Warming climates induce Mediterranean Sea level rise, which is destined to have major impacts on Rhône Delta habitats, biocoenosis, and escorting biota, including fish. Based on their bioecological features, a number of fish species in the Rhône Delta will be affected by such sea level rise. Others will adapt and positive ecological feedback loops may fuel further changes. Sea level variation was and is likely to be one of the key stress factors for fish in the Rhône Delta.