In recent years, there has been an increasing interest in the protection of sea bed habitats that are important for commercially exploited fish species ('Essential Fish Habitats', EFH) and may be vulnerable to anthropogenic activities such as bottom fishing or aggregate extraction. Locating such habitats in the vast space of the sea, however, is difficult. The concept of habitat selection based on 'Ideal free distribution' theory suggests that areas of high suitability may attract larger quantities of fish than less suitable or unsuitable areas. Here, we used catch data from groundfish surveys to identify areas of consistently high densities of whiting (Merlangius merlangus), cod (Gadus morhua), haddock (Melanogrammus aeglefinus), in the Irish Sea and plaice (Pleuronectes platessa), sole (Solea solea), lemon sole (Microstomus kitt) in the English Channel over a period of 9 and 10 years respectively.A method was developed to identify areas of the seabed that may constitute EFHs and may therefore merit further investigations. In addition, the number of potential EFHs identified and the number of stations where no fish were caught gave an indication of the site specificity of the fish species analysed. For the gadoids, whiting was found to be less site specific than cod and haddock, while for the flatfish plaice and sole were less site specific then lemon sole. Our findings are discussed in the context of previously published studies on dietary specialism. The site specificity of demersal fish has implications for the siting process for marine protected areas as fish species with a strong habitat affinity can be expected to benefit more from such management schemes.