Page 97 - Freshwater-Biology-and-Ecology-Handbook

Figure 2.6
Underwater view of kick sampling with net held a short
distance downstream in the silt cloud but far enough away for
The nets used for RIVPACS kick sampling are stones to drop before reaching the net Photo credit: Tim Flood
based on a standard Freshwater Biological
Association (FBA)-pattern pond net.

As mentioned earlier, RIVPACS sampling is based on a 1
mm mesh net. The net is a critical component for sample
standardisation. It collects invertebrates of a sufficient
size for effective laboratory sorting and identification, and
is less prone to blockage than finer meshes which helps
its efficiency in the field. Most other European national
methods use a 500 μm mesh.

The net must be made of soft-woven multifilament polyester.
This is much easier to repair than hard monofilament nylon
nets, which are also difficult to empty. Because the size of
the mesh is critical, the condition of the nets is important and
damaged nets must not be used. Always take spare nets
19 - 22cm
with you when collecting samples.
Nets and frames vary slightly between manufacturers, but
their basic features should not differ from those described
48 - 52cm
below and in Figure 2.7:
• The frame must have a straight lower edge of 20–25 cm 20 - 25cm
and straight, vertical sides of 19–22 cm.
• Use nets which are 50 cm in depth. They are less easily
blocked because of their greater mesh surface. Figure 2.7
• The pond net handle should be about 1.5 metres in length. Standard pond net for invertebrate sampling
• Periodically check that the bottom edge of the frame is
not bent because this reduces its sampling efficiency.
Thin gauge aluminium frames are prone to this type of
damage but are easily straightened.

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