Page 207 - Freshwater-Biology-and-Ecology-Handbook

Drought

Less flow
Less turbulence: smooth flow, stagnant pools
Less surface area between air and water (flow underground)

January May August

3.6 Quantitative sampling

Most quantitative samplers are suitable only for shallow
gravelly riffles. They include Surber samplers and cylinder
samplers in which a known area of substrate is sampled,
to about 5 cm depth, so providing information about the
numbers per unit area of this habitat.
Both are described in Hellawell (1978), together with other
(56)
quantitative devices. In most cases, they cannot provide
an estimate of population size or density because most
invertebrates are not restricted to this particular habitat
(many adult insects are not even aquatic), and because small
juvenile instars may pass through the net.

In deeper waters, artificial substrates (Section 3.1) enable
quantitative sampling of the fouling or benthic community,
particularly SAufU because of their standardised design.

Figure 4.19
Front cover of Magand et al. (2020), a key
reference for assessing and managing
intermittent rivers and ephemeral streams (70)

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