Fish-Finding definition of Fish-Finding in the Free Online Encyclopedia.

Fish-Finding

a method of locating (for commercial purposes) and studying the behavior of fish, marine mammals, and other aquatic organisms by means of active and passive underwater sonar detection. Fish-finding systems generally are of an active type that can determine the species, size, and number of fish, as well as the position of the schools.

The basic difference between fish-finding and underwater sonar detection (hydrolocation) lies in the sound reflection and scattering characteristics of aquatic organisms. Since the acoustic properties of fish tissues and seawater are similar, the scattering and absorption characteristics are determined mainly by the swim bladder. There is a very substantial difference between the acoustic impedances of water and of the gas within the bladder. According to calculations, the swim bladder should reflect approximately 50 times more sound energy than the body. However, measurements show that this energy is two to five times less. The apparatus used in fish-finding includes both underwater sonar detectors and echometers.

The effectiveness of fish-finding can be reduced by the presence of scattering layers that are created, for example, by plank-tonic organisms. The layers may also be created by reverberation (surface, bottom, and volume), which is often difficult to distinguish from the reflections of schools; by temperature non-uniformities (horizontal and vertical), which register like scattering layers; by wake echoes that are frequently encountered when a large number of vessels are operating in an area, and by interference from beams emitted by sonar detectors and echometers on various vessels.

REFERENCES

See references under BIOHYDROACOUSTICS.

V. M. LIFSHITS

Mentioned in	?		References in periodicals archive	?		Encyclopedia browser	?		Full browser	?
No references found	Wood's boat is a 38 ft Aquastar and carries full safety, navigation and fish-finding equipment with a 60-mile C. MY apologies to Mike Wood, skipper [...] by Evening Chronicle (Newcastle, England) Portsmouth-based Raymarine - which supplies autopilot, GPS and fish-finding technology - has been looking for a partner after warning in June that it was operating close to the limit of its current bank facilities. Marine firm wants a partner by Daily Post (Liverpool, England) OAWRS allows the team to take images of an area some 100 kilometers (approximately 62 miles) in diameter every 75 seconds, which is a vast improvement over conventional techniques such as fish-finding echo-sounders. Genesis of mass migration of fish observed for first time by Asian News International	fish protein concentrate Fish Pump FISH queue fish screen Fish Spear Fish Springs National Wildlife Refuge fish stakes fish stock fish tape Fish Wintering fish wire Fish, Carl Russell Fish, Gennadii Fish, Gennadii Semenovich Fish, Hamilton Fish, Nicholas Fish, Stanley Eugene Fish, Stuyvesant Fish-and-Duck Farm fish-bellied fish-bone antenna Fish-Dressing Machine fish-eye lens fish-eye stone Fish-Filleting Machine Fish-Finding Fish-Finding Equipment Fish-meal Equipment Fish-Processing Refrigerator Ship Fishbein, Morris Fishburne, Larry fished joint Fisher Fisher County Fisher Grove State Park Fisher King Fisher Poets Gathering Fisher's ideal index Fisher's inequality Fisher, Andrew Fisher, Clarence Stanley Fisher, Donald G. Fisher, Dorothy Canfield Fisher, Fort Fisher, Frederick John Fisher, Geoffrey Francis Fisher, Irving Fisher, John Fisher, John Arbuthnot Fisher, John Arbuthnot Fisher, 1st Baron Fisher, M. F. K.	Fish, Game and Wildlife Fish, Gennadii Fish, Gennadii Semenovich Fish, Hamilton Fish, Nicholas Fish, Stanley Eugene Fish, Stuyvesant Fish, Wildlife and Conservation Biology Fish, Wildlife and Energy Working Group Fish, Wildlife, and Parks Fish-and-chip fish-and-chip shop Fish-and-Duck Farm Fish-bellied Fish-bellied Fish-block fish-bone antenna Fish-Dressing Machine Fish-eye Fish-eye Fish-Eye Disease Fish-eye lens Fish-eye lens fish-eye stone fish-farm Fish-farming Fish-Filleting Machine Fish-Finding Fish-Finding Equipment fish-fly fish-handler's disease fish-hook Fish-liver oil Fish-louse Fish-louse Fish-meal Equipment Fish-oil Fish-oil Fish-oil Fish-Processing Refrigerator Ship Fish-sticks Fish-sticks Fish-sticks Fish-tackle Fish-tail Fish-tail burner Fish-tail propeller Fish-tape FISH-TSA fish-worship fishable fishable fishable FishAmerica Foundation Fishbach and Moore, Inc. Fishball Fishballs Fishbeck, Thompson, Carr & Huber, Inc.

Mentioned in

References in periodicals archive

Encyclopedia browser

Full browser

No references found

Wood's boat is a 38 ft Aquastar and carries full safety, navigation and fish-finding equipment with a 60-mile C.

MY apologies to Mike Wood, skipper [...] by Evening Chronicle (Newcastle, England)

Portsmouth-based Raymarine - which supplies autopilot, GPS and fish-finding technology - has been looking for a partner after warning in June that it was operating close to the limit of its current bank facilities.

Marine firm wants a partner by Daily Post (Liverpool, England)

OAWRS allows the team to take images of an area some 100 kilometers (approximately 62 miles) in diameter every 75 seconds, which is a vast improvement over conventional techniques such as fish-finding echo-sounders.

Genesis of mass migration of fish observed for first time by Asian News International

fish protein concentrate

Fish Springs National Wildlife Refuge