7849 - Laserfiche WebLink

Home Browse Search

As runoff flows decreased, use of the electrofishing john boat throughout the river was progressively limited, and became impossible during the post run-off period. Backwater habitat was reduced in number and depth, and was often unsuitable for large, adult fish. At this time, net sampling was restricted to large pools and eddies. Efficiency of sampling nets was reduced from time to time in these habitats during the baseflow period by the presence of drifting masses of Cladophora, which invariably clogged the net mesh after 30 min or less. Access to the study area river reaches was practical during the late summer and fall portions of the post runoff period only by canoe. Nets would be set in pool and eddy habitats and angling would be used from shore or the canoe to capture fish. Following attempts to capture fish by angling, the canoe and canoe paddle would be used to create noise disturbance in an attempt to move fish into the nets. Seining with various small-mesh seines (3-6 mm) was used in available shallow water habitat and aquatic vegetation throughout a given river reach to determine the presence of young- of-the-year (YOY) gamefish. Angling was used as a supplementary capture technique during periods when boat electrofishing was not possible or netting was ineffective. Data collected at sampling sites included date, time, river mile location to the nearest 0.1 mile, habitat type sampled, presence and location of adjoining habitat types, water temperatures in the habitat sampled and main channel, and presence of potential fish cover and aquatic vegetation. All gamefish species captured were enumerated by gear type and sample location, measured for total length, and weighed. From 1986 through 1989, all northern pike collected and released were tagged by inserting a Floy tag near the base of the dorsal rm. During May and June 1990, northern pike collected at Craig or upstream were processed as above and transported in a live tank equipped with bottled oxygen and airstone to Elkhead Reservoir, located north of state highway 40 midway between Craig and Hayden, Colorado. These northern pike were acclimated to reservoir water temperature for 20-30 minutes and released in the reservoir. Northern pike and smallmouth bass collected downstream of Craig were killed and analyzed for stomach contents, sex and spawning stage. Channel catfish were floy-tagged only in 1987 and 1988 for recapture data. In 1989 and later, stomach samples were taken from channel catfish for food habit analysis. Sex and spawning stage were also determined for channel catfish starting in 1989. In 1991, all gamefish species collected were also measured for mouth gape, including height and width of the mouth opened to its fullest extent. Stomach contents of all gamefish were analyzed for the presence and identity of fish prey. Gamefish stomach contents were removed and examined for identifiable fish prey ingested. Ingested fish were identified to species, counted and measured for total length. Total length was estimated from fish remains if the head and body of the prey were intact. All ingested fish prey requiring confirmation of species identification would be measured, preserved in 10% formalin, and the sample identified by individual northern pike and date and location of capture. These samples were submitted to the Larval Fish Lab for identification, if possible, from the specimen's remains. Other food items were noted and identified by major taxa (Family or Order). 8