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2-6 . Chapter 2 A. Season J o J B. Time of Day Sunset Final Report 1982, U.S. Fish and Wildlife Service 1987, McAda et al. 1994). A Gill nets were 30.5 m long and 1.8 m deep with 3.8 or 5 .1-cm square mesh (100 ft x 6 ft deep, 1.5 or 2-in mesh). Experimental gill nets were also used with four sections of 1.3, 2.5, 3.8, 5.1-cm mesh (0.5, 1, 1.5, and 2-in). Trammel nets were 22,9 m long and 1.8 m deep (75 ft x 6 ft) with three panels of netting--two outer walls of 30.5-cm (l2-in) mesh and one inner panel of 1.3, 2.5, or 3.8-em mesh (0.5, I, or 1.5-in). Gill and trammel nets were made of double knotted #139 multifilament twine with 1.3-cm (0.5-in) diameter braided polyfoamcore float line and 0.8-em (5/16-in) leadcore line. Gill and trammel nets were typically tied to shore, and stretched along the channel bed with net weights anchoring each end of the leadline (Fig. 2-4). Polypropylene mesh bags were filled with rocks and used as net weights. White mooring buoys were tied to the distal end of each net line as marker floats to facilitate relocation and retrieval of nets, and to alert boaters of submerged nets. Nets were also suspended in the water column to sample midwater habitat. Nets were checked at intervals of about 2 hr to minimize stress and reduce mortality of entangled fish. Nets clogged with algae (Cladophora glomerata) or debris were replaced and cleaned regularly. Fig. 2-3. Temporal stratified sampling design for seasons (A) and time of day (8). summer (June-August), and fall (September- November), and by time of day to represent night, dawn, day, and dusk. Since day length and photoperiod varied with season, a computer program (Sun and Moon Events Worksheet, Heizer Software, Inc., Palo Alto, CA) was used to appropriately adjust diel time blocks. FISH SAMPLING METHODS Twenty-four different gear types'or methods were used to sample fish. Descriptions and codes for each type or method are presented in Table 2-2. Gill and Trammel Nets Gill and trammel nets were the primary gear used to sample assemblages of large fish in deep habitats and to capture adult humpback chub for implanting radio transmitters. Nets were used to collect fish for comparing distribution and abundance by area and time, as well as to characterize general adult fish habitat to supplement radiotelemetry data. These types of nets are commonly used to survey and monitor other populations of humpback chub in the Upper Colorado River Basin (Valdez and Clemmer Hoop Nets Hoop nets were used in various shoreline habitats. Three sizes of hoop nets used included 0.6 m x 3.0 m x 1.3-cm (2 ft x 10 ft x 0.5-in), 0.9 m x 4.0 m x 2.5-em (3 ft x 13 ft x I-in), and 1.2 m x 4.9 m x 1.3-cm (4 ft x 16 ft x I-in) (diameter x length x square mesh). Two 7.6-m (25-ft) wings with 2.5- em (I-in) mesh were attached to the opening of the hoop nets. Hoop nets were set by anchoring the rear of the net with a length of rebar and orienting the throat in a downstream direction to capture fish moving upstream (Fig. 2-5). Hoop nets were checked at least every 8 hr to minimize stress and mortality to fish.