Istiophorus
| Sailfish Temporal range: 59–0 Ma Paleogene to present |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Perciformes |
| Family: | Istiophoridae |
| Genus: |
Istiophorus Lacépède, 1801 |
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A sailfish is a fish of the genus Istiophorus of billfish living in colder areas of all the seas of the earth. They are predominantly blue to gray in colour and have a characteristic erectile dorsal fin known as a sail, which often stretches the entire length of the back. Another notable characteristic is the elongated bill, resembling that of the swordfish and other marlins. They are therefore described as billfish in sport-fishing circles.
Two sailfish species have been recognized. No differences have been found in mtDNA, morphometrics or meristics between the two supposed species and most authorities now only recognized a single species, (Istiophorus platypterus), found in warmer oceans around the world.FishBase continues to recognize two species:
Sailfish grow quickly, reaching 1.2–1.5 m (3 ft 11 in–4 ft 11 in) in length in a single year, and feed on the surface or at middle depths on smaller pelagic forage fish and squid. Sailfish can supposedly reach very high swimming speeds of over 100 km/h (Lane 1941). Recent studies, however, do not support these claims and suggests that sailfish do not exceed swimming speeds of 36 km/h (22 mph). Generally, sailfish do not grow to more than 3 m (9.8 ft) in length and rarely weigh over 90 kg (200 lb). Sailfish have been reported to use their bill for hitting schooling fish by tapping (short-range movement) or slashing (horizontal large range movement) at them.
The sail is normally kept folded down when swimming and raised only when the sailfish attack their prey. It has been shown that the raised sail reduces sideways oscillations of the head which is likely to make the bill less detectable by prey fish. This strategy allows sailfish to put their bill close to fish schools or even into them without being noticed by the prey before hitting them.
Sailfish usually attack one at a time and the small teeth on their bills inflict injuries on their prey fish in terms of scale and tissue removal. On average about two prey fish are injured during a sailfish attack but only 24% of attacks result in capture. As a result injured fish increase in number over time in a fish school under attack. Given that more injured fish are easier to catch, sailfish benefit from the attacks of their conspecifics but only up to a particular group size. A mathematical model showed that that sailfish in groups of about to 70 individuals should gain benefits in this way. The underlying mechanism was termed proto-cooperation because it doesn’t require any spatial coordination of attacks and could be a pre-cursor to more complex forms of group-hunting.
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Wikipedia