Ridgehead | |
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Scopelogadus mizolepis mizolepis | |
Scientific classification | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Beryciformes |
Family: | Melamphaidae T. N. Gill, 1893 |
Genera | |
Ridgeheads, also known as bigscales, are a family (Melamphaidae, from the Greek melanos [black] and amphi [by both sides]) of small, deep-sea stephanoberyciform fish. The family contains approximately 37 species in five genera; their distribution is worldwide, but ridgeheads are absent from the Arctic Ocean and Mediterranean Sea. Although the family is one of the most widespread and plentiful of deep-sea families, none of its members are of interest to commercial fishery.
These fish are named for their large scales and pronounced cranial ridges, as well as for their typically dark brown to black coloration. Ridgeheads are the largest and most diverse family of their order.
Typical of the Stephanoberyciformes, the melamphid body is robust, oblong, subcylindrical, and slightly compressed laterally. The head is large and scaleless, with its profile either bluntly rounded or with a sharp frontal angle; it is conspicuous for its prominent ridges, which are covered by thin skin. The head is also cavernous, being riddled by muciferous canals—similar structures are found in the beryciform slimehead (Trachichthyidae) and fangtooth (Anoplogastridae) families. Sharp spines and serrations may further adorn the head in some species. The mouth is large and oblique; the long jaws extend to or exceed the posterior margin of the eye, and are lined with villiform (brushlike) teeth. The vomer, palatines, endopterygiod, and ectopterygiods all lack teeth. The eyes are usually fairly small, but in Poromitra megalops they may exceed 20 per cent of the head's length in diameter.
The large scales are cycloid and imbricate; they are arranged in a longitudinal series of 12–40. Usually deciduous, these scales are largest in Scopelogadus species; in these and some other species, the scales' circuli (concentric lines) are clearly visible to the unaided eye. The lateral line (excluding the network of cranial canals) is largely absent; when present, it is reduced to 1–2 pored scales following the operculum's upper edge. The caudal peduncle is relatively long; the caudal fin is forked to emarginate and possesses 3–4 procurrent spines. The single dorsal fin originates behind the pectoral and pelvic fins and contains 1–3 weak spines and 9–18 soft rays; the pectoral fins are elongate and tapered (the superior rays being longer than the inferior rays) and contain 12–16 soft rays. The pelvic fins are thoracic to subthoracic with one spine and 6–8 soft rays; the anal fin is small and set far back, with one spine and 7–11 soft rays.
The branchiostegal rays number 7–8 and the vertebrae 24–31. The largest species recorded is Poromitra curilensis, a Pacific ridgehead related to the crested bigscale, [1] at up to 18 centimetres standard length (SL; a measurement excluding the caudal fin). [2] Most ridgeheads are well under 10 centimetres SL.
Ridgeheads are meso- to bathypelagic; they have been trawled at depths as shallow as 150 metres (490 ft) to as deep as 3,400 metres (11,200 ft). Some species undergo diel vertical migrations of several hundred metres; that is, they remain at aphotic depths (below ca. 400 metres) during the day but rise to surface waters (10–100 metres) at night to feed and (presumably) to avoid predators. Ridgeheads feed primarily on zooplankton, such as copepods, euphausiids, and other small pelagic crustaceans. There is also a marked segregation of life stages: larval and juvenile ridgeheads are present within the upper 200 metres of the water column, whereas adults are typically found much farther down.
The family is sometimes termed pseudoceanic because, rather than having an even distribution in open water, ridgeheads occur in significantly higher abundances around structural oases, notably seamounts and over continental slopes. This is also true of other deep-sea pelagic groups, such as the lanternfish (Myctophidae), marine hatchetfish (Sternoptychidae), and lightfish (Phosichthyidae or Photichthyidae) families. The phenomenon is explained by the likewise abundance of prey species which are also attracted to the structures.
As oviparous pelagic spawners, ridgeheads produce many tiny eggs which are fertilized externally; the eggs and larvae (and early juveniles) are buoyant and planktonic, drifting with the currents near the surface until the juveniles have reached the point where they are strong enough to determine their own direction. Study of the spawning habits of twospine bigscales (Scopelogadus mizolepis bispinosus) indicates spawning occurs year-round, with no definite peaks.
Although their deep-living nature protects them from predation to some degree, ridgeheads are prey to large seabirds such as albatrosses; large squid such as the Jumbo Squid (Dosidicus gigas) and Sevenstar Flying Squid ( Martialia hyadesii ); oceanic dolphins (family Delphinidae); and large pelagic fish, such as tuna and other scombrids.
Slimeheads, also known as roughies and redfish, are mostly small, exceptionally long-lived, deep-sea beryciform fish constituting the family Trachichthyidae. Found in temperate to tropical waters of the Atlantic, Indian, and Pacific Oceans, the family comprises about 50 species in eight genera. Slimeheads are named for the network of muciferous canals riddling their heads.
The Zeidae are a family of large, showy, deep-bodied zeiform marine fish—the "true dories". Found in the Atlantic, Indian, and Pacific Oceans, the family contains just six species in two genera. All species are important and highly regarded food fish supporting commercial fisheries, and some—such as the John Dory —are enjoyed in large public aquaria. These fish are caught primarily by deep-sea trawling.
The Atlantic horse mackerel, also known as the European horse mackerel or common scad, is a species of jack mackerel in the family Carangidae, the jacks, pompanos and trevallies. It is found in the eastern Atlantic Ocean off Europe and Africa and into the south-eastern Indian Ocean. It is an important species in commercial fisheries and is listed as a Vulnerable species on The IUCN Red List of Threatened Species.
The parore also known as luderick, black bream or blackfish is a species of marine ray-finned fish, a sea chub from the family Kyphosidae which is found in the southwestern Pacific Ocean off Australia and New Zealand. Parore or paraore is the common name in New Zealand but in Australia luderick is preferred.
Pentaceros richardsoni, the pelagic armourhead, Richardson's boarfish or southern boarfish, is a species of marine ray-finned fish, an armourhead from the family Pentacerotidae. It has a wide distribution in the oceans of the southern hemisphere. It is commercially important as a food fish.
Mycteroperca microlepis, the gag, gag grouper, velvet rockfish or charcoal belly, is a species of marine ray-finned fish, a grouper from the subfamily Epinephelinae which is part of the family Serranidae, which also includes the anthias and sea basses. It comes from warmer parts of the West Atlantic, including the Caribbean and Gulf of Mexico. It is a drab, mottled-gray fish lacking the distinguishing features of most other groupers. Its pattern of markings resemble the box-shaped spots of the black grouper. It lacks the streamer-points on the tail fin that scamp and yellowmouth grouper have, and lacks yellow coloration around the mouth.
The Atlantic threadfin is a species of ray-finned fish a threadfin from the family Polynemidae which is native to subtropical and temperate waters of the western Atlantic Ocean and the Gulf of Mexico.
King-of-the-salmon, Trachipterus altivelis, is a species of ribbonfish in the family Trachipteridae. Its common name comes from the legends of the Makah people west of the Strait of Juan de Fuca, which hold that this fish leads the salmon annually to their spawning grounds. Catching or eating king-of-the-salmon was forbidden, as it was feared killing one would stop the salmon run. This myth is reflected by a former specific epithet used for this fish, rex-salmonorum, rex being Latin for "king". The king-of-the-salmon is found in the eastern Pacific Ocean from Alaska to Chile. It is usually found in the open ocean to a depth of 900 meters, though adults sometimes feed on the sea bottom.
The blurred lanternshark is a little-known species of dogfish shark in the family Etmopteridae, found around the world in benthic and pelagic habitats from a depth of 110 m (360 ft) to over 1 km (0.62 mi) down. This shark forms the E. pusillus species group with the smooth lanternshark, which are distinguished from other members of its family by having irregularly arranged, flat-topped dermal denticles that give them a "smooth" appearance. Both species are slender-bodied with long heads, two dorsal fins bearing spines, no anal fins, and light-emitting photophores. The blurred lanternshark is larger, reaching 67 cm (26 in) or more in length. This species feeds on small squid, fishes, and fish eggs, and is ovoviviparous. It has been assessed as of Least Concern by the International Union for Conservation of Nature, because of its wide distribution and lack of threat from fishing pressure.
Holacanthus bermudensis, the blue angelfish or Bermuda blue angelfish, is a species of marine ray-finned fish, amarine angelfish belonging to the family Pomacanthidae. It occurs in the western Atlantic Ocean.
Epinephelus albomarginatus, the white-edged grouper, white-edged rockcod or captain fine, is a species of marine ray-finned fish, a grouper from the subfamily Epinephelinae which is part of the family Serranidae, which also includes the anthias and sea basses. It is found in the southwestern Indian Ocean and it is associated with coral reefs. It is a target species for commercial and recreational fisheries.
The longfin trevally, also known as the longfin kingfish, longfin cavalla or armed trevally, is a species of inshore marine fish in the jack family, Carangidae. The species is common in tropical to subtropical waters of the Indo-Pacific, ranging from South Africa in the west to Japan in the east, typically inhabiting inshore reefs and bays. The species is easily distinguished by its elongate dorsal and anal fin lobes and filamentous dorsal rays, as well as its scaleless breast. Longfin trevally are pelagic predators, taking a variety of small fish, cephalopods and crustaceans, and reach sexual maturity at around 21 cm. The species has a maximum known length of 57 cm and weight of 3.5 kg. The longfin trevally has a very complex taxonomic history which is closely intertwined with another currently valid species, Carangoides ciliarius, which may yet prove to be synonymous. Longfin trevally are of minor importance to fisheries throughout their range and are considered good table fish, and are occasionally taken by anglers.
Poromitra crassiceps, commonly called the crested bigscale is a species of deep sea fish in the ridgehead family.
Chaetodon hoefleri, the four-banded butterflyfish, is a species of marine ray-finned fish, a butterflyfish from the family Chaetodontidae. It is native to the tropical eastern Atlantic and has been recorded in the Mediterranean.
The smooth lumpfish is a species of lumpfish native to the North Pacific where it is found at depths down to 1,700 metres (5,600 ft). This species grows to a length of 41 centimetres (16 in) TL. It is the only known member of its genus.
Taractichthys steindachneri, the sickle pomfret, is a species of marine ray-finned fish, a pomfret of the family Bramidae. It is found in the Indian and Pacific Oceans.
Kyphosus azureus, the zebra-perch sea chub, zebra perch or zebra sea chub, is a species of marine ray-finned fish, a sea chub from the family Kyphosidae which is native to the eastern Pacific Ocean coasts of North America.
Polydactylus sextarius, the blackspot threadfin, is a species of marine ray-finned fish, a threadfin from the family Polynemidae which is native to the western Pacific and eastern Indian Oceans.
Pempheris multiradiata, the bigscale bullseye, large-scaled bullseye or common bullseye, is a species of marine ray-finned fish, a sweeper from the family Pempheridae which is found in the coastal waters of southern Australia.
The paradise threadfin is a species of catadromous ray-finned fish, a threadfin from the family Polynemidae which is found in south and southeast Asia in freshwater rivers where it is a valued food fish.