Spurdog. The spurdog is a type of small shark or dogfish, said to make the best eating of all the dogfish. Also known as rock salmon. It is useful for its medium oily white flesh and is generally versatile. It grows 2-3 metres in length.or nursehound or, in some places, as rock salmon or rock eel. Spurdog, smoothound and tope are all sold as huss. It is an excellent addition to soups because of its texture. It feeds on shellfish which flavours its own firm, white flesh.