Introduction to Skates and Rays
Skates and Rays, fish closely related to sharks. Like sharks, skates and rays have skeletons of cartilage rather than bone. Most skates and rays have bodies that are flattened from top to bottom. Their large pectoral fins, often called wings, are attached to the head. Skates live in cold seas; rays live in warm seas and in some tropical rivers. There are about 100 species of skates and about 240 species of rays.
Skates have flat bodies and large pectoral fins attached to the head.Skates range in length from a few inches to about 8 feet (2.4 m). Most, however, are less than 2 feet (60 cm) long. Rays range in length from less than 6 inches (15 cm) to more than 35 feet (11 m). Skates and rays are usually brown or gray above, often with various markings. They are whitish below, blending in well with their environment.
Skates and most rays live on the bottom of the waters they inhabit. Skates are sluggish animals that either lie on the bottom or slowly cruise, looking for the clams, snails, shrimp, and other small animals that they eat. Rays are far more active, constantly moving about and often rolling and jumping along the ocean floor. Their food is similar to that of skates and they sometimes take a heavy toll of clam and oyster beds.
The mouth in almost all skates and rays is on the underside of the body. Skates and bottom-dwelling rays take in water through openings, called spiracles, at the top of the head. The water is transferred to the gills, on the underside of the head. Those rays that do not live on the bottom take in water through the mouth, like other fish. Skates and rays have five pairs of gill slits.
The skin of skates is generally covered with numerous scales, but some skates and most rays have smooth skin. The tail is often slender and whiplike. Most rays have one or more sharp barbs on the ends of their tails; the barbs can inflict pain on humans. Sometimes these barbs contain poison. Skates do not have barbed tails, but some have organs along the sides of the tail that can produce an electric shock. The voltage they emit is generally low.
Young skates hatch from eggs contained in leathery, protective capsules. Rays do not lay eggs, but give birth to live young.
Skates and rays are eaten throughout the world. They are not popular in the United States for food but are used to make fertilizer and fish meal. The pectoral fins of some species are used to make imitation scallops in the United States.
Some Interesting Skates and Rays
The little skate is found in the Atlantic from North Carolina to Nova Scotia. It is one of the smaller skates, reaching a length of about 20 inches (50 cm) and a weight of little more than one pound (450 g). The winter skate has a similar range. It grows up to 3 1/2 feet (1.1 m) in length and can weigh 12 pounds (5.4 kg). The big skate, found off the Pacific coast of North America, can reach a length of about 8 feet (2.4 m). The upper side of each wing is marked with a dark spot surrounded by a white ring.
The electric rays, or torpedoes, have an electricity-producing organ on each wing near the head. One of the largest electric rays is the Atlantic torpedo, which can grow up to 6 feet (1.8m) long. This ray can discharge an electrical shock of about 200 volts. Electric rays use their electric organs to stun their prey and to defend themselves against predators.
The sawfish, found in tropical waters, is a ray with an elongated snout that bears teeth on either side and resembles a double-edged saw. The sawfish uses its “saw” to dig up the sea floor in search of food and to club its prey. It can inflict painful wounds and is of concern to fishermen because it damages fishnets. (Despite many cartoons on this subject, sawfish do not saw holes in wooden boats.) Some sawfish can grow to more than 35 feet (11 m) long and weigh more than 5,000 pounds (2,270 kg).
Among the rays with venomous barbs at the ends of their tails are the stingrays, Stingray venom affects the circulatory system of the victim, especially the heart. The venom c#n be fatal to humans. Most stingrays are shallow-water species. The blunt-nose stingray is an Atlantic species; the ribbontail ray (or blue-spotted stingray) is found in the Pacific and Indian oceans.
The manias, or devil rays, are quite active, often jumping out of the water. Many devil rays are extremely large and powerful with large wings. (One of the largest devil rays known measured 22 feet [6.7 m] between wing tips.) These fish are capable of overturning small boats. Mantas are found in warm-temperate to tropical seas.
Skates and rays make up the order Rajiformes, or Batoidei. Skates make up the family Rajidae The little skate is Raja erinacea; the winter skate, R. occllata; the big skate, R. binoculata. Electric rays make up the family Torpedinidae. The Atlantic torpedo is Torpedo nobiliana. Sawfish make up the family Pristidae. Stingrays make up the family Dasyatidae. The bluntnose stingray is Dasyatis sayi; the ribbontail ray, Taeniura lymtna. Mantas make up the family Mobulidae.