The taxonomy of sailfish has been a subject of dispute, with some experts recognizing one species while others recognize two. However, most authorities now acknowledge a single species, Istiophorus platypterus, found in warmer oceans across the globe. FishBase, a comprehensive database, still recognizes two species: the Atlantic sailfish (Istiophorus albicans) and the Indo-Pacific sailfish (Istiophorus platypterus).
Sailfish are predominantly blue to gray in color, boasting a distinctively large dorsal fin known as the sail. This prominent sail stretches the entire length of their back, making sailfish instantly recognizable. Another notable feature is their elongated rostrum, or bill, resembling that of other marlins and swordfish. These billfish are highly sought after in sport fishing circles.
Growing rapidly, sailfish can reach lengths of 1.2–1.5 meters (4–5 feet) in just a year. They primarily feed on smaller pelagic forage fish and squid, hunting near the water's surface or at middle depths. While it was previously believed that sailfish could reach speeds of up to 35 meters per second (125 kilometers per hour), recent research suggests that their actual speeds range from 10–15 meters per second (35–55 kilometers per hour). Despite this adjustment, sailfish still hold the record for the highest speed among all marine animals.
Sailfish employ remarkable hunting strategies, utilizing their bills to strike schooling fish. Their bill movement can either involve tapping (short-range movement) or slashing (horizontal large-range movement) at their prey. To make their bills less detectable, sailfish keep their sail folded down while swimming, raising it only when attacking. This raised sail reduces sideways oscillations, allowing sailfish to approach fish schools unnoticed until the decisive strike.
During a single sailfish attack, approximately two prey fish are injured through scale and tissue removal, but not all attacks result in capture. In fact, only 24% of attacks lead to successful captures. However, injured fish become easier targets, and as a result, sailfish benefit from the attacks of their conspecifics up to a certain group size. This form of protoco-operation, where no spatial co-ordination is required, may serve as a precursor to more complex group hunting behaviors.
Individual sailfish display preferences for hitting either the right or left side during their attacks. The strength of these side preferences positively correlates with capture success. However, if sailfish with strong side preferences became predictable to their prey, it could hinder their hunting effectiveness. To overcome this potential issue, living in groups offers a solution. In larger sailfish groups, the frequency of individuals with right- and left-sided preferences tends to balance out, making it harder for prey fish to anticipate the direction of the next attack.
Sailfish are epipelagic and oceanic species with a notable tendency to approach continental coasts, islands, and reefs in tropical and temperate waters of the Pacific and Indian oceans. They often rely on coral reefs as areas for feeding and breeding, emphasizing the importance of preserving these habitats. The disappearance of coral reefs in a sailfish's habitat may lead to the decline or even disappearance of the species in that area.
When sailfish are freshly hatched, they are hunted by smaller fishes that primarily feed on plankton. However, as sailfish grow, their predators increase in size. Adult sailfish are generally not preyed upon by anything other than larger predatory fish such as open ocean sharks, orcas, and dolphinfish.
In some rare instances, sailfish have been documented attacking humans in self-defense. One such incident involved a 100-pound sailfish that stabbed a woman in the groin when her party attempted to catch it. These occurrences, though infrequent, serve as a reminder of the power and agility possessed by these incredible marine creatures.