A record of plankton on the echo-sounder

Cushing, D. H.; Richardson, I. D.

doi:10.1017/s0025315400009085

Cited by 9 publications

(2 citation statements)

References 4 publications

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“…The echo-sounder is the only instrument capable of giving an indication of the extent of the shoals of pelagic fish which prey on macroplankton (Hodgson, 1950;Richardson, 1951;Cushing, 1952;Cushing & Richardson, 1955;Cushing, 1957a). Work since the war has shown how large these shoals may be, both adult fish and young too agile to be captured by conventional nets (Hodgson & Richardson, 1948;Burd & Lee, 1951;Cushing, 1957b). '…”

Section: Echo-soundingmentioning

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: Echo-soundingmentioning

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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“…Apart from the vertically migrating scattering layers, non-migratory layers occur frequently (Gushing et al, 1956» Weston, 1958Hersey and Backus), These layers are normally associated with some major discontinuity of the water column such as a pycnocline or thermcline, Hersey and Backus suggest that such occurrences may represent the "trapping" of organisms at some optimal level of physical or chemical parameters. The present study deals with an example of this phenomenon in the Arctic Ocean,…”

Section: Introductionmentioning

confidence: 99%

Scattering Layers, Oxygen Distribution and the Copepod Plankton in the Upper 300 Metres of the Beaufort Sea

Hansen¹,

Bulleid²,

Dunbar³

1971

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METHODS AND EQUIPMENT Sonar Two fathometers operated by the Lamont-Doherty Geological Observatory were used. These werei (1) a 12 kHz Precision depth recorder with a standard Edo transducer, Gifft sonar transceiver, and spark-type rotating drum recorder? the time base advanced 1 cm/hr, and the pulse length was 80 mseci and (2) a Ross model 200A Pineline depth sounder and recorder with a 365 m (200 fm) range and 100 kHz frequency. The beam angle is 10° x 5°. The chart paper speed is variable from 6 to 24 in/hr, and the pulse duration is 0,4 or 1,5 msec. The instrument operates by switching through 90 m increments 1 thus the whole thickness of the layer could not be viewed instantaneously. A reasonable facsimile of the full range of scatterer distribution could be obtained however, by switching every minute, thus obtaining a narrow cross-sectional view in a 4-minute period. Hydrography Routine hydrocasts were made during the study. Temperature was measured using a thermistor and Wheatstone bridge. Salinity samples were stored and then sent to the Bedford Institute, Dartmouth, Nova Scotia, for analysis. Biological Sampling Plankton: Mesh nets numbers 6 and 0 mounted on 0.5 and 1 m rings were used throughout the study. Both vertical and horizontal tows were made. Horizontal tows were made using the drift of the island during periods of high wind, when drift speeds up to 0.5 knot relative to the water beneath can occur. The actual relative drift rate and filtration-coefficient of the nets can be estimated only roughly, but the multiple-net horizontal tows gave excellent simultaneous collections from various depths. This method involves hanging the net rings on a heavily weighted cable, one above the other, so that the net will stream at the desired depth (Figure 5). Corrections of depth for wire angle were made in the field. It was found that with practice one could attach or remove the nets from a moving cable, so that they were set or hauled with a minimum of contamination from depths other than those under scrutiny.

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Bibliography

1973

The Detection of Fish

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A record of plankton on the echo-sounder

Cited by 9 publications

References 4 publications

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

Scattering Layers, Oxygen Distribution and the Copepod Plankton in the Upper 300 Metres of the Beaufort Sea

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