There are approximately 14 species of butterfly rays in the Gymnuridae family, including the Japanese, California, and smooth ray. These rays have flat bodies encased by a broad disc of pectoral fins that emerge from the head. Butterfly ray bodies can range in size from 12 inches (31 cm) to more than 13 feet (4 m) long. A butterfly ray’s tail is typically very short and thin. They are sometimes found in estuaries, but generally this type of ray roams warm ocean waters.
The Japanese butterfly ray, or Gymnura japonica, is found in shallow ocean waters from Japan to Cambodia. Its body is sandy colored with light spots, allowing this ray to hide along the muddy bottom. The diet of the Japanese butterfly ray is not well documented, but evidence suggests that it prefers small fish and other ray species. This species can grow to a width of more than 4 feet (121.92 cm).
The California butterfly ray roams a much larger territory, including the western coast of Central and South America, as well as that of the United States. In addition to shallow water, this ray is found near coral reefs and in intertidal marshes and saline lagoons. It feeds on small crustaceans, mollusks, and bivalves. The triangular body of this species is usually gray or brown and can have dark spots.
Although the longtail butterfly ray’s body shape is typical for the family as a whole, this species can be distinguished by its long tail of black and white rings. Its snout also ends in a pointed projection. This species lives in sandy bottoms in the Indo-West Pacific and near French Polynesia. Mollusks and crustaceans are preferred foods. The longtail can give birth to up to seven young at a time but is known to abort when captured.
The smooth butterfly ray or diamond skate lives off the eastern coast of the United States and the western coast of Senegal, Sierra Leone, and the Democratic Republic of the Congo. This ray will sometimes enter estuaries. Its diamond-shaped body varies between dark gray, light green, and brown, with a protruding snout and short tail. The smooth butterfly ray feeds on crabs, shrimp, and bivalves.
Several species of butterfly ray are endangered despite the fact that they are generally harmless to humans. These rays are vulnerable to commercial fishing and can be caught up in nets and trawls. Fishing for butterfly rays is a popular and often unregulated tourist industry in various countries. They can also be filleted and eaten.