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be used when the macrophytes are too tall to allow use of a dredge. The macrophytes that are removed should be inspected carefully for attached invertebrates and for invertebrates that burrow into stems.

Field Sampling Activities

Benthic invertebrate sampling, algal sampling, habitat assessment, and measurements of water-chemistry and physical properties, such as discharge, nutrients, dissolved-oxygen concentration, conductivity, and pH, are activities that are typically carried out on visits to a basic fixed site. Consequently, there must be close coordination among sampling teams to minimize interference while keeping the time spent at a site to a minimum. Once on site, the habitat crew establishes the beginning and ending points of the sampling reach(es) and conducts riparian and flood-plain characterizations while the algal and invertebrate teams cooperatively collect samples. Alternatively, the habitat crew can establish the sampling reach(es) and conduct all or part of the riparian and flood-plain characterization procedures on one or more prior visits to the sampling site. This approach greatly facilitates the efficiency of the ecological survey sampling. Upstream disturbance is minimized during sample collection by be ginning with the most downstream sampling location and progressing upstream. When collections are made at sites with multiple sampling reaches, all sampling activities are completed within a sampling reach before proceeding to the next reach.

The combined invertebrate and algal sampling teams start by identifying the locations of appropriate instream habitat types for the semi-quantitative (RTH and DTH) and qualitative (QMH) sampling of invertebrates and algae. When the appropriate habitat type for RTH sampling can be determined in advance (through literature review or input from local biologists), then RTH samples are collected first followed by DTH and QMH samples. If the appropriate habitat type for RTH sampling cannot be determined in advance (for example, in many large rivers), then the QMH samples are collected first and the appropriate RTH and DTH instream habitat types are identified based on the QMH sampling. If fish are to be collected at the same site, fish sampling is done after all invertebrate samples are collected to avoid disturbing the site.

Care must be exercised to ensure that sampling sites are typical of the chosen instream habitat type within the sample reach--that is, reasonably similar with respect to substrate type, current velocity, depth, and debris accumulation. Sites below upstream obstructions and along the edges of adjacent instream habitats are avoided. A minimum of five samples, apportioned within and among examples of the targeted instream habitat type, are composited into a single RTH or DTH sample. Examples of the target ed habitat type are collected from across the length and width of the sampling reach.

A hypothetical example of semi-quantitative samples collected from a sampling reach consisting of a sequence of alternating pools and riffles is illustrated in figure 6. In this example, six samples are collected with a Hess sampler from each of the two riffles (total area sampled is 0.51 m2), and six samples are collected from the two pools using a petite Ponar sampler (total area sampled is 0.14 m2). The samples from each habitat are