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Fisheries Acoustics
Fisheries acoustics includes a range of research and practical application topics using acoustical devices as sensors in aquatic environments. Acoustical techniques can be applied to sensing aquatic animals, zooplankton, and physical and biological habitat characteristics. Basic Theory Biomass estimation is a method of detecting and quantifying fish and other marine organisms using sonar technology.Simmonds J. & MacLennan D. (2005). ''Fisheries Acoustics: Theory and Practice'', second edition. Blackwell An acoustic transducer emits a brief, focused pulse of sound into the water. If the sound encounters objects that are of different density than the surrounding medium, such as fish, they reflect some sound back toward the source. These echoes provide information on fish size, location, and abundance. The basic components of the scientific echo sounder hardware function is to transmit the sound, receive, filter and amplify, record, and analyze the echoes. While there are many ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fishfinder
A fishfinder or sounder (Australia) is an instrument used to locate fish underwater by detecting reflected pulses of sound energy, as in sonar. A modern fishfinder displays measurements of reflected sound on a graphical display, allowing an operator to interpret information to locate schools of fish, underwater debris, and the bottom of body of water. Fishfinder instruments are used both by sport and commercial fishermen. Modern electronics allows a high degree of integration between the fishfinder system, marine radar, compass and GPS navigation systems. Fathometer Fish finders were derived from ''fathometer''s, active sonar instruments used for navigation and safety to determine the depth of water. The fathom is a unit of water depth, from which the instrument gets its name. The fathometer is an echo sounding system for measurement of water depth. A fathometer will display water depth and can make an automatic permanent record of measurements. Since both fathometers and fis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal-to-noise Ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. SNR, bandwidth, and channel capacity of a communication channel are connected by the Shannon–Hartley theorem. Definition Signal-to-noise ratio is defined as the ratio of the power of a signal (meaningful input) to the power of background noise (meaningless or unwanted input): : \mathrm = \frac, where is average power. Both signal and noise power must be measured at the same or equivalent points in a system, and within the same system bandwidth. Depending on whether the signal is a constant () or a random variable (), the signal-to-noise ratio for random noise becomes: : \mathrm = \frac where E refers to the expected value, i.e. in this case ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orange Roughy
The orange roughy (''Hoplostethus atlanticus''), also known as the red roughy, slimehead and deep sea perch, is a relatively large deep-sea fish belonging to the slimehead family (Trachichthyidae). The UK Marine Conservation Society has categorized orange roughy as "vulnerable to exploitation". It is found in , deep (bathypelagic, ) waters of the Western Pacific Ocean, eastern Atlantic Ocean (from Iceland to Morocco; and from Walvis Bay, Namibia, to off Durban, South Africa), Indo-Pacific (off New Zealand and Australia), and in the eastern Pacific off Chile. The orange roughy is notable for its extraordinary lifespan, attaining over 200 years. It is important to commercial deep-trawl fisheries. The fish is a bright, brick-red color, fading to a yellowish-orange after death. Like other slimeheads, orange roughy is slow-growing and late to mature, resulting in a very low resilience, making them extremely susceptible to overfishing. Many stocks (especially those off New Zealand and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anadromous
Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres. Such migrations are usually done for better feeding or to reproduce, but in other cases the reasons are unclear. Fish migrations involve movements of schools of fish on a scale and duration larger than those arising during normal daily activities. Some particular types of migration are ''anadromous'', in which adult fish live in the sea and migrate into fresh water to spawn; and ''catadromous'', in which adult fish live in fresh water and migrate into salt water to spawn. Marine forage fish often make large migrations between their spawning, feeding and nursery grounds. Movements are associated with ocean currents and with the availability of food in different areas at different times of year. The migratory movements ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beam Pattern
Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized group of electrically charged particles ***Cathode ray, or electron beam or e-beam, streams of electrons observed in discharge tubes ***X-ray beam, a penetrating form of high-energy electromagnetic radiation ** Molecular beam, a beam of particles moving at approximately equal velocities Arts, entertainment and media * Beam (music), a connection line in musical notation * Beam, to transport matter using the Transporter in the ''Star Trek'' fictional universe * Beam (rapper), American hip hop artist * BEAM.TV, an online digital delivery and content management platform * BEAM Channel 31, a Philippines television network * Beam (website), later Mixer, a former video game live streaming platform * BeamNG.drive, an open-world vehicle simulation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piezoelectric
Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied Stress (mechanics), mechanical stress. The word ''piezoelectricity'' means electricity resulting from pressure and latent heat. It is derived from the Greek language, Greek word ; ''piezein'', which means to squeeze or press, and ''ēlektron'', which means amber, an ancient source of electric charge. The piezoelectric effect results from the linear electromechanical interaction between the mechanical and electrical states in crystalline materials with no Centrosymmetry, inversion symmetry. The piezoelectric effect is a reversible process (thermodynamics), reversible process: List of piezoelectric materials, materials exhibiting the piezoelectric effect also exhibit the reverse piezoelectric effect, the internal generation of a mechanical strain resulting from an appli ... [...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 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 ton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fishfinder
A fishfinder or sounder (Australia) is an instrument used to locate fish underwater by detecting reflected pulses of sound energy, as in sonar. A modern fishfinder displays measurements of reflected sound on a graphical display, allowing an operator to interpret information to locate schools of fish, underwater debris, and the bottom of body of water. Fishfinder instruments are used both by sport and commercial fishermen. Modern electronics allows a high degree of integration between the fishfinder system, marine radar, compass and GPS navigation systems. Fathometer Fish finders were derived from ''fathometer''s, active sonar instruments used for navigation and safety to determine the depth of water. The fathom is a unit of water depth, from which the instrument gets its name. The fathometer is an echo sounding system for measurement of water depth. A fathometer will display water depth and can make an automatic permanent record of measurements. Since both fathometers and fis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlantic Cod
The Atlantic cod (''Gadus morhua'') is a benthopelagic fish of the family Gadidae, widely consumed by humans. It is also commercially known as cod or codling.''Atlantic Cod'' . Seafood Portal. Dry cod may be prepared as unsalted stockfish,''Oxford English Dictionary'', 3rd ed. "milwell, ''n.''" Oxford University Press (Oxford), 2002.''Oxford English Dictionary'', 1st ed. "stock-fish , 'stockfish, ''n.''" Oxford University Press (Oxford), 1917. and as cured |
European Sprat
The European sprat (''Sprattus sprattus''), also known as bristling, brisling, garvie, garvock, Russian sardine, russlet, skipper or whitebait, is a species of small marine fish in the herring family Clupeidae. Found in European waters, it has silver grey scales and white-grey flesh. Specific seas in which the species occurs include the Irish Sea, Black Sea, Baltic Sea and Sea of the Hebrides. The fish is the subject of fisheries, particularly in Scandinavia, and is made into fish meal, as well as being used for human consumption. When used for food it can be canned, salted, breaded, fried, boiled, grilled, baked, deep fried, marinated, broiled, and smoked. Taxonomy This fish was first described by Carl Linnaeus in 1758 in the 10th edition of Systema Naturae. He called it ''Clupea sprattus'', but it was later transferred to the genus ''Sprattus''. Three subspecies are recognised; ''S. sprattus balticus'' from the Baltic Sea; ''S. sprattus phalericus'' from the Mediterranean, Adri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Sea Bream
Red seabream is a name given to at least two species of fish of the family Sparidae, ''Pagrus major'' and ''Pagellus bogaraveo''. ''Pagrus major'' ''Pagrus major'' is of great culinary and cultural importance in Japan, and is known as madai in Japanese. It is considered an auspicious fish, eaten during Japanese New Year and other special occasions, such as weddings. It is also eaten in Taiwan and Korea, where it is known as chamdom. File:Redseabreamji1.jpg, Wild madai in the waters near Yamagata, Japan File:Osakatenman-gu Osaka Japan05-r.jpg, Madai as an auspicious object, with straw bindings and coins at Osaka Tenmangū shrine File:Red sea bream sashimi (27992669723).jpg, Madai sashimi File:Madai-fried-tokyoarea-sept23-2016.jpg, Fried madai File:Painting of a Red Sea Bream (Tai) by Ogawa Haritsu, 18th century.jpg, ''Tai on Bamboo Leaves'', painting by Ogawa Haritsu (1663-1747) ''Pagellus bogaraveo'' ''Pagellus bogaraveo'' is also known as blackspot sea bream. In Sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raymond Rallier Du Baty
Raymond Rallier du Baty (30 August 1881 – 7 May 1978) was a French sailor and explorer, from Lorient in Brittany, who carried out surveys of the subantarctic Kerguelen Islands in the southern Indian Ocean in the early 20th century. Rallier du Baty took part in the 1904-1907 Third French Antarctic Expedition led by Jean-Baptiste Charcot. From September 1907 to July 1909 Captain Raymond Rallier du Baty sailed from Boulogne to Melbourne in a French fishing ketch, known as the J. B. Charcot. The J. B. Charcot weighed forty-eight tons and completed this trip in 15,000 miles. The reason for this voyage was primarily to chart the subantarctic Kerguelen Islands. Du Baty and his brother Henri du Baty funded this expedition by harvesting the oil of the southern elephant seals in the area. Raymond Rallier du Baty wrote a book detailing his experience on the J. B. Charcot, entitled 15,000 Miles in a Ketch. They returned again in 1913-1914 in ''La Curieuse'' to carry out further surveys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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