ASTM E1201 - 87(2012)

    Standard Practice for Sampling Zooplankton with Conical Tow Nets

    Active Standard ASTM E1201 | Developed by Subcommittee: D19.24

    Book of Standards Volume: 11.02

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    Significance and Use

    3.1 The advantages of using conical tow nets are as follows:

    3.1.1 They are relatively inexpensive and highly versatile in a variety of inland, estuarine, coastal, and marine waters.

    3.1.2 They can be used from a small or large powered boat with a minimum of auxiliary equipment.

    3.1.3 They can be used to collect qualitative samples and semiquantitative samples when fitted with a flowmeter and even better samples when fitted with a companion meter on the outside of the hoop to monitor filtering efficiency.

    3.2 The disadvantages of conical tow nets are as follows:

    3.2.1 When equipped with a flowmeter they require frequent maintenance including calibration and, in some types, lubrication.

    3.2.2 They are effective only where drawn through a stream of water having considerable thickness. They are not suitable for collecting samples from a small or restricted region.

    3.2.3 They are not suitable for collecting in very shallow water.

    3.2.4 They are clogged by grass beds, coelenterates, and filamentous algae.

    3.2.5 When used with a flowmeter, they collect only qualitative samples, or semiquantitative samples.

    3.2.6 When sampling discrete depths using a horizontal tow, the sample can be contaminated from other depths during the deployment and retrieval of the samples if opening and closing devices are not used.

    3.3 There are several special considerations that shall be observed when using conical tow nets. They are:

    3.3.1 Conical tow net samplers are designed to be towed at speeds less than three knots; however, greater speeds have been used for the larger nets with a concomitant increase in capture.2

    3.3.2 A conical tow net 0.5 m in diameter or larger shall be used to reduce avoidance by organisms.2

    3.3.3 The nets shall be washed frequently and inspected for pin-size holes, tears, net deterioration, and other anomalies.

    3.3.4 Nets should be allowed to dry while suspended full length in air and in subdued light prior to storage.

    3.3.5 Lower catches per sample may result when collections are made during the day. These are particularly noted in the larger zooplanktons.

    TABLE 1 Size of Common ZooplanktonA





    Size Range 


    Size Range  

    Protozoans (single cells)


    6 to 1,000 μ


    −2.0 mm

    Ciliophora (ciliated single cells)

    few fresh

    22 to 600 μ




    few fresh (Hydras)

    <20 mm







    10 to 121 mm

    Platyhelminthes (flatworms)


    1 to 30 mm

    inland waters

    0.5 to 40 mm

    Nemertea (Proboscus worms)


    <20 mm

    great variation

    5 mm to 6.5 m

    Nematoda (Round worms)


    <2.3 mm


    7 mm

    Nematomorpha (horsehair

    pools, slow brooks

    10 to 70 cm




    most fresh (shallow)

    70 μ–615 μ




    90 percent fresh

    80 μ–1,500 μ



    Bryozoa (moss animals)

    some fresh;


    most species encrusting




    0.4 to >1.0 mm



    Chaetognatha (arrowworms)



    high salinity

    up to 40 mm

    Annelida (segmented worms)






    most fresh

    0.5 to 5 mm

    very few



    few fresh


    most spp. small except Nereis

    up to 50 cm


    most fresh (standing

    adults 5 mm to 45.7 cm

    few marine


















    most fresh

    3 mm to 30 mm

    some marine

    10 mm


    most fresh
    (lenthic waters)

    up to 3 mm; 0.2 to 18.0 mm
    0.6, 0.3, 0.4 mm; 1.7, 1.0, 0.9 mm

    few marine
    most estuarine/marine
    in top of
    bottom sediment














    nauplius—<4.0 mm


    0.5 to 10.0 mm



    nauplius—<3.0 mm


    <0.5 to 1.0 mm



    nauplius—1.0 mm


    <0.5 to 1.0 m


    some fresh

    5 to 25 mm

    some estuarine

    5.5 to 25 mm







    few in cold lakes

    8 to 30 mm




    some fresh

    5 to 25 mm


    5 to 30 mm


    some associated with debris

    15 to 200 mm


    2.0 mm to 20 to 40 cm

    Insecta (aquatic)

    most fresh
















    adults <2 to 70 mm


    8 to 80 mm trochophore


    some fresh

    adults 2 to 250 mm

    most have free
    swimming larvae







     Fish eggs/larvae

    eggs 0.75 to 3 mm

    400 μ to 505 μ




    larvae 1.5 mm




    A Sage, L. E., “Zooplankton ,” In: Methods for the Assessment and Prediction of Mineral Mining Impacts on Aquatic Communities: A Review and Analysis, Fish Wildlife Service/Office of Biological Services, Vol 78/No. 30, April 1978, pp 55–65.

    1. Scope

    1.1 This practice covers the procedure for obtaining qualitative samples of a zooplankton community by use of conical tow nets. Nets will collect most zooplankton, but some forms will avoid nets.

    1.2 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

    ICS Code

    ICS Number Code 13.060.30 (Sewage water)

    UNSPSC Code

    UNSPSC Code 41104000(Sampling equipment)

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/E1201-87R12

    Citation Format

    ASTM E1201-87(2012), Standard Practice for Sampling Zooplankton with Conical Tow Nets, ASTM International, West Conshohocken, PA, 2012,

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