Thornback rays or roker are an inshore to slope species, belonging to the Rajidae family of skates and rays. Thornback rays have been described as showing philopatric behaviour (tendency of a migrating animal to return to a specific location in order to breed or feed). Females can grow to 118cm in length and 18kg in weight, while males can reach 98cm in length. Females mature between 60 and 85cm while males mature between 60 and 77cm (in both cases corresponding to an age of 5 to 10 years). The species has a maximum recorded age of 16 years. There are 13 species of ray and skate Rajidae and 7 to 8 demersal shark species in the North Sea ecoregion.