Sharks are commonly termed fish, even though they are only distantly related to the classical (bony) fish. What differentiates a shark from a bony fish? Sharks have a spinal column and are thus vertebrates. However, their skeleton is not made of bones, but of cartilage, and together with their nearest relatives the rays and the chimeras they form the class of cartilaginous fish. Since the late 1980s trade in shark fin was considered to be one of the most valuable fishery products in the world. Another valuable shark product is cartilage. Shark meat has been used as food in coastal regions for over 5000 years. Small sharks are preferred for meat in many markets. In Germany, the belly flaps of spiny dogfish (Squalus acanthias) are smoked as "Schillerlocken", an expensive gourmet item. The question came up to us recently if we were able to detect whether shark muscle were heat-treated as in the case of smoking or not. Different tariffs for heated and untreated fishery products make it important for processors to label their products correctly. According to customs departments this necessitates investigations into whether the declaration of goods is true or not. Looking at the relevant literature, papers dealing with thermal stability of shark muscle were very scarce. Therefore, we decided to perform DSC measurements on a variety of shark using a SETARAM MicroDSC VII and to compare the DSC patterns obtained. Beside thermal stability the colour of different shark meats were also measured instrumentally. To answer the question of whether DSC measurement can differentiate previously heat treated sharks from those lacking this treatment, the cutlets from smooth-hound (Mustelus spp.) underwent thermal treatment in the range from 40 to 70 degrees C. DSC patterns of the shark muscle and the skin were used to observe the influence of heat treatment. (C) 2007 Elsevier B.V. All rights reserved.