| Affiliation: | (1) Department of Fish and Wildlife Resources, University of Idaho, Moscow, Idaho 83844-1136, USA;(2) Tiller Ranger District, U.S. Forest Service, Tiller, Oregon 97484, USA;(3) Present address: National Marine Fisheries Service, 2900 NW Stewart Parkway, Roseburg, Oregon 97232, USA;(4) Present address: Forest Sciences Laboratory, U.S. Forest Service, 860 North, 1200 East, Logan, UT 84321, USA |
| Abstract: | The effect of electroshocking and walking on the substrate on macroinvertebrate drift was evaluated in three streams located in southwestern Oregon, USA. A randomized block experimental design was used to determine treatment (electroshocking and walking, electroshocking-only, walking-only) and drift distance effects on the number, biomass, and length of macroinvertebrates drifting up to 30 m downstream. In all streams, electroshocking caused significantly (p < 0.05) greater number of macroinvertebrates to drift compared to merely walking on the substrate. The differences among treatments decreased the farther downstream the macroinvertebrates drifted. No significant difference (p > 0.05) was observed in mean biomass between electroshocking and walking on the substrate among the drift distances. The longest macroinvertebrates were collected from the electroshocking treatment at the shortest drift distance (2.5 m) in all of the streams. The length of macroinvertebrates collected between electroshocking and walking on the substrate were similar at drift distances of 10 m and greater and represented predominately the smaller, poor swimming taxa. |
