Elasmobranch fishes provide multiple products that are commercialized for different usages. The most common products taken from these animals include meat, fins, liver, skin, cartilage, and jaws (Musick, 2004).
Even though the study of elasmobranch remains in archeological sites is problematic (Rick et al., 2002), it seems that shark meat has been used as food in
coastal regions for at least 5000 years, when the Cretans and the Persians caught and sold sharks in the Persian Gulf and the Mediterranean (Vannuccini, 1999). A major problem when it comes to consumption of shark meat is that sharks retain urea in their blood and tissues as part of their osmoregulatory physiology (Evans et al., 2004), and when the shark dies the urea breaks down into ammonia which releases a strong smell from the flesh, which may even be toxic in high concentrations (Musick, 2004). Since the late 1950’s, shark meat started to be more favorably accepted, mainly due to the better handling associated with the use of ice and freezing for processing the flesh.
Nowadays, the flesh of some species such as the threshers (Alopias spp.) the shortfin mako (Isurus oxyrinchus) and the porbeagle, whose meat is particularly appreciated fresh in the USA and Europe can reach relatively high prices, similar to swordfish (Vannuccini, 1999).
While the livers of deep water squalid sharks are usually kept and commercialized, the rest of the animal has a low or null commercial value and is usually discarded. Some exceptions do however occur, such as the case of the flesh of C. squamosus and the Portuguese dogfish, Centroscymnus coelolepis that in France are commercialized under the generic common name “siki” and whose landings in recent years have been increasing (Girard et al., 2000).
The most valuable product obtained from sharks, that is in fact one of the most valuable fish products in the world are the fins of some species (Camhi et al., 1998) that are marketed in the oriental markets, especially Hong Kong and Singapore, where they are used to make the traditional Chinese shark fin soup (Vannuccini, 1999). Even thought the fins of all shark species larger than 1.5m are commercially valuable, some species are considered excellent, namely the blue shark, the dusky shark (Carcharhinus obscurus), the giant guitarfishes (Rhynchobatus spp.), the
hammerheads (Sphyrna spp.), the shortfin mako, the oceanic whitetip shark (Carcharhinus longimanus) and the sandbar shark (Vannuccini, 1999). In most sharks, the first dorsal, the pectorals and the lower lobe of the caudal fins are the most valuable and these are usually sold as a set from each shark (Musick, 2004). The high value leads to the slaughter of tens of millions of sharks every year for their fins, and once these structures are removed the rest of the carcasses is usually discarded overboard (Fordham, 2006). This finning practice represents a considerable waste of resources, as the fins on average make up only about 5% of the total weight of sharks (Vannuccini, 1999).
The liver of sharks, apart from being the organ for storing energy and conserving energy, is also the hydrostatic organ. In deep sea sharks, buoyancy is achieved by means of a large liver, which contains large quantities of uncommon low density oils, mainly squalene and diacyl glyceryl ether (DAGE) (Deprez et al., 1990).
Deep water sharks have long been caught for their livers, and more specifically for the oil extracted from them. One of the first commercial uses of this oil was during the XIX century when it was used as fuel for street lamps (Vannuccini, 1999). During the 2nd world war, squalid shark livers were an important source for vitamin A, but more recently this vitamin started to be artificially synthesized and no longer extracted from shark liver oil (Vannuccini, 1999). In the last decades, squalid shark livers started to be commercialized for the lipids present in high quantities in their livers, specifically the squalene and the DAGE (Deprez et al., 1990). The relative weight of the liver in deep water squalid sharks can range from 15% to 26% of the total body weight (Hernández-Pérez et al., 1997) and squalene typically represents 50 to 82% of the oil in the liver (Bakes and Nichols, 1995). Squalane (C30H50) is a colorless, odorless, tasteless, stable, transparent and inert oil that is readily miscible with the human skin
lipids. Squalane aids the absorption of pharmaceuticals through the skin and reduces water loss, so it is an excellent cosmetic base, lubricant and emollient (Deprez et al., 1990). Squalene has also been experimentally used for tumor growth inhibition, and it seems especially efficient when combined with conventional chemotherapeutic agents (Cho and Kim, 2002). DAGE seems to help reducing the severity of certain types of cancer, promote formation of blood cells, and provide protection against radiation injury (Wetherbee and Nichols, 2000).
Over the last decades there has been a false popular belief that shark cartilage, after been dried and pulverized into a powder can prevent and treat cancer. This controversy come from the false belief that elasmobranchs, with skeleton made of cartilage, do not develop cancer and that solid forms of shark cartilage may cure cancer in animals and humans (Gingras et al., 2000). The market for shark cartilage pills expanded greatly in recent years, but there is now evidence that the ingestion of cartilage powder pills is worthless for treating cancer in humans (Gingras et al., 2000;
Cho and Kim, 2002). However, shark cartilage has been used to extract some biologically active substances, that have been shown to have antiangiogenic and antitumor properties, by retarding the development of blood vessels necessary for the development of the cancer, and that are being tested for the treatment of some forms of cancers (Gingras et al., 2000; Cho and Kim, 2002).