Advantages and Disadvantages of Remote Sampling

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Advantages and disadvantages of remote sampling Advantages Remote sampling y Disadvantages y y y y Allows precise measurement of densities of the smaller sediment fauna No depth or time limitations on sampling Field operation relatively simple Standard equipment readily available Water turbidity unimportant Will not reliably sample: Deep-burrowing megafauna Large, mobile animals (eg. Nephrops) Large epifauna at low densities (eg. sea pens) Gives little information on bottom topography or bur
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    Advantages and disadvantages of remote sampling Advantages   Disadvantages    Remote sampling    y   Allows precise measurement of densities of the smaller sedimentfauna y    N o depth or time limitations onsampling y   F ield operation relatively simple y   S tandard equipment readily available y   W ater turbidity unimportant W ill not reliably sample:Deep-burrowing megafaunaLarge, mobile animals (eg.  N  ephrops )Large epifauna at low densities (eg. sea pens)Gives little information on bottom topographyor burrow types S tandard sampling area very small (0.1 m 2 per grab)Analysis of samples time-consuming andlabour-intensiveEquipment needs hard boat to operate. May beunable to access very shallow areas or enclosed inlets  Diving    y   Allows first-hand observation atclose range y   Allows accurate densitymeasurements of sea floor features(burrow openings, sea pens) y   Allows repeated monitoring of fixedstudy sites y   B enthic samples can be collected(eg. hand-cores, burrow resin casts) y   Equipment readily available,relatively inexpensive compared withROVs or underwater video y   C an be carried out from small boatsor from the shore, allowing access to S trict depth and time constraintsHas potential physical hazards (eg.decompression sickness)Operations subject to strict legislative controlsOnly possible to cover small areas onindividual divesEffectiveness can be limited by water turbidity  very shallow or semi-enclosedwaters T  owed underwater video   y   Able to survey large expanses of seafloor quickly y   Allows precise densitymeasurements of features of interest(eg. burrow openings, sea pens) y    N o depth or time constraints (incoastal waters) y   Gives much information on sea bedtopography and burrow types present, also on behaviour of benthicanimals.Equipment needs hard boat to operate. May beunable to access very shallow waters or enclosed inletsEquipment readily available but expensiveAnalysis of videotapes can be very time-consuming  N ot possible to collect benthic samplesProvides no information on smaller sedimentfaunaEffectiveness can be limited by water turbidity C are required in choice of towing path (needto avoid wrecks, rock outcrops and other submarine obstructions)  Remotely-operated vehicles (ROVs   y    N o time constraints. Depth rangelimited by length of umbilical butmost models can access depths likelyto be encountered in UK coastalwaters y   Able to cover wide areas (relative tocapacity of human divers) y   Mobility allows close-upexamination of sea bed y   Give much information on sea bedtopography and burrow types present y   Deployment areas less restricted thantowed video. C an be used over mixed substrata or in areas withsubmarine obstructions y   S ome models able to collect benthicsamplesEquipment needs a hard boat to operate. May be unable to access very shallow waters or enclosed inletsEquipment very expensivePrecise quantification of sea bed featuresdifficult due to changes in field of viewEffectiveness can be limited by water turbidity(the ROV motors themselves may disturb the bottom sediments)Provide only limited information on smaller sediment fauna S ampling of sea floor features is non-random   A coustic surveys   y    N o depth (within coastal waters) or time limitations y   Allows substrata to be mappedrapidly over large areas y   W ater turbidity unimportantEquipment needs a hard boat to operate. May be unable to access very shallow waters or enclosed inletsEquipment very expensiveResults need to be µground-truthed¶ by other methods (eg. grab sampling, towed video)Does not provide details of biologicalcommunity composition or species abundance  N ot able to collect benthic samplesReferences 1.   N eed for Sampling:   S ometimes there is a need for sampling. S uppose we want to inspect the eggs, the bullets,the missiles and the tires of some firm. The study may be such that the objects are destroyed  during the process of inspection. Obviously, we cannot afford to destroy all the eggs and the bullets etc. W e have to take care that the wastage should be minimum. This is possible only insample study. Thus sampling is essential when the units under study are destroyed.2.   Saves Time and Cost:  As the size of the sample is small as compared to the population, the time and costinvolved on sample study are much less than the complete counts. F or complete count hugefunds are required. There is always the problem of finances. A small sample can be studied in alimited time and total cost of sample study is very small. F or complete count, we need a big teamof supervisors and enumeration who are to be trained and they are to be paid properly for thework they do. Thus the sample study requires less time and less cost.3.   R  eliability:  If we collect the information about all the units of population, the collected informationmay be true. B ut we are never sure about it. W e do not know whether the information is true or iscompletely false. Thus we cannot say anything with confidence about the quality of information. W e say that the reliability is not possible. This is a very important advantage of sampling. Theinference about the population parameters is possible only when the sample data is collectedfrom the selected sample.4.   S ometimes the experiments are done on sample basis. The fertilizers, the seeds and themedicines are initially tested on samples and if found useful, then they are applied onlarge scale. Most of the research work is done on the samples.5.   S ample data is also used to check the accuracy of the census data.
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