 The rough skin ( called " <unk> " ) of the nursehound was once used to polish wood and alabaster , to smooth arrows and barrels , and to raise the hairs of beaver hats as a replacement for pumice . <unk> was so valued that a pound of it was worth a hundredweight of sandpaper . The liver was also used as a source of oil , and the carcasses cut up and used to bait crab traps . The meat of this species is marketed fresh or dried and salted , though it is considered " coarse " in some quarters . In the United Kingdom , it is one of the species sold under the names " flake " , " catfish " , " huss " " rock eel " , or " rock salmon " . In France , it is sold as grande <unk> or <unk> , as after being skinned and beheaded it resembles salmon . This species is also sometimes processed into fishmeal , or its fins dried and exported to the Asian market . In European waters , commercial production of this species is led by France , followed by the UK and Portugal ; it is caught using bottom trawls , gillnets , bottom set longlines , handlines and fixed bottom nets . In 2004 , a total catch of 208 tons was reported from the northeastern Atlantic . 
