Blue runner

Species of fish

The blue runner (Caranx crysos), also known as the bluestripe jack, Egyptian scad, hardtail jack or hardnose, is a common species of moderately large marine fish classified in the jack family, Carangidae. The blue runner is distributed across the Atlantic Ocean, ranging from Brazil to Canada in the western Atlantic and from Angola to Great Britain including the Mediterranean in the east Atlantic. The blue runner is distinguished from similar species by several morphological features, including the extent of the upper jaw, gill raker count and lateral line scale counts. The blue runner is known to reach a maximum length of 70 cm and 5.05 kg in weight, but is much more common below 35 cm. The species inhabits both inshore and offshore environments, predominantly over reefs, however it is known to congregate around large, man made, offshore structures such as oil platforms. Juveniles tend to inhabit shallower reef and lagoon waters, before moving to deeper waters as adults. The blue runner is a schooling, predatory fish, predominantly taking fish in inshore environments, as well as various crustaceans and other invertebrates. Fish living offshore feed nearly exclusively on zooplankton. The species reaches sexual maturity at between 225 and 280 mm across its range, with spawning occurring offshore year round, although this peaks during the warmer months. Larvae and juveniles live pelagically, often under sargassum mats or jellyfish until they move inshore. The blue runner is of high importance to fisheries, with an annual catch of between 6000 and 7000 tonnes taken from the Americas in the last five years. The species is also a light tackle gamefish, taking baits, lures, and flies; but is often used as bait itself, being a mediocre table fish. There has been some suggestion that the eastern Pacific species Caranx caballus, the green jack, may be conspecific with C. crysos, although this currently remains unresolved.

The blue runner is classified within the genus Caranx, one of a number of groups known as the jacks or trevallies. Caranx itself is part of the larger jack and horse mackerel family Carangidae, part of the order Carangiformes. The species was first scientifically described by the American ichthyologist Samuel L. Mitchill in 1815, based on a specimen taken from the waters of New York Bay, USA which was designated to be the holotype. He named the species Scomber crysos and suggested a common name of 'yellow mackerel', with the specific epithet reflecting this, meaning "gold" in Greek. The species has been independently redescribed three times, first as Caranx fusus, which is still incorrectly used by some authors (occasionally as Carangoides fusus), and later as Caranx pisquetus and Trachurus squamosus. These names are considered invalid junior synonyms under ICZN rules. The species has many common names, with the most common being 'blue runner'. Other less commonly used names include 'bluestripe jack', 'Egyptian scad', 'hardtail jack', 'hardnose', 'white back cavalli', 'yellow tail cavalli', as well as a variety of broad names such as 'mackerel', 'runner' and 'crevalle'. There have been suggestions that the blue runner may be conspecific with the eastern Pacific species Caranx caballus (green jack), although no specific studies have been undertaken to examine this relationship. Both species were included in a recent genetic analysis of the entire family Carangidae, with results showing both species are very closely related, although the authors did not comment on genetic distance between the two.

The blue runner is moderately large in size, growing to a maximum confirmed length of 70 cm and 5.05 kg in mass, but is more common at lengths less than 35 cm. The posterior section of the eye is covered by a moderately well developed adipose eyelid, and the posterior extremity of the jaw is vertically under the center of the eye. The dorsal fin is in two parts, the first consisting of 8 spines and the second of 1 spine followed by 22 to 25 soft rays. The anal fin consists of 2 anteriorly detached spines followed by 1 spine and 19 to 21 soft rays. The lateral line has a pronounced but short anterior arch, with the curved section intersecting the straight section below the spine of the second dorsal fin. The straight section contains 0 to 7 scales followed by 46 to 56 very strong scutes, with bilateral keels present on the caudal peduncle. There are a total of 86 to 98 scales and scutes over the entire lateral line. The chest is completely scaled. The upper jaw contains an irregular series of outer canines with an inner band of small, regularly spaced teeth, while the lower jaw contains a single band of small teeth. and Galicia, Spain. The furthest north it has been reported is southern Great Britain, where two specimens were taken in 1992 and 1993. There has been a trend of having this and other tropical species found further north more often, with publications indicating the blue runner has recently established stable populations in the Canary Islands, where it had been rarely sighted. Some authors have attributed this northward migration to rising sea surface temperatures, possibly the result of climate change.

The blue runner is primarily an inshore fish throughout most of its range, however it is known to live on reefs in water depths greater than 100 m. Fishermen have also taken the species in the Mississippi delta, indicating it can tolerate lower salinities in almost estuarine environments. Blue runner are easily attracted to any large underwater or floating device, either natural or man made. Several studies have shown the species congregates around floating buoy like fish aggregating devices (FADs), both in shallower waters, as well as in extremely deep (2500 m) waters, indicating the species may move around pelagically. In these situations, blue runner always form small aggregations at the water surface, while other larger species tend to congregate slightly deeper. Purpose built artificial reefs and marine aquaculture cage structures are also known to attract the species, with the former having the added benefit of dispersing wayward food scraps.

The blue runner normally moves either in small schools or as solitary individuals, The biology, particularly reproductive and growth biology has been quite extensively studied in the blue runner due to this high abundance in the Atlantic, and its importance to fisheries and the ecology of its environment.

The blue runner is a fast swimming predator which primarily takes small benthic fishes as prey in inshore waters. More detailed research in Cape Verde found as well as fish, blue runner take shrimp, prawns, lobsters, jellyfish and other small invertebrates. The diet of juveniles is more zooplankton dominated, with young fish predominantly taking cyclopoid and calanoid copepods, and gradually moving to a more fish based diet. Adult blue runner living offshore or aggregating around oil and gas platforms tend to have less fish in their diet, foraging extensively on larger zooplankton during the summer months, with larval decapods and stomatopods, hyperiid amphipods, pteropods, and larval and juvenile fishes also taken. Studies around these platforms has found blue runner feed with equal intensity during both day and night, with larger prey such as fish taken preferentially at night, with smaller crustaceans taken during the day. The species is also known to eat the dolphins excrement.

The blue runner reaches sexual maturity at slightly different lengths throughout its range, with all such studies occurring in the west Atlantic. Research in northwest Florida found a length at maturity of 267 mm, a study in Louisiana showed the species reaches sexual maturity at 247–267 mm in females and 225 mm in males, and in Jamaica lengths of 260 mm for males and 280 for females were estimated. Spawning appears to occur offshore year round, although several peaks in spawning activity have been found in different areas through the species range. Peak spawning season in the Gulf of Mexico occurs from June to August, with a secondary peak in spawning during October in northwest Florida. The blue runner's larval stage has been extensively described, with distinguishing features including a slightly shallower body than other larval Caranx, and a heavily pigmented head and body. During this early juvenile stage, there are several dark vertical bars clearly present on the side. As the fish grow, they often move to more inshore lagoons and reefs, before slowly making their way to deeper outer reefs at the onset of sexual maturity. In all cases studied, there are more females in the adult population than males, with female to male ratios ranging from 1.15F:1M to 1.91F:1M. In the Americas, recent catch data suggests an increased amount of the species is being taken (or reported), with the 2006 and 2007 catch averaging between 6000 and 7000 tonnes, while during the 1980s and 1990s, there was rarely an annual catch greater than 1000 tonnes. Throughout its range the blue runner is commercially taken by haul seines, lampara nets, purse seines, gill nets, and hook and line methods. The species is also a target for light tackle saltwater fly fishermen, and can push 6 weight fly tackle to its limits. The IGFA world record for Blue Runner stands at 5.05 kg (11 lbs 2 oz) caught off Dauphin Island by Stacey Moiren in 1997, previous records have also come from the eastern North Atlantic. The blue runner is used extensively as live bait for larger fish, including billfish, cobia and amberjack. It is considered a fairly low quality table fish,