Roundscale spearfish | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Istiophoriformes |
Family: | Istiophoridae |
Genus: | Tetrapturus |
Species: | T. georgii |
Binomial name | |
Tetrapturus georgii R. T. Lowe, 1841 | |
The roundscale spearfish (Tetrapturus georgii) is an Istiophoridae species of marlin living in the epipelagic zone of the Atlantic Ocean. It has long been misidentified as white marlin but can be differentiated thanks to their scale shapes that gives its name. Not much is known about this species. It could reach a length of 160 cm and 21,5 kg and has no conservation status yet due to a lack of data.
The roundscale spearfish, described in 1841 by Lowe, is a Teleostei fish of the order of the Carangformes (jacks) and of the family of Istiophoridae (Billfishes). With angustirostris, belone and pfluegeri, T. Georgii share the genus Tetrapturus meaning “four fins” in Greek [2]
Tetrapturus georgii have long been misidentified with the white marlin previously Tetrapturus albicans. But in 2006, genetic discoveries have led to a genus change for the white marlin to Kajikia albidia and to a validation of the species Tetrapturus georgii thanks to molecular and morphological evidence. [3] [4] [5] The identification of the specie can be done with the scale shape or with genetic analysis. [5] This identification problem for years led to a miscounting of both species population and is one of the reason for a bad population assessment. With lacking data for a proper population assessment simulation, an uncertainty hangs over the needed conservation status and management. However the population trends suggest a more worrying situation than it was previously suggested. [6]
'Tetrapturus georgii' has a robust and not very compressed body. [7] Tetrapturus species are not known to show a sexual dimorphism in morphological features and color pattern. For T.georgii as well, females (150 cm body length; and 20 kg body weight) are mostly the same dimension as the males (160 cm body length and 21.5 kg body weight) [8]
'Tetrapturus georgii' is characterized by its moderately long, slender rostrum, rounded in cross section (length usually at least equal to head). Its body is slim, and it has a moderate hump on the nape. It is dark blue above, coppery on the sides and silver below colors and may display iridescent bars on body. [9] The branchiostegal membranes on the sides of its head are completely united but free from the isthmus. The jaws and palate have small, file-like teeth. It has two dark blue dorsal fins. The first is higher at the front, with a rounded lobe, extending from the head to just before the second dorsal fin which is smaller. Two anal fins are present, the first being high and rounded, and the second like the second dorsal fin. The pectoral fins are long, almost equal to the pelvic fins. The caudal peduncle has keels on each side. The lateral line is simple. The scales on the sides of the body are soft, while those on the dorsal and ventral parts are stiff. The color of the rostrum may not have bars on the body, and the first dorsal fin is often unspotted. Its flesh is distinctly redder than that of T. belone and more like Kajikia albidia. [7]
As said before, the identification between T. georgii and Kajikia albida (white marlin) can be done thanks to a close scale shape examination. Roundscale spearfish are described as having more soft, rounded anteriorly scales with a few large posterior points. White marlin scales, on the other hand, are more rigid pointed anteriorly as well as posteriorly. [3] [8] The scales used are often arbitrarily sampled on the mid-body of the animal. [5] Another way of identification between the two species, without doing a genetic test, is by measuring the distance between the anal opening and the anal fin. In roundscale spearfish, the anal opening is further away from the anal fin (greater than half the length of the anal fin) than it is for the white marlin. [6]
Tetrapturus georgii has asymmetrical gonads and a presence of swim bladder, consisting of many small bubble-shaped chambers essential for buoyancy regulation. [10]
Tetrapturus georgii is endemic to the Atlantic Ocean. Most specimens of this species are found in Madeira, Sicily, the Straits of Gibraltar, and the adjacent Atlantic Ocean off southern Portugal. But observations have been made all around the Atlantic Ocean from North to South and East to West. [3] It's not unusual for them to make long migrations across the ocean. The nursery areas for larval and juveniles stages remain unknown.
Feeding habits of Tetrapturus georgii have not been reported in scientific literature. But the same way as their related cousins, the roundscale spearfish probably feed on schooling fishes, bony fishes, squid, octopuses and cuttlefishes. The billfishes are high trophic levelpredators. [11]
Tetrapturus georgii could be a host of the parasite Capsala laevis. [12]
Their rostrum and powerful speed burst is useful to stun and catch preys. Tetrapturus georgiii spends more than 60% of its time at depths of less than 10m and is thus an epi-pelagic fish. [5]
Little is known about Tetrapturus behaviors. This lonely migratory predators, sometimes meet in high prey density areas. But much of the available research focuses on individual movements and habitat use, rather than exploring group dynamics. The lack of comprehensive data on billfish species, combined with the challenges of studying these elusive marine animals, lead to poor social structure and behavioral understanding. [13]
Very little is known on its reproductive biology, mating display and sexual behavior. Tetrapturus georgii is an dioecious species laying eggs in batches in tropical regions. Those eggs hatch into planktonic larvae growing to become juveniles. [4] The maximum lifespan could be between 8 and 15 years according to their closest relatives [14]
Tetrapturus georgii and other billfishes are not targeted by commercial fisheries but represents an important bycatch in longline tuna and swordfish fisheries. As T.gerogii has long been misidendified as white marlin, no specific total landings or stock assessment are existing. [5] According to a study, [6] about 30% of the white marlin landings registered should have been identified as roundscale spearfishs. The white marlin benefits from a long landings historical record. With a maximum of 4900mt in 1965, [10] white marlin (and thus roundscale spearfish) landings have decreased till 350mt in 2011. [15] This diminution is partially due to the conservation recommendations of the international commission for tune conservation (ICCAT) to release alive marlins. But since then, total landings have difficulties in staying below the total allowed catch (TAC) of 400mt putting at risk the stock recovery. The projections are full of uncertainty because of bad fish mortality assessment due to an inadequate reporting of discards as well as a lack of data from recreational fisheries. [16] In addition, a stock assessment of two species at the same time may be detrimental and hide strong threats to one or both of them.
Some gear selectivity improvement such as circle hooks instead of j-hooks seems promising for a billfish bycatch reduction. Combine with a respect of TAC, size limitation and quick release, it could represent some practical solution for a reduce human footprint. [16] [17]
By only accounting for 5% of the total landing, [10] recreational fisheries represents a multimilliard dollar sector in developed countries targeting white marlin and roundscale spearfish seamlessly. But despite a high alive release, the energy expenditure and the physiological stress resulting from capture and handling lead to a possible post-release mortality of about 20%. [17] With more than 10 000 catches per year just in the US, this represent a real impact not enough documented.
All this make the roundscale spearfish's situation seem precarious, even though it has not been evaluated and assessed yet. [18]
Marlins are fish from the family Istiophoridae, which includes 11 species.
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through convergent evolution they have independently evolved external superficial fish-like body plans adapted to their marine environments, including most numerously fish, but also mammals such as cetaceans, and even extinct ancient marine reptiles such as various known species of ichthyosaurs. Most species have only one dorsal fin, but some have two or three.
The albacore, known also as the longfin tuna, is a species of tuna of the order Scombriformes. It is found in temperate and tropical waters across the globe in the epipelagic and mesopelagic zones. There are six distinct stocks known globally in the Atlantic, Pacific, and Indian oceans, as well as the Mediterranean Sea. The albacore has an elongate, fusiform body with a conical snout, large eyes, and remarkably long pectoral fins. Its body is a deep blue dorsally and shades of silvery white ventrally. Individuals can reach up to 1.4 m in length.
Spearfish may refer to:
The white marlin, also known as Atlantic white marlin, marlin, skilligalee, is a species of billfish that lives in the epipelagic zone of the tropical and subtropical Atlantic Ocean. They are found between the latitudes of 45° N and 45° S in waters deeper than 100 m. Even though white marlin are found in bodies of water that are deeper than 100 m they tend to stay near the surface. White marlin have been found near banks, shoals, and canyons, but they are not limited to those locations. They prefer warm surface temperatures greater than 22 °C.
The Atlantic blue marlin is a species of marlin endemic to the Atlantic Ocean. It is closely related to, and usually considered conspecific with, the Indo-Pacific blue marlin, then simply called blue marlin. Some authorities consider both species distinct.
The International Commission for the Conservation of Atlantic Tunas (ICCAT) is a tuna regional fishery management organisation, responsible for the management and conservation of tuna and tuna-like species in the Atlantic Ocean and adjacent seas. The organization was established in 1966, at a conference in Rio de Janeiro, Brazil, and operates in English, French and Spanish. The organisation has been strongly criticised by scientists for its repeated failure to conserve the sustainability of the tuna fishery by consistently supporting over-fishing – an internal review branded ICCAT's policies on the eastern Atlantic bluefin tuna fishery a "travesty of fisheries management", and an "international disgrace". Conservationists often refer to ICCAT as "The International Conspiracy to Catch All Tuna".
The billfish are a group of saltwater predatory fish characterised by prominent pointed bills (rostra), and by their large size; some are longer than 4 m (13 ft). Extant billfish include sailfish and marlin, which make up the family Istiophoridae; and swordfish, sole member of the family Xiphiidae. They are often apex predators which feed on a wide variety of smaller fish, crustaceans and cephalopods. These two families are sometimes classified as belonging to the order Istiophoriformes, a group which originated around 71 million years ago in the Late Cretaceous, with the two families diverging around 15 million years ago in the Late Miocene. However, they are also classified as being closely related to the mackerels and tuna within the suborder Scombroidei of the order Perciformes. However, the 5th edition of the Fishes of the World does recognise the Istiophoriformes as a valid order, albeit including the Sphyraenidae, the barracudas.
The striped marlin is a species of marlin found globally in tropical to temperate oceans not far from the surface. It is a desirable commercial and game fish, although conservation measures are in place to restrict its commercial landings. An epipelagic predator, it hunts during the day in the top 100 metres (330 ft) or so of the water column, often near the surface. One of its chief prey is sardines.
Marlin fishing or billfishing is offshore saltwater game fishing targeting several species of fast-swimming pelagic predatory fish with elongated rostrum collectively known as billfish, which include those from the families Istiophoridae and Xiphiidae (swordfish). It is considered by some fishermen to be a pinnacle of big-game fishing, due to the size, speed and power of the billfish and their relative elusiveness.
The shortbill spearfish, sometimes called the short-nosed spearfish, is a species of marlin native to the Indian and Pacific Oceans, with occasional records from the Atlantic Ocean. This species occurs in open waters not far from the surface. This species can reach a length of 230 cm (91 in), though most do not exceed 190 cm (75 in). The maximum recorded weight for this species is 52 kg (115 lb). It is of minor importance to commercial fisheries and is also a game fish. Short bill spearfish are characterized by a slim frame with a blue body that is silver underneath. Shortbill also possess a very short bill extending from their upper jaw.
The spearfish remora is a species of remora with a worldwide distribution in tropical and subtropical seas. Remoras attach themselves to other fish with a sucker on the head and this fish is almost exclusively found living on billfishes or swordfishes, and sometimes on sharks.
Tetrapturus is a genus of marlins commonly called spearfish, found in tropical and subtropical oceans throughout the world. Some are popular sport fish in big-game fishing.
Blochius is an extinct genus of prehistoric billfish from the Eocene. It is only known from the Monte Bolca deposits in Italy, and was likely restricted to shallow, tropical waters of the Tethys Sea.
Plectorhinchus albovittatus, the two-striped sweetlips or giant sweetlips, is a species of marine ray-finned fish, a sweetlips belonging to the subfamily Plectorhinchinae, part of the grunt family Haemulidae. It is native to the Indian Ocean and the western Pacific Ocean.
The Indo-Pacific blue marlin is a species of marlin belonging to the family Istiophoridae.
The longbill spearfish is a species of marlin native to the Atlantic Ocean where it is found above the thermocline in open waters between 40°N and 35°S. This species can reach a length of 254 centimetres (100 in) FL and the maximum weight recorded is 58 kilograms (128 lb). It feeds on pelagic fishes such as needlefish, tuna, and jack, as well as squids. They spawn once a year. The specific name honours the Florida game fisherman and taxidermist Albert Pflueger Sr, who died in 1962.
Kajikia is a genus of billfishes found in all subtropical oceans.
Of the twelve species of billfish, there are six species of Billfish in the Indian Ocean.
Rhamphoichthys is an extinct genus of billfish-like plethodid ray-finned fish from Late Cretaceous (Cenomanian). It contains one valid species, R. taxidiotis from the Hesseltal Formation of Germany and the Sannine Formation of Lebanon, in addition to two dubious species that are considered nomina nuda due to their fragmentary nature.
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