Rainbow Runner

The rainbow runner (Elagatis bipinnulata), also referred to as the rainbow yellowtail, Spanish jack, and Hawaiian salmon, is a prevalent pelagic marine fish belonging to the Carangidae family. This species is distributed extensively across tropical and subtropical waters worldwide, inhabiting both coastal and offshore regions. As the sole member of the genus Elagatis, established 15 years following the initial species description, the rainbow runner shares a close relation to the amberjacks. It is easily identifiable by its distinctive body shape and vibrant coloration, which lends the fish its name. The rainbow runner is a swift predator, consuming small fish, cephalopods, and a variety of planktonic crustaceans. Sexual maturity is reached at approximately 60 cm (24 in), with spawning periods varying among populations – some reproduce year-round, while others do so during specific seasons. Renowned as a game fish, the rainbow runner is captured using various fishing techniques and is esteemed as a table fish. Though not a primary commercial species like tuna or herring, it contributes significantly as bycatch in tuna and shark fishing operations and is subsequently marketed. The maximum reported lifespan is 6 years.

As the singular species in the monotypic genus Elagatis, the rainbow runner belongs to one of 30 genera within the Carangidae family. Carangidae is a family of perciform fishes classified under the suborder Percoidei. Initially scientifically described in 1825 by French zoologists Jean René Constant Quoy and Joseph Paul Gaimard, the type specimen was collected from the 🌊 Indian Ocean, likely within the Malay Archipelago.

The expansive range of this species has led to numerous local common names, with "rainbow runner" being the most prevalent in English due to its coloration. Other commonly used names include rainbow yellowtail, Hawaiian salmon, Spanish jack, and salmon del alto (Cuba), among over 20 others in different languages.

Distinguished by its atypical jack family body form, the rainbow runner possesses a subcylindrical, elongated, almost fusiform body, characterized by a long, pointed head and snout and a tapering rear before the caudal fin. The species’ relatively small eyes and villiform band-arranged teeth are complemented by minute teeth on the palate and tongue. Notably, the fish has two dorsal fins, with posterior rays of the lengthy second fin forming a finlet.

The species exhibits striking coloration: a dark olive blue to green upper body that fades to white underneath, complemented by two narrow, light blue to bluish-white longitudinal stripes with a broader olive to yellow stripe in between. The maximum length, subject to some debate, is generally reported between 107 and 120 cm (42–47 in), although some sources claim it can reach up to 180 cm (71 in). The confirmed maximum weight stands at 46.2 kg, as documented by the International Game Fish Association.

With a circumtropical distribution, the rainbow runner thrives in tropical and certain subtropical waters globally, demonstrating a high migratory behavior. In the Western Atlantic, its range extends from Massachusetts and 🇧🇲 Bermuda to northeastern 🇧🇷 Brazil, incorporating the 🌊 Gulf of Mexico, the 🇧🇸 Bahamas, and the Greater and Lesser Antilles, reaching eastward to at least the Azores. Its presence is widespread across the 🌊 Pacific Ocean yet appears less common in segments of the 🌊 Indian Ocean and is rare or absent in the 🌊 Persian Gulf. Additionally, it is an occasional visitor to the Mediterranean Sea, generally as a Lessepsian migrant through the Suez Canal (🇪🇬 Egypt), without establishing a permanent presence like some other species.

Primarily pelagic, the rainbow runner inhabits the upper 164 m of the water column, occasionally venturing close to land above rocky and coral reef systems, and distant offshore. The species sometimes approaches shorelines, momentarily residing in lagoons, with juveniles spotted in 🇹🇼 Taiwanese estuaries. Like other carangids such as yellowtail kingfish, rainbow runners are readily attracted to fish-attracting devices (FADs) and have been noted to use the water zone around these devices, up to 12 m deep and 10 m wide, similarly as if they were stationary objects.

The species tends to form schools of varying sizes, from a few individuals to several hundred, and is known to contain unusual high levels of docosahexaenoic acid in their muscles, possibly due to low lipid content in these tissues and accumulation in other organs.

As rapid-swimming carnivores, rainbow runners capture a diverse range of prey, comprising small fishes, cephalopods, and pelagic or planktonic crustaceans like shrimp and crabs. Notable selectivity is exhibited with Pacific populations favoring Decapterus macarellus, a small fish. Preying on open-ocean insects such as sea-skaters (Halobates spp.) is also documented, further highlighting their dietary versatility.

Conversely, rainbow runners themselves fall prey to larger species, including Fraser's dolphin (Lagenodelphis hosei) and several seabird species in the Laridae family.

Despite their limited commercial prominence, significant quantities are caught as bycatch. Their flesh quality is described as fair to excellent, contingent on personal taste, though generally fetching low market prices owing to relative unfamiliarity. Historical data from Kapingamarangi and Nukuoro Atolls in 🇫🇲 Micronesia indicates prehistoric populations capturing rainbow runners through trolling from canoes.