Cobia

The cobia (Rachycentron canadum) is a species of perciform marine fish, the only representative of the genus Rachycentron and the family Rachycentridae. Other common names include black kingfish, black salmon, ling, lemonfish, crabeater, prodigal son and black bonito. Attaining a maximum length of 2 m (78 in) and maximum weight of 78 kg (172 lb), the cobia has an elongated, fusiform (spindle-shaped) body and a broad, flattened head. The eyes are small and the lower jaw projects slightly past the upper. Fibrous villiform teeth line the jaws, the tongue, and the roof of the mouth. The body of the fish is smooth with small scales. It is dark brown in color, grading to white on the belly with two darker brown horizontal bands on the flanks. The stripes are more prominent during spawning, when they darken and the background color lightens. The large pectoral fins are normally carried horizontally, perhaps helping the fish attain the profile of a shark. The first dorsal fin has six to nine independent, short, stout, sharp spines. The family name Rachycentridae, from the Greek words rhachis ('spine') and kentron ('sting'), was inspired by these dorsal spines. The mature cobia has a forked, slightly lunated tail, which is usually dark brown. The fish lacks a swim bladder. The juvenile cobia is patterned with conspicuous bands of black and white and has a rounded tail. The largest cobia taken on rod and reel came from Shark Bay, Australia, and weighed 60 kg (135 lb). The cobia resembles its close relatives, the remoras of the family Echeneidae. It lacks the remora's dorsal sucker and has a stouter body. The cobia is normally solitary except for annual spawning aggregations, and it sometimes congregates at reefs, wrecks, harbours, buoys, and other structural oases. It is pelagic, but it may enter estuaries and mangroves in search of prey. It is found in warm-temperate to tropical waters of the West and East Atlantic Ocean, throughout the Caribbean, and in the Indian Ocean off the coast of India, Australia, and off the Pacific coast of Japan. It is eurythermal, tolerating a wide range of temperatures, from 1.6 to 32.2°C. It is also euryhaline, living at salinities of 5.0 to 44.5 ppt. The cobia feeds primarily on crabs, squid, and fish. It follows larger animals such as sharks, turtles, and manta rays to scavenge. It is a very curious fish, showing little fear of boats. The predators of the cobia are not well documented, but the mahi-mahi (Coryphaena hippurus) is known to feed on juveniles and the shortfin mako shark (Isurus oxyrinchus) eats the adult.