Comparative Effectiveness of the Standard Surber Sampler and a Hydraulic Modification for Estimating Bottom Fauna Populations

Abstract

FOR MORE THAN 30 YEARS, aquatic biologists have been using the Surber [10] square-foot bottom sampler to obtain qualitative and quantitative measurements of stream bottom fauna. This sampler consists of two brass frames, each 1 foot square, hinged together so that they form a right angle when extended. One frame then fits over the square foot of streambed to be sampled, and the other is provided with a net into which organisms drift as they are dislodged from the streambed. The net generally is constructed from 23-mesh silk or nylon bolting cloth. In practice, the biologist hand stirs the bottom material within the square-foot area to a depth of a few inches. The dislodged organisms then drift into the collecting net. A major disadvantage of this procedure is the time required to obtain a thorough scrubbing of the substrate. A lesser disadvantage, that of the numbing effect on hands and arms after long periods of exposure to cold water, can be partially overcome by full-arm-length rubber gauntlets. Fishery biologists have used hydraulic units for the past several years to sample salmon eggs and preemergent fry in streambed gravels [7]. These samplers consist of a portable centrifugal pump (usually mounted on a packboard or a small raft), a water_ intake hose, and an outlet or exhaust hose, terminating in a 3-foot length of pipe. A jet of mixed air and water, regulated in force by the pump throttle, is controlled by aiming the pipe into the sample area. This water force loosens and stirs up gravel and the associated fish and invertebrate life, which wash down into a collecting net immediately below the sample area. At times, numerous aquatic insects and other bottom organisms have been observed in these egg and fry samples.