This study describes estuary associated fish species characteristics together with the factors influencing their habitats, migrations and dynamics. The Severn Estuary ecosystem is briefly described with special detail to its physical characteristics and its fish fauna. The suitable habitat conditions for the Dover sole and the European eel are examined in particular and the Suitability Index curves against various environmental variables are designed. The configuration of different environmental variables spatially in the estuary is obtained by different means such as long term studies, GIS data or predictions from an eco-hydraulics model. The habitat requirements of the two fish species are linked with the environmental conditions and the distribution of the Habitat Suitability Index values of 1 and 0.5 is estimated. Some of the effects of developing the marine renewable schemes across the estuary are discussed as well as a number of predicted consequences that the climate change will have on the habitat of the two analysed species. The study shows that the effects induced by the tidal energy array in the habitat of the sole and the eel would be generally positive mainly due to the decrease of water depths and water flow velocities among other aspects. However the temperature and salinity profiles alteration together with the turbine associated injuries to migrant fish are key issues to consider regarding the negative impact of the tidal structure. The climate change effects are predicted to have a few positive aspects on some species habitat such as changes on certain variables; nevertheless the combination of changes in different environmental parameters is likely to have a negative overall impact.