CONTENTS Introduction Intensively Monitored Watersheds Smolt/Adult Monitoring Skagit River Lake Washington Green River Deschutes Hood Canal Dungeness Grays Harbor Lower Columbia River Wenatchee River Trapping Gear Publications Data Salmonscape

Trapping Gear [Adult Traps] [Smolt Traps] Adult Traps : Adult traps are associated with such structures as fishways, fish ladders and (permanent or temporary) weirs.  These traps direct the stream flow to attract upstream migrants into holding (impoundment) areas.  Captured fish are enumerated by species and age, sampled for biological information (species, age, sex, and size), and for any external marks (partially-clipped fins, jaw tags, etc).  Migrants are also sampled for coded-wire tags, and a portion is sacrificed for tag recovery to determine their origin (hatchery or wild).  The remaining fish are released upstream from the trap -- either through direct-access chutes, or in holding tanks on a truck that transports them around the barrier -- to allow them to spawn naturally. The adult traps for our study streams are designed to capture all upstream migrants.  These include Big Beef, Bingham, and Elk creeks, the Deschutes and South Fork Skykomish rivers, and Baker Dam, on the Skagit River. Smolt traps: [Fan Traps] [Fence Traps] [Scoop Traps] [Screw Traps] Fan Traps: These are used where WDFW maintains a permanent smolt monitoring station.  Aluminum fan traps are placed into the metal weir supports mounted to a concrete slab weir structure that is oriented perpendicular to the stream flow.  The fans screen water through a 14-gauge perforated plate with folded, V-shaped troughs; wider at the upstream entrance and tapering to a narrower downstream end, they guide juveniles to a live box at the rear of the fan.  Several fan traps are set at different levels so that during low flow, only the lowest trap operates; as stream flow increases, more fans are activated.  A flexible rubber sheet provides a fish-tight seal between the adjustable traps and the stationary weir supports. Stop-logs beneath the fans, within the weir support channels and in all other bays create the elevated pool necessary for trap operation.  The fans must be monitored regularly, but especially maintained during high stream flows, as debris accumulation (e.g. leaves, flower parts, and other flotsam) on the fans impedes water passage.  During freshets, continuous debris removal is necessary to prevent the stream from topping the weir.  Flooding over the weir allows migrants to pass the barrier uncounted, or could damage the fans and the weir itself. We currently use fan traps in the permanent weirs at our Big Beef Creek and Bingham Creek long-term monitoring stations. Fence traps (weir): These temporary barriers span the width of the stream and direct the entire stream flow through a series of screened panels.  A PVC pipe or box flume delivers migrating fish into the live-box located downstream of the weir, in a calm pool area that provides sufficient depth to accommodate a large catch. Temporary weirs are generally configured in a “V” or “W”-shape (apex pointing downstream), and designed to capture coho, steelhead and cutthroat smolts.  The fences are constructed with wood-framed screen panels covered with ½ x ½ -inch vinyl-coated steel mesh.  Metal fence posts and galvanized fencing wire hold the screen panels and live-boxes in place.  Woven nylon cloth is placed under the length of the weir to prevent erosion of the streambed.  Gravel bags anchor the sheeting, help support the screen panels, and are used to stabilize the banks around the edges of the weir and around the live-box and flume area. Because these temporary structures are designed and constructed for small streams, wash-outs may occur during high flows.  Panels may be removed to relieve pressure on the weir, and can be easily replaced as the water recedes.  Constant monitoring and removal of accumulated debris is required during high flows.  A reverse weir can be incorporated into the structure to allow the passage of fish migrating upstream. Scoop trap: The floating inclined-plane screen trap, commonly called a “scoop trap,” was developed by the Department of Fish and Wildlife to collect downstream migrants in large rivers.  Its adjustable inclined-screen “scoop” permits trapping a range of stream velocities and depths, and is especially efficient in streams with high flows.  The screen section is constructed of ¼-inch galvanized woven-wire mesh riveted to an angle iron frame, and measures 18-ft long, with an upstream opening of 6x6-ft.  The screen is suspended inside a pontoon barge from support winches at the corners of the fore and aft decks.  Winches mounted at the front of each pontoon run anchor lines out through blocks that are secured to large stationary structures on shore. When the trap is lowered into the current, downstream migrants are swept up the screen incline and are deposited into a protected live box at the back.  Water velocity through the trap must exceed migrant swimming speed: swimming ability is directly related to body length; thus, higher velocities are required to trap large migrants.  Trapping the larger migrants, such as steelhead smolts (up to 250 mm), requires more than 6 fps; fry (under 50 mm fork length) may be captured at relatively low velocities.  At less than optimal velocities, larger migrants may avoid or swim out of the trap.  If velocities into the trap are excessive, the screens require more frequent cleaning, because of the greater volume of water being strained.  As the screen accumulates debris, its ability to pass water decreases and the depth and velocity over the incline increases, causing turbulence in the holding chamber.  Debris load is affected by stream bank vegetation, weather (rain and wind transport debris into the river) and, most importantly, river discharge.  Trap operation through a freshet requires that the screens are carefully monitored and constantly cleaned and that the catch is regularly removed from the live-box and processed.  Trap position may be adjusted as stream flows change to maintain trap efficiency without stressing captured migrants. We currently use scoop traps in the Skagit and Chehalis Rivers, and for fry trapping on the Cedar River and Big Bear Creek.  We also used scoop traps on the SF Skykomish River for 9 years, and for the first 13 years of trapping in the Deschutes River. Screw Trap: The floating “screw” trap was patented by an Oregon company, E.G. Solutions.  This gear functions in lower velocities, and traps fish using the stream flow to power an auger that gently forces migrants into a live box at the rear of the trap.  Two tapered flights, wrapped 360-degrees around a shaft form the basic trap.  These flights are housed inside a perforated plate-covered cone-shaped frame.  The shaft is aligned with the flow and is lowered to the water’s surface via davits and winches mounted on two pontoons.  Water current acting on the flights causes the trap to rotate.  With every 180-degrees of rotation, a flight enters the water while the other emerges.  As the leading edge of a flight emerges from the water, it prevents the escape of migrants that have entered the trap.  A small “trash” drum screen located at the rear of the live-box removes organic debris. We currently use screw traps on the Skagit, Green, and Deschutes Rivers, at Cedar River and Big Bear Creek, and in three lower Columbia River tributaries.