There are four species of fish with the common name marlin. These fish are classified into two genera. In the strictest sense, marlins belong to the genus Makaira. Examples of marlins in this genus are the blue marlin (Makaira nigricans) and the black marlin (Makaira indica). Two additional species with the common name marlin are the striped marlin (Tetrapturus audax) and the white marlin (Tetrapterus albidus).
Blue marlins are colored blue or gray-blue on the back, and their shading gets lighter toward their belly, which is silver. These marlins measure between 10-15 ft (3-4.6 m) in body length. Their mature weight commonly varies from about 200-400 lb (91-181 kg), but they can weigh more than 1,800 lb (800 kg). These fish have a streamlined body with a crescent shaped tail. They live in tropical and temperate seas throughout the world. They are found in temperate seas in the eastern Atlantic, ranging from northern Spain south to South Africa, and in the western Atlantic as far north as Massachusetts and as far south as Uruguay. Blue marlins swim in open seas and make regular seasonal migrations to the equator in the winter and away from it in the summer. They swim in surface waters and are a highly prized sporting fish.
The black marlin is the largest of all of the billfish. It reaches 16 ft (5 m) in body length and can weigh more than 1,500 lb (681 kg). Its pectoral fins are rigid and do not fold into its body. It lives in the Pacific Ocean near the surface of warm, open waters from southern California to Chile.
The striped marlin is similar in appearance to the blue marlin, having an elongated bill and a streamlined body. The striped marlin lives in the Indian and Pacific Oceans and is more likely to inhabit temperate waters, such as from Oregon to Chile. It lives in the open sea, but sometimes will occur in inshore waters. This species is distinguished by dark-blue or white vertical bars on its sides. Additionally, its pelvic fins are much longer than its pectoral fins and it has a relatively high dorsal fin. The striped marlin spawns from May to August in the Northern Pacific. It grows to about 10 ft (3 m) in length and eats fish and various species of deepwater and surface squid. It is a highly specialized sportfish and also an excellent food fish.
The white marlin usually weighs about 50 lb (23 kg), but can measure as much as 10 ft (3 m) in length and weigh up to 180 lb (82 kg). This migratory fish is found in the eastern part of the Atlantic Ocean, from south of Portugal to the southwestern Mediterranean, and in the western Atlantic from Nova Scotia south to Brazil. It has also occurs in the Gulf of Mexico and the Caribbean. The white marlin is bluish-green, brown, or gray on top and silver underneath.
Marlins are among the most popular sporting fish in the world. However, their numbers are decreasing because of intense commercial and sport over-fishing. Because they are relatively large, old fish, they frequently have naturally high concentrations of mercury in their flesh, and concerns about the potential human-health hazard of eating these species limits the commercial hunt to some degree. There is a pressing need for better conservation measures in support of these valuable species, or they will become endangered.
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