202
Exercise 13
such as the modified Hess sampler (Waters and Knapp, 1961) and so-called
pot-samplers (Coleman and Hynes, 1970) represent improvements, but small
(Fig. 13.2) and large emergence traps (Needham, 1908; Sprules, 1947; Munie
1957), covering the entire stream (Illies, 1971; Hall et ai., 1980) (see Fig. 13.3), have
the greatest possible potential for quantitative sampling of the domihant stream
insects that leave the water as flying adults. Some ofthe advantages oflarge emergence
traps are: (1) integration of estimates from heterogeneous habitats; (2) tedious sorting
from debris and sediments is avoided; and (3) most adult stages can be identified to
species. Except for the confounding influence of strong water currents, the general
procedures for sampling and analysis of benthic invertebrates are essentially the same
as those described in Exercise 12. The sampling procedures for stream benthos and
the efficacy of different techniques are discussed in detail by Ide (1940), Macan
(1958), Cummins (1962), Ulfstrand (1967), Radford and Hartland-Rowe (1971), Mason
et ai. (1973), Peckarsky (1984), and Davies (1984).
EXERCISES
OPTION 1.
We shall compare the results of a Surber sampler with those from a sediment core in a rime
and/or a pool area of a stream.
Procedures
1. Collect three samples of sediment to a depth of 15 cm with a coring device in a rime and/or
a pool area of a shallow stream (see Exercises 5 and 12).
2. Sieve the samples with the finest-sized mesh screen that time will permit to remove a major
portion of the sediments. Transfer the remaining sample into strong plastic bags, add 70%
alcohol, and transport to the laboratory.
3. In the laboratory, sort and collect the organisms from the samples [See also Mason and
Yevish (1967).J A comparison of manual-visual sorting to a flotation method on samples
should be made. Empty each sample into a white procelain or plastic pan and sort individual
organisms and debris into small aluminum weighing pans. For samples containing
organisms with case, e.g., caddisfly larvae and snails, the cases or shells must be removed
before weighing or measuring.
4. Identify the organisms to the most specific level possible under the conditions of time and
experience. It should be possible to separate organisms at least according to taxonomic
order. Enumerate the organisms in each category.
5. Determine the biomass of the benthic organisms by dry weight and organic weight analyses.
6. In the same rime and/or pool, if possible, collect five samples using a Surber sampler. The
Surber sampler is designed for shallow flowing streams. Ideally the water depth should be
< 45 cm deep. The sampler consists of a silk or nylon net (approximately 60 cm long)
supported by a folding solid-brass framework having sampling and net inlet areas of
30.5 x 30.5 cm.
The frame should be positioned securely on the substrate. Hold the sampler in position
in the current by applying pressure with one or both knees. Pick up all large stones from
inside the frame area and wash all attached organisms into the net. After the larger stones
have been removed, picked, washed and discarded, the remaining substrate should be
churned gently with the fingers to release all burrowing forms. When finished, pick up the
sampler and allow water to consolidate all of the organisms and debris at the end of the
Exercise 13
such as the modified Hess sampler (Waters and Knapp, 1961) and so-called
pot-samplers (Coleman and Hynes, 1970) represent improvements, but small
(Fig. 13.2) and large emergence traps (Needham, 1908; Sprules, 1947; Munie
1957), covering the entire stream (Illies, 1971; Hall et ai., 1980) (see Fig. 13.3), have
the greatest possible potential for quantitative sampling of the domihant stream
insects that leave the water as flying adults. Some ofthe advantages oflarge emergence
traps are: (1) integration of estimates from heterogeneous habitats; (2) tedious sorting
from debris and sediments is avoided; and (3) most adult stages can be identified to
species. Except for the confounding influence of strong water currents, the general
procedures for sampling and analysis of benthic invertebrates are essentially the same
as those described in Exercise 12. The sampling procedures for stream benthos and
the efficacy of different techniques are discussed in detail by Ide (1940), Macan
(1958), Cummins (1962), Ulfstrand (1967), Radford and Hartland-Rowe (1971), Mason
et ai. (1973), Peckarsky (1984), and Davies (1984).
EXERCISES
OPTION 1.
We shall compare the results of a Surber sampler with those from a sediment core in a rime
and/or a pool area of a stream.
Procedures
1. Collect three samples of sediment to a depth of 15 cm with a coring device in a rime and/or
a pool area of a shallow stream (see Exercises 5 and 12).
2. Sieve the samples with the finest-sized mesh screen that time will permit to remove a major
portion of the sediments. Transfer the remaining sample into strong plastic bags, add 70%
alcohol, and transport to the laboratory.
3. In the laboratory, sort and collect the organisms from the samples [See also Mason and
Yevish (1967).J A comparison of manual-visual sorting to a flotation method on samples
should be made. Empty each sample into a white procelain or plastic pan and sort individual
organisms and debris into small aluminum weighing pans. For samples containing
organisms with case, e.g., caddisfly larvae and snails, the cases or shells must be removed
before weighing or measuring.
4. Identify the organisms to the most specific level possible under the conditions of time and
experience. It should be possible to separate organisms at least according to taxonomic
order. Enumerate the organisms in each category.
5. Determine the biomass of the benthic organisms by dry weight and organic weight analyses.
6. In the same rime and/or pool, if possible, collect five samples using a Surber sampler. The
Surber sampler is designed for shallow flowing streams. Ideally the water depth should be
< 45 cm deep. The sampler consists of a silk or nylon net (approximately 60 cm long)
supported by a folding solid-brass framework having sampling and net inlet areas of
30.5 x 30.5 cm.
The frame should be positioned securely on the substrate. Hold the sampler in position
in the current by applying pressure with one or both knees. Pick up all large stones from
inside the frame area and wash all attached organisms into the net. After the larger stones
have been removed, picked, washed and discarded, the remaining substrate should be
churned gently with the fingers to release all burrowing forms. When finished, pick up the
sampler and allow water to consolidate all of the organisms and debris at the end of the