Skates (Fish): The common name for all members of the Rajidae family. Skates and rays are members of the same order (Rajiformes). Skates have weak electric organs.Fishes: A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.Elasmobranchii: A subclass of cartilaginous fish comprising the SHARKS; rays; skates (SKATES (FISH);), and sawfish. Elasmobranchs are typically predaceous, relying more on smell (the olfactory capsules are relatively large) than sight (the eyes are relatively small) for obtaining their food.Fish Diseases: Diseases of freshwater, marine, hatchery or aquarium fish. This term includes diseases of both teleosts (true fish) and elasmobranchs (sharks, rays and skates).Fish Oils: Oils high in unsaturated fats extracted from the bodies of fish or fish parts, especially the LIVER. Those from the liver are usually high in VITAMIN A. The oils are used as DIETARY SUPPLEMENTS. They are also used in soaps and detergents and as protective coatings.Electric Fish: Fishes which generate an electric discharge. The voltage of the discharge varies from weak to strong in various groups of fish. The ELECTRIC ORGAN and electroplax are of prime interest in this group. They occur in more than one family.Sharks: A group of elongate elasmobranchs. Sharks are mostly marine fish, with certain species large and voracious.Skating: Using ice skates, roller skates, or skateboards in racing or other competition or for recreation.Cholestanols: Cholestanes substituted in any position with one or more hydroxy groups. They are found in feces and bile. In contrast to bile acids and salts, they are not reabsorbed.Fish Products: Food products manufactured from fish (e.g., FISH FLOUR, fish meal).