Rainbow Runner

The rainbow runner's body is atypical of the jack family, which generally have deep, compressed bodies. The rainbow runner has a subcylindrical, elongated to almost fusiform body, with a long, pointed head and snout and a tapering rear end before the caudal fin emerges. The eyes are relatively small and the teeth are arranged on jaws in villiform bands, with minute teeth also present on the roof of the mouth and tongue. The fish has two dorsal fins, although the posterior rays of the long second fin have separated into a finlet. The first dorsal consists of six spines, the second of a single spine and 25 to 30 soft rays, with the last two as a separate finlet. About 4% of rainbow runners have only five spines in the first dorsal fin, and are apparently born without them.

The rainbow runner has a circumtropical distribution, inhabiting tropical and some subtropical waters worldwide. In the Western Atlantic, the species occurs from Massachusetts and Bermuda to northeastern Brazil, including the northern and southern Gulf of Mexico, the Bahamas, and the Greater and Lesser Antilles, extending east to at least the Azores.

The species is widespread throughout the Pacific Ocean, but appears to be slightly less abundant in parts of the Indian Ocean, and rare or absent in the Persian Gulf.

The species is an occasional visitor to the Mediterranean Sea, generally as a Lessepsian immigrant through the Suez Canal, but has not taken up permanent residence like other species. The species also inhabits the nearby Canary Islands, possibly entering the Mediterranean from the east, also.

The species is primarily pelagic, inhabiting the upper 164 m of the water column,

Rainbow runners are fast-swimming carnivores that take a wide range of prey, including a wide variety of small fishes, cephalopods, and pelagic or planktonic crustaceans, including, shrimp and crabs. The species shows selectivity of its prey, with fish in the Pacific Ocean taking higher numbers of Decapterus macarellus, a small fish, than any other prey available. Rainbow runners may increase their swimming and prey-searching abilities rapidly with their growth, becoming more efficient at finding their preferred prey items. Rainbow runners are also one of a number of pelagic fishes that prey on open-ocean species of sea-skaters (Halobates spp.), a type of insects which rest on the surface of the ocean.

The size at sexual maturity is only confidently known for the female of the species, being around 600 mm in fork length, although the male has been estimated to reach maturity between 600 and 650 mm.

In the Atlantic, the species is known to spawn from spring through to early autumn,

although fish living in waters greater than 27 °C spawn year round. However, even when year-round spawning occurs, seasonal peaks are seen, with fish in the Western Pacific Ocean showing these peaks in May and in December–January.

Rainbow runners are not a major commercial species like tuna or herring, but are taken in large quantities as bycatch. Their flesh is said to be of fair to excellent standard, depending on personal preferences, but generally fetch a low price at markets because they are relatively unknown. Archaeological evidence from the Kapingamarangi and Nukuoro Atolls in the Caroline Islands of Micronesia suggests the prehistoric people of these islands caught large numbers of rainbow runner as food, thought to have been captured by 'trolling' lure hooks from canoes.