Fish Population Characterization Near the Drop Structure Goals and - PowerPoint PPT Presentation

Fish Population Characterization Near the Drop Structure

Goals and Objectives • Determine the location of the first fish passage barrier downstream of the drop structure • Determine the amount of suitable spawning and rearing habitat for rainbow and cutthroat in the isolated reach • Determine the fish species present in the isolated reach • Determine the population size and age/size structure of all fish species in the isolated reach • Determine upstream migration timing of any species present

Methods • Analysis of Upstream Barrier – Surveying and Photos • Quantification of Spawning and Rearing Habitat – Habitat Characterization (Habitat Typing, Stream widths, Gradients, Substrate Composition, etc.) – Fish Passage Priority Index Calculation • Fisheries Investigations – Electrofishing – Length and Weight Measurements • Determination of Upstream Migration – Netting below the drop structure • Literature Review – Examined potential for injury of fish passing over drop structures during spill events (See Fish Population Characterization Report)

Study Area • A 1464 ft section of Lake Creek from the drop structure downstream to the first identified natural barrier. • This location is consistent with the physical habitat assessment conducted in 2004.

Analysis of Upstream Barrier • A definite barrier was located 1464 ft (RM 5.4) below the drop structure • The barrier was surveyed in conjunction with fisheries investigations on 8/23/06 • The barrier possessed an 11.80 ft fall at a base flow release of 3.5 cfs from the drop structure • The falls exceeds the leaping capabilities of rainbow trout and other resident species potentially present in Lake Creek

Barrier Barrier at RM 5.4

Quantification of Spawning and Rearing Habitat • Three 30 m study sites (SS) were evenly placed and surveyed between the drop structure and the barrier at RM 5.4 • A distinct habitat break existed near Study Site 2 downstream of which, gradients increased from approximately 1.40% to 6.20% • Spawning gravel at all three site comprised less than 5% of the total substrate

Lake Creek Habitat Characteristics Below the Drop Structure

Calculation of Fish Passage Priority Index • After all data was collected, a Habitat Quality Modifier (HQM) was applied to wetted and bankfull width numbers • Total wetted and bankfull width habitat for rearing in the isolated reach was determined to be 395.0 m 2 and 797.6 m 2 respectively • Total wetted and bankfull width habitat for spawning in the isolated reach was determined to be 9.1 m 2 and 19.6 m 2 respectively

Passage Priority Index Calculation of Fish

Calculation of Fish Passage Priority Index (Cont.)

Calculated Priority Indices

Fisheries Investigations • To assure consistency between this study and the Fish Species Distribution and Composition Study, fish presence information was gathered at the 3 study sites concurrent with spawning and rearing habitat measurements in August, 2006 • The entire 1464 ft reach was surveyed for species information on October 17 th and 18 th , 2006.

August 2006 Sampling Period • Two electrofishing passes were made at each study site • A total of 5 rainbow were captured – Three at SS#3 (furthest downstream, just above the barrier) – Two at SS#2 • The fish ranged in length from 40 mm to 140 mm and in weight from 1.0 g to 28.0 g • No other species were observed

August 2006 Fish Sampling Data Fish Population Characterization Below Drop Structure Rainbow Trout Fork Length vs. Weight (August 2006) 30.0 25.0 20.0 eight (g) 15.0 Rainbow Trout W 10.0 5.0 0.0 40 110 120 125 140 Length (mm)

October 2006 Sampling Period • The entire 1464 ft reach was electrofished • Reaches between 150-200 ft were blocked off with nets and two passes were made • A total of 12 rainbow were captured • The fish measured between 70 mm and 165 mm and weighed between 3.7 g and 39.5 g • No other species were observed

October 2006 Fish Sampling Data Fish Population Characterization Below Drop Structure Rainbow Trout Fork Length vs. Weight (October 2006) 45 40 35 30 Weight (g) 25 Rainbow 20 15 10 5 0 70 75 75 80 82 115 123 123 125 127 135 165 Length (mm)

Length vs. Weight Correlation for Rainbow Trout Captured Length vs. Weight Correlation for Rainbow Trout Captured Below the Drop Structure (2006) 45.0 y = 0.0019x 2 - 0.0642x 40.0 R 2 = 0.9699 35.0 30.0 eight (g) 25.0 W 20.0 15.0 10.0 5.0 0.0 0 20 40 60 80 100 120 140 160 180 Length (mm) Rainbow Poly. (Rainbow)

Determination of Upstream Migration Timing • A fyke net was used to capture fish potentially attempting an upstream migration near the drop structure • The net was in place from mid-July through late October, 2006 (Heavy snow and high flows creating overtopping events precluded netting from beginning any earlier) • Only 1 rainbow measuring 220 mm was captured in the net • Multiple overtopping events occurred in May and June 2006 • Many rainbow, (up to 20 at one time), measuring between 200 mm to 300 mm were observed multiple times near the outflow of the fish flow pipe after overtopping had stopped

Fyke Net Location

Work Left To Do • As conditions allow in 2007: – Begin netting below the Drop Structure in February – June – Complete census of fish population in the affected reach in June