Skagit System Cooperative, 2003. Estuarine Fish Sampling Methods. Skagit System Cooperative, La Conner, WA. pp. 9.

Small net beach seine methods are used for sampling shallow intertidal shoreline areas of Skagit and Padilla Bays or distributary channel habitat in the Skagit tidal delta and Swinomish Channel. The areas seined are typically less than 4ft deep (1.2m) and have relatively homogeneous habitat features such as: water depth and velocity, substrate, and vegetation. Small net beach seine methodology uses an 80’ (24.4m) by 6’ (1.8m) by 1/8” (0.3cm) mesh knotless nylon net (Figure 1). The net is set in “round haul” fashion by fixing one end of the net on the beach while the other end is deployed by wading the net “upstream” against the water current using a floating tote, and then returning to the shoreline in a ½ circle. Both ends of the net are then retrieved yielding a catch. We typically conduct three sets per site. Large net beach seine methods are used for sampling the intertidal-subtidal fringe of the Skagit and Padilla Bays. These areas are typically deeper than the areas seined by small net beach seine, ranging from 6-15ft (1.8-4.6m) requiring a longer and deeper net. Large net beach seine methodology uses a 120’ (36.6m) by 12’ (3.7m) by 1/8” (0.3cm) mesh knotless nylon net where one end of the net is fixed on the beach while the other end is set by boat across the current at an approximate distance of 60% of the net’s length (Figure 2). After the set has been held open against the tidal current for a period of about 4 minutes, the boat end is brought to the shoreline edge and both ends are retrieved yielding a catch in the net’s bunt section. We typically conduct three sets per site. Fyke trap methods are used for sampling blind tidal channel habitat in the Skagit tidal delta, Swinomish Channel corridor, and southern Padilla Bay. Fyke trap methodology uses nets constructed of 1/8” (0.3cm) mesh knotless nylon with a 2’ (0.6m) by 9’ (2.7m) diameter cone sewn into the net to collect fish draining out of the blind channel site (Figure 3). Overall net dimensions (length and depth) are variable depending on the site’s cross-sectional channel dimensions. All nets are sized to completely block fish access at high tide. The net is set across the blind channel site at high tide and “fished” through the ebb tide yielding a catch. The juvenile chinook catch is adjusted by a trap recovery efficiency (RE) estimate that is derived from mark-recapture experiments using a known number of marked fish released upstream of the trap at high tide. RE is usually related to hydraulic characteristics unique to the site (e.g., change in water surface elevation during trapping, or water surface elevation at the end of trapping). Multiple RE tests (several times per season) at each site are used to develop a regression model to convert the “raw” juvenile chinook catch to an estimated population within the habitat upstream of the fyke trap on any sampling day.