Recent Echo Sounder Studies

Trout, G. C.; Lee, A. J.; Richardson, I. D.; Jones, Frank

doi:10.1038/170071b0

Cited by 12 publications

(4 citation statements)

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“…It is assumed that these traces were also due to the same type of organisms as type I, again largely below the thermocline, and that the multiple traces were due to variation in water layering in the region (west of the Isles of Scilly) where the plankton evidence suggests a good deal of mixing. The association between plankton, thermoclines and scatter layers has been discussed by Trout, Lee, Richardson & Harden-Jones (1952), Cushing, Lee & Richardson (1956), and by Richardson et al (1959). At St. 19 there were about 40 large organisms per cubic metre of water sampled and thus 2200 in the water column below 1 m2 to 55 m depth.…”

Section: Discussionmentioning

confidence: 99%

The distribution of some plankton animals in the English Channel and approaches: ii. Surveys with the Gulf iii high-speed sampler, 1958-60

Southward

1962

J. Mar. Biol. Ass.

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SUMMARYComparison of the recent surveys with investigations back to 1903 confirms earlier suggestions of a general tendency towards an increase in southern forms (including south-western species) and a decrease in northern forms (including north-western species) in the western English Channel, although there has been considerable fluctuation from time to time. These and other biological changes in the area during the past 58 years are believed to be largely a result of rising temperatures and a consequent general shifting of boundaries of distribution. There appears to be no real evidence that the changes in plankton distribution are due to a change in fertility in the water or of variation in strength of inflow of oceanic water. However, these aspects cannot be separated from the changes that have taken place in populations of fish, and will be discussed further in a later paper.

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Section: Discussionmentioning

confidence: 99%

The distribution of some plankton animals in the English Channel and approaches: ii. Surveys with the Gulf iii high-speed sampler, 1958-60

Southward

1962

J. Mar. Biol. Ass.

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“…Approaches used to classify, count, and possibly identify acoustic targets depend, in part, on the distribution and packing density of organisms. If animals are dispersed throughout the water column and at low densities, it is possible to detect, measure, and count echoes from individual fish or zooplankton (Trout et al ., 1952). The original purpose of echo counting was to estimate the density of organisms by counting the number of targets and dividing by the sample volume.…”

Section: How Does Underwater Acoustic Technology Work?mentioning

confidence: 99%

Acoustic approaches to remote species identification: a review

Horne

2000

Fisheries Oceanography

208

137

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Noninvasive species identification remains a long‐term goal of fishers, researchers, and resource managers who use sound to locate, map, and count aquatic organisms. Since the first biological applications of underwater acoustics, four approaches have been used singly or in combination to survey marine and freshwater environments: passive sonar; prior knowledge and direct sampling; echo statistics from high‐frequency measures; and matching models to low‐frequency measures. Echo amplitudes or targets measured using any sonar equipment are variable signals. Variability in reflected sound is influenced by physical factors associated with the transmission of sound through a compressible fluid, and by biological factors associated with the location, reflective properties, and behaviour of a target. The current trend in acoustic target identification is to increase the amount of information collected through increases in frequency bandwidth or in the number of acoustic beams. Exclusive use of acoustics to identify aquatic organisms reliably will require a set of statistical metrics that discriminate among a wide range of similar body types at any packing density, and incorporation of these algorithms in routine data processing.

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“…Trout et al first used this method to obtain the numeric density, number of organisms per cubic meter. Most of the time, fish will form schools, making echo counting impossible [63]. Medwin and Clay measured the acoustic backscattering cross section (bs/m 2 ) and target strength (TS = 20 log 10 relative acoustic pressure) [62].…”

Section: Sonar Applications For the Study Of Fishmentioning

confidence: 99%

The Development of SONAR as a Tool in Marine Biological Research in the Twentieth Century

Fornshell

Teseï²

2013

International Journal of Oceanography

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The development of acoustic methods for measuring depths and ranges in the ocean environment began in the second decade of the twentieth century. The two world wars and the “Cold War” produced three eras of rapid technological development in the field of acoustic oceanography. By the mid-1920s, researchers had identified echoes from fish, Gadus morhua, in the traces from their echo sounders. The first tank experiments establishing the basics for detection of fish were performed in 1928. Through the 1930s, the use of SONAR as a means of locating schools of fish was developed. The end of World War II was quickly followed by the advent of using SONAR to track and hunt whales in the Southern Ocean and the marketing of commercial fish finding SONARs for use by commercial fisherman. The “deep scattering layer” composed of invertebrates and fish was discovered in the late 1940s on the echo sounder records. SONARs employing high frequencies, broadband, split beam, and multiple frequencies were developed as methods for the detection, quantification and identification of fish and invertebrates. The study of fish behavior has seen some use of passive acoustic techniques. Advancements in computer technology have been important throughout the last four decades of the twentieth century.

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Recent Echo Sounder Studies

Cited by 12 publications

References 1 publication

The distribution of some plankton animals in the English Channel and approaches: ii. Surveys with the Gulf iii high-speed sampler, 1958-60

The distribution of some plankton animals in the English Channel and approaches: ii. Surveys with the Gulf iii high-speed sampler, 1958-60

Acoustic approaches to remote species identification: a review

The Development of SONAR as a Tool in Marine Biological Research in the Twentieth Century

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