The rainbow runner (Elagatis bipinnulata), also known as the rainbow yellowtail, Spanish jack and Hawaiian salmon.
The rainbow runner inhabits tropical and some subtropical waters worldwide. In the Western Atlantic, the species occurs from Massachusetts and Bermuda to north eastern 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 also called Erythrean invasion 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, sometimes close to land over rock and coral reef systems, as well as far offshore. The species occasionally comes quite close to shore, known to inhabits lagoons for short periods, and juveniles have even been reported in a Taiwanese estuary system. Rainbow runner, like other carangids such as Yellowtail kingfish are easily attracted to special Fish Attracting Devices (FAD's), floating buoy type structures. The species has been shown to occupy a water zone outside of the FAD up to 12 m deep and 10 m wide, treating it as if it were a stationary object.
The colour of the fish is possibly the easiest way to identify the rainbow runner. The upper body is a dark olive blue to green and fading to white underneath. There are two narrow light blue to bluish white stripes running longitudinally along the sides, with a broader olive to yellow stripe between them. The maximum length of the species is somewhat contentious, with most sources giving a known maximum length of between 107 cm (42 in) and 120 cm (47 in) cm, while one source asserts the species reaches 180 cm (71 in) in length. The maximum known weight is confidently known to be 46.2 kg, The rainbow runner has a body that is sub-cylindrical, elongated to almost fusiform body, with a long pointed head and snout and a tapering rear end before the caudal fin emerges. The eye is 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 rear rays of the long second fin have separated into a finlet. The first dorsal consists of 6 spines, the second of a single spine and 25 to 30 soft rays, with the last two as a separate finlet. Approximately 4% of rainbow runner have only five spines in the first dorsal fin, and are apparently born without them. The anal fin consists of one spine detached from the fin anteriorally, while the main fin has a single spine and 18 to 22 soft rays, with the last two detached to form a finlet like the dorsal fin. The dorsal and anal fins are quite low, and the dorsal fin is much longer than the anal. The pectoral fin is small for a carangid, about the length of the pelvic fin and is non-falcate with 20 rays. The pelvic fin consists of one spine and five branched soft rays. The caudal fin is deeply forked and consisting of 17 caudal rays, 9 dorsally and 8 ventrally. The lateral line has a slight anterior arch and there are no scutes present on the line, but possesses about 100 scales. The scales covering the body and parts of the gill cover, cheek, pectoral fins, pelvic fins. The species has 24 vertebrae.
Rainbow runner are fast swimming carnivores that take a wide range of prey including a wide variety of small fishes, inkfish and pelagic or planktonic crustaceans including, shrimps and crabs. It has been demonstrated that the species shows selectivity of its prey, with fish in the Pacific Ocean taking higher amounts of Mackerel scad, a small fish, than any other prey available. It was also found in the same study that rainbow runner may increase the swimming and prey searching abilities rapidly with their growth, becoming more efficient at finding their preferred prey items. Rainbow runner are also one of a number of pelagic fishes that prey on open-ocean species of sea-skaters/striders, a type of insect which rest on the surface of the ocean.
Taken while trolling for other species such as tuna and mackerel, but are often targeted inshore by anglers on the west coast of the Americas using surface 'popper' style lures. The fish are caught on a wide variety of lures and baits, with deep diving lures, surface lures and even saltwater flies used to good measure. The species takes a wide variety of baits including live and cut fish, squid, octopus.
Their flesh is said to be of fair to excellent standard, depending on personal preferences. At least one case of ciguatera poisoning has been reported from this species on the Virgin Islands.
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 at 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 degrees Celsius spawn year round. However, even when year-round spawning occurs, there are seasonal peaks, with fish in the Western Pacific Ocean showing these peaks in May and in December – January. The fish is oviparous, producing pelagic eggs and larvae, with the diagnostic features of the larvae include a supraoccupital crest and distinctive patterns of pigment and melanophores. The growth of the fish has also been studied, with the size of fish at 1, 2, 3, 4 and 5 years ages are estimated to be 30, 46, 59, 69 and 77 cm in length respectively.
The species themselves are also commonly used as bait, either as live bait or dead bait rigged to be trolled behind game boats for larger species such as billfish and tuna.
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