Page 98 - Freshwater-Biology-and-Ecology-Handbook

CHAPTER 2 7.3 – 7.5 7.3 3-minute sweeping

with long-handled pond
net from deep narrow

rivers

The long-handled pond net is essentially the
same as the FBA-pattern pond net, but it has a
much longer handle, up to 4 m long, usually in
three screw-together sections.

From the bank, reach out into the main channel and sweep
the surface while bringing the net back to you. Rotate the
net before lifting it so that you do not lose any material that
you have collected. Repeat as many times as you can for 3
minutes from different places along both banks.

In silty rivers it is particularly important to ensure good
washing of silty samples. Working upstream may reduce
silt contamination.

Supplement the long-handled pond net sweep of the main
channel with a 1-minute marginal sweep (Section 7.5).
The search will not always be fruitful but must always be Figure 2.8
undertaken.
Long-handled pond net
7.4 3-minute airlift

sampling from deep

wide rivers

Only the Yorkshire-pattern airlift sampler is
appropriate for this procedure.

Figure 2.9 shows different Yorkshire-pattern
airlifts. The aluminium airlift in the centre is a newer,
lightweight version that is easier and safer to use.

Figure 2.9
Airlift samplers. The silver model is a lightweight aluminium version with
low pressure air feed developed for use by the Environment Agency.

98 | Freshwater Biology and Ecology Handbook
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