Sailfish (Istiophorus platypterus): Facts, Speed and Sail

What does a sailfish look like?

A sailfish has a long, slender, flattened body that tapers to a deeply forked, crescent-shaped tail. The upper jaw extends into a bill that is round in cross-section and about twice as long as the lower jaw. Both jaws and the bill are covered in tiny, file-like teeth.

Its most famous feature is the sail, the first dorsal fin, which has 42–49 rays and runs along most of the back. When raised, it is much taller than the body is deep. The sail is dark blue to black with small black spots. The pelvic fins are also remarkable: long and narrow, they hang below the body almost to the anal fin. All these fins can fold down into grooves when the fish is cruising.

The back is dark blue, the sides are bluish to brown, and the belly is silvery white. About 20 vertical bars made of light blue dots run down each side. Body color varies with the fish’s level of excitement, and sailfish can light up or darken their stripes within seconds.

One species or two?

The scientific name describes the fish well: Istiophorus comes from Greek words meaning “sail-bearer”, and platypterus means “broad-finned”. Sailfish belong to the family Istiophoridae, together with the marlins and spearfishes. The swordfish is a more distant relative in a family of its own. All of these long-billed fish are known as billfish.

For decades scientists argued over whether there are one or two species of sailfish: the Indo-Pacific sailfish (Istiophorus platypterus) and the Atlantic sailfish (Istiophorus albicans). Studies have found no consistent differences in body measurements, fin counts or mitochondrial DNA between the two, so most authorities, including the IUCN, now recognize a single worldwide species. Some databases, such as FishBase, still list two. A 2023 genome study found that Atlantic and Indo-West Pacific sailfish form distinct populations, which shows the debate is not entirely settled.

How big do sailfish get?

Sailfish are among the smaller billfish, but they grow remarkably fast. Females grow larger than males, and Pacific sailfish average bigger than those in the Atlantic.

Lengths for billfish include the bill, which makes up a large share of the total. Young sailfish can reach 1.2–1.5 m (4–5 ft) in their first year, after which growth slows.

Where do sailfish live?

Sailfish live in tropical and subtropical waters of the Atlantic, Pacific and Indian Oceans, and move into temperate seas during warm seasons. In the western Atlantic they range from about 40°N to 40°S and are most abundant in the Gulf of Mexico, off Florida’s Atlantic coast and in the Caribbean. There is also a large population off West Africa. In the Pacific they are common off Central America, Hawaii, the Philippines and Papua New Guinea. A few reach the Mediterranean.

They are epipelagic fish, meaning they live in the sunlit upper layer of the ocean, usually above the thermocline, the boundary where warm surface water meets colder water below. They prefer water of about 21–28 °C (70–83 °F) but dive deeper at times. Unlike most billfish, sailfish often come close to coasts, islands and reef edges, where schools of small fish gather.

Sailfish follow warm water and food through the year. At the northern and southern edges of their range they appear mainly in the warm season, while off southeast Florida they are most common in winter, when cold fronts push schools of baitfish south along the coast. Tagged sailfish have traveled hundreds of kilometers or more, although many seem to stay within one ocean region for long periods.

What do sailfish eat and how do they hunt?

Sailfish are carnivores that eat small schooling fish such as sardines, anchovies, mackerels, jacks, halfbeaks and needlefish, as well as squid and octopus. They feed both at the surface and in midwater.

Their hunting has been filmed in detail off Mexico’s Yucatán Peninsula, where groups of sailfish attack schools of sardines. A sailfish approaches slowly with its sail raised, slips its bill into or beside the school without causing panic, then either taps an individual fish or slashes sideways through the school. These bill movements are among the fastest accelerations ever recorded in an aquatic vertebrate. Only about a quarter of attacks catch a fish, but almost every attack injures more than one sardine, and injured fish are easier to catch later.

Sailfish in a group take turns attacking rather than all striking at once, and individual fish tend to slash consistently to the left or to the right. How the sail helps in all this is explained in Why do sailfish have a sail?

How fast is a sailfish?

Sailfish are often listed as the fastest fish in the sea, at about 110 km/h (68 mph). That number comes from old timings of hooked fish pulling line off fishing reels, not from measurements of swimming fish.

Modern research tells a different story. High-speed video and motion sensors on hunting sailfish recorded bursts of about 25 km/h (16 mph), and a 2016 study of sailfish muscle estimated a top speed of about 30 km/h (19 mph). The details are covered in How fast is a sailfish?, and the sailfish is compared with other speed record holders in the fastest animals.

Behavior, color changes and a warm brain

Sailfish usually travel alone or in small groups, gathering in larger numbers where prey is plentiful. Tagged sailfish have been recorded spending most of their time near the surface, with regular dives into deeper, cooler water.

Their ability to change color is one of their most striking behaviors. Hunting sailfish often flash bright blue stripes and dark bars as they attack. Scientists think these displays may signal to other sailfish in the group or help confuse prey, but their exact purpose is not known.

Like other billfish, sailfish have a special heater organ behind the eyes, made from modified eye muscle, that warms the eyes and brain above the temperature of the surrounding water. This is thought to keep their vision sharp and their reactions quick when they dive into cold water.

Reproduction and life cycle

Sailfish spawn in warm tropical and subtropical waters. In the western North Atlantic, spawning peaks in summer, and in some tropical areas it happens all year. A female swims slowly near the surface with her sail above the water, followed by one or more males, and eggs and sperm are released into the open water. A large female can release about 4.5 million eggs in a season.

The newly hatched larvae are only a few millimeters long and look nothing like adults. They have short jaws and spiny heads, and the bill begins to grow when they are about 6 mm (0.25 in) long. By about 20 cm (8 in), a young sailfish has adult features. The maximum recorded age is about 13 years.

Predators and threats

Adult sailfish have few natural predators. Large sharks and orcas can catch them, but their speed and size protect them from most hunters. Young sailfish face many more enemies, including dolphinfish, other large predatory fish and seabirds.

The main threat comes from fishing. Most sailfish caught worldwide are taken as bycatch, meaning they are caught accidentally on longlines and in gillnets set for tunas and swordfish. They are also targeted by some commercial fisheries and by recreational anglers, although many sport-caught fish are released. Some local populations may also suffer where coral reefs that attract their prey are degraded.

Conservation status

The IUCN lists the sailfish as Vulnerable, in an assessment carried out in 2021 and published in 2022. The listing reflects declines in numbers caused mainly by fishing pressure, and the species’ long ocean migrations make it hard for any one country to protect.

International fisheries commissions set rules for billfish catches in each ocean. In the United States, commercial fishing vessels may not keep or sell Atlantic sailfish, and recreational anglers must follow federal permit and size rules.

Sailfish and people

The sailfish is one of the world’s most popular game fish, prized for its leaps and speed on the line. The Atlantic sailfish has been Florida’s official state saltwater fish since 1975, and the town of Stuart, Florida, calls itself the “Sailfish Capital of the World”. Catch-and-release fishing is now common for the species in Florida and Central America.

Sailfish meat is eaten fresh, smoked or as sashimi in parts of Asia and the Pacific, but in the Atlantic it is considered tough and has little commercial value. For many people, the most memorable encounters are those of divers and snorkelers who watch groups of sailfish, sails raised and colors flashing, as they hunt schools of sardines in clear blue water.