There is a pressing need to identify the characteristics of habitats that have an important or 'essential' functional role for particular species or type e.g. piscivores/herbivores/omnivores or flatfish/roundfish. Identifying such habitat characteristics and quantifying the spatial extent of fish habitat resources is fundamental to the successful management of these habitats and species. No general methodology has yet been developed to describe which elements might constitute an essential fish habitat. The acoustics ground-discrimination system QTC was used to identify the linkage between epibenthic and demersal fish assemblages and their species to provide a remote means to infer important habitat features appropriate for their delineation.A strong correlation with the acoustic seabed properties of this classification system was found. Eight different study sites, selected for their differences in demersal fish abundance, were sampled using a 3-m and 2-m beam trawl in the Irish Sea. Multivariate analyses were used to identify benthic and fish assemblage structure, and to characterise their habitats. Distinct benthic and fish assemblages were associated with statistically different seabed classification data derived from QTC. These were in turn strongly, although not exclusively, associated with changes in water depth. Fish assemblages showed a stronger correlation with acoustic classifications than epibenthos, indicating that QTC provides a robust method for seabed classification and mapping of fish habitats.