ASTM D4134-82(2012)

4.1.1 It will sample a discrete depth or multiple depths, depending upon the sampling design.

4.1.2 It is a slow to medium speed sampler requiring a towing speed of 3 to 5 knots.

4.1.3 The sample size can be easily controlled.

4.1.4 The sampler is light-weight and can be used without auxiliary equipment.

4.1.5 It has a relatively high filtration efficiency factor of 0.88.

4.1.6 It is a versatile sampler and can be used in all but the shallowest waters.

4.1.7 The flowmeter records the amount of water that passes into the net.

4.1.8 Overspill of water at the mouth of the net due to excess speed of towing is of minimal consequence.

4.2.1 The flowmeter requires frequent maintenance including calibration and lubrication.

4.2.2 It is not suitable for use in very small areas or shallow waters.

4.2.3 Because of the use of a net as a filtration material, the sample is semiquantitative.

4.3.1 The flowmeter should be calibrated and serviced frequently to ensure efficient and accurate operation.

4.3.2 The sampler is relatively fragile, particularly the closing device and flowmeter. This necessitates careful deployment and recovery procedures.

4.3.3 Following each collection, the net must be thoroughly washed.

4.3.4 Special attention must be given to the strength of the cable and its attachment to avoid loss of the sampler.

4.3.5 The sampler should not be used in beds of macrophytes, in waters containing submerged objects, or close to the bottom.

4.3.6 The net should be inspected frequently for pin-size holes, tears, net deterioration, and other anomalies.

4.3.7 Following use, the wet net should be suspended full length in air and in subdued light and allowed to dry.