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, are found in oceans worldwide, they are aptly named after their conspicuous use of bioluminescence. Their sister family, the Neoscopelidae, are much fewer in number but superficially similar. Sampling via deep trawling indicates lanternfish account for as much as 65% of all deep-sea fish biomass. Indeed, lanternfish are among the most distributed and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. With an estimated global biomass of 550–660 million metric tonnes, several times the entire world fisheries catch, lanternfish account for much of the biomass responsible for the deep scattering layer of the world's oceans. In the Southern Ocean, myctophids provide an alternative food resource to krill for predators such as squid and the king penguin. Although plentiful and prolific only a few commercial lanternfish fisheries exist: limited operations off South Africa, in the sub-Antarctic, in the Gulf of Oman.
Lanternfish have a slender, compressed body covered in small, silvery deciduous cycloid scales, a large bluntly rounded head, large elliptical to round lateral eyes, a large terminal mouth with jaws set with rows of small teeth. The fins are small, with a single high dorsal fin, a forked caudal fin, an adipose fin; the anal fin is supported by a cartilaginous plate at its base, originates under, or behind, the rear part of the dorsal fin. The pectoral fins with eight rays, may be large and well-developed to small and degenerate, or absent in a few species. In some species, such as those of the genus Lampanyctus, the pectorals are elongated. Most lanternfish have a gas bladder, but it degenerates or fills with lipids during the maturation of a few species; the lateral line is uninterrupted. In all but one species, Taaningichthys paurolychnus, a number of photophores are present; some may possess specialised photophores on the caudal peduncle, in proximity to the eyes, luminous patches at the base of the fins.
The photophores emit a weak blue, green, or yellow light, are known to be arranged in species-specific patterns. In some species, the pattern varies between females; this is true for the luminous caudal patches, with the males' being 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, while deeper-living species are dark brown to black, they are the most populous fish species in the open ocean with an approximate density of one per cubic metre. Lanternfish are well known for their diel vertical migrations: during daylight hours, most species remain within the gloomy bathypelagic zone, between 300 and 1,500 m deep, but towards sundown, the fish begin to rise into the epipelagic zone, between 10 and 100 m deep; the lanternfish are thought to do this to avoid predation, because they are following the diel vertical migrations of zooplankton, upon which they feed.
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 schooling over the continental slope. Different species are known to segregate themselves by depth, forming dense, discrete conspecific layers 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. Migration patterns may depend on life stage, sex and season; the arrangements of lanternfish photophores are different for each species, so their bioluminescence is thought to play a role in communication in shoaling and courtship behaviour. The concentration of the photophores on the flanks of the fish indicate the light's use as camouflage. A major source of food for many marine animals, lanternfish are an important link in the food chain of many local ecosystems, being preyed upon by whales and dolphins, large pelagic fish such as salmon and sharks, grenadiers and other deep-sea fish, sea birds, notably penguins, large squid such as the jumbo squid, Dosidicus gigas.
Lanternfish themselves have been found to feed on bits of plastic debris accumulating in the oceans. At least one lantern fish was found with over 80 pieces of plastic chips in its gut, according to scientists monitoring ocean plastic in the Pacific Ocean's eastern garbage patch. Sonar operators, using the newly developed sonar technology during World War II, wer
A factory ship 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 and their use for fishing has grown dramatically; some factory ships are equipped to serve as a mother ship. Contemporary factory ships have their origins in the early whalers; these vessels sailed into remote waters and processed the whale oil on board, discarding the carcass. Whalers converted the entire whale into usable products; the efficiency of these ships and the predation they carried out on whales contributed to the animals' steep decline. Contemporary factory ships are automated and enlarged versions of these earlier whalers, their use for fishing has grown dramatically. For a while, Russia and Korea operated huge fishing fleets centred on factory ships, though in recent times this use has been declining. On the other hand, the use of factory ships by the United States has increased.
Some factory ships can 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. They serve as the main ship in a fleet operating in waters a great distance from their home ports. Fish processing ships consist of various types, including freezer trawlers, longline factory vessels, purse seine freezer vessels, stern trawlers and squid jiggers. A factory stern trawler is a large stern trawler which has additional onboard processing facilities and can stay at sea for days or weeks at a time. A stern trawler hauls the catch up a stern ramp; these can be either demersal. A freezer trawler 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 go to sea for six weeks at a time with a crew of over 35 people.
They process fish into fillets within hours of being caught. Onboard fishmeal plants process the waste product; the world's 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. She is able to process 350 tonnes of fish a day, can carry 3,000 tons of fuel, store 7,000 tons of graded and frozen catch, she uses on board forklift trucks to aid discharging. These automated bottom longliners fish using hooks strung on long lines; the hooks are baited automatically and the lines are released fast. Many thousands of hooks are set each day, the retrieval and setting of these hooks is a continuous 24-hour-a-day operation; these ships go to sea for six weeks at a time. They contain factories for processing fish into fillets, which are frozen in packs, ready for market, within hours of being caught.
These vessels sometimes have fishmeal plants on board. A purse seiner is a fishing vessel which uses a traditional method of catching tuna and other school fish species. A large net is set in a circle around a school of fish while on the surface; the net is pursed, closing the bottom of the net pulling up the net until the fish are caught alongside the vessel. Most of these types of vessels transfer the fish into a tank filled with brine; this freezes large amounts of fish quickly. Trip lengths can vary from 20 to 70 days depending on the fishing; the fish is held in refrigerated brine tanks and unloads either directly to the canneries or is trans-shipped to carrier vessels to freight to the canneries, leaving the purse seine vessel close to the fishing grounds to continue fishing. Purse seiners longer than 70 metres are called super seiners. A factory squid jigger is a specialized ship that uses powerful lights to attract squid and "jigs" many thousands of hooked lures from hundreds of separate winches.
These predominantly Japanese and Korean factory vessels and their crews may fish the oceans continuously for two years, periodically transferring their catch at the fishing grounds to larger refrigerated vessels. Some barges are floating fish processing factories, which can be towed across navigable waters to receive catches from commercial fishing vessels; the barges contain living quarters for the factory workers. The 8,145-ton MV Nisshin Maru is the mothership of the Japanese whaling fleet and is the world's only remaining whaler factory ship; the ship is owned by Tokyo-based company Kyodo Senpaku Kaisha Ltd. and is contracted by the Japanese Institute of Cetacean Research. Commercial fish processing ships can affect birds, dolphins and sharks by their broad reach methods of catching fish. Purse seine ships, with nets up to two kilometres in circumference, can encircle whole shoals of pelagic fish, such as mackerel and tuna. A major international scientific study released in November 2006 in the journal Science found that about one-third of all fishing stocks worldwide have collapsed, that if current trends continue all fish stocks worldwide will collapse within fifty years.
The FAO State of World Fisheries and Aquaculture 2004 report estimates that in 2003, of the main fish stocks or groups of resourc
In ecology, a habitat is the type of natural environment in which a particular species of organism lives. It is characterized by both biological features. A species' habitat is those places where it can find food, shelter and mates for reproduction; the physical factors are for example soil, range of temperature, light intensity as well as biotic factors such as the availability of food and the presence or absence of predators. Every organism has certain habitat needs for the conditions in which it will thrive, but some are tolerant of wide variations while others are specific in their requirements. A habitat is not a geographical area, it can be the interior of a stem, a rotten log, a rock or a clump of moss, for a parasitic organism it is the body of its host, part of the host's body such as the digestive tract, or a single cell within the host's body. Habitat types include polar, temperate and tropical; the terrestrial vegetation type may be forest, grassland, semi-arid or desert. Fresh water habitats include marshes, rivers and ponds, marine habitats include salt marshes, the coast, the intertidal zone, reefs, the open sea, the sea bed, deep water and submarine vents.
Habitats change over time. This may be due to a violent event such as the eruption of a volcano, an earthquake, a tsunami, a wildfire or a change in oceanic currents. Other changes come as a direct result of human activities; the introduction of alien species can have a devastating effect on native wildlife, through increased predation, through competition for resources or through the introduction of pests and diseases to which the native species have no immunity. The word "habitat" has been in use since about 1755 and derives from the Latin habitāre, to inhabit, from habēre, to have or to hold. Habitat can be defined as the natural environment of an organism, the type of place in which it is natural for it to live and grow, it is similar in meaning to a biotope. The chief environmental factors affecting the distribution of living organisms are temperature, climate, soil type and light intensity, the presence or absence of all the requirements that the organism needs to sustain it. Speaking, animal communities are reliant on specific types of plant communities.
Some plants and animals are generalists, their habitat requirements are met in a wide range of locations. The small white butterfly for example is found on all the continents of the world apart from Antarctica, its larvae feed on a wide range of Brassicas and various other plant species, it thrives in any open location with diverse plant associations. The large blue butterfly is much more specific in its requirements. Disturbance is important in the creation of biodiverse habitats. In the absence of disturbance, a climax vegetation cover develops that prevents the establishment of other species. Wildflower meadows are sometimes created by conservationists but most of the flowering plants used are either annuals or biennials and disappear after a few years in the absence of patches of bare ground on which their seedlings can grow. Lightning strikes and toppled trees in tropical forests allow species richness to be maintained as pioneering species move in to fill the gaps created. Coastal habitats can become dominated by kelp until the seabed is disturbed by a storm and the algae swept away, or shifting sediment exposes new areas for colonisation.
Another cause of disturbance is when an area may be overwhelmed by an invasive introduced species, not kept under control by natural enemies in its new habitat. Terrestrial habitat types include forests, grasslands and deserts. Within these broad biomes are more specific habitats with varying climate types, temperature regimes, soils and vegetation types. Many of these habitats grade into each other and each one has its own typical communities of plants and animals. A habitat may suit a particular species well, but its presence or absence at any particular location depends to some extent on chance, on its dispersal abilities and its efficiency as a coloniser. Freshwater habitats include rivers, lakes, ponds and bogs. Although some organisms are found across most of these habitats, the majority have more specific requirements; the water velocity, its temperature and oxygen saturation are important factors, but in river systems, there are fast and slow sections, pools and backwaters which provide a range of habitats.
Aquatic plants can be floating, semi-submerged, submerged or grow in permanently or temporarily saturated soils besides bodies of water. Marginal plants provide important habitat for both invertebrates and vertebrates, submerged plants provide oxygenation of the water, absorb nutrients and play a part in the reduction of pollution. Marine habitats include brackish water, bays, the open sea, the intertidal zone, the sea bed and deep / shallow water zones. Further variations include rock pools, sand banks, brackish lagoons and pebbly beaches, seagrass beds, all supporting their own flora and fauna; the benth
Google Earth is a computer program that renders a 3D representation of Earth based on satellite imagery. The program maps the Earth by superimposing satellite images, aerial photography, GIS data onto a 3D globe, allowing users to see cities and landscapes from various angles. Users can explore the globe by using a keyboard or mouse; the program can be downloaded on a smartphone or tablet, using a touch screen or stylus to navigate. Users may use the program to add their own data using Keyhole Markup Language and upload them through various sources, such as forums or blogs. Google Earth is able to show various kinds of images overlaid on the surface of the earth and is a Web Map Service client. In addition to Earth navigation, Google Earth provides a series of other tools through the desktop application. Additional globes for the Moon and Mars are available, as well as a tool for viewing the night sky. A flight simulator game is included. Other features allow users to view photos from various places uploaded to Panoramio, information provided by Wikipedia on some locations, Street View imagery.
The web-based version of Google Earth includes Voyager, a feature that periodically adds in-program tours presented by scientists and documentarians. Google Earth has been viewed by some as a threat to privacy and national security, leading to the program being banned in multiple countries; some countries have requested that certain areas be obscured in Google's satellite images areas containing military facilities. The core technology behind Google Earth was developed at Intrinsic Graphics in the late 1990s. At the time, the company was developing 3D gaming software libraries; as a demo of their 3D software, they created a spinning globe that could be zoomed into, similar to the Powers of Ten film. The demo was popular, but the board of Intrinsic wanted to remain focused on gaming, so in 1999, they created Keyhole, Inc. headed by John Hanke. Keyhole developed a way to stream large databases of mapping data over the internet to client software, a key part of the technology, acquired patchworks of mapping data from governments and other sources.
The product, called "Keyhole EarthViewer", was sold on CDs for use in fields such as real estate, urban planning and intelligence. Despite making a number of capital deals with Nvidia and Sony, the small company was struggling to make payroll, employees were leaving. Fortunes for the company changed in early 2003 when CNN received a discount for the software in exchange for placing the Keyhole logo on-air whenever the map was used. Keyhole did not expect it would amount to more than brief 5 or 10 second prerecorded animation clips, but it was used extensively by Miles O'Brien live during the 2003 invasion of Iraq, allowing CNN and millions of viewers to follow the progress of the war in a way that had never been seen before. Public interest in the software exploded and Keyhole servers were not able to keep up with demand. Keyhole was soon contacted by the Central Intelligence Agency's venture capital firm, In-Q-Tel, the National Geospatial-Intelligence Agency, for use with defense mapping databases, which gave Keyhole a much-needed cash infusion.
Intrinsic Graphics was sold in 2003 to Vicarious Visions after its gaming libraries did not sell well, its core group of engineers and management transitioned to Keyhole with Hanke remaining at the head. At the time, Google was finding that over 25% of its searches were of a geospatial character, including searches for maps and directions. In October 2004, Google acquired Keyhole as part of a strategy to better serve its users. Google Earth's imagery is displayed on a digital globe, which displays the planet's surface using a single composited image from a far distance. After zooming in far enough, the imagery transitions into different imagery of the same area with finer detail, which varies in date and time from one area to the next; the imagery is retrieved from satellites or aircraft. Before the launch of NASA and the USGS's Landsat 8 satellite, Google relied on imagery from Landsat 7, which suffered from a hardware malfunction that left diagonal gaps in images. In 2013, Google used datamining to remedy the issue, providing what was described as a successor to the Blue Marble image of Earth, with a single large image of the entire planet.
This was achieved by combining multiple sets of imagery taken from Landsat 7 to eliminate clouds and diagonal gaps, creating a single "mosaic" image. Google now uses Landsat 8 to provide imagery with greater frequency. Imagery is hosted on Google's servers, which are contacted by the application when opened, requiring an Internet connection. Imagery resolution ranges from 15 meters of resolution to 15 centimeters. For much of the Earth, Google Earth uses digital elevation model data collected by NASA's Shuttle Radar Topography Mission; this creates the impression of three-dimensional terrain where the imagery is only two-dimensional. Every image created from Google Earth using satellite data provided by Google Earth is a copyrighted map. Any derivative from Google Earth is made from copyrighted data which, under United States Copyright Law, may not be used except under the licenses Google provides. Google allows non-commercial personal use of the images as long as copyrights and attributions are preserved.
By contrast, images created with NASA's globe software World Wind use The Blue Marble, Landsat, or USGS imagery, each of, in the public domain. In version 5.0, Google introduced Historical Imagery. Clicking the clock icon in the toolbar opens a time slider, which marks the tim
An anchovy is a small, common forage fish of the family Engraulidae. Most species are found in marine waters, but several will enter brackish water and some in South America are restricted to fresh water; the more than 140 species are placed in 17 genera. Anchovies are classified as oily fish. Anchovies are small, green fish with blue reflections due to a silver-colored longitudinal stripe that runs from the base of the caudal fin, they range from 2 to 40 cm in adult length, their body shapes are variable with more slender fish in northern populations. The snout is blunt with 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 resemble in other respects; the anchovy eats plankton and hatched fish. Anchovies are found in scattered areas throughout the world's oceans, but are concentrated in temperate waters, are rare or absent in cold or warm seas.
They are very accepting of a wide range of temperatures and salinity. Large schools can be found in brackish areas with muddy bottoms, as in estuaries and bays; the European anchovy is abundant in the Mediterranean in the Alboran Sea, Aegean Sea and the Black Sea. This species is caught along the coasts of Crete, Sicily, France, Turkey and Spain, they are found on the coast of northern Africa. The range of the species 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 near the surface of the water. The anchovy is a significant food source for every predatory fish in its environment, including the California halibut, rock fish, shark and coho salmon, it is extremely important to marine mammals and birds. Anchovies, like most clupeoids, are filter-feeders; 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 in winter. The largest catch is in December; the Peruvian anchovy fishery is one of the largest in the world, far exceeding catches of the other anchovy species. In 1973 it collapsed catastrophically due to the combined effects of overfishing and El Niño and did not recover for two decades. A traditional method of processing and preserving anchovies is to gut and salt them in brine, allow them to cure, pack them in oil or salt; this results in a characteristic strong flavor and the flesh turns deep grey. Pickled in vinegar, as with Spanish boquerones, anchovies are milder and the flesh retains a white color. In Roman times, anchovies were the base for the fermented fish sauce garum. Garum had a sufficiently long shelf life for long-distance commerce, was produced in industrial quantities. Anchovies were eaten raw as an aphrodisiac. Today, they are used in small quantities to flavor many dishes; because of the strong flavor, they are an ingredient in several sauces and condiments, including Worcestershire sauce, Caesar salad dressing, Gentleman's Relish, many fish sauces, in some versions of Café de Paris butter.
For domestic use, anchovy fillets are packed in oil or salt in small tins or jars, sometimes rolled around capers. Anchovy paste is available. Fishermen use anchovies as bait for larger fish, such as tuna and sea bass; the strong taste people associate with anchovies is due to the curing process. Fresh anchovies, known in Italy as alici, have a much milder flavor. In Sweden and Finland, the name anchovies is related to a traditional seasoning, hence the product "anchovies" is made of sprats and herring can be sold as "anchovy-spiced". Fish from the family Engraulidae are instead known as sardell in Sweden and sardelli in Finland, leading to confusion when translating recipes. Anchovies portal Sardine Chavez FP, Ryan J, Lluch-Cota SE and Ñiquen CM From Anchovies to Sardines and Back: Multidecadal Change in the Pacific Ocean Science 229217–221. Froese and Daniel Pauly, eds.. "Engraulidae" in FishBase. January 2006 version. Miller DJ "Anchovy" CalCOFI Reports, 5: 20–26. Nizinski MS and Munroe TA FAO species catalogue, volume 2: Clupeoid Fishes of the World, Anchovies Pages 764–780, FAO Fisheries Synopsis 125, Rome.
ISBN 92-5-102340-9. Pacific States Marine Fisheries Commission Northern Anchovy The dictionary definition of anchovy at Wiktionary Fisheries Ebb and Flow in 50-Year Cycle National Geographic News. Chisholm, Hugh, ed.. "Anchovy". Encyclopædia Britannica. Cambridge University Press
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 moving boat, or by winding the line in when fishing from a static position, or sweeping the line from side-to-side, e.g. when fishing from a jetty. Trolling is used to catch pelagic fish such as salmon and kingfish. Trolling can be phonetically 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 for commercial fishing. Trolling from a moving boat involves moving quite through the water; this can be accomplished with the use of a special trolling motor. Multiple lines are used, outriggers can be used to spread the lines more and reduce their chances of tangling. Downriggers can be used to keep the lures or baits trailing at a desired depth. Outriggers are poles. A boat which trolls enough lines can simulate a school of fish.
Downrigger are devices used while trolling to lure at the desired depth. In practice, fish swim at different depths according to factors such as the temperature and amount of light in the water, the speed and direction of water currents. A downrigger consists of a one or two metre horizontal pole which supports a weight about three kilograms of lead, on a steel cable. A clip called a "line release" attaches the fishing line to the weight, the bait or lure is attached to the release; the fishing line is reeled in by a spool powered either 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 in commercial tuna fishing operations; these kites have various shapes, such as arrowhead paravanes, flexi-wing paravanes, bi-wing paravanes. The devices can place the bait at designated depths and positions. "Spreaders" lures to be trolled from a single line.
There are many inventive spreader designs, such as devices which cause the baited hooks or lures to move in helical patterns, in a sophisticated emulation of the schooling behaviour of a group of fish. Planer boards are trolled, they allow multiple lines to be trolled. They come in dual inline board designs. Dual board designs consist of two boards that are spaced apart and attached by a line to a mast near the front of the boat with a separate fishing line in a spring tension release clip that separates when the fishing line is set. Inline boards are attached directly to the fishing line and a spring tension clip that releases upon setting or tripping the planer board so it slides down the fishing line to a swivel tied several feet in front of the lure. 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 To be effective, trolling baits and lures must have the visual ability to attract fish and intrigue them with the way they move through the water.
Most trolling lures are injured, or fast moving fish. They include: Surface lures known as top water lures, they float and resemble prey, on top of the water. They can make a popping sound from a concave-cut head, a burbling sound from "side fins" or scoops or a buzzing commotion from one or several propellers. Plugs are known as crankbaits; these lures have a fishlike body shape and as they troll through the water they make various movements caused by instability due to a scoop under their heads. Swimbait, a minnow-like soft plastic bait, reeled like a plug; some have swimming tails. Spoon lures resemble the inside of a table spoon, they flash in the light while randomly wobbling or darting due to their shape. Spinnerbait, pieces of wire bent at about a 60 degree angle with a hook on the lower end and a flashy spinner mechanism on the upper end. Trolling baits and lures are either tied with a knot, such as the improved clinch knot, or connected with a tiny safety pin-like device called a "snap" onto the fishing line, in turn connected to the reel.
The reel is attached to a rod. The motion is of the lure is made by winding line back on to the reel, by sweeping the fishing rod, jigging movements with the fishing rod, or by trolling behind a moving boat. Lures can be contrasted with artificial flies called flies by fly fishers, which either float on the water surface sink or float underwater, in imitation some form of insect fish food; however some flies, such as the trolling tandem streamer fly, are designed for trolling behind a moving boat. As an example, marlin lures are 7-14 inches or more long with a shaped plastic or metal head and a plastic skirt; the design of the lure head its face, gives the lure its individual action when trolled through the water. Lure actions range from an active side-to-side swimming pattern to pushing water aggressively on the surface to, most tracking along in a straight line with a regular surface pop and bubble trail. Besides the shape and size of the lure head, the length and
Lift nets called lever nets, are a method of fishing using nets that are submerged to a certain depth and lifted out of the water vertically. The nets can be shaped like a bag, a rectangle, a pyramid, or a cone. Lift nets can be boat-operated, or shore-operated, they use bait or a light-source as a fish-attractor. Lift nets are sometimes called "dip nets", though that term applies more to hand nets. Portable hand lift nets are small lift nets operated manually, they have a rigid frame, attached to a long pole. They are used to catch fish and crustaceans, may be submerged just below the water surface or close to the bottom. A person using hand lift nets operate it from the shore, on bridges, from harbor walls. Stationary lift nets are larger than hand lift nets and are attached permanently to a shore-built structure. Lifting the nets may be done by hand through the use of counterweights, or they may use mechanized winches. Bait or a strong source of light is placed in the middle of the net, they are placed near beaches or riverbanks.
Boat-operated lift nets are lift nets operated from water vessels. They may be lifted up by mechanical winches, they utilize several long poles attached to one side of the boat or surrounding the boat. Bait or a strong source of light is used to attract the fish. Cast net Butterfly net Fish aggregating device Trawling