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Fishfinder
A fishfinder or sounder (Australia) is a sonar instrument used on boats to identify aquatic animals, bathymetry, underwater topography and other objects by detecting reflection (physics), reflected sound wave, pulses of sound energy, usually during fishing activities. A modern fishfinder displays measurements of reflected sound on a display device, graphical display, allowing an operator to interpret information to locate shoaling and schooling, schools of fish, underwater debris and freshwater snag, snags, and the bottom of a body of water. Fishfinder instruments are used both by recreational fishing, recreational and commercial fishing, commercial fishermen, as well as by marine biologists. Modern electronics allow a high degree of integration between the fishfinder system, marine radar, compass and GPS navigation systems. Fathometer Fishfinders were derived from ''fathometer, fathometers'', active sonar instruments used for navigation and safety to determine the depth of water ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sonar
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances ( ranging), communicate with or detect objects on or under the surface of the water, such as other vessels. "Sonar" can refer to one of two types of technology: ''passive'' sonar means listening for the sound made by vessels; ''active'' sonar means emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used for robot navigation, and sodar (an upward-looking in-air sonar) is used for atmospheric investigations. The term ''sonar'' is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low ( infrasonic) to e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forage Fish
Forage fish, also called prey fish or bait fish, are small pelagic fish that feed on planktons (i.e. planktivores) and other small aquatic organisms (e.g. krill). They are in turn preyed upon by various predators including larger fish, seabirds and marine mammals, this making them keystone species in their aquatic ecosystems. The typical ocean forage fish feed at the lower trophic level of the food chain, often by filter feeding. They include particularly fishes of the order Clupeiformes (herrings, sardines, shad, hilsa, menhaden, anchovies, and sprats), but also other small fish, including halfbeaks, Atheriniformes, silversides, Smelt (fish), smelt such as capelin and goldband fusiliers. Forage fish compensate for their small size by forming shoaling and schooling, schools. Some swim in synchronised grids with their mouths open so they can efficiently filter plankton. These schools can become immense Shoaling and schooling, shoals which move along coastlines and Fish migration, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echo Sounding
Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth (coordinate), depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; the resulting time of flight, along with knowledge of the speed of sound in water, allows determining the distance between sonar and target. This information is then typically used for navigation purposes or in order to obtain depths for Nautical chart, charting purposes. Echo sounding can also be used for ranging to other targets, such as fish schools. Hydroacoustic assessments have traditionally employed mobile surveys from boats to evaluate fish biomass and spatial distributions. Conversely, fixed-location techniques use stationary transducers to monitor passing fish. The word ''Depth sounding, sounding'' is used for all types of depth measurements, including those that don't use sound, and is unrelated in origin to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recreational Fishing
Recreational fishing, also called sport fishing or game fishing, is fishing for leisure, exercise or competition. It can be contrasted with commercial fishing, which is occupational fishing activities done for profit; or subsistence fishing, which is fishing for survival and livelihood. The most common form of recreational fishing is angling, which is done with a rig of rod, reel, line, hooks and any one of a wide range of baits, as well as other complementary devices such as weights, floats, swivels and method feeders, collectively referred to as '' terminal tackles''. Lures are frequently used instead of fresh bait when fishing for predatory fishes. Some hobbyists hand-make custom tackles themselves, including plastic lures and artificial flies. Other forms of recreational fishing include spearfishing, which is done with a speargun or harpoon usually while diving; and bowfishing, which is done from above the water with archery equipments such as a co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fathometer
Echo sounding or depth sounding is the use of sonar for ranging, normally to determine the depth of water (bathymetry). It involves transmitting acoustic waves into water and recording the time interval between emission and return of a pulse; the resulting time of flight, along with knowledge of the speed of sound in water, allows determining the distance between sonar and target. This information is then typically used for navigation purposes or in order to obtain depths for charting purposes. Echo sounding can also be used for ranging to other targets, such as fish schools. Hydroacoustic assessments have traditionally employed mobile surveys from boats to evaluate fish biomass and spatial distributions. Conversely, fixed-location techniques use stationary transducers to monitor passing fish. The word '' sounding'' is used for all types of depth measurements, including those that don't use sound, and is unrelated in origin to the word ''sound'' in the sense of noise or tone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baitfish
300px, Feeder Goldfish are common baitfish. Bait fish (or baitfish) are small-sized fish caught and used by anglers as bait to attract larger predatory fish, particularly game fish. Baitfish species are typically those that are common and breed rapidly, making them easy to catch and in abundant supply. Overview Examples of marine bait fish are anchovies, gudgeon, halfbeaks such as ballyhoo, and scad. Some larger fish such as menhaden, flying fish or ladyfish may be considered bait fish in some circles, depending on the size of the gamefish being pursued. Freshwater bait fish include minnows from the carp family (Cyprinidae), sucker family (Catostomidae), topminnows from the killifish suborder (Cyprinodontoidei), shad family ( Clupeidae), sculpin of the order Scorpaeniformes and sunfish family ( Centrarchidae), excluding black basses and crappies. Bait fish can be contrasted with forage fish. ''Bait fish'' is a term used particularly by recreational fishermen, although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sport Fishfinder
Sport is a physical activity or game, often competitive and organized, that maintains or improves physical ability and skills. Sport may provide enjoyment to participants and entertainment to spectators. The number of participants in a particular sport can vary from hundreds of people to a single individual. Sport competitions may use a team or single person format, and may be open, allowing a broad range of participants, or closed, restricting participation to specific groups or those invited. Competitions may allow a "tie" or "draw", in which there is no single winner; others provide tie-breaking methods to ensure there is only one winner. They also may be arranged in a tournament format, producing a champion. Many sports leagues make an annual champion by arranging games in a regular sports season, followed in some cases by playoffs. Sport is generally recognised as system of activities based in physical athleticism or physical dexterity, with major competitions admitt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mineral-rich waters, such as chalybeate springs. Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/ sleet and graupel, and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams, as well as groundwater contained in aquifers, subterranean rivers and lakes. Water is critical to the survival of all living organisms. Many organisms can thrive on salt water, but the great majority of vascular plants and most insects, amphibians, reptiles, mammals and birds need fresh water to survive. Fresh water is the water resource that is of the most and immediate use to humans. Fresh water is n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Encyclopædia Britannica
The is a general knowledge, general-knowledge English-language encyclopaedia. It has been published by Encyclopædia Britannica, Inc. since 1768, although the company has changed ownership seven times. The 2010 version of the 15th edition, which spans 32 volumes and 32,640 pages, was the last printed edition. Since 2016, it has been published exclusively as an online encyclopedia, online encyclopaedia. Printed for 244 years, the ''Britannica'' was the longest-running in-print encyclopaedia in the English language. It was first published between 1768 and 1771 in Edinburgh, Scotland, in three volumes. The encyclopaedia grew in size; the second edition was 10 volumes, and by its fourth edition (1801–1810), it had expanded to 20 volumes. Its rising stature as a scholarly work helped recruit eminent contributors, and the 9th (1875–1889) and Encyclopædia Britannica Eleventh Edition, 11th editions (1911) are landmark encyclopaedias for scholarship and literary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophone
A hydrophone () is a microphone designed for underwater use, for recording or listening to underwater sound. Most hydrophones contains a piezoelectric transducer that generates an electric potential when subjected to a pressure change, such as a sound wave. A hydrophone can also detect airborne sounds but is insensitive of them because it is designed to match the acoustic impedance of water, a denser fluid than air. Sound travels 4.3 times faster in water than in air, and a sound wave in water exerts a pressure 60 times more than what is exerted by a wave of the same amplitude in air. Similarly, a standard microphone can be buried in the ground, or immersed in water if it is put in a waterproof container but will give poor performance because of the similarly-bad acoustic impedance match. History The first hydrophones consisted of a tube with a thin membrane covering the submerged end and the observer's ear of the equipment. The design of effective hydrophones must take into a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
