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.
3.1 The advantages of using conical tow nets are as follows:
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.
3.3 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.
Species | Fresh | Marine | ||
Habitat | Size Range | Habitat | Size Range | |
Protozoans (single cells) |
| 6 to 1,000 μ |
| −2.0 mm |
Ciliophora (ciliated single cells) | few fresh | 22 to 600 μ |
|
|
Coelenterata | few fresh (Hydras) | <20 mm |
|
|
Ctenophora |
|
|
| 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 |
|
|
Gastrotricha | most fresh (shallow) | 70 μ–615 μ |
|
|
Rotifera | 90 percent fresh | 80 μ–1,500 μ |
|
|
Bryozoa (moss animals) | some fresh; |
| most species encrusting |
|
| statoblasts | 0.4 to >1.0 mm | statoblasts |
|
Chaetognatha (arrowworms) |
|
| high salinity | up to 40 mm |
Annelida (segmented worms) |
|
|
|
|
Oligochaeta | most fresh | 0.5 to 5 mm | very few |
|
Polychaeta | few fresh |
| most spp. small except Nereis | up to 50 cm |
Hirundinea | most fresh (standing | adults 5 mm to 45.7 cm | few marine |
|
| waters) |
|
|
|
Arthropoda |
|
|
|
|
Crustacea |
|
|
|
|
Branchlopoda | most fresh | 3 mm to 30 mm | some marine | 10 mm |
Cladocerans | most fresh | up to 3 mm; 0.2 to 18.0 mm | few marine |
|
Ostracoda |
|
|
|
|
Copepoda |
|
|
|
|
Calenoida |
| nauplius—<4.0 mm |
| 0.5 to 10.0 mm |
Cyclopoida |
| nauplius—<3.0 mm |
| <0.5 to 1.0 mm |
Harpacticoid |
| nauplius—1.0 mm |
| <0.5 to 1.0 m |
Ectoparasites | some fresh | 5 to 25 mm | some estuarine | 5.5 to 25 mm |
Cirripedia |
|
| estuarine/marine:nauplii |
|
Mysidacea | few in cold lakes | 8 to 30 mm |
|
|
Amphipoda | some fresh | 5 to 25 mm |
| 5 to 30 mm |
Decapoda | some associated with debris | 15 to 200 mm |
| 2.0 mm to 20 to 40 cm |
Insecta (aquatic) | most fresh |
|
|
|
Mollusca |
|
|
|
|
Gastropoda |
|
|
|
|
|
| adults <2 to 70 mm |
| 8 to 80 mm trochophore |
Pelecypoda | some fresh | adults 2 to 250 mm | most have free |
|
Echinodermata |
|
|
|
|
Fish eggs/larvae | eggs 0.75 to 3 mm | 400 μ to 505 μ |
|
|
| larvae 1.5 mm |
|
|
|
SDO | ASTM: ASTM International |
Document Number | E1201 |
Publication Date | Dec. 1, 2012 |
Language | en - English |
Page Count | 3 |
Revision Level | 87(2012) |
Supercedes | |
Committee | D19.24 |