In riffle areas, a common sense seine is used to conduct a technique known as "kick seining" (Hendricks and others, 1980; Matthews, 1986; Bramblett and Fausch, 1991). Kick seining is very effective for collecting fish species that live in association with riffles because it involves disturbing the bed material and letting the water current carry specimens into the seine. When kick seining, two persons hold the seine in a vertical position above the water and perpendicular to the flow at the downstream edge of a riffle. They then thrust the poles and lead line of the seine to the stream bottom. The poles are allowed to slant downstream so that the flow forms a slight pocket in the seine. A third person, upstream of the seine, disturbs or kicks the substrate, working downstream toward the seine. This procedure is continued from one shoreline across the width of the channel to the other shoreline so that the entire riffle is sampled. The seine is then lifted out of the water and the fish removed. A sample collected by kick seining is taken at every riffle within the sampling reach. The samples from all riffles are combined, and the fish are processed before release.
In wadeable sampling reaches that are relatively free of obstructions, the bag seine is used. Local fish ecologists should be consulted to assess the length of bag seine that has proven to be the most efficient for sampling the fish community in the st udy unit. Sampling with a bag seine involves sweeping the bag seine through the water, keeping the lead line as close as possible to the stream bottom, and finishing the haul by dragging the bag seine onto the shore. Seining downstream has proven to be the most effective in collecting fish (Hendricks and others, 1980). If the seine cannot be dragged onto shore easily, the bottom ends of the poles can be brought as close to shore as possible. The seine is then quickly stretched between the poles, lifted out of the water, and carried onto shore. Three bag seine hauls are conducted in the sampling reach, each covering an area of about 50 m, and taken from the upper, middle, and lower sections of the sampling reach. The fish from the three seine hauls a recombined and processed before release.
Nonwadeable streams can be sampled using a beach seine in wadeable shoreline areas, if present. As with the bag seine, the exact length of the beach seine should be determined after consultation with local fish ecologists. Beach seining is conducted by maintaining one end of the seine stationary on the shore while the remainder of the seine is deployed into the water so that it is roughly perpendicular to the shore. The seine is then pulled in a downstream direction and hauled through the water in a semi-circular movement. Three beach seine hauls are conducted in the nonwadeable sampling reach, the length of each equaling that of the seine. The three samples should be taken from accessible parts of the upper, lower, and middle sections of the nonwadeable sampling reach. The fish from the three seine hauls are combined and processed before release.
Other sampling methods in wadeable or nonwadeable streams may be necessary to obtain a representative sample of the fish community for NAWQA. In most cases, electrofishing and seining can be conducted in a sampling reach. However, there may be instanc es where these methods may not be effective in producing a representative sample.