Predatory fish are fish that prey upon other fish or animals. Some predatory fish include perch, muskie, pike, walleye and salmon.
The beak, bill, and/or rostrum is an external anatomical structure of birds that is used for eating and for preening, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young. The terms beak and rostrum are also used to refer to a similar mouth part in some ornithischians, pterosaurs, turtles, cetaceans, dicynodonts, anuran tadpoles, monotremes ,sirens, pufferfish, billfishes and cephalopods.
In anatomy, the term rostrum is used for a number of phylogenetically unrelated structures in different groups of animals.
Billfish are pelagic and highly migratory. They are found in all oceans, although they usually inhabit tropical and subtropical waters; swordfish are found in temperate waters, as well. Billfish use their long spears or sword-like upper beaks to slash at and stun prey during feeding. Their bills can also be used to spear prey, and have been known to spear boats (probably accidentally), but they are not normally used in that way. They are highly valued as gamefish by sports fishermen.
Pelagic fish live in the pelagic zone of ocean or lake waters – being neither close to the bottom nor near the shore – in contrast with demersal fish, which do live on or near the bottom, and reef fish, which are associated with coral reefs.
The term billfish refers to the fishes of the families Xiphiidae and Istiophoridae. These large fishes are "characterized by the prolongation of the upper jaw, much beyond the lower jaw into a long rostrum which is flat and sword-like (swordfish) or rounded and spear-like (sailfishes, spearfishes, and marlins)."
The 12 species of true billfish are divided into two families and five genera. One family, Xiphiidae, contains only one species, the swordfishXiphias gladius, and the other family, Istiophoridae, contains 11 species in four genera, including marlin, spearfish, and sailfish. Controversy exists about whether the Indo-Pacific blue marlin, Makaira mazara, is the same species as the Atlantic blue marlin, M. nigricans. FishBase follows Nakamura (1985) in recognizing M. mazara as a distinct species, "chiefly because of differences in the pattern of the lateral line system".
Swordfish, also known as broadbills in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a popular sport fish of the billfish category, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood. These fish are found widely in tropical and temperate parts of the Atlantic, Pacific, and Indian Oceans, and can typically be found from near the surface to a depth of 550 m (1,800 ft). They commonly reach 3 m (9.8 ft) in length, and the maximum reported is 4.55 m (14.9 ft) in length and 650 kg (1,430 lb) in weight.
A marlin is a fish from the family Istiophoridae, which includes about 10 species. It has an elongated body, a spear-like snout or bill, and a long, rigid dorsal fin which extends forward to form a crest. Its common name is thought to derive from its resemblance to a sailor's marlinspike. Even more so than their close relatives, the scombrids, marlins are fast swimmers, reaching speeds of about 80 km/h (50 mph).
Tetrapturus is a genus of marlins found in tropical and subtropical oceans throughout the world. Some are popular in big-game fishing.
The Indo-Pacific sailfish is a sailfish native to the Atlantic, Indian and Pacific Oceans. It has entered the Mediterranean Sea via the Suez Canal as a Lessepsian migrant. It is dark blue on top, brown-blue laterally, silvery white underbelly; upper jaw elongated in the form of a spear; first dorsal fin greatly enlarged in the form of a sail, with many black cones, its front squared off, highest at its midpoint; pelvic fins very narrow, reaching almost to the anus; body covered with embedded scales, blunt at end; lateral line curved above pectoral fin, then straight to base of tail. They have a large and sharp bill, which they use for hunting. They feed on tuna and mackerel, some of the fastest fish in the Ocean. Some authorities only recognise a single species of sailfish, I. platyperus.
A number of other fishes have pronounced bills or beaks, and are sometimes referred to as billfish, despite not being true billfish. Halfbeaks look somewhat like miniature billfish, and the sawfish and sawshark, which are cartilaginous fishes with long, serrated rostrums. Needlefish are sometimes confused with billfish, but they are "easily distinguished from the true billfish by having both jaws prolonged, the dorsal and anal fins both single and similar in size and shape, and the pelvic fins inserted far behind the pectorals."Paddlefish have elongated rostrums containing electroreceptors that can detect weak electrical fields. Paddlefish are filter feeders and may use their rostrum to detect zooplankton.
The halfbeaks, also called spipe fish or spipefish are a geographically widespread and numerically abundant family of epipelagic fish inhabiting warm waters around the world. The halfbeaks are named for their distinctive jaws, in which the lower jaws are significantly longer than the upper jaws. The similar viviparous halfbeaks have often been included in this family.
Sawfishes, also known as carpenter sharks, are a family of rays characterized by a long, narrow, flattened rostrum, or nose extension, lined with sharp transverse teeth, arranged in a way that resembles a saw. They are among the largest fish with some species reaching lengths of about 7–7.6 m (23–25 ft). They are found worldwide in tropical and subtropical regions in coastal marine and brackish estuarine waters, as well as freshwater rivers and lakes.
A sawshark or saw shark is a member of a shark order (Pristiophoriformes) bearing a unique long, saw-like rostrum edged with sharp teeth, which they use to slash and disable their prey. There are eight species within the Pristiophoriformes, including the longnose or common sawshark, shortnose sawshark, Japanese sawshark, Bahamas sawshark, sixgill sawshark, African dwarf sawshark, Lana's sawshark and the tropical sawshark.
Structure and function of the bill
Billfish have a long, bony, spear-shaped bill, sometimes called a snout, beak or rostrum. The swordfish has the longest bill, about one-third its body length. Like a true sword, it is smooth, flat, pointed and sharp. The bills of other billfish are shorter and rounder, more like spears.
Billfish normally use their bills to slash at schooling fish. They swim through the fish school at high speed, slashing left and right, and then circle back to eat the fish they stunned. Adult swordfish have no teeth, and other billfish have only small file-like teeth. They swallow their catch whole, head-first. Billfish don't normally spear with their bills, though occasionally a marlin will flip a fish into the air and bayonet it. Given the speed and power of these fish, when they do spear things the results can be dramatic. Predators of billfish, such as great white and mako sharks, have been found with billfish spears embedded in them. Pelagic fish generally are fascinated by floating objects, and congregate about them. Billfish can accidentally impale boats and other floating objects when they pursue the small fish that aggregate around them. Care is needed when attempting to land a hooked billfish. Many fisherman have been injured, some seriously, by a billfish thrashing its bill about.
Billfish are large swift predators which spend most of their time in the epipelagic zone of the open ocean. They feed voraciously on smaller pelagic fish, crustaceans and small squid. Some billfish species also hunt demersal fish on the seafloor, while others descend periodically to mesopelagic depths. They may come closer to the coast when they spawn in the summer. Their eggs and larvae are pelagic, that is they float freely in the water column. Many grow over three metres (10feet) long, and the blue marlin can grow to five metres (16feet). Females are usually larger than males.
Like scombroids (tuna, bonito and mackerel), billfish have both the ability to migrate over long distances, efficiently cruising at slow speeds, and the ability to generate rapid bursts of speed. These speed bursts can be quite astonishing, and the Indo-Pacific sailfish has been recorded making a burst of 68 miles per hour (110km/h), nearly top speed for a cheetah and the highest speed ever recorded for a fish.
Some billfish also descend to considerable mesopelagic depths. They have sophisticated swim bladders which allow them to rapidly compensate for pressure changes as the depth changes. This means that when they are swimming deep, they can return swiftly to the surface without problems. "Like the large tuna, some billfish maintain their body temperature several degrees above ambient water temperatures; this elevated body temperature increases the efficiency of the swimming muscles, especially during excursions into the cold water below the thermocline."
In 1936 the British zoologist James Gray posed a conundrum which has come to be known as Gray's paradox. The problem he posed was how dolphins can swim and accelerate so fast when it seemed their muscles lacked the needed power. If this is a problem with dolphins it is an even greater problem with billfish such as swordfish, which swim and accelerate faster than dolphins. In 2009, Taiwanese researchers from the National Chung Hsing University introduced new concepts of "kidnapped airfoils and circulating horsepower" to explain the swimming capabilities of swordfish. The researchers claim this analysis also "solves the perplexity of dolphin's Gray paradox". They also assert that swordfish "use sensitive rostrum/lateral-line sensors to detect upcoming/ambient water pressure and attain the best attack angle to capture the body lift power aided by the forward-biased dorsal fin to compensate for most of the water resistance power."
Billfish have prominent dorsal fins. Like tuna, mackerel and other scombroids, billfish streamline themselves by retracting their dorsal fins into a groove in their body when they swim. The shape, size, position and colour of the dorsal fin varies with the type of billfish, and can be a simple way to identify a billfish species. For example, the white marlin has a dorsal fin with a curved front edge and is covered with black spots. The huge dorsal fin, or sail of the sailfish is kept retracted most of the time. Sailfish raise them if they want to herd a school of small fish, and also after periods of high activity, presumably to cool down.
Distribution and migration
Billfish occur worldwide in temperate and tropical waters. They are highly migratoryoceanic fish, spending much of their time in the epipelagic zone of international water following major ocean currents. Migrations are linked to seasonal patterns of sea surface temperatures. They are sometimes referred to as "rare event species" because the areas they roam over in the open seas are so large that researchers have difficulty locating them. Little is known about their movements and life histories, so assessing how they can be sustainably managed is not easy.
Unlike coastal fish, billfish usually avoid inshore waters unless there is a deep dropoff close to the land. Instead, they swim along the edge of the continental shelf where cold nutrient rich upwellings can fuel large schools of forage fish. Billfish can be found here, cruising and feeding "above the craggy bottom like hawks soaring along a ridge line".
Over the years, billfish tournaments have transformed into big business enterprises. Many prestigious tournaments now have enormous calcuttas and purses as well as large numbers of participating anglers. With huge purses and egos on the line, concern often arises whether all participants are adhering to the letter of the rules. – IGFA Conservation Director, Jason Schratwieser
Billfish are among the most coveted of big gamefish, and major recreational fisheries cater to the demand. In North America, "the apex of the salt water pursuits is billfishing, the quest for elusive blue marlin and sailfish in the deep blue water about 60 miles out." A lot of resources are committed to the activity, particularly in the construction of private and charter billfishing boats to participate in the billfishing tournament circuit. These are expensive purpose-built offshore vessels with powerfully driven deep sea hulls. They are often built to luxury standards and equipped with many technologies to ease the life of the deep sea recreational fisherman, including outriggers, flying bridges and fighting chairs, and state of the art fishfinders and navigation electronics.
The boats cruise along the edge of the continental shelf where billfish can be found down to 200 metres (600ft), sometimes near weed lines at the surface and submarine canyons and ridges deeper down. Commercial fishermen usually use drift nets or longlines to catch billfish, but recreational fishermen usually drift with bait fish or troll a bait or lure. Billfish are caught deeper down the water column by drifting with live bait fish such as ballyhoo, striped mullet or bonito. Alternatively, they can be caught by trolling at the surface with dead bait or trolling lures designed to imitate bait fish.
Most recreational fishermen now tag and release billfish. A 2003 study surveyed 317,000 billfish known to have been tagged and released since 1954. Of these, 4122 were recovered. The study concluded that, while tag and release programs have limitations, they provided important information about billfish that cannot currently be obtained by other methods.
Hooked striped marlin
Hooked billfish can leap spectacularly out of the water
* indicates methylmercury only was analyzed (all other results are for total mercury)
Billfish are primarily marketed in Japan, where they are eaten raw as sashimi. They are marketed fresh, frozen, canned, cooked and smoked. It is not usually a good idea to fry billfish. Swordfish and marlin are best grilled or broiled, or eaten raw as in sashimi. Sailfish and spearfish are somewhat tough and are better cooked over charcoal or smoked.
Billfish are exploited both as food and as fish. Marlin and sailfish are eaten in many parts of the world, and many sport fisheries target these species. Swordfish are subject to particularly intense fisheries pressures, and although their survival is not threatened worldwide, they are now comparatively rare in many places where once they were abundant. The istiophorid billfishes (marlin and spearfish) also suffer from intense fishing pressures. High mortality levels occur when they are caught incidentally by longline fisheries targeting other fish. Overfishing continues to "push these declines further in some species". Because of these concerns about declining populations, sport fishermen and conservationists now work together to gather information on billfish stocks and implement programs such as catch and release, where fish are returned to the sea after they have been caught. However, the process of catching them can leave them too traumatised to recover. Studies have shown that circle fishing hooks do much less damage to billfish than the traditional J-hooks, yet they are at just as effective for catching billfish. This is good for conservation, since it improves survival rates after release.
The stocks for individual species in billfish longline fisheries can "boom and bust" in linked and compensatory ways. For example, the Atlantic catch of blue marlin declined in the 1960s. This was accompanied by an increase in sailfish catch. The sailfish catch then declined from the end of the 1970s to the end of the 1980s, compensated by an increase in swordfish catch. As a result, overall billfish catches remained fairly stable.
"Many of the world's fisheries operate in a data poor environment that precludes predictions about how different management actions will affect individual species and the ecosystem as a whole." In recently years pop-up satellite archival tags have been used to monitor billfish. The capability of these tags to recover useful data is improving, and their use should result in more accurate stock assessments. In 2011, a group of researchers claimed they have, for the first time, standardized all available data about scombrids and billfishes so it is in a form suitable for assessing threats to these species. The synthesis shows that those species which combine a long life with a high economic value, such as the Atlantic blue marlin and the white marlin, are generally threatened. The combination puts such species in "double jeopardy".
A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae (mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna up to the Atlantic bluefin tuna. The bluefin averages 2 m (6.6 ft), and is believed to live up to 50 years.
Mackerel is a common name applied to a number of different species of pelagic fish, mostly from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment.
The Atlantic sailfish is a species of marine fish in the family Istiophoridae of the order Perciformes. It is found in the Atlantic Oceans and the Caribbean Sea, except for large areas of the central North Atlantic and the central South Atlantic, from the surface to depths of 200 m (656 ft). The Atlantic sailfish is related to the marlin.
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 still consider both species distinct.
A sailfish is a fish of the genus Istiophorus of billfish living in colder areas of all the seas of the earth. They are predominantly blue to gray in colour and have a characteristic dorsal fin known as a sail, which often stretches the entire length of the back. Another notable characteristic is the elongated bill, resembling that of the swordfish and other marlins. They are, therefore, described as billfish in sport-fishing circles.
Makaira is a genus of marlin in the Istiophoridae family. It includes the Atlantic blue, and Indo-Pacific blue marlins. In the past, the black marlin was also included in this genus, but today it is placed in its own genus, Istiompax.
The shortbill 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.
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.
The roundscale spearfish is a species of marlin native to the eastern Atlantic Ocean from Portugal to Madeira, the Canary Islands to northern Africa and the western Mediterranean Sea to Sicily. It is suspected that it may be more widespread. It is believed to inhabit open waters. This species can reach a length of 184 centimetres (72 in) FL and the heaviest recorded fish weighed in at 21.5 kilograms (47 lb).
Thunnus is a genus of ocean-dwelling, ray-finned bony fish from the Scombridae (mackerel) family. More specifically, Thunnus is one of five genera which make up the Thunnini tribe – a tribe that is collectively known as the tunas. Also called the true tunas or real tunas, Thunnus consists of eight species of tuna, divided into two subgenera. The word Thunnus is the Middle Latin form of the Ancient Greek: θύννος, translit. (thýnnos), lit. 'tunny-fish' – which is in turn derived from θύνω (thynō), "to rush; to dart". The first written use of the word was by Homer.
The Indo-Pacific blue marlin is a species of marlin belonging to the family Istiophoridae.
Euthynnus is a genus of ray-finned bony fish in the family Scombridae, or mackerel family, and in the tribe Thunnini, more commonly known as the tunas.
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.
The Mediterranean spearfish is a species of marlin native to the Mediterranean Sea where it is particularly common around Italy, although there is a probable record of one caught off Madeira. It is an open-water fish, being found within 200 metres (660 ft) of the surface. This species can reach a length of 240 centimetres (94 in) TL. The heaviest recorded specimen weighed in at 70 kilograms (150 lb) This species is of minor importance to commercial fisheries.
Thunnus (Thunnus) is a subgenus of ray-finned bony fishes in the Thunnini, or tuna, tribe. More specifically, Thunnus (Thunnus) is a subgenus of the genus Thunnus, also known as the "true tunas". Thunnus (Thunnus) is sometimes referred to as the bluefin group, and comprises five species:
Istiophoriformes is an order of bony fish which is not recognised by some authorities while others include the two extant billfish families, Xiphiidae and Istiophoridae, and others include the barracudas, the family Sphyraenidae.
↑ Santini, F.; Sorenson, L. (2013). "First molecular timetree of billfishes (Istiophoriformes: Acanthomorpha) shows a Late Miocene radiation of marlins and allies". Italian Journal of Zoology. 80 (4): 481–489. doi:10.1080/11250003.2013.848945.