (CEPF) and its support to establish and manage FCZs in the Indo-Burma Hotspot in the countries of Cambodia, Lao PDR, Myanmar, Thailand, and Vietnam.