1.
Trolling (fishing)
–
Trolling is a method of fishing where one or more fishing lines, baited with lures or bait fish, are drawn through the water. This may be behind a boat, or by slowly winding the line in when fishing from a static position, or even sweeping the line from side-to-side. Trolling is used to catch fish such as salmon, mackerel. Trolling can be confused with trawling, a different method of fishing where a net is drawn through the water instead of lines. Trolling is used both for recreational and commercial fishing whereas trawling is used mainly for commercial fishing, Trolling from a moving boat involves moving quite slowly through the water. This can be accomplished with the use of a special trolling motor, multiple lines are often used, and outriggers can be used to spread the lines more widely and reduce their chances of tangling. Downriggers can also be used to keep the lures or baits trailing at a desired depth, outriggers are poles which allow a boat to troll several lines in the water without tangling. A boat which trolls enough lines can simulate a school of fish, downrigger are devices used while trolling to keep a bait or lure at the desired depth. In practice, fish swim at different depths according to such as the temperature and amount of light in the water. A downrigger consists of a one or two metre horizontal pole which supports a weight, typically about three kilograms of lead, on a steel cable. A clip called a release attaches the fishing line to the weight. The fishing line is reeled in by a spool powered either by manual cranking or by an electric motor, using a downrigger can be hazardous. For example, man-made reservoirs can contain submerged trees and other structures beneath the surface which downriggers can snag, paravanes are sometimes used as depth controlling devices, particularly in commercial tuna fishing operations. These kites have various shapes, such as arrowhead paravanes, flexi-wing paravanes, the devices can place the lure or bait at designated depths and positions, and in this way multiple devices can be towed at the same time without the devices and bait interfering with each other. Spreaders allow multiple baited hooks or lures to be trolled from a single line, planer boards are trolled devices designed to spread fishing lures out away from the fishing vessel. They allow multiple lines to be trolled and they come in dual board and inline board designs. Inlines are popular with walleye fishermen, once tripped they offer much less resistance when reeling in a fish. Planing Floats with Direction Control Paul Lieb US Patent 6,874,271 are planer boards that flip direction when given a tug, planer Boards with Direction Control Shore Fishing Techniques using patented mini planer boards with direction control
Trolling (fishing)
–
"Trolling for blue fish"
lithograph by
Currier & Ives, 1866.
Trolling (fishing)
–
Artist's conception of tuna trolling operation, using outriggers to tow multiple trolling lines and give the appearance of
schooling fish
Trolling (fishing)
–
Fishing lures are made in various creative designs like this top-water lure
Trolling (fishing)
–
Aluminium
bass boat with
trolling motor
2.
Fishing
–
Fishing is the activity of trying to catch fish. Fish are normally caught in the wild, techniques for catching fish include hand gathering, spearing, netting, angling and trapping. Fishing may include catching aquatic animals other than fish, such as molluscs, cephalopods, crustaceans, the term is not normally applied to catching farmed fish, or to aquatic mammals, such as whales where the term whaling is more appropriate. According to United Nations FAO statistics, the number of commercial fishermen. Fisheries and aquaculture provide direct and indirect employment to over 500 million people in developing countries, in 2005, the worldwide per capita consumption of fish captured from wild fisheries was 14.4 kilograms, with an additional 7.4 kilograms harvested from fish farms. In addition to providing food, modern fishing is also a recreational pastime, Fishing is an ancient practice that dates back to at least the beginning of the Upper Paleolithic period about 40,000 years ago. Isotopic analysis of the remains of Tianyuan man, a 40. Archaeology features such as middens, discarded fish bones, and cave paintings show that sea foods were important for survival. During this period, most people lived a lifestyle and were, of necessity. However, where there are examples of permanent settlements such as those at Lepenski Vir. The British dogger was a type of sailing trawler from the 17th century. The Brixham trawler that evolved there was of a build and had a tall gaff rig. They were also sufficiently robust to be able to tow large trawls in deep water, the great trawling fleet that built up at Brixham, earned the village the title of Mother of Deep-Sea Fisheries. The small village of Grimsby grew to become the largest fishing port in the world by the mid 19th century, an Act of Parliament was first obtained in 1796, which authorised the construction of new quays and dredging of the Haven to make it deeper. It was only in the 1846, with the expansion in the fishing industry. The foundation stone for the Royal Dock was laid by Albert the Prince consort in 1849, the dock covered 25 acres and was formally opened by Queen Victoria in 1854 as the first modern fishing port. The elegant Brixham trawler spread across the world, influencing fishing fleets everywhere, by the end of the 19th century, there were over 3,000 fishing trawlers in commission in Britain, with almost 1,000 at Grimsby. These trawlers were sold to fishermen around Europe, including from the Netherlands, twelve trawlers went on to form the nucleus of the German fishing fleet
Fishing
–
Stilts fishermen, Sri Lanka
Fishing
–
Fishing with nets, Mexico
Fishing
–
Stone Age
fish hook made from bone
Fishing
–
Painting of A Brixham trawler by
William Adolphus Knell. The painting is now in the
National Maritime Museum.
3.
Fishing net
–
A fishing net is a net used for fishing. Nets are devices made from fibers woven in a grid-like structure, some fishing nets are also called fish traps, for example fyke nets. Fishing nets are usually formed by knotting a relatively thin thread. Early nets were woven from grasses, flaxes and other plant material. Modern nets are made of artificial polyamides like nylon, although nets of organic polyamides such as wool or silk thread were common until recently and are still used. Fishing nets have been used widely in the past, including by stone age societies, the oldest known fishing net is the net of Antrea, found with other fishing equipment in the Karelian town of Antrea. The net was made from willow, and dates back to 8300 BC, the remnants of another fishing net dates back to the late Mesolithic, and were found together with sinkers at the bottom of a former sea. Some of the oldest rock carvings at Alta have mysterious images, american Native Indians on the Columbia River wove seine nets from spruce root fibers or wild grass, again using stones as weights. For floats they used sticks made of cedar which moved in a way which frightened the fish, with the help of large canoes, pre-European Maori deployed seine nets which could be over one thousand metres long. The nets were woven from green flax, with weights and light wood or gourd floats. Fishing nets are well documented in antiquity and they appear in Egyptian tomb paintings from 3000 BC. In ancient Greek literature, Ovid makes many references to fishing nets, including the use of cork floats, pictorial evidence of Roman fishing comes from mosaics which show nets. In a parody of fishing, a type of gladiator called retiarius was armed with a trident and he would fight against a secutor or the murmillo, who carried a short sword and a helmet with the image of a fish on the front. Between 177 and 180 the Greek author Oppian wrote the Halieutica and he described various means of fishing including the use of nets cast from boats, scoop nets held open by a hoop, and various traps which work while their masters sleep. Then the fishers on either side hasten with the ropes to draw the net ashore, in Norse mythology the sea giantess Rán uses a fishing net to trap lost sailors. References to fishing nets can also be found in the New Testament, jesus Christ was reputedly a master in the use of fishing nets. The tough, fibrous bark of the pawpaw was used by Native Americans and settlers in the Midwest for making ropes. The archaeological site at León Viejo has fishing net artifacts including fragments of pottery used as weights for fishing nets, Fishing nets have not evolved greatly, and many contemporary fishing nets would be recognized for what they are in Neolithic times
Fishing net
–
Nylon fishing net with float line attached to small plastic floats
Fishing net
–
Mosaic, 4th century BC, showing a
retiarius or "net fighter", with a trident and cast net, fighting a
secutor
Fishing net
–
Cucuteni-Trypillian ceramic weights
Fishing net
–
Fragments from the
net of Antrea 8300 BC
4.
Commercial trawler
–
A fishing trawler, also known as a dragger, is a commercial fishing vessel designed to operate fishing trawls. Trawling is a method of fishing that involves actively dragging or pulling a trawl through the water one or more trawlers. Trawls are fishing nets that are pulled along the bottom of the sea or in midwater at a specified depth, a trawler may also operate two or more trawl nets simultaneously. There are many variants of trawling gear and they vary according to local traditions, bottom conditions, and how large and powerful the trawling boats are. A trawling boat can be an open boat with only 30 horsepower or a large factory ship with 10,000 horsepower. Trawl variants include beam trawls, large-opening midwater trawls, and large bottom trawls, during the 17th century, the British developed the Dogger, an early type of sailing trawler commonly operated in the North Sea. The Dogger takes its name from the Dutch word dogger, meaning a vessel which tows a trawl. Doggers were slow but sturdy, capable of fishing in the conditions of the North Sea. The modern fishing trawler was developed in the 19th century, at the English fishing port of Brixham. The Brixham trawler that evolved there was of a build and had a tall gaff rig. They were also sufficiently robust to be able to tow large trawls in deep water, the great trawling fleet that built up at Brixham, earned the village the title of Mother of Deep-Sea Fisheries. The small village of Grimsby grew to become the largest fishing port in the world by the mid 19th century, with the tremendous expansion in the fishing industry, the Grimsby Dock Company was opened in 1854 as the first modern fishing port. The elegant Brixham trawler spread across the world, influencing fishing fleets everywhere, by the end of the 19th century, there were over 3,000 fishing trawlers in commission in Britain, with almost 1,000 at Grimsby. These trawlers were sold to fishermen around Europe, including from the Netherlands, twelve trawlers went on to form the nucleus of the German fishing fleet. The earliest steam powered fishing boats first appeared in the 1870s and used the system of fishing as well as lines. These were large boats, usually 80–90 feet in length with a beam of around 20 feet and they weighed 40–50 tons and travelled at 9–11 knots. The earliest purpose built fishing vessels were designed and made by David Allan in Leith in March 1875, in 1877, he built the first screw propelled steam trawler in the world. She was of construction with two masts and carried a gaff rigged main and mizen using booms, and a single foresail
Commercial trawler
–
The Irish RSW Pelagic Trawler Brendelen SO709 in
Skagen harbour
Commercial trawler
–
Painting of A Brixham trawler by
William Adolphus Knell. The painting is now in the
National Maritime Museum.
Commercial trawler
–
Armed trawler
HNoMS Honningsvåg off
Iceland.
Commercial trawler
–
Decca Navigator (Mark 21) and Decca Track Plotter (the forerunners of modern GPS navigation and plotting equipment) on the bridge of this (rather dated) trawler.
5.
Horsepower
–
Horsepower is a unit of measurement of power. There are many different standards and types of horsepower, two common definitions being used today are the mechanical horsepower, which is approximately 746 watts, and the metric horsepower, which is approximately 735.5 watts. The term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of engines with the power of draft horses. It was later expanded to include the power of other types of piston engines, as well as turbines, electric motors. The definition of the unit varied among geographical regions, most countries now use the SI unit watt for measurement of power. With the implementation of the EU Directive 80/181/EEC on January 1,2010, units called horsepower have differing definitions, The mechanical horsepower, also known as imperial horsepower equals approximately 745.7 watts. It was defined originally as exactly 550 foot-pounds per second [745.7 N. m/s), the metric horsepower equals approximately 735.5 watts. It was defined originally as 75 kgf-m per second is approximately equivalent to 735.5 watts, the Pferdestärke PS is a name for a group of similar power measurements used in Germany around the end of the 19th century, all of about one metric horsepower in size. The boiler horsepower equals 9809.5 watts and it was used for rating steam boilers and is equivalent to 34.5 pounds of water evaporated per hour at 212 degrees Fahrenheit. One horsepower for rating electric motors is equal to 746 watts, one horsepower for rating Continental European electric motors is equal to 735 watts. Continental European electric motors used to have dual ratings, one British Royal Automobile Club horsepower can equal a range of values based on estimates of several engine dimensions. It is one of the tax horsepower systems adopted around Europe, the development of the steam engine provided a reason to compare the output of horses with that of the engines that could replace them. He had previously agreed to take royalties of one third of the savings in coal from the older Newcomen steam engines and this royalty scheme did not work with customers who did not have existing steam engines but used horses instead. Watt determined that a horse could turn a mill wheel 144 times in an hour, the wheel was 12 feet in radius, therefore, the horse travelled 2.4 × 2π ×12 feet in one minute. Watt judged that the horse could pull with a force of 180 pounds-force. So, P = W t = F d t =180 l b f ×2.4 ×2 π ×12 f t 1 m i n =32,572 f t ⋅ l b f m i n. Watt defined and calculated the horsepower as 32,572 ft·lbf/min, Watt determined that a pony could lift an average 220 lbf 100 ft per minute over a four-hour working shift. Watt then judged a horse was 50% more powerful than a pony, engineering in History recounts that John Smeaton initially estimated that a horse could produce 22,916 foot-pounds per minute
Horsepower
–
A team of six horses mowing hay in
Lancaster County, Pennsylvania
6.
Factory ship
–
A factory ship, also known as a fish processing vessel, is a large ocean-going vessel with extensive on-board facilities for processing and freezing caught fish or whales. Modern factory ships are automated and enlarged versions of the earlier whalers, some factory ships are equipped to serve as a mother ship. Contemporary factory ships have their origins in the early whalers and these vessels sailed into remote waters and processed the whale oil on board, discarding the carcass. Later whalers converted the entire whale into usable products, the efficiency of these ships and the predation they carried out on whales contributed greatly to the animals steep decline. Contemporary factory ships are automated and enlarged versions of these earlier whalers and their use for fishing has grown dramatically. For a while, Russia, Japan and Korea operated huge fishing fleets centred on factory ships, on the other hand, the use of factory ships by the United States has increased. Some factory ships can also function as mother ships, the basic idea of a mother ship is that it can carry small fishing boats that return to the mother ship with their catch. But the idea extends to include factory trawlers supporting a fleet of smaller catching vessels that are not carried on board and they serve as the main ship in a fleet operating in waters a great distance from their home ports. Fish processing ships consist of types, including freezer trawlers, longline factory vessels, purse seine freezer vessels, stern trawlers. A factory stern trawler is a stern trawler which has additional onboard processing facilities. A stern trawler tows a trawl net and hauls the catch up a stern ramp. These can be either demersal, pelagic, or pair trawling, a freezer trawler fully processes the catch on board to customers’ specifications, into frozen-at-sea fillet, block or head and gutted form. Factory freezer trawlers can run to 60 to 70 meters in length and they process fish into fillets within hours of being caught. Onboard fishmeal plants process the product so everything is utilized. The worlds largest freezing trawler by gross tonnage is the 144-metre-long Annelies Ilena ex Atlantic Dawn, in 2015, the Annelies Ilena was detained by the Irish Navy and the Sea Fisheries Protection Agency for breach of regulations. The owners were subsequently fined 105,000 Euros for illegally fishing in Irish waters and she is able to process 350 tonnes of fish a day, can carry 3,000 tons of fuel, and store 7,000 tons of graded and frozen catch. She uses on board forklift trucks to aid discharging and these automated bottom longliners fish using hooks strung on long lines. The hooks are baited automatically and the lines are released very fast, many thousands of hooks are set each day, the retrieval and setting of these hooks is a continuous 24-hour-a-day operation
Factory ship
–
The German factory ship Kiel NC 105.
Factory ship
–
The
Polish factory trawler Wiesbaden
Factory ship
–
Arctic Warrior freezer trawler working out of Hull in England
Factory ship
–
The Spanish Trawler Nuevo Virgen De La Barca in North Atlantic waters
7.
Pair trawling
–
Pair trawling is a fishing activity carried out by two boats, with one towing each warp. As the mouth of the net is kept open by the pull of the individual vessels. As doors are not necessary, the arrangements are simplified. Setting and hauling of the nets are carried out by one boat, while the other is used for towing. Pair trawling is effective on all demersal species, in shallow waters, where the noise from a single vessel may scatter fish, two vessels operating a distance apart tend to herd fish into the path of the net. Catch per vessel often considerably exceeds that attainable through standard bottom trawling, Pair trawlers targeting cod off the coast of New England have reported average per vessel catches of three to six times that from single trawls. This has caused controversy, due to the high level of marine mammal bycatch associated. Thomson, David, Pair trawling and pair seining
Pair trawling
–
The
European seabass (Dicentrarchus labrax), once target of a pair-trawl fishery in the
English Channel, now banned due to the high level of
cetacean bycatch
Pair trawling
–
Fishing industry
Pair trawling
–
Aquaculture
Pair trawling
–
Fisheries
8.
Fishing line
–
A fishing line is a cord used or made for angling. Important parameters of a line are its length, material. Most modern lines are made from nylon or silk, fish are caught with a fishing line by encouraging a fish to bite on a fish hook. A fish hook will pierce the mouthparts of a fish and is normally barbed to make escape less likely, another method is to use a gorge, which is buried in the bait such that it would be swallowed end first. The tightening of the line would fix it cross-wise in the stomach or gullet. Fishing with a hook and line is called angling, in addition to the use of the hook and line used to catch a fish, a heavy fish may be landed by using a landing net or a hooked pole called a gaff. Trolling is a technique in which a fishing lure on a line is drawn through the water, trolling from a moving boat is a technique of big-game fishing and is used to catch large open-water species such as tuna and marlin. Trolling is also an angling technique often used to catch salmon, northern pike, muskellunge. This technique allows anglers to cover a large body of water in a short time, long-line fishing, also known as a trot line is a commercial fishing technique that uses many baited hooks hanging from a single line. Snagging is a technique where the object is to hook the fish in the body, generally, a large treble hook with a heavy sinker is cast into a river containing a large amount of fish, such as a Salmon, and is quickly jerked and reeled in. Due to the illegal nature of this method some practitioners have added methods to disguise the practice. As written in 1667 by Samuel Pepys, the lines in his time were made from catgut. Later, silk fishing lines were used around 1724, the most common type is monofilament, made of a single strand. Fishermen often use monofilament because of its buoyant characteristics and its ability to stretch under load, the line stretch has advantages, such as dampening the force when setting the hook and when fighting strong fish. On very far distances the dampening may become a disadvantage, recently, other alternatives to standard nylon monofilament lines have been introduced made of copolymers or fluorocarbon, or a combination of the two materials. Fluorocarbon fishing line is made of the fluoropolymer PVDF and it is valued for its refractive index, fluorocarbon is also a denser material, and therefore, is not nearly as buoyant as monofilament. Anglers often utilize fluorocarbon when they need their baits to stay closer to the bottom without the use of heavy sinkers, braided, thermally fused, and chemically fused varieties of superlines are now readily available. Fly lines consist of a braided or monofilament core, wrapped in a thick waterproof plastic sheath
Fishing line
–
Fishing line with hooks attached
Fishing line
–
A spool of fishing line
Fishing line
–
Fishing line
Fishing line
–
Fish hook
9.
Recreational fishing
–
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with fishing, which is fishing for profit, or subsistence fishing. The most common form of fishing is done with a rod, reel, line, hooks. Other devices, commonly referred to as terminal tackle, are used to affect or complement the presentation of the bait to the targeted fish. Some examples of terminal tackle include weights, floats, and swivels, lures are frequently used in place of bait. Some hobbyists make handmade tackle themselves, including plastic lures and artificial flies, the practice of catching or attempting to catch fish with a hook is known as angling. Big-game fishing is conducted from boats to catch large species such as tuna, sharks. Noodling and trout tickling are also recreational activities, the early evolution of fishing as recreation is not clear. For example, there is evidence for fly fishing in Japan as early as the ninth century BCE. But for the early Japanese and Macedonians, fly fishing was likely to have been a means of survival and it is possible that antecedents of recreational fly fishing arrived in England with the Norman conquest of 1066. Although the point in history where fishing could first be said to be recreational is not clear, the earliest English essay on recreational fishing was published in 1496, shortly after the invention of the printing press. The authorship of this was attributed to Dame Juliana Berners, the prioress of the Benedictine Sopwell Nunnery, the essay was titled Treatyse of Fysshynge wyth an Angle, and was published in the second Boke of Saint Albans, a treatise on hawking, hunting, and heraldry. During the 16th century the work was read, and was reprinted many times. Treatyse includes detailed information on fishing waters, the construction of rods and lines, and it also includes modern concerns about conservation and angler etiquette. Another Civil War veteran to enthusiastically take up fishing, was Richard Franck and he was the first to describe salmon fishing in Scotland, and both in that and trout-fishing with artificial fly he was a practical angler. He was the first angler to name the burbot, and commended the salmon of the River Thames, Compleat Angler was written by Izaak Walton in 1653 and described the fishing in the Derbyshire Wye. It was a celebration of the art and spirit of fishing in prose and verse,6 verses were quoted from John Dennyss earlier work, a second part to the book was added by Waltons friend Charles Cotton. More than 300 editions of The Compleat Angler have been published, the pastoral discourse was enriched with country fishing folklore, songs and poems, recipes and anecdotes, moral meditations, and quotes from classic literature
Recreational fishing
–
Izaak Walton 's
Compleat Angler, published in 1653 helped popularize fly fishing as a sport. Woodcut by
Louis Rhead
Recreational fishing
–
Sketch of
Juliana Berners, author of the earliest essay on recreational fishing.
Recreational fishing
–
Trading card of the Ustonson company, an early firm specializing in fishing equipment, and holder of a
Royal Warrant from the 1760s.
Recreational fishing
–
The Fly-fisher's Entomology by Alfred Ronalds had a great influence on the development of fly fishing when it was first published in 1836.
10.
Commercial fishing
–
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the earth, large-scale commercial fishing is also known as industrial fishing. This profession has gained in popularity with the development of such as Deadliest Catch, Swords. The major fishing industries are not only owned by major corporations, the industry has had to adapt through the years in order to keep earning a profit. A study taken on some small family-owned commercial fishing companies showed that they adapted to continue to earn a living but not necessarily make a large profit. Commercial fishermen harvest a variety of animals, ranging from tuna, cod, carp, and salmon to shrimp, krill, lobster, clams, squid. There are large and important fisheries worldwide for species of fish, mollusks, crustaceans. However, a small number of species support the majority of the worlds fisheries. Some of these species are herring, cod, anchovy, tuna, flounder, mullet, squid, shrimp, salmon, crab, lobster, oyster and scallops. All except these last four provided a catch of well over a million tonnes in 1999, with herring. Many other species are fished in smaller numbers, commercial fishing may offer an abundance of jobs, but the pay varies from boat to boat, season to season. That may be true, but there are also the boats who dont do well, a 2009 paper in Science estimates, for the first time, the total world fish biomass as somewhere between 0.8 and 2.0 billion tonnes. Sustainability of fisheries is improved by using equipment that eliminates or minimizes catching non-targeted species. Fishing methods vary according to the region, the species being fished for, a commercial fishing enterprise may vary from one man with a small boat with hand-casting nets or a few pot traps, to a huge fleet of trawlers processing tons of fish every day. Billions of dollars are spent each year in researching/developing new techniques to reduce the injury, in fact, there was a study taken in 2000 on different deterrents and how effective they are at deterring the target species. The study showed that most auditory deterrents helped prevent whales from being caught while more physical barriers helped prevent birds from getting tangled within the net. During 2000–2006, commercial fishing was one of the most dangerous occupations in the United States, falling overboard specifically killed 182 fishermen in the period between 2000 and 2010. This fatality rate is 3 times that of the next most dangerous job in the U. S. also, between the years of 1919 and 2005,4111 fishermen died in fishing related accidents in the United Kingdom industry alone
Commercial fishing
–
Commercial
crab fishing
Commercial fishing
–
Seabirds with longline
fishing vessel
Commercial fishing
–
Trawl fishermen wearing personal flotation devices
Commercial fishing
–
Wild
11.
Myctophid
–
Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera and they are aptly named after their conspicuous use of bioluminescence. Sampling via deep trawling indicates lanternfish account for as much as 65% of all deep-sea fish biomass, indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. In the Southern Ocean, myctophids provide a food resource to krill for predators such as squid. Although plentiful and prolific, currently only a few commercial fisheries exist, limited operations off South Africa, in the sub-Antarctic. The fins are small, with a single high dorsal fin, a forked caudal fin. The anal fin is supported by a plate at its base, and originates under, or slightly behind. The pectoral fins, usually with eight rays, may be large and well-developed to small and degenerate, in some species, such as those of the genus Lampanyctus, the pectorals are greatly elongated. Most lanternfish have a gas bladder, but it degenerates or fills with lipids during the maturation of a few species, in all but one species, Taaningichthys paurolychnus, a number of photophores are present, these are paired and concentrated in ventrolateral rows on the body and head. Some may also possess specialised photophores on the peduncle, in proximity to the eyes. The photophores emit a blue, green, or yellow light. In some species, the pattern varies between males and females and this is true for the luminous caudal patches, with the males being typically above the tail and the females being below the tail. Lantern fish are small fish, ranging from about 2 to 30 cm in length, with most being under 15 cm. In life, shallow-living species are an iridescent blue to green or silver and it is the most populous fish species in the open ocean with a density of approximately one per cubic metre. The lanternfish are thought to do this to avoid predation, after a night spent feeding in the surface layers of the water column, the lanternfish begin to descend back into the lightless depths and are gone by daybreak. Most species remain near the coast, schooling over the continental slope, different species are known to segregate themselves by depth, forming dense, discrete conspecific layers, probably to avoid competition between different species. Due to their gas bladders, these layers are visible on sonar scans and give the impression of a false bottom, great variability in migration patterns occurs within the family. Some deeper-living species may not migrate at all, while others may do so only sporadically, migration patterns may also depend on life stage, sex, latitude, and season
Myctophid
12.
Bottom trawling
–
Bottom trawling is trawling along the sea floor. It is also referred to as dragging, the scientific community divides bottom trawling into benthic trawling and demersal trawling. Benthic trawling is towing a net at the bottom of the ocean. Bottom trawling can be contrasted with midwater trawling, where a net is towed higher in the water column, Trawling is done by a trawler, which can be a small open boat with only 30 hp or a large factory trawler with 10,000 hp. Bottom trawling can be carried out by one trawler or by two trawlers fishing cooperatively, an early reference to fishery conservation measures comes from a complaint about a form of trawling dating from the 14th century, during the reign of Edward III. A petition was presented to Parliament in 1376 calling for the prohibition of a subtlety contrived instrument called the wondyrchoum, until the late 18th century sailing vessels were only capable of towing small trawls. However, in the years of that century a type of vessel emerged that was capable of towing a large trawl. The development of type of craft, the sailing trawler, is credited to the fishermen of Brixham in Devon. The new method proved to be far more efficient than traditional long-lining, at first its use was confined to the western half of the English Channel, but as the Brixham men extended their range to the North Sea and Irish Sea it became the norm there too. By the end of the 19th century there were more than 3,000 sailing trawlers in commission in UK waters, despite the availability of steam, trawling under sail continued to be economically efficient, and sailing trawlers continued to be built until the middle of the 1920s. Some were still operating in UK waters until the outbreak of World War II, and in Scandinavia, English commissions in the 19th century determined that there should be no limitation on trawling. They believed that bottom trawling, like tilling of land, actually increased production, as evidence, they noted that a second trawler would often follow a first trawler, and that the second trawler would often harvest even more fish than the first. Bottom trawling has been implicated in the population collapse of a variety of fish species, locally and worldwide, including orange roughy, barndoor skate, shark. The size and design of net used is determined by the species being targeted and this method is mainly used on smaller vessels, fishing for flatfish or prawns, relatively close inshore. Otter trawling derives its name from the large rectangular otter boards which are used to keep the mouth of the net open. They also act like a plough, digging up to 15 cm into the seabed, creating a turbid cloud, the net is held open vertically on an otter trawl by floats and/or kites attached to the headline, and weighted bobbins attached to the foot rope. These bobbins can also be designed to lift the net off the seabed when they hit an obstacle and these are known as rock-hopper gear. The body of the trawl is funnel-like, wide at its mouth and narrowing towards the cod end and it is long enough to assure adequate flow of water and prevent fish from escaping the net, after having been caught
Bottom trawling
–
The Celtic Explorer, a
research vessel engaged in bottom trawling
Bottom trawling
–
A bottom trawler at
Viveiro in Spain
Bottom trawling
–
Design of an early beam trawl
Bottom trawling
–
Bobbins (lower left) and floats (lower right - upper right) on a trawl net
13.
Midwater trawling
–
Midwater trawling is trawling, or net fishing, at a depth that is higher in the water column than the bottom of the ocean. It is contrasted with bottom trawling, Midwater trawling is also known as pelagic trawling and bottom trawling as benthic trawling. In midwater trawling, a net can be towed behind a single boat and spread by trawl doors. Whereas bottom trawling can leave serious incidental damage to the sea bottom in its trail, trawling Bottom trawling FAO Fisheries, Midwater Pair Trawls Midwater trawls
Midwater trawling
–
Midwater (pelagic) otter trawl 1: trawl warp, 2: otter boards, 3: longline chains, 4 hunter, 5: weights 6: headline with floats, 7: pre-net, 8: tunnel and belly, 9: codend
Midwater trawling
–
Fishing industry
Midwater trawling
–
Aquaculture
Midwater trawling
–
Fisheries
14.
Water column
–
A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediments. Water columns are used chiefly for environmental studies evaluating the stratification or mixing of the thermal or chemically stratified layers in a lake, stream or ocean. Some of the common parameters analyzed in the column are pH, turbidity, temperature, salinity, total dissolved solids, various pesticides, pathogens. The concept of water column is important, since many aquatic phenomena are explained by the incomplete vertical mixing of chemical, physical or biological parameters. Hydrostatic pressure can be analyzed by the height of a water column, the term water column is also commonly used in scuba diving to describe the area in which divers ascend and descend. Hydrological transport model Pelagic zone Thermal pollution Water column ecology
Water column
–
Fisheries science
Water column
–
Waves
Water column
–
Management
15.
Pelagic zone
–
Any water in a sea or lake that is neither close to the bottom nor near the shore can be said to be in the pelagic zone. The word pelagic is derived from Greek πέλαγος, meaning open sea, the pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes from the surface of the sea almost to the bottom. Conditions differ deeper in the water such that as pressure increases with depth. Depending on the depth, the column, rather like the Earths atmosphere. The pelagic zone occupies 1,330 million km3 with a depth of 3.68 km. Pelagic life decreases with increasing depth and it is affected by light intensity, pressure, temperature, salinity, the supply of dissolved oxygen and nutrients, and the submarine topography, which is called bathymetry. In deep water, the zone is sometimes called the open-ocean zone. In other contexts, coastal water not near the bottom is still said to be in the pelagic zone, the pelagic zone can be contrasted with the benthic and demersal zones at the bottom of the sea. The benthic zone is the region at the very bottom of the sea. It includes the sediment surface and some subsurface layers, Marine organisms living in this zone, such as clams and crabs, are called benthos. The demersal zone is just above the benthic zone and it can be significantly affected by the seabed and the life that lives there. Demersal fish are known as bottom feeders and groundfish. Depending on how deep the sea is, the zone can extend over up to five horizontal layers in the ocean. From the top down, these are, From the surface down to around 200 m This is the zone at the surface of the sea where enough light is available for photosynthesis. Nearly all primary production in the ocean occurs here, consequently, plants and animals are largely concentrated in this zone. Examples of organisms living in this zone are plankton, floating seaweed, jellyfish, tuna, many sharks, from 200 m down to around 1,000 m The name for this zone stems from Greek μέσον, meaning middle. Although some light penetrates this second layer it is insufficient for photosynthesis, at about 500 m the water also becomes depleted of oxygen. Organisms survive this environment by having more efficient gills or by minimizing movement, examples of animals that live here are swordfish, squid, Anarhichadidae or wolffish and some species of cuttlefish
Pelagic zone
–
The pelagic
sooty tern spends months at a time flying at sea, returning to land only for breeding.
Pelagic zone
–
General
Pelagic zone
–
Marine
16.
Pelagic fish
–
The marine pelagic environment is the largest aquatic habitat on Earth, occupying 1,370 million cubic kilometres, and is the habitat for 11% of known fish species. The oceans have a depth of 4000 metres. About 98% of the water volume is below 100 metres. Marine pelagic fish can be divided into pelagic coastal fish and oceanic pelagic fish, coastal fish inhabit the relatively shallow and sunlit waters above the continental shelf, while oceanic fish inhabit the vast and deep waters beyond the continental shelf. Pelagic fish range in size from small forage fish, such as herrings and sardines, to large apex predator oceanic fishes, such as bluefin tuna. They are usually agile swimmers with streamlined bodies, capable of sustained cruising on long-distance migrations, the Indo-Pacific sailfish, an oceanic pelagic fish, can sprint at over 110 kilometres per hour. Some tuna species cruise across the Pacific Ocean, many pelagic fish swim in schools weighing hundreds of tonnes. Others are solitary, like the ocean sunfish weighing over 500 kilograms. Epipelagic fish inhabit the epipelagic zone, the epipelagic zone is the water from the surface of the sea down to 200 metres. It is also referred to as the waters or the sunlit zone. The photic zone is defined as the surface waters down to the point where the sunlight has attenuated to 1% of the surface value and this depth depends on how turbid the water is, but in clear water can extend to 200 metres, coinciding with the epipelagic zone. The photic zone has sufficient light for phytoplankton to photosynthese, the epipelagic zone is vast, and is the home for most pelagic fish. The zone is well lit so visual predators can use their eyesight, is well mixed and oxygenated from wave action. However, it is an almost featureless habitat and this lack of habitat diversity results in a lack of species diversity, so the zone supports less than 2% of the worlds known fish species. Epipelagic fish can be divided into small forage fish and larger predator fish which feed on them. Forage fish school and filter feed on plankton, most epipelagic fish have streamlined bodies capable of sustained cruising on migrations. In general, predatory and forage fish share the same morphological features, predator fish are usually fusiform with large mouths, smooth bodies, and deeply forked tails. Many use vision to predate zooplankton or smaller fish, while others feed on plankton
Pelagic fish
–
A
school of large pelagic
predator fish (
giant trevally) sizing up a school of small pelagic
prey fish (
anchovies)
Pelagic fish
Pelagic fish
–
Large epipelagic
predator fish, like this
Atlantic bluefin tuna, have a deeply forked tail and a smooth body shaped like a spindle tapered at both ends and
countershaded with silvery colours.
Pelagic fish
–
Small epipelagic
forage fish, like this
Atlantic herring, share the same body features listed for the predator fish above
17.
Anchovies
–
An anchovy is a small, common salt-water forage fish of the family Engraulidae. The 144 species are placed in 17 genera, they are found in the Atlantic, Indian, and Pacific Oceans, and in the Black Sea, Anchovies are usually classified as oily fish. Anchovies are small, green fish with blue reflections due to a longitudinal stripe that runs from the base of the caudal fin. They range from 2 to 40 cm in length. The snout is blunt with tiny, sharp teeth in both jaws, the snout contains a unique rostral organ, believed to be sensory in nature, although its exact function is unknown. The mouth is larger than that of herrings and silversides, two fish which anchovies closely resemble in other respects, the anchovy eats plankton and recently hatched fish. Anchovies are found in scattered areas throughout the oceans, but are concentrated in temperate waters. They are generally accepting of a wide range of temperatures. Large schools can be found in shallow, brackish areas with muddy bottoms, as in estuaries and they are abundant in the Mediterranean, particularly in the Alboran Sea, Aegean Sea and the Black Sea. The species is caught along the coasts of Crete, Greece, Sicily, Italy, France, Turkey. They are also found on the coast of northern Africa, the range of the species also extends along the Atlantic coast of Europe to the south of Norway. Spawning occurs between October and March, but not in water colder than 12 °C, the anchovy appears to spawn at least 100 km from the shore, near the surface of the water. The anchovy is a significant food source for almost every predatory fish in its environment, including the California halibut, rock fish, yellowtail, shark, chinook, and coho salmon. It is also important to marine mammals and birds, for example, breeding success of California brown pelicans. Anchovies, like most clupeoids, are filter-feeders that open their mouths as they swim, as water passes through the mouth and out the gills, food particles are sieved by gill rakers and transferred into the esophagus. * Type species On average, the Turkish commercial fishing fleet catches around 300,000 tons per year, the largest catch is in November and December. The Peruvian anchovy fishery is one of the largest in the world, in 1973 it collapsed catastrophically due to the combined effects of overfishing and El Niño and did not recover fully for two decades. A traditional method of processing and preserving anchovies is to gut and salt them in brine, allow them to mature and this results in a characteristic strong flavor and the flesh turns deep grey
Anchovies
–
Anchovies
Anchovies
–
European anchovy, Engraulis encrasicolus
Anchovies
Anchovies
–
Still Life with Anchovies, 1972,
Antonio Sicurezza
18.
Shrimp
–
The SHRIMP is primarily used for geological and geochemical applications. The most common application of the instrument is in uranium-thorium-lead geochronology, although the SHRIMP can be used to some other isotopic. The instrument was built from 1975 and 1977 with testing and redesigning from 1978, the first successful geological applications occurred in 1980. The first major impact was the discovery of Hadean zircon grains at Mt. Narryer in Western Australia. These results and the SHRIMP analytical method itself were initially questioned, sHRIMP-I also pioneered ion microprobe studies of titanium, hafnium and sulfur isotopic systems. Growing interest from companies and other academic research groups, notably Prof. Refined ion optic designs in the mid-1990s prompted development and construction of the SHRIMP-RG with improved mass resolution, further advances in design have also led to multiple ion collection systems, negative-ion stable isotope measurements and on-going work in developing a dedicated instrument for light stable isotopes. Fifteen SHRIMP instruments have now been installed around the world and SHRIMP results have been reported in more than 2000 peer reviewed scientific papers, other significant milestones include the first U/Pb ages for lunar zircon and Martian apatite dating. More recent uses include the determination of Ordovician sea surface temperature, in a typical U-Pb geochronology analytical mode, a beam of 1− primary ions are produced from a high-purity oxygen gas discharge in the hollow Ni cathode of a duoplasmatron. The ions are extracted from the plasma and accelerated at 10 kV, the primary column uses Köhler illumination to produce a uniform ion density across the target spot. The spot diameter can vary from ~5 µm to over 30 µm as required, typical ion beam density on the sample is ~10 pA/µm2 and an analysis of 15–20 minutes creates an ablation pit of less than 1 µm. The primary beam is 45° incident to the plane of the surface with secondary ions extracted at 90°. Three quadrupole lenses focus the secondary ions onto a source slit, a Schwarzschild objective lens provides reflected-light direct microscopic viewing of the sample during analysis. The secondary ions are filtered and focussed according to their energy by a 1272 mm radius 90° electrostatic sector. The electromagnet has a 1000 mm radius through 72. 5° to focus the secondary ions according to their mass/charge ratio according to the principles of the Lorentz force. Essentially, the path of a massive ion will have a greater curvature through the magnetic field than the path of a more massive ion. Thus, altering the current in the electromagnet focuses a particular mass species at the detector, the ions pass through a collector slit in the focal plane of the magnetic sector and the collector assembly can be moved along an axis to optimise the focus of a given isotopic species. In typical U-Pb zircon analysis, a secondary electron multiplier is used for ion counting
Shrimp
19.
Tuna
–
A tuna is a saltwater fish that belongs to the tribe Thunnini, a sub-grouping of the mackerel family – which together with the tunas, also includes the bonitos, mackerels, and Spanish mackerels. Thunnini comprises fifteen species across five genera, the sizes of which vary greatly, the bluefin averages 2 m, and is believed to live for up to 50 years. Tuna and mackerel sharks are the species of fish that can maintain a body temperature higher than that of the surrounding water. An active and agile predator, the tuna has a sleek, streamlined body, found in warm seas, it is extensively fished commercially, and is popular as a game fish. As a result of over-fishing, stocks of tuna species such as the southern bluefin tuna have been reduced dangerously close to the point of extinction. The term tuna ultimately derives from Thunnus, the Middle Latin form of the Ancient Greek, θύννος tunny-fish – which is in turn derived from θύνω, rush, the following cladogram illustrates the relationship between the tunas and other tribes of the family Scombridae. The true tunas are those that belong to the genus Thunnus, until recently, it was thought that there were seven Thunnus species, and that Atlantic bluefin tuna and Pacific bluefin tuna were subspecies of a single species. In 1999, Collette established that based on molecular and morphological considerations, they are in fact distinct species. The genus Thunnus is further classified into two subgenera, Thunnus, and Thunnus, the Thunnini tribe also includes seven additional species of tuna across four genera. They are, The tuna is a sleek and streamlined fish and it has two closely spaced dorsal fins on its back, The first is depressible – it can be laid down, flush, in a groove that runs along its back. Seven to ten yellow finlets run from the fins to the tail. The caudal peduncle, to which the tail is attached, is quite thin, the tunas dorsal side is generally a metallic dark blue, while the ventral side, or underside, is silvery or whitish, for camouflage. Thunnus are widely but sparsely distributed throughout the oceans of the world, generally in tropical, all tunas are able to maintain the temperature of certain parts of their body above the temperature of ambient seawater. For example, bluefin can maintain a body temperature of 25–33 °C. However, unlike typical endothermic creatures such as mammals and birds, tunas achieve endothermy by conserving the heat generated through normal metabolism. In all tunas, the heart operates at ambient temperature, as it receives cooled blood, also unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red myotomal muscles derive their color from myoglobin, an oxygen-binding molecule, the oxygen-rich blood further enables energy delivery to their muscles. For powerful swimming animals like dolphins and tuna, cavitation may be detrimental, even if they have the power to swim faster, dolphins may have to restrict their speed, because collapsing cavitation bubbles on their tail are too painful
Tuna
Tuna
–
Tuna
Tuna
–
Relative sizes of various tunas, with the
Atlantic bluefin tuna (top) at about 8 ft (2.4 m) in this sample
Tuna
–
Tuna being weighed on Greek quay-side
20.
Mackerel
–
Mackerel is a common name applied to a number of different species of pelagic fish, mostly, but not exclusively, from the family Scombridae. They are found in temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment. Mackerel typically have stripes on their backs and deeply forked tails. Many species are restricted in their ranges, and live in separate populations or fish stocks based on geography. Some stocks migrate in schools along the coast to suitable spawning grounds. After spawning they return the way they came, in smaller schools, from there they may move offshore into deeper waters and spend the winter in relative inactivity. Smaller mackerel are forage fish for larger predators, including larger mackerel, flocks of seabirds, as well as whales, dolphins, sharks and schools of larger fish such as tuna and marlin follow mackerel schools and attack them in sophisticated and cooperative ways. Mackerel is high in oils and is intensively harvested by humans. In 2009, over five tons were landed by commercial fishermen. Sport fishermen value the fighting abilities of the king mackerel, over thirty different species, principally belonging to the family Scombridae, are commonly referred to as mackerel. The term mackerel means marked or spotted, the term mackerel derives from the Old French maquerel, c.1300, meaning a pimp or procurer. The connection is not altogether clear, but mackerel spawn enthusiastically in shoals near the coast, about 21 species in the family Scombridae are commonly called mackerel. The type species for the mackerel is the Atlantic mackerel. Until recently, it was thought that Atlantic chub mackerel and Indo-Pacific chub mackerel were subspecies of the same species, in 1999 Collette established, on molecular and morphological considerations, that these are separate species. Mackerel are smaller with shorter life cycles than their relatives, the tuna. The true mackerels belong to the tribe Scombrini, the tribe consists of seven species, each belonging to one of two genera, Scomber and Rastrelliger. The Spanish mackerels belong to the tribe Scomberomorini, which is the tribe of the true mackerels. This tribe consists of 21 species in all—18 of those are classified into the genus Scomberomorus, in addition, a number of species with mackerel-like characteristics in the families Carangidae, Hexagrammidae and Gempylidae are commonly referred to as mackerel
Mackerel
–
Some species of mackerel
migrate in
schools for long distances along the coast and other species cross oceans
Mackerel
Mackerel
–
Still life with mackerel, lemon and tomato,
Van Gogh, 1886
Mackerel
–
Mackerel, such as these
Pacific jack mackerel, usually have vertical stripes on their sides which provide "schooling marks", visual clues that help them stay in formation as they
school.
21.
Groundfish
–
Groundfish are fish that live on, in, or near the bottom of the body of water they inhabit. Some typical saltwater groundfish species are cod, flounder, halibut, related terms used in different contexts include demersal fish and whitefish, and bottom feeder. Saltwater groundfish harvesting is subject to federal regulations in the United States, such as 50 CFR679. Freshwater groundfish harvesting is not subject to federal regulation per se, bottom feeder Demersal fish Whitefish Amendment from April 06,2006 §679.27 Improved Retention/Improved Utilization Program. Archived from the original on September 30,2007
Groundfish
–
About
fish
22.
Cod
–
Cod is the common name for the genus Gadus of demersal fishes, belonging to the family Gadidae. Cod is also used as part of the name for a number of other fish species. Gadus morhua was named by Linnaeus in 1758, Cod is popular as a food with a mild flavour and a dense, flaky, white flesh. Cod livers are processed to make cod liver oil, an important source of vitamin A, vitamin D, vitamin E, young Atlantic cod or haddock prepared in strips for cooking is called scrod. In the United Kingdom, Atlantic cod is one of the most common ingredients in fish and chips, along with haddock, at various times in the past, taxonomists included many species in the genus Gadus. Most of these are now classified in other genera, or have been recognized as simply forms of one of three species. All these species have a number of names, most of them ending with the word cod, whereas other species. However, many other, unrelated species also have names ending with cod. The usage often changes with different localities and at different times, three species in the Gadus genus are currently called cod, Cod forms part of the common name of many other fish no longer classified in the genus Gadus. The tadpole cod family has now placed in Gadidae. Gadiformes include, Some fish have common names derived from cod, such as codling, Some fish commonly known as cod are unrelated to Gadus. Part of this confusion is market-driven. Severely shrunken Atlantic cod stocks have led to the marketing of cod replacements using culinary names of the form x cod, the common names for the following species have become well established, note that all inhabit the Southern Hemisphere. Most are better known as groupers, and belong to the family Serranidae, Some fish that do not have cod in their names are sometimes sold as cod. Haddock and whiting belong to the family, the Gadidae. Haddock Melanogrammus aeglefinus Whiting Merlangius merlangus Cods of the genus Gadus have three rounded dorsal and two anal fins, the pelvic fins are small, with the first ray extended, and are set under the gill cover, in front of the pectoral fins. The upper jaw extends over the jaw, which has a well-developed chin barbel. The eyes are medium-sized, approximately the same as the length of the chin barbel, Cod have a distinct white lateral line running from the gill slit above the pectoral fin, to the base of the caudal or tail fin
Cod
–
Atlantic cod
Cod
Cod
–
The
Atlantic cod, Gadus morhua
Cod
–
A fish with its gills infested with two
cod worms
23.
Squid
–
Squid are cephalopods of the order Teuthida, which comprises around 304 species. Like all other cephalopods, squid have a head, bilateral symmetry, a mantle. Squid, like cuttlefish, have eight arms arranged in pairs, squid are strong swimmers and certain species can fly for short distances out of the water. Squid are members of the class Cephalopoda, subclass Coleoidea, order Teuthida, Teuthida is the largest cephalopod order with around 300 species classified into 29 families. The order Teuthida is a member of the superorder Decapodiformes, two other orders of decapodiform cephalopods are also called squid, although they are taxonomically distinct from Teuthida and differ recognizably in their gross anatomical features. They are the bobtail squid of order Sepiolida and the rams horn squid of the monotypic order Spirulida, the vampire squid, however, is more closely related to the octopuses than to any squid. Class Cephalopoda Subclass Nautiloidea, nautilus Subclass Coleoidea, squid, octopus, what before may have been the foot of the ancestor is modified into a complex set of tentacles and highly developed sense organs, including advanced eyes similar to those of vertebrates. The ancestral shell has been lost, with only an internal gladius, or pen, the pen is a feather-shaped internal structure that supports the squids mantle and serves as a site for muscle attachment. It is made of a chitin-like material, the main body mass is enclosed in the mantle, which has a swimming fin along each side. These fins, unlike in other organisms, are not the main source of locomotion in most species. The skin is covered in chromatophores, which enable the squid to change color to suit its surroundings, the underside is also almost always lighter than the topside, to provide camouflage from both prey and predator. Under the body are openings to the cavity, which contains the gills and openings to the excretory. At the front of the mantle cavity lies the siphon, which the squid uses for locomotion via precise jet propulsion, in this form of locomotion, water is sucked into the mantle cavity and expelled out of the siphon in a fast, strong jet. The direction of the siphon can be changed, to suit the direction of travel, inside the mantle cavity, beyond the siphon, lies the visceral mass, which is covered by a thin, membranous epidermis. Under this are all the internal organs. The giant axon, which may be up to 1 mm in diameter in some species, innervates the mantle. As cephalopods, squid exhibit relatively high intelligence among invertebrates, for example, groups of Humboldt squid hunt cooperatively, using active communication. In females, the ink sac is hidden from view by a pair of white nidamental glands, also, red-spotted accessory nidamental glands are present
Squid
Squid
Squid
–
Bathyteuthis abyssicola
Squid
–
Grimalditeuthis bonplandi
24.
Halibut
–
Halibut is a common name principally applied to the two flatfish in the genus Hippoglossus from the family of right-eye flounders. Less commonly, and in some regions only, other species of flatfish are also referred to as being halibuts, the word is derived from haly and butte, for its popularity on Catholic holy days. Halibut are demersal fish and are regarded as a food fish. The IGFA record was broken off the waters of Norway in July 2013 by a 515-pound 8.6 foot fish. This is awaiting certification as of 2013, in July 2014, 76-year-old Jack McGuire caught a 482-pound Pacific halibut in Glacier Bay, Alaska. Halibut are dark brown on the top side with an off-white underbelly and have small scales invisible to the naked eye embedded in their skin. At birth, they have an eye on each side of the head, after six months, one eye migrates to the other side, making them look more like flounder. At the same time, the stationary-eyed side darkens to match the top side and this color scheme disguises halibut from above and from below and is known as countershading. Halibut feed on almost any fish or animal they can fit into their mouths, juvenile halibut feed on small crustaceans and other bottom-dwelling organisms. Animals found in their stomachs include sand lance, octopus, crab, salmon, hermit crabs, lamprey, sculpin, cod, pollock, herring, and flounder, as well as other halibut. Halibut live at depths ranging from a few meters to hundreds, in most ecosystems, the halibut is near the top of the marine food chain. In the North Pacific, their predators are the sea lion, the killer whale. The North Pacific commercial halibut fishery dates to the late 19th century, the fishing vessel retrieves the line after several hours to a day. The effects of long-line gear on habitats are poorly understood, but could include disturbance of sediments, benthic structures, International management is thought to be necessary, because the species occupies waters of the United States, Canada, Russia, and possibly Japan, and matures slowly. Halibut do not reproduce until age eight, when about 30 in long, so commercial capture below this length prevents breeding and is against US, Pacific halibut fishing is managed by the International Pacific Halibut Commission. For most of the era, halibut fishery operated as a derby. Regulators declared time slots when fishing was open and fisherman raced to catch as many pounds as they could within that interval and this approach accommodated unlimited participation in the fishery while allowing regulators to control the quantity of fish caught annually by controlling the number and timing of openings. The approach led to unsafe fishing, as openings were necessarily set before the weather was known, the approach limited fresh halibut to the markets to several weeks per year, when the gluts would push down the price received by fishermen
Halibut
–
Fishermen in
Seward, Alaska with a fresh catch of halibut. June 2015.
Halibut
–
Halibut tend to be a mottled dark brown on their upward-facing side and white on their downside
Halibut
–
Halibut caught off the coast of
Raspberry Island, Alaska, in 2007: The two fish being held up are 70 to 80 lb (32 to 36 kg)
Halibut
–
Filleting of Pacific Halibut taken in
Cook Inlet, Alaska. Each halibut yields four fillets; the yield percentage is higher than for most types of fish.
25.
Sebastidae
–
Sebastidae is a family of marine fish in the order Scorpaeniformes. Their common names include rockfishes, rock perches, ocean perches, sea perches, thornyheads, scorpionfishes, sea ruffes, despite the latter name, they are not closely related to the cods in the genus Gadus, nor the rock cod, Lotella rhacina. Not all authorities recognise this family as distinct from Scorpaenidae, fishBase does recognise it, but ITIS does not. Of about 130 species in family, the substantial majority belong to genus Sebastes. They are found in the Atlantic, Pacific and Indian Oceans, over 100 of the species are viviparous, and these occur mainly in the North Pacific. All species have venom glands in their dorsal, anal, and pelvic spines
Sebastidae
–
Sebastidae
26.
Benthic
–
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos, e. g. the benthic community, including crustaceans. The organisms generally live in relationship with the substrate bottom. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, the benthic region of the ocean begins at the shore line and extends downward along the surface of the continental shelf out to sea. The continental shelf is a gently sloping benthic region that extends away from the land mass, at the continental shelf edge, usually about 200 meters deep, the gradient greatly increases and is known as the continental slope. The continental slope drops down to the sea floor. The deep-sea floor is called the plain and is usually about 4,000 meters deep. The ocean floor is not all flat but has submarine ridges, for comparison, the pelagic zone is the descriptive term for the ecological region above the benthos, including the water-column up to the surface. For information on animals that live in the areas of the oceans see aphotic zone. Generally, these life forms that tolerate cool temperatures and low oxygen levels. Benthos are the organisms live in the benthic zone, and are different from those elsewhere in the water column. Many are adapted to live on the substrate, in their habitats they can be considered as dominant creatures, but they are often a source of prey for Carcharhinidae such as the lemon shark. Many organisms adapted to deep-water pressure cannot survive in the parts of the water column. The pressure difference can be very significant, because light does not penetrate very deep into ocean-water, the energy source for the benthic ecosystem is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain, most organisms in the zone are scavengers or detritivores. Some microorganisms use chemosynthesis to produce biomass, Benthic organisms can be divided into two categories based on whether they make their home on the ocean floor or an inch or two into the ocean floor. Those living on the surface of the floor are known as epifauna. Those who live burrowed into the floor are known as infauna
Benthic
–
Photomicrograph of typical benthic animals, (from top to bottom) including
amphipods, a
polychaete worm, a
snail, and a
chironomous midge larva
27.
Knot (unit)
–
The knot is a unit of speed equal to one nautical mile per hour, approximately 1.151 mph. The ISO Standard symbol for the knot is kn, the same symbol is preferred by the IEEE, kt is also common. The knot is a unit that is accepted for use with the SI. Etymologically, the term derives from counting the number of knots in the line that unspooled from the reel of a log in a specific time. 1 international knot =1 nautical mile per hour,1.852 kilometres per hour,0.514 metres per second,1.151 miles per hour,20.254 inches per second,1852 m is the length of the internationally agreed nautical mile. The US adopted the definition in 1954, having previously used the US nautical mile. The UK adopted the international nautical mile definition in 1970, having used the UK Admiralty nautical mile. The speeds of vessels relative to the fluids in which they travel are measured in knots, for consistency, the speeds of navigational fluids are also measured in knots. Thus, speed over the ground and rate of progress towards a distant point are given in knots. Until the mid-19th century, vessel speed at sea was measured using a chip log, the chip log was cast over the stern of the moving vessel and the line allowed to pay out. Knots placed at a distance of 8 fathoms -47 feet 3 inches from each other, passed through a sailors fingers, the knot count would be reported and used in the sailing masters dead reckoning and navigation. This method gives a value for the knot of 20.25 in/s, the difference from the modern definition is less than 0. 02%. On a chart of the North Atlantic, the scale varies by a factor of two from Florida to Greenland, a single graphic scale, of the sort on many maps, would therefore be useless on such a chart. Recent British Admiralty charts have a latitude scale down the middle to make this even easier, speed is sometimes incorrectly expressed as knots per hour, which is in fact a measure of acceleration. Prior to 1969, airworthiness standards for aircraft in the United States Federal Aviation Regulations specified that distances were to be in statute miles. In 1969, these standards were amended to specify that distances were to be in nautical miles. At 11000 m, an airspeed of 300 kn may correspond to a true airspeed of 500 kn in standard conditions. Beaufort scale Hull speed, which deals with theoretical estimates of maximum speed of displacement hulls Knot count Knotted cord Metre per second Orders of magnitude Rope Kemp
Knot (unit)
–
Graphic scale from a Mercator projection world map, showing the change with latitude
28.
By-catch
–
Bycatch, in the fishing industry, is a fish or other marine species that is caught unintentionally while catching certain target species and target sizes of fish, crabs etc. Bycatch is either of a different species, the wrong sex, the term bycatch is also sometimes used for untargeted catch in other forms of animal harvesting or collecting. In 1997, the Organisation for Economic Co-operation and Development defined bycatch as total fishing mortality, Bycatch contributes to fishery decline and is a mechanism of overfishing for unintentional catch. Given the popularity of fishing throughout the world, a small local study in the US in 2013 suggested that discards may be an important unmonitored source of fish mortality. The highest rates of incidental catch of species are associated with tropical shrimp trawling. In 1997, the Food and Agriculture Organization of the United Nations documented the estimated bycatch and they found discard rates as high as 20,1 with a world average of 5.7,1. Shrimp trawl fisheries catch 2% of the total catch of all fish by weight. American shrimp trawlers produce bycatch ratios between 3,1 and 15,1, trawl nets in general, and shrimp trawls in particular, have been identified as sources of mortality for cetacean and finfish species. When bycatch is discarded, it is dead or dying. Tropical shrimp trawlers often make trips of several months without coming to port, a typical haul may last 4 hours after which the net is pulled in. Just before it is pulled on board the net is washed by zigzagging at full speed, the contents are then dumped on deck and are sorted. An average of 5.7,1 means that for every kilogram of shrimp there are 5.7 kg of bycatch, in tropical inshore waters the bycatch usually consists of small fish. The shrimps are frozen and stored on-board, the bycatch is discarded, recent sampling in the South Atlantic rock shrimp fishery found 166 species of finfish,37 crustacean species, and 29 other species of invertebrate among the bycatch in the trawls. Another sampling of the same fishery over a two-year period found that rock shrimp amounted to only 10% of total catch weight, iridescent swimming crab, dusky flounder, inshore lizardfish, spot, brown shrimp, longspine swimming crabs, and other bycatch made up the rest. Cetaceans, such as dolphins, porpoises, and whales, can be affected by entanglement in fishing nets and lines. Cetacean bycatch is increasing in intensity and frequency, in some fisheries, cetaceans are captured as bycatch but then retained because of their value as food or bait. In this fashion, cetaceans can become a target of fisheries, one example of bycatch is dolphins caught in tuna nets. As dolphins are mammals and do not have gills they may drown while stuck in nets underwater and this bycatch issue has been one of the reasons of the growing ecolabelling industry, where fish producers mark their packagings with disclaimers such as dolphin friendly to reassure buyers
By-catch
–
Shrimp bycatch
By-catch
–
Double-rigged shrimp
trawler hauling in the
nets
By-catch
–
Shrimp bycatch
By-catch
–
Group of
Fraser's dolphins.
