The D-frame kick net collections are supplemented with visual collections and, where appropriate, with seines to collect highly-motile invertebrates. Visual collections involve manually collecting large rocks, coarse organic debris, clay from stream marg ns, root wads, and macrophytes or other substrates, and visually locating and removing any associated organisms. This method is particularly useful for collecting firmly attached organisms, such as sponges, and organisms that burrow into hard substrates (Tortopus), plant tissues (Donacia), or sponges (Climacia).
Seining along point bars and islands in mid- to high-order streams is an effective means of collecting larger, highly-motile invertebrates such as many of the amphipods, siphlonurid mayflies, and freshwater prawns. A common minnow seine with 3.2-mm (1/8-in.) mesh can be used for this purpose. Specimens collected using seines and visual methods are placed in an appropriate container and labeled. (See section on Sample Processing and Labeling for details.) Other sampling techniques and equipment, such as Hess samplers (fig. 3B), Surber samplers (fig. 3C), hand screens (fig. 3D), and core samplers (fig. 3E), are used in wadeable habitats as appropriate.
The choice of collection method for QMH samples from nonwadeable habitats depends upon the depth of the water, current velocity, and bed material. For example, grab samplers (grabs), such as Ekman (fig. 3F), Ponar (fig. 3G), or Petersen (fig. 3H) grabs, are suitable for sand or fine gravel substrates in moderate-current conditions and waters of medium depths. Shipek (fig. 3I) and Van Veen (fig. 3J) samplers are useful in extremely deep and fast rivers with sand or fine gravel bottoms (Wells and Demas, 1 979). However, grabs and Shipek samplers do not work well in deep rivers where the bed material is composed of large gravel, cobble, boulder, or bedrock. A diver-operated Dome sampler (fig. 3K) or artificial substrates (fig. 3L, -M, and -N) are required in these situations. Where appropriate, baited traps may also be used to obtain difficult-to-catch organisms, such as crayfish, in large rivers with coarse substrates.
QMH sample collections in large, nonwadeable rivers are distributed among the different instream habitat types and along at least two channel transects. Transect sampling is usually done with appropriate grab samplers or artificial substrates. Samples a recollected at the ends of the transects (near the shoreline), in the middle of the channel, and at points midway between the in-shore and mid-channel samples (total of five samples). Transect sampling is usually combined with the habitat assessment of large, nonwadeable rivers.
Qualitative sampling employs a variety of samplers and techniques, including visual collections of leaves, wood, and rocks. When the collection technique involves using a net, the mesh size of the net must be 210 µm. Samples are elutriated, sieved, and split in the field to reduce the bulk of the composite sample to less than 0.75 L. This processing is done using 212-µm sieves [USA Standard Testing Sieve, American Society for Testing of Materials (ASTM) number 70 or Tyler equivalent 65 mesh]. The composited qualitative sample is placed in an appropriate sample container, preserved in 10-percent formalin, and properly labeled.