IDAHO COOPERATIVE FISH AND WILDLIFE RESEARCH UNIT

Transcription

1 Technical Report 99-2 IDAHO COOPERATIVE FISH AND WILDLIFE RESEARCH UNIT DISTRIBUTION AND MOVEMENTS OF NORTHERN PIKEMINNOW AND SMALLMOUTH BASS DURING OPERATION OF A SURFACE- BYPASS AND COLLECTION SYSTEM FOR JUVENILE SALMONIDS AT LOWER GRANITE DAM, by T.C. Bjornn and R.M. Piaskowski U.S. Geological Survey Idaho Cooperative Fish and Wildlife Research Unit University of Idaho, Moscow, ID

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3 Technical Report 99-2 DISTRIBUTION AND MOVEMENTS OF NORTHERN PIKEMINNOW AND SMALLMOUTH BASS DURING OPERATION OF A SURFACE-BYPASS AND COLLECTION SYSTEM FOR JUVENILE SALMONIDS AT LOWER GRANITE DAM, Prepared by: T.C. Bjornn and R.M. Piaskowski U.S. Geological Survey Idaho Cooperative Fish and Wildlife Research Unit University of Idaho, Moscow, ID for U.S. Army Corps of Engineers Walla Walla District 999

4 Table of Contents Abstract...iii Introduction... Study Area...4 Methods...7 Fish Collection... 7 Surgical Implantation of Radio Transmitter... 8 Fixed-Site Receiver Monitoring... 9 Distribution Surveys in the Tailrace and Forebay... Diel Activity of Northern Pikeminnow... 5 Distribution of Northern Pikeminnow in Little Goose Reservoir... 5 Results...5 Fish in Surface-Bypass and Collection System... 5 Distribution of Northern Pikeminnow in the Forebay... 6 Distribution of Northern Pikeminnow in the Tailrace... 7 Diel Activity of Northern Pikeminnow Distribution of Northern Pikeminnow in Little Goose Reservoir Distribution of Smallmouth Bass in the Forebay Distribution of Smallmouth Bass in the Tailrace Discussion References Appendix A Appendix B ii

5 Abstract Radio telemetry was used to monitor the distribution and movements of 67 adult northern pikeminnows Ptychocheilus oregonensis and 3 adult smallmouth bass Micropterus dolomieui near Lower Granite Dam to evaluate the potential for increased predation on juvenile salmonids during operation of a prototype surface bypass and collector (SBC) from April to September 996 and 997. Four northern pikeminnow monitored in the forebay in 996, and 7 northern pikeminnow and 6 smallmouth bass monitored in 997 consistently inhabited nearshore areas. In early June 996, all four radio-tagged northern pikeminnow released in the forebay left the survey area; two were caught by anglers 49 km and 94 km upstream from Lower Granite Dam in late June and July. Upstream movement from the forebay and downstream from the tailrace was also observed in some smallmouth bass (maximum upstream movement 97 km, downstream 39 km). The reasons for the movement were not determined. In the tailrace, the distribution of northern pikeminnow was limited to shorelines and protected low velocity areas during the spring runoff when there was continuous spill. Some individuals temporarily moved downstream of the tailrace during periods of peak river discharge and spill. Northern pikeminnow moved into the spillway stilling basin and downstream from the turbines when river flows decreased and there was no spill. The shift in distribution may have been related to spawning behavior or changes in metabolism and foraging opportunity. Northern pikeminnow numbers decreased in the tailrace in late summer as fish migrated into the reservoir, perhaps to overwintering areas. Activity of northern pikeminnow peaked after dawn and again during the evening, based on hourly monitoring of individuals during consecutive 24-h periods. Light levels during crepuscular and nighttime periods may be advantageous for foraging northern pikeminnow and daily peaks in salmon smolt numbers occur from about 800 to 0500 hours. Losses of juvenile salmonids to predation by northern pikeminnow and smallmouth bass vary seasonally and depend on river conditions. The potential for predation on iii

6 juvenile salmonids by northern pikeminnow in close proximity to the SBC in the forebay, or by smallmouth bass in either the forebay or tailrace, is not very high because of small numbers of predators and they did not congregate near the SBC. Predation would most likely occur when juvenile salmonids move close to shorelines of Little Goose and Lower Granite reservoirs. In the tailrace, predation by northern pikeminnow on juvenile salmonids could be significant if river flows are low and there is little or no spill when juvenile salmonids are passing through the SBC and over spillbay. iv

7 Introduction The U.S. Army Corps of Engineers (COE) installed a prototype surface bypass and collector (SBC) at Lower Granite Dam in winter 996 to evaluate surface bypass and collection as a means to improve juvenile salmonid (Oncorhynchus spp.) passage and survival at mainstem Columbia and Snake river dams. The SBC was located in the forebay in front of powerhouse turbines 4, 5, and 6 with discharge from the SBC through spillbay (Figure ). National Marine Fisheries Service recently directed the COE to investigate surface bypass and collection as part of Snake River salmon recovery efforts (NMFS 995). The Northwest Power Planning Council has also encouraged the COE to study new means of bypassing fish at dams, including surface bypass systems (NPPC 994). Although improvement of juvenile salmonid passage and survival at dams is the goal of using surface collection and bypass, there was a concern that losses of juvenile salmonids to predation may increase during operation of the SBC. If large numbers of juvenile salmonids use the SBC at Lower Granite Dam, predatory fish may be attracted to areas where juvenile salmonids become concentrated near the SBC in the forebay and downstream from spillbay in the tailrace. Northern pikeminnow Ptychocheilus oregonensis (formerly northern squawfish) are recognized as potential predators of juvenile salmonids (Ricker 94). In John Day Reservoir, northern pikeminnow were responsible for 78% of the total loss of juvenile salmonids to predation (Rieman et al. 99). Northern pikeminnow abundance has increased with construction of reservoirs in the Columbia River basin. The highest concentrations of northern pikeminnow have been found in tailraces of lower and middle Columbia River reservoirs, and in lower Snake River reservoirs (Rieman et al. 99; Ward et al. 995). A disproportionately high amount (26%) of northern pikeminnow predation in John Day Reservoir was found to occur in the tailrace of McNary Dam (Rieman et al. 99).

8 N Spillbay SBC Powerhouse = SBC fish entrance Snake River Lower Granite Dam Flow Scale in meters Figure. Location of surface bypass and collector (SBC) in the forebay of Lower Granite Dam. 2

9 Northern pikeminnow appear to respond to changes in salmonid density. Higher rates of predation by northern pikeminnow on juvenile salmonids (as suggested by a higher mean number of salmonids per gut) was observed following releases of juvenile salmonids from Dworshak National Fish Hatchery, Clearwater River, Idaho (Shively et al. 996a). Switching by northern pikeminnow from other prey to juvenile salmonids has been documented in areas below dams and at hatchery release sites when juvenile salmonid densities were high (Thompson 959; Thompson and Tuffs 967; Vigg 988; Collis et al. 995). Smallmouth bass Micropterus dolomieui may also be an important predator of juvenile salmonids. Although salmonids were relatively unimportant in the diet of smallmouth bass in the lower Columbia and Snake rivers (Keating 970; Poe et al. 99), smallmouth bass may be a major predator of juvenile salmonids in some situations (Tabor et al. 993). In reservoirs of the lower Columbia and Snake rivers, smallmouth bass density was found to be highest in forebay and mid reservoir reaches (Beamesderfer and Rieman 99; Zimmerman and Parker 995), and most abundant in the Lower Granite forebay (Zimmerman and Parker 995). To evaluate the potential for increased predation on juvenile salmonids during operation of the SBC, our study objectives were to:. Monitor the distribution of northern pikeminnow (996 and 997) and smallmouth bass (997) near Lower Granite Dam during the juvenile salmonid migration season, and during operation of the SBC. 2. Monitor movements of individual radio-tagged northern pikeminnow (996 and 997) in the tailrace of Lower Granite Dam and relate these movements to juvenile salmonid migration and operation of the SBC. 3

10 Study Area Lower Granite Dam was put into operation in 975 as the last of four dams in the lower Snake River. Lower Granite Dam, located at river kilometer (rkm) 73 in the lower Snake River in southeastern Washington, is the first dam encountered by most seaward-migrating juvenile salmonids from the Snake River basin (Figure 2). Lower Granite Dam has a powerhouse on the south shore, a spillway in the center, a navigation lock, and an embankment on the north end. Lower Granite Reservoir is 63 km long, has an average depth of 6.6 m, and a surface area of 3,603 ha. The Clearwater River enters into Lower Granite Reservoir at the upstream end at Lewiston, Idaho. We defined the Lower Granite forebay as the area extending 4 km upstream from Lower Granite Dam. Water velocities in the forebay are relatively low, but they increase near the turbine intakes, and spillway when water is spilled. The forebay is relatively wide (60 m) and deep (35 m) near the dam at a reservoir operating level of 223 m above mean sea level. Little Goose Reservoir, downstream from Lower Granite Dam, was created with the completion of Little Goose Dam in 97. Little Goose Reservoir is 59.9 km long, has an average width of 0.5 km, an average depth of 7. m, and a surface area of 3,887 ha. Water temperatures range annually from 4 to 23 o C. No major tributaries enter the reservoir. The upper end of Little Goose Reservoir extends to the tailrace of Lower Granite Dam. Water velocities in the tailrace vary widely depending on river flow, spill discharge, turbine discharge, and position within the tailrace (Isaak 994, unpublished data). Lock discharges produce upwellings of water near the southwest corner of the lock. North of the lock and at the southeast corner of the lock are areas of low velocity water, protected from main channel flows and discharges from the lock, spillway, and powerhouse. During spring and summer 996, river discharge ranged from 32 to 202 kcfs (896 to 5656 m 3 /s), spill discharge from 0 to 0 kcfs (0 to 3080 m 3 /s), and water temperature from 7 to 22 o C. During spring and summer 997, river discharge ranged 4

11 from 29 to 220 kcfs (82 to 660 m 3 /s), spill discharge from 0 to 4 kcfs (0 to 392 m 3 /s), and water temperature from 7.5 to 20.5 o C (Figure 3). Columbia River Snake River Clearwater River Salmon River Lower Granite Dam Spillway Lock Powerhouse Flow Scale in meters Figure 2. Study area and location of Lower Granite Dam on the lower Snake River in southeastern Washington. Study area extended from the forebay of Lower Granite Dam to the forebay of Little Goose Dam. 5

12 River flow and spill (kcfs) Temperature (C), outflow, and spill (m3/s/00) Apr -May -Jun -Jul -Aug -Sep River flow Spill Water temperature (C) Figure 3. River flow, water temperature, and spill at Lower Granite Dam during spring and summer 996 and

13 Three species of anadromous salmonids migrate past Lower Granite Dam: steelhead O. mykiss, chinook salmon O. tschawytscha, and sockeye salmon O. nerka. Steelhead, sockeye salmon, and spring and summer runs of chinook salmon migrate seaward in April, May, and June. Fall chinook salmon migrate seaward in June, July, and August. Prior to 996, seaward migrating juvenile salmonids could pass Lower Granite Dam over the spillway and through the powerhouse. Screens in the powerhouse turbine intakes diverted 40-70% of the smolts into the bypass system when there was no spill (Swan et al. 990). During 996 and 997, juvenile salmonids were also diverted past the dam and into the tailrace through the SBC. The SBC extended from the water surface down 8 m, and was 6 m wide and 00 m long. Fish could enter through three entrances (each 5 m wide x 5 m high) along the upstream face of the SBC, travel northward in front of the powerhouse, and then be spilled over spillbay into the tailrace (Figure ). Methods Radio telemetry was used to monitor the distribution and movements of northern pikeminnow and smallmouth bass during the outmigration of juvenile salmonids, and during operation of the SBC. Fish Collection A total of 70 adult northern pikeminnow and 3 smallmouth bass were collected during 996 and 997 by electrofishing and angling. Collection efforts were limited to the tailrace area, 4.5 km downstream from Lower Granite Dam, and the forebay area, 4.5 km upstream from Lower Granite Dam to avoid recapture of fish we tagged that were migrating to original habitats outside of the study area. Electrofishing, parallel to shore, occurred from April through June during 996 and 997 with a 6 m-long shocking boat. One person operated the electrofishing boat while two people netted fish from the bow. Of the 70 northern pikeminnow collected, 5 were captured in the forebay in 996, and 44 and 2 were captured in the tailrace during 996 and 997, respectively. No 7

14 northern pikeminnow >30 mm were collected in the forebay during 997. Of the 3 smallmouth bass collected in 997, 7 were captured in the forebay and 6 in the tailrace. Twenty-six northern pikeminnow collected by electrofishing in 996 were outfitted with radio transmitters. Transmitters were placed in 7 pikeminnow and 9 smallmouth bass collected by electrofishing in 997. In late June 996, 9 northern pikeminnow were obtained from a private angler operating a down-rigger with hook-and-line equipment in the tailrace and fishing primarily near the downstream end of the south guide wall to the navigation lock. The angler kept the northern pikeminnow in an aerated livewell until they were removed for measurements and transmitter implantation. In 997, four smallmouth bass were caught by angling, outfitted with transmitters, and released in the forebay of Lower Granite Dam. One northern pikeminnow in 996 and three in 997 were captured in the adult trap at the fish ladder, outfitted with transmitters, and released into the tailrace. Surgical Implantation of Radio Transmitter Radio transmitters were implanted in 67 northern pikeminnow (total lengths in 996 ranged from 274 to 545 mm, mean 400 mm; in 997 they ranged from 372 to 539 mm, mean 465 mm) and 3 smallmouth bass (total lengths ranged from 34 to 480 mm, mean 367 mm; Appendix A). Surgical implantation of the transmitter followed a technique reported by Isaak and Bjornn (996b). Fish were held for 6-2 h to allow recovery from collection stress and to insure good condition prior to implantation of transmitters. Northern pikeminnow or smallmouth bass were initially anesthetized individually in 30 mg/l or 00 mg/l solutions of tricaine methanesulfonate and river water. Once anesthetized, a fish was placed in dorsal recumbency on a u-shaped board covered with foam and lined with wetted towels. During surgery, gills of the fish were continuously irrigated with an anesthetic solution of tricaine methanesulfonate and river water of 00 mg/l for northern pikeminnow and 80 mg/l for smallmouth bass. The solution was pumped from a 5-L recirculating reservoir. 8

15 A 3-cm incision was made along the ventral midline, midway between the gill opercals and anus (anterior to the pelvic girdle in northern pikeminnow; Figure 4-A). A 6-gauge needle was then inserted 3 to 5 cm posterior to the incision (between the pelvic girdle and anus in northern pikeminnow) to allow the transmitter antenna to exit from a point separate from the abdominal incision (Figure 4-B). The needle was pushed anteriorally, with the needle tip guided by a nasal speculum, until the point exited the abdominal incision. The transmitter antenna was then threaded through the needle from cranial to caudal until it exited the posterior end of the needle (Figure 4-C). The needle was removed and the transmitter body was then placed into the abdominal cavity, round-end first, and positioned in line with the incision (Figure 4-D). Finally, a single layer closure using absorbable sutures (synthetic 3.0 metric coated Vicryl, Ethicon, Inc.) in a simple interrupted pattern was performed to close the incision (Figure 4-E). Transmitters were 0.9 x 43 mm, had an antenna length of 44 cm, weighed 3.5 g in water, and had an expected battery life of 80 days (Lotek Engineering, Ontario, Canada; part number MCFT-3MB). After transmitter implantation, a fish was placed in a 9-L livewell containing river water and was visually monitored until recovered from anesthesia (approximately 0-20 min). The fish was then released as close as possible to the point of collection (Figure 5). Transmitter channel and code, fish length (fork and total lengths), time anesthetized, beginning and ending time of surgery, and release date, time, and location were recorded for each fish outfitted with a radio transmitter. Fixed-Site Receiver Monitoring To provide continuous coverage for radio-tagged northern pikeminnow within the SBC during spring 996, six underwater coaxial antennas were installed 6 m down, midchannel within the SBC, and connected to a Lotek SRX-400 radio-telemetry 9

16 A ventral midline incision B needle C transmitter D E absorbable sutures whip antenna Figure 4. Technique for surgically implanting radio transmitters intraperitoneally in northern pikeminnow and smallmouth bass. Diagram depicts technique as applied to northern pikeminnow. 0

17 Boyer Marina N Scale in meters Flow = Radio-tagged squawfish release locations = Radio-tagged smallmouth bass release locations Offield Ldg Figure 5. Release locations of radio-tagged northern pikeminnow and smallmouth bass near Lower Granite Dam during 996 and 997. Releases were made as close as possible to points of collection. receiver. A 9-kg lead weight was attached to the underwater end to hold the antenna in position inside the SBC. When a radio-tagged northern pikeminnow was within 6 m of one of the SBC underwater antenna ends, the receiver recorded the transmitter channel and code, time, date, and signal strength of each transmitter broadcast. Distribution Surveys in the Tailrace and Forebay To observe the distribution of radio-tagged northern pikeminnow and smallmouth bass in the tailrace and forebay, surveys were conducted from Lower Granite Dam (rkm 73) downstream to Boyer Marina (rkm 70.3), and from the dam upstream to rkm 76. When there was no spill, we used a 6 m-long jet boat and a 4 m-long open flatbottom boat, each equipped with a radio-telemetry receiver (part number SRX-400, Lotek Engineering, Ontario, Canada) and a six-element yagi antenna (part number PLC-6, Cushcraft Corp., Manchester, New Hampshire), to search for fish with transmitters. During surveys by boat, we covered a continuous route along shorelines, dam structures, and through midchannel areas near the dam (Figure 6). Locations of tagged fish were determined during boat surveys by following the axis of maximum transmitter signal strength and reducing the gain on approach to the fish. Once the signal had

18 Lower Granite Dam N Flow Scale in meters Figure 6. Area covered by boat during radio-telemetry surveys to locate radiotagged northern pikeminnow and smallmouth bass near Lower Granite Dam in 996 and 997. Lower Granite Dam Scale in meters Figure 7. Division of the Lower Granite Dam tailrace into cells for analysis of radiotagged northern pikeminnow and smallmouth bass observations. 2

19 been crossed or was determined to be between the boat and a fixed structure, the location was noted on a map and also assigned to one of eight habitat cells (Figure 7). The accuracy of the locating method by boat was tested using a Lotek SRX-400 radiotelemetry receiver and an underwater coaxial antenna (reception range radius about 6 m) deployed from the boat. We did not enter the boat restricted zone (BRZ) at Lower Granite Dam tailrace when there was high spill because it was unsafe. During such times, surveys were completed from the dam and along the shorelines at several predetermined locations with a radiotelemetry receiver and a three-element hand-held yagi antenna. Locations of fish obtained from shore or from dam structures in the tailrace were estimated by recording the axis of maximum signal strength from several directions while standing at the predetermined shore stations. Locations were then assigned to one of the eight habitat cells, as with surveys by boat (Figure 7). During boat and shore surveys, we attempted to locate all radio-tagged northern pikeminnow and smallmouth bass within the study area. In the forebay, surveys were conducted one to three times per week during daylight hours (Table ). In the tailrace, to observe the diel distribution of northern pikeminnow and smallmouth bass, surveys were conducted two to three times per week during four consecutive time intervals (morning: hours, day: hours, evening: hours, and night: hours; Table ). Point location, habitat cell code, date, time, transmitter channel, and individual transmitter codes were recorded each time a fish was located. For statistical analysis of northern pikeminnow tailrace distribution data, fish locations were assigned to one of three habitat cells (Figure 8). Cell boundaries were based largely on prevailing river flow characteristics. Chi-square (χ 2 ) goodness of fit tests (α < 0.05) were used to test the null hypothesis that there was no difference in distribution by habitat cells of northern pikeminnow in Lower Granite Dam tailrace with or without spill. To meet the assumption of independence, goodness of fit tests were 3

20 performed separately for 996 and 997, and separately for morning, day, evening, and night survey periods. Table. Number and date range of northern pikeminnow and smallmouth bass distribution surveys conducted in the forebay and tailrace of Lower Granite Dam during 996 and 997. Tailrace Forebay Number of surveys Morning Day Evening Night Total Dates of surveys 2 May-30 Jul 8 Apr-5 Aug 0 May-3 May Jun-24 Jul Lower Granite Dam Scale in meters Figure 8. Cell boundaries used to partition northern pikeminnow observations in Lower Granite Dam tailrace for statistical analysis. 4

21 Diel Activity of Northern Pikeminnow Twenty-four-hour surveys were conducted by boat to observe individual northern pikeminnow activity patterns near Lower Granite Dam. Five or more randomly selected radio-tagged northern pikeminnow were relocated hourly in the tailrace during 24-hour periods. Method of location was conducted as described for distribution surveys. Movement rates based on northern pikeminnow diel activity were calculated by dividing the straight-line distance between two consecutive locations by the intervening time interval for consecutive locations with an intervening time interval of <90 min. Each movement rate was assigned to the nearest even hour within a 24-h day and to one of three spill categories (24-h/d spill, 2-h/d spill, or no spill). Data lacked normality and were transformed by ranking simultaneously. Ranked data were analyzed by conducting one-way ANOVA s on 996 and 997 data sets separately. A posteriori pairwise multiple comparisons were conducted using Tukey s HSD. Distribution of Northern Pikeminnow in Little Goose Reservoir In 996 and 997, movements of radio-tagged northern pikeminnow were observed by boat along the shoreline from Lower Granite Dam (rkm 73) downstream to Central Ferry (rkm 33). The method of location is described above for distribution surveys. Location, date, time, transmitter channel, and transmitter code were recorded for each fish found. Distributions were compared by assigning point locations of northern pikeminnow to the tailrace, upper third, and middle third of Little Goose Reservoir. Results Fish in Surface-Bypass and Collection System During the April through June 996 period of operation, two of four radio-tagged northern pikeminnow released in the forebay of the dam were recorded inside or within 3 m of the SBC in May. Northern pikeminnow 32-7 was recorded on 2 different days between 6 May and 2 June. Northern pikeminnow 33-5 was recorded on two different 5

22 days between 7 May and 0 May. Based on receiver records, northern pikeminnow were in the SBC mostly during late night and early morning hours. Distribution of Northern Pikeminnow in the Forebay The four different radio-tagged northern pikeminnow released in the forebay were observed 4 times in the forebay, primarily along the north and south shorelines, of Lower Granite Dam between 0 May and 3 May 996 (Figure 9). Two northern pikeminnow were recorded six times about 00 m south of the SBC during daylight. The other two northern pikeminnow were not located near the powerhouse or spillway. N Flow Offield Ldg Fish channel-code Release date May May 5 May 5 May Date last located in forebay 3 May 6 May 22 May 22 May Figure 9. Locations of radio-tagged northern pikeminnow in the forebay of Lower Granite Dam during May 996. In early June, all four radio-tagged northern pikeminnow released in the forebay left the survey area or moved to depths outside of radio reception (>0 m). Two of the radio-tagged northern pikeminnow were later caught by anglers 49 km and 94 km upstream from Lower Granite Dam: 26 June at Clarkston (rkm 224.2) and 4 July from the Snake River downstream from Beamers Landing (rkm ). A third northern 6

23 pikeminnow passed downstream through the Lower Granite Dam juvenile fish bypass system on 2 June, as determined from fixed-site telemetry equipment operating within the powerhouse fish gallery and downstream at the bypass facility. Distribution of Northern Pikeminnow in the Tailrace Sixty-two northern pikeminnow released in the tailrace were observed a total of,677 and 824 times during spill and no-spill periods in the Lower Granite Dam tailrace during 996 and 997. During both years, northern pikeminnow were found mostly in areas with low water velocity. No diel usage pattern in the tailrace was evident. When spill occurred, northern pikeminnow were observed almost exclusively in areas of quiet water north and south of the navigation lock (cell ; Figures 0 and ). Conversely, when there was no spill, with the exception of during the morning in 997, northern pikeminnow were observed more frequently in cell 2 than in cells and 3 (Figures 0 and ). The null hypothesis that there was no difference in northern pikeminnow distribution among cells with and without spill was rejected, based on separate analysis of morning, day, evening, and nighttime data sets for 996 and 997 (996: morning χ2=4.22, p=0.0000, df=2; day χ2=45.28, p=0.0000, df=2; evening χ 2 =3.7, p=0.0000, df=2; night χ 2 =8.4, p=0.0000, df=2; 997: morning χ 2 =62.9, p=0.0000, df=2; day χ 2 =20.75, p=0.0000, df=2; evening χ 2 =6.6, p=0.0000, df=2; night χ 2 =53.85, p=0.0000, df=2; Table 2). Northern pikeminnow used habitats that had low water velocities during both years, based on distribution of fish in habitat cells -8 (Figure 7). During spill periods in both years, northern pikeminnow were located in areas protected from spill discharge during all times of the day (Figures 2 and 3). During no-spill periods, northern pikeminnow were observed throughout the tailrace (Figures 4 and 5). Northern pikeminnow use of particular cells during times when no spill was present was not consistent at all times of the day, however, no diel usage pattern was evident (Figures 4 and 5). 7

24 00 Morning Percentage of observations Spill (n = 2) No spill (n = 7) Day Spill (n = 6) No spill (n = 5) 22 3 Cell Cell 2 Cell 3 2 Figure 0. Distributions of northern pikeminnow in Lower Granite Dam tailrace during spill and no-spill conditions in morning, day, evening, and night in 996. The number of northern pikeminnow observations is shown above each bar. Survey sample sizes are shown below bars. 8

25 Percentage of observations Evening Spill (n = 5) No spill (n = 4) Night Spill (n = 6) No spill (n = 6) Cell Cell 2 Cell Figure 0. Continued. 9

26 Percentage of observations Morning Spill (n =28) No spill (n = ) Day Spill (n = 28) No spill (n = 5) 9 Cell Cell 2 Cell Figure. Distributions of northern pikeminnow in Lower Granite Dam tailrace during spill and no-spill conditions in morning, day, evening, and night in 997. The number of northern pikeminnow observations is shown above each bar. Survey sample sizes are shown below bars. 20

27 00 90 Evening Percentage of observations Spill (n = 27) No spill (n = 9) Night Spill (n = 25) No spill (n = 3) Cell Cell 2 Cell Figure. Continued. 2

28 Table 2. Distribution of northern pikeminnow observations by cell, with and without spill in Lower Granite Dam tailrace, during morning, day, evening, and night time periods in 996 and 997, and Chi Square analysis. Condition Observed Expected χ 2 Percent of observations 996 Morning Spill Cell Cell Cell Total No spill Cell Cell Cell Total Day Spill Cell Cell Cell Total No spill Cell Cell Cell Total Evening Spill Cell Cell Cell Total No spill Cell Cell Cell Total

29 Table 2. Continued. Condition Observed Expected χ 2 Percent of observations Night Spill Cell Cell Cell Total No spill Cell Cell Cell Total Morning Spill Cell Cell Cell Total No spill Cell Cell Cell Total Day Spill Cell Cell Cell Total No spill Cell Cell Cell Total

30 Table 2. Continued. Condition Observed Expected χ 2 Percent of observations Evening Spill Cell Cell Cell Total No spill Cell Cell Cell Total Night Spill Cell Cell Cell Total No spill Cell Cell Cell Total When spill occurred only from spillbays and 2 for operation of the SBC, we observed 7 northern pikeminnow 236 times between 27 June and 3 July 997 (Figure 6). Northern pikeminnow were observed in all parts of the tailrace, including the spillway stilling basin. The distribution of radio-tagged northern pikeminnow changed immediately following significant changes in spill level. For example, in late June and early July 996, spill (>60.7 kcfs; >700 m 3 /s) occurred primarily between midnight and 0600 hours for an -day period. At the cessation of the nighttime spill period, northern pikeminnow moved from the slackwater area north of the navigation lock into the BRZ (Figure 7). 24

31 Spill, 996 Morning Day n=63 n=43 7 n=8 2 n=25 6 n=2 4 n=4 5 n=4 3 n=9 7 n=4 2 n=0 6 n=0 4 n=0 5 n= 3 n=8 Evening Night n=42 n=24 7 n=5 2 n=9 6 n=0 4 n=0 5 n=0 3 n=0 7 n=7 2 n=9 6 n=3 4 n= 5 n=7 3 n=4 0-5% 6-0% -25% 26-50% 5-75% 76-00% Figure 2. Distributions of northern pikeminnow in Lower Granite Dam tailrace when spill was occurring during the morning, day, evening, and night in

32 Spill, 997 Morning Day n=70 n=70 7 n= 2 n=6 6 n= 4 n= 5 n=3 3 n=37 7 n=0 2 n=7 6 n=0 4 n= 5 n=3 3 n=27 Evening Night n=73 n=64 7 n=2 2 n=3 6 n=3 4 n=0 5 n=2 3 n=5 7 n= 2 n=9 6 n= 4 n=0 5 n=0 3 n=06 0-5% 6-0% -25% 26-50% 5-75% 76-00% Figure 3. Distributions of northern pikeminnow in Lower Granite Dam tailrace when spill was occurring during the morning, day, evening, and night in

33 No spill, 996 Morning Day n=0 n=8 7 n=26 2 n=6 6 n=4 4 n=3 5 n=33 3 n= 7 n=3 2 n=5 6 n=2 4 n=7 5 n=7 3 n=5 Evening Night n=49 n=2 7 n=7 2 n=5 4 n=3 3 n=8 6 n=8 5 n=32 7 n=3 2 n=4 6 n= 4 n=0 3 n=4 5 n=27 0-5% 6-0% -25% 26-50% 5-75% 76-00% Figure 4. Distributions of northern pikeminnow in Lower Granite Dam tailrace when spill was not occurring during the morning, day, evening, and night in

34 No spill, 997 Morning Day n=0 n=0 7 n=3 2 n=8 6 n= 4 3 n=9 n=8 5 n=4 7 n=0 2 n=5 6 n=3 4 3 n=2n=35 5 n=24 Evening Night n=2 n=0 7 n=8 2 n=8 6 n=6 4 n=0 3 n=22 5 n=34 7 n=3 2 n=8 6 n= 4 3 n=9 n=8 5 n=4 0-5% 6-0% -25% 26-50% 5-75% 76-00% Figure 5. Distributions of northern pikeminnow in Lower Granite Dam tailrace when spill was not occurring during the morning, day, evening, and night in

35 When spilling began again later the same day, northern pikeminnow immediately moved from the BRZ and back to the slackwater area north of the navigation lock (Figure 7). This shift in distribution was observed over three different days only during the nighttime spill period. Diel Activity of Northern Pikeminnow During four and five continuous 24-h tracking surveys in the tailrace of Lower Granite Dam during times of no spill in 996 and 997, 22 and 3 different radio-tagged northern pikeminnow were tracked for and 40.4 hours. Mean movement rate estimates differed significantly by hour of day in 996 (F=2.064, p=0.097) and 997 (F=2.7939, p=0.006; Figure 8; Table 3). Mean movement rates had a bimodal pattern during times of no spill. Mean movement rates in 996 were lowest at 0800 hours (8.76 m/h) and 2000 hours (42.35 m/h), and highest at 0600 hours (88.06) and 800 hours (23.3 m/h). Mean movement rates in 997 were lowest at 0400 hours (7.77 m/h) and 400 hours (49.29 m/h), and highest at 0800 hours (74.87 m/h) and 800 hours (09.83 m/h). During four and two continuous 24-h tracking surveys in the tailrace of Lower Granite Dam during times of 24-h/d and 2-h/d spill operation in 996, and 9 different radio-tagged northern pikeminnow were tracked for 27.0 and 88.5 hours. Mean movement rate estimates did not differ significantly by hour of day during 24-h/d spill (F=0.6582, p=0.7773). Lack of observations did not permit an ANOVA for 2-h/d spill movement rates. Mean movement rates during 24-h/d spill in 996 were at a general mean level across most hours of the day, lowest at midnight (73.76 m/h) and 600 hours (62.6 m/h), and highest at 0400 hours (04.04 m/h) and 2200 hours (48.47 m/h; Figure 9). Mean movement rates during 2-h/d spill were generally lower during the day (minimum 25.0 m/h occurring at 200 hours) and higher during the night (maximum m/h occurring at 0200 hours), considering only hours with more than one observation (Figure 9). 29

36 SBC spill only, 997 Morning Day n=5 n=6 7 n=2 2 n=5 6 n=5 4 n=0 5 n=7 3 n=9 7 n= 2 n=4 6 n=5 4 n=8 5 n=0 3 n=26 Evening Night n=6 n=5 7 n=9 2 n= 6 n=5 4 n=4 5 n=20 3 n=9 7 n=0 2 n=3 6 n=6 4 n=9 5 n=26 3 n=8 0-5% 6-0% -25% 26-50% 5-75% 76-00% Figure 6. Distributions of northern pikeminnow in Lower Granite Dam tailrace when spill was occurring for operation of the SBC only during the morning, day, evening, and night in

37 No-spill, hours Flow Spill, hours Flow Figure 7. Distribution of northern pikeminnow in the tailrace of Lower Granite Dam during one no-spill and spill period on 25 June

38 Mean movement rate (m/h) Hour of day Figure 8. Mean movement rates calculated from 24-hour monitoring of northern pikeminnow in the tailrace of Lower Granite Dam during no-spill periods in 996 and 997. Sample size is above each bar. Lines above and below each mean represent +SE. 32

39 Table 3. ANOVA of ranked movement rates calculated from continuous 24-hour surveys of northern pikeminnow in the tailrace of Lower Granite Dam during 996 and 997. Source D.F. Sum of Mean F p-value squares squares 996 Between groups Within groups Total Between groups Within groups Total The number of movements observed varied under different spilling regimes, however no distinct activity pattern was evident across different times of the day (Table 4). Based on the number of movements observed, northern pikeminnow were more active during times of spill in 996 (24-h/d spill=79.5% active; 2-h/d spill 64.% active) than during times of no spill in 996 and 997 (43.3% and 33.0% active). Northern pikeminnow were active across all times of the day during 24-h/d spill and 2-h/d spill, with the exception of during the daytime under 2-h/d spill (4.9% active); a time when spill was generally not occurring. Northern pikeminnow were generally inactive across different times of the day during no spill operation. Northern pikeminnow moved between the immediate tailrace (within km of the dam) and downstream areas during periods of spill and no spill (Table 5). During periods of continuous spill, 3% to 70% of the northern pikeminnow remained within km of the dam, 3% and 25% moved -3 km downstream from the dam, and 55% and 73% moved downstream more than 3 km during the two years. Of those that moved >3 km downstream, 36% and 45% moved back upstream into the tailrace. Later in the summer when there was no spill, 8% and 6% of fish present remained within km of 33

40 Mean movement rate (m/h) h/d h/d Hour of day Figure 9. Mean movement rates calculated from 24-hour monitoring of northern pikeminnow in the tailrace of Lower Granite Dam during 24-h/d and 2-h/d spill times in 996. Sample size is above each bar. Lines above and below each mean represent +SE. 34

41 Table 4. Number and percent occurrence of active (>30 m movement observed) or inactive periods (no movement observed; 0 m) during hourly observations of radiotagged northern pikeminnow. Time Active Inactive h/d spill Morning 34 (82.9%) 7 (7.%) Day 0 (82.%) 22 (7.9%) Evening 27 (79.4%) 7 (20.6%) Night 43 (7.7%) 7 (28.3%) Total 205 (79.5%) 53 (20.5%) 2-h/d spill Morning 8 (88.9%) (.%) Day 3 (4.9%) 8 (58.%) Evening 9 (56.3%) 7 (43.7%) Night 29 (80.6%) 7 (9.4%) Total 59 (64.%) 33 (35.9%) No spill Morning 24 (24.0%) 76 (76%) Day 6 (5.3%) 58 (48.7%) Evening 7 (58.6%) 2 (4.4%) Night 56 (47.9%) 6 (52.%) Total 58 (43.3%) 207 (56.7%) 997 No spill Morning 22 (3.9%) 47 (68.%) Day 62 (36.9%) 06 (63.%) Evening 30 (47.6%) 33 (52.4%) Night 26 (2.0%) 98 (79.0%) Total 40 (33.0%) 284 (67.0%) the dam, 68% and 85% moved downstream more than 3 km, and quite a few of the fish moved back to within km of the dam. 35

42 Distribution of Northern Pikeminnow in Little Goose Reservoir Twenty-four and 6 different radio-tagged northern pikeminnow were located 60 and 68 times during four surveys of Little Goose Reservoir between 5 August and October 996, and between 7 June and 5 September 997. No surveys were conducted during the spring runoff and continuous spill period in 996. During the spring runoff and continuous spill period in 997, most observations of northern pikeminnow outfitted with transmitters were in the tailrace, but some were also found as far as 36 km downstream of Lower Granite Dam (Figure 20). After flows decreased, observations of radio-tagged northern pikeminnow in the tailrace increased. The highest number of northern pikeminnow observations occurred in the tailrace in August during both years. Observations of radio-tagged northern pikeminnow in the tailrace decreased with increased observations in the upper and middle third of Little Goose Reservoir. The number of northern pikeminnow in the tailrace and downstream in the reservoir shifted during late summer. The number of fish in the tailrace steadily decreased, while those in the reservoir generally increased between July and October of both years (Table 6). 36

43 Table 5. Number and percent of radio-tagged northern pikeminnow moving between Lower Granite Dam and downstream areas during continuous spill (24 h/d) and no or low (2 h/d in 996, spill from spillbays and 2 only in 997) spill periods in 996 and 997. Information based on northern pikeminnow tagged prior to 9 May 996 and 7 April 997. Number of northern pikeminnow observed Northern pikeminnow tagged 20 5 Continuous spill period Date range of spill Apr-20 Jun Apr-24 Jun Northern pikeminnow that: Remained within km of dam 4 of 20 (20%) 2 of 5 (3.3%) Moved downstream of dam: -3 km 5 of 20 (25%) 2 of 5 (3.3%) more than 3 km of 20 (55%) of 5 (73.3%) Moved back upstream within km of dam after moving downstream: -3 km 2 of 5 (40%) 2 of 2 (00%) more than 3 km 4 of (36%) 5 of (45%) No or low spill period Date range of no spill 2 Jun-5 Aug 26 Jun-5 Aug Northern pikeminnow that: Remained within km of dam through 5 Aug 3 of 9 (6%) of 3 (7.5%) Moved downstream of dam before 5 Aug: -3 km 3 of 9 (6%) of 3 (7.5%) more than 3 km 3 of 9 (68%) of 3 (85%) Moved back upstream within km of dam before 5 Aug: -3 km 2 of 3 (67%) of (00%) more than 3 km 4 of 3 (3%) 8 of (73%) 37

44 Percentage of observations Tailrace Upper reservoir Middle reservoir Aug 29 Aug 6 Sep Oct Jun 2 Jul 7 Aug 25 Aug 5 Sep Figure 20. Percentage of radio-tagged northern pikeminnow in the Little Goose Reservoir between Lower Granite Dam tailrace (rkm 73) and Central Ferry (rkm 33). 38

45 Table 6. Number and percent of radio-tagged northern pikeminnow observed in the tailrace of Lower Granite Dam (within 3 km of dam) and in Little Goose Reservoir (>3 km downstream of dam) during July to October 996 and 997. Northern pikeminnow observed in both the tailrace and reservoir for a particular month were counted as being in the tailrace only. Number and percent of fish observed Tailrace Reservoir Total Tailrace Reservoir Total July 36 of 42 4 of of 42 7 of 9 of 9 8 of 9 (86%) (9%) (95%) (90%) (5%) (95%) August 9 of 40 of of 40 4 of 8 of 8 5 of 8 (22%) (28%) (50%) (78%) (5%) (83%) September 5 of 40 0 of 40 5 of 40 9 of 8 3 of 8 2 of 8 (3%) (25%) (50%) (50%) (7%) (67%) October 2 of 40 7 of 40 9 of 40 2 of 8 (5%) (8%) (23%) (%) Distribution of Smallmouth Bass in the Forebay Seven different radio-tagged smallmouth bass were observed a total of 56 times on 7 different days in the forebay of Lower Granite Dam between June and 3 August 997. Radio-tagged smallmouth bass were not located near the SBC (within 50 m); they remained along shorelines near points of capture during June and early July (Figure 2). By July, no smallmouth bass were located within the forebay survey area. Five of the seven radio-tagged smallmouth bass were located upstream of the forebay during late July and August. Maximum observed travel distances for smallmouth bass in the forebay were 37 and 97 km upstream from Lower Granite Dam and occurred in late June and July. 39

46 N Flow Scale in meters Channel-code Release date 24 Jun 97 Jun Apr 97 9 Jun Jun 97 5 Jun 97 0 Jul 97 Date last located in forebay 2 Jul Jun 97 2 Jun 97 2 Jul 97 3 Jul Jun 97 Jul 97 Figure 2. Locations of radio-tagged smallmouth bass in the forebay of Lower Granite Dam during June and July 997. Distribution of Smallmouth Bass in the Tailrace Six different radio-tagged smallmouth bass were observed a total of 322 times (during morning, day, evening, and night surveys) on 35 different days in the tailrace of Lower Granite Dam between 20 June and October 997. Generally, smallmouth bass remained along shorelines near points of capture across all times of the day during late June and July (Figure 22). One of the six smallmouth bass was collected, released with a transmitter, and regularly located in the tailrace BRZ (including within adult fishways), but it was not located near the SBC outflow during times of SBC operation. This smallmouth bass was also considerably more active than the other 40

47 radio-tagged smallmouth bass in the tailrace. Three of the six radio-tagged smallmouth bass moved downstream during July and August. No upstream movement back into the tailrace was observed. Maximum observed travel distances for smallmouth bass captured and released in the tailrace were and 39 km downstream from Lower Granite Dam and occurred in August and September N Flow scale in meters Release Located downstream Channel-code date of tailrace Jun Jun Yes Jun Jun Yes Jul Yes 25-8 Jun Figure 22. Locations of radio-tagged smallmouth bass in the tailrace of Lower Granite Dam during June and July in

48 Discussion During the spring runoff with continuous spill, the distribution of northern pikeminnow near Lower Granite Dam was limited to shorelines and areas with low velocity. High velocities present during peak river discharge and spill forced some individuals temporarily downstream of the tailrace. After the spring runoff and continuous spill, northern pikeminnow moved into the spillway stilling basin and downstream from the turbines. We could not determine if shift in distribution was related to spawning behavior or changes in foraging opportunity. The number of northern pikeminnow in the tailrace declined during late summer and appeared to be a downstream migration into the reservoir, perhaps to overwintering areas. The confined distribution of radio-tagged northern pikeminnow during the spring runoff and continuous spill period was consistent with distributions reported in similar studies (Bentley and Dawley 98; Faler et al. 988; Isaak and Bjornn 996b; Shively et al. 996b). Northern pikeminnow consistently used areas protected from high velocities in the main channels and spillways. During the spring runoff of both 996 and 997, velocities in the tailrace often exceeded m/s. Mesa and Olson (993) reported that adult northern pikeminnow forced to swim in 2 o C water with m/s velocity fatigued within 20 minutes, based on laboratory swimming performance tests. If results from those tests were transferable to conditions in the river, northern pikeminnow would not have been able to occupy high velocity areas in the tailrace during much of the spring runoff period. Northern pikeminnow are known to be significant predators of downstream migrating juvenile salmonids in the Columbia and Snake rivers, especially below dams (Brown and Moyle 98; Rieman et al. 99; Ward et al. 995), and, as suggested by Beamesderfer and Rieman (99), may respond numerically to high abundance of juvenile salmonids during spring. Juvenile salmonid abundance peaked during the spring runoff of both years. We observed that 25% and 3.3% of the radio-tagged northern pikeminnow captured and released in the tailrace remained within 3 km of the 42

49 dam throughout the spring runoff during 996 and 997, and then dispersed downstream later in summer and fall. Northern pikeminnow predation of juvenile salmonids may be taking place along the margins of relatively high velocity areas. We observed northern pikeminnow along shorelines, along the margin of the main river channel, or near hydroelectric facility structures adjacent to high velocity discharge from the dam. In a similar study, Shively et al. (996b) observed northern pikeminnow near shore or hydroelectric facility structures a majority of the time. Shiveley et al. (996b) proposed that water velocity alone does not explain this usage pattern, perhaps an indication of preference for shallow and near shore areas. An alternative hypothesis is that northern pikeminnow use areas away from shore or structure, but are at depths >0 m, outside of radiotelemetry range. Northern pikeminnow spend considerable time foraging for benthic prey (Poe et al. 99). During this study, we did have indications that individual northern pikeminnow were periodically using habitats >0 m deep within the tailrace, based on observations during fish collection and radio-telemetry surveys. High river flows and spill may limit the congregation of northern pikeminnow in the tailrace. Isaak and Bjornn (996b) observed that the number of radio-tagged northern pikeminnow moving upstream into the tailrace peaked in early May, declined during peak river flows and spill, and then peaked a second time after river discharge and spill had decreased. Although capture and release locations prohibited speculating about northern pikeminnow abundance in the tailrace prior to continued spill operation, we observed that 55% and 73.3% of the northern pikeminnow captured, radio tagged, and released in the tailrace, moved >3 km downstream during high spill operation during 996 and 997, and 74% and 65% of those moving >3 km downstream did not move back upstream until continuous spill had ended. Some northern pikeminnow navigated high velocities in the tailrace to get to the slackwater area at the southeast corner of the lock (adjacent to the north fishway) and downstream areas. Although water velocity was not measured during this study, surface velocities in the BRZ below the spillway have been estimated to range between 43