IDAHO COOPERATIVE FISH AND WILDLIFE RESEARCH UNIT. ADULT PACIFIC LAMPREY MIGRATION AND BEHAVIOR AT McNARY DAM

Transcription

1 Technical Report IDAHO COOPERATIVE FISH AND WILDLIFE RESEARCH UNIT ADULT PACIFIC LAMPREY MIGRATION AND BEHAVIOR AT McNARY DAM Matthew L. Keefer, Charles T. Boggs, Christopher C. Caudill University of Idaho Fish Ecology Research Laboratory Department of Fish and Wildlife and Mary L. Moser Northwest Fisheries Science Center NOAA Fisheries 2725 Montlake Blvd Seattle WA, For U.S. Army Corps of Engineers Walla Walla District, Walla Walla WA 2011

2 Technical Report ADULT PACIFIC LAMPREY MIGRATION AND BEHAVIOR AT McNARY DAM A Report for USACE contract W91EF-08-D0007 Task 0006 Matthew L. Keefer, Charles T. Boggs, and Christopher C. Caudill University of Idaho Fish Ecology Research Laboratory Department of Fish and Wildlife and Mary L. Moser Northwest Fisheries Science Center NOAA Fisheries 2725 Montlake Blvd Seattle WA, For U.S. Army Corps of Engineers Walla Walla District 2011 ii

3 Acknowledgements We would like to thank Travis Dick, Maya Friedman, Steve Lee, Dennis Quaempts, and Paul Peterson for their effort in maintaining monitoring sites and efforts during lamprey collection and tagging. Steve Lee, Mark Morasch, Eric Johnson, Dan Joosten, and Bill Daigle helped with HDX and radio equipment construction and installation. Jim Simonson and Jeff Moser from the NOAA Fisheries Pasco Research Station fabricated and installed the traps used in this study. Brian Burke, Kinsey Frick, Tami Clabough and Mike Jepson helped with radio-telemetry and HD PIT database maintenance and interpretation. We also thank the staff of Pacific States Marine Fisheries Commission s Kennewick Field Office, especially Darren Chase and Don Warf. The U.S. Army Corps of Engineers provided funding for this study; we thank Derek Fryer, Brad Eby, and Mark Plummer. Administrative assistance was provided by Tom Ruhele, Doug Dey and Paula McAteer. iii

4 Table of Contents Executive Summary... v Introduction... 1 Methods... 2 Lamprey Collection... 2 Tagging Procedures... 2 Monitoring Sites... 3 Data Analyses... 4 Results... 5 River Environment and Dam Operations... 5 Lamprey Runs and Samples Collected... 6 Lamprey Detection and Passage Efficiencies at McNary Dam... 8 Lamprey Use of McNary Fishways Lamprey Passage Times Last Recorded Sites for All Radio-Tagged Lampreys Evidence for Constraints on Upstream Migration Distance Discussion References Appendix 1. McNary fishway entrance velocity experiment iv

5 Executive Summary This report synthesizes results from adult Pacific lamprey radiotelemetry studies conducted at McNary Dam from In total, 276 lampreys were radio-tagged and released downstream from the dam; record low run size limited the tagged sample to 18 lampreys in On average, 58% of the released fish were detected at McNary fishways and 37% eventually passed the dam. Fishway passage efficiencies averaged 64% from fishway approach to ladder exit and 84% from fishway entry to ladder exit. Year-to-year variability in passage efficiency metrics was high from release through the tailrace and relatively low through the fishways. The likelihood of lamprey return to McNary Dam, lamprey passage of McNary Dam, and lamprey detection at Snake River or upper Columbia River sites was highest for larger and earliertimed migrants. Similar patterns were observed using independent datasets from lamprey counts at dams and lampreys PIT tagged at Bonneville Dam. The combined size and timing results indicate likely environmental and/or physiological factors strongly influence migration distance in adult Pacific lamprey. Lampreys that entered McNary fishways were increasingly likely to pass the dam the higher up the fishways they moved in all years. Apparent difficult passage areas were at fishway entrances and in transition pools. More fish turned around and exited to the tailrace from these sites than turned around at any other sites. Lampreys moved relatively quickly through overflow-weir sections of the ladders and past count windows, and relatively slowly through the tailrace and transition pools. Passage times through monitored areas at McNary Dam were quite variable, a result that was consistent with findings in other adult lamprey studies. Of 102 lampreys that passed McNary Dam, 34 (33%) were subsequently detected at Priest Rapids or Wanapum dams and 9 (9%) were detected at one or more Snake River dams. Fish that returned to the Snake and upper Columbia migrated at similar times (relatively early) and were among the largest in the tagged samples. There were no clear explanations for the relatively limited use of the Snake River, but environmental cues such as relatively lower discharge from the Snake River versus upper Columbia River or pheromone signals may have been important. A two-year fishway velocity experiment ( ), where night-time velocity was reduced at Oregon shore fishway entrances, proved inconclusive because low run sizes and sample sizes limited statistical power in the experiment. However, the weight of evidence from this and studies at other dams and in experimental fishway experiments suggests that reduced fishway entrance velocity likely provided a benefit to lamprey passage. v

6 Introduction Anadromous Pacific lamprey (Lampetra tridentata) populations have declined in many rivers of the Pacific Northwest in recent years, likely due to a similar combination of factors responsible for the decline of anadromous salmon and steelhead (Oncorhynchus spp). In the Columbia and Snake rivers, counts of migrating adult Pacific lampreys have decreased precipitously since construction of the federal hydropower dams and run size estimates based on visual counts began (Close et al. 1995; USFWS 2010). Though little is known about historic abundance, the information available suggests that the greatest losses have been for Pacific lampreys that use interior Columbia River basin tributaries. Beginning in 1997, radiotelemetry and PIT-tag studies funded by the USACE have examined adult lamprey passage in the lower Columbia River, focusing at Bonneville Dam (e.g., Moser et al. 2002; 2003; 2004; 2005) and later expanding to include The Dalles, John Day, McNary and Ice Harbor dams (Cummings 2007; Boggs et al. 2009; Johnson et al. 2009a, 2009b; Keefer et al. 2009a). Results indicated that Pacific lampreys did not readily pass dams and poor passage conditions at dams could represent a critical limitation to migration success (e.g., Close et al. 1995; Moser et al. 2002). Specifically, the monitoring studies by the University of Idaho and the National Marine Fisheries Service found that fishway entrances, collection/transition areas, count stations, diffuser gratings, and serpentine weirs impeded adult Pacific lamprey dam passage at lower Columbia River dams. In some years and at some projects, more than 50% of the lamprey recorded in the tailrace area of a dam failed to pass that dam (Moser 2002; Boggs et al. 2009; Keefer et al. 2010a). In an effort to improve monitoring of Pacific lamprey in the basin, half-duplex (HD) passive integrated transponder (PIT) tag monitoring sites were deployed at dams starting in 2005 to complement radiotelemetry studies (e.g., Keefer et al. 2009a, 2009b). PIT tags are relatively inexpensive and small, are uniquely identifiable, are not limited by battery life, and are easy to implant (Gibbons and Andrews 2004). Therefore, once detectors were installed, PIT tags could be used to cost-effectively monitor relatively large numbers of fish as they passed through constricted areas like dam fishways. HD tags were selected for Pacific lamprey passage evaluations to avoid potential tag collisions with the full-duplex (FDX) PIT tags used to monitor salmonids in the basin and because of their greater detection ranges. In 2005 through 2010, radiotelemetry and HD-PIT tag studies at McNary Dam evaluated adult lamprey behavior and dam passage efficiencies as well as identified areas that may pose particular difficulties for migrating lampreys. In these years, a total of 276 adult lampreys were trapped at McNary Dam and tagged with a radio-transmitter and HD PIT tag and released about one kilometer downstream from McNary Dam. In 2010, record low returns of adults and tagging guidelines agreed upon by regional fisheries managers precluded tagging the target number of adults. Here we summarize estimates of fishway use, passage efficiencies, and passage times as well as describe fishway preference, fishway exits, and the final recorded distribution of lamprey upstream and downstream from McNary Dam. The 2010 study included the second year of a reduced velocity experiment at McNary fishway entrances (see Boggs et al and Appendix 1 for experiment details); the small lamprey sample in 2010 precluded direct evaluation of this experimental condition. In all years, many tagged lampreys did not return to McNary Dam after release (see 1

7 Results), and we therefore used both HD PIT-tagged lampreys from samples collected at Bonneville Dam and lamprey count data from John Day and McNary dams to identify potential environmental factors or lamprey traits associated with this migration behavior. Lamprey Collection Methods Adult Pacific lampreys were captured in the Oregon-shore fishway and tagged at the Juvenile Fish Facility of McNary Dam, Columbia River kilometer (rkm) 470 (Figure 1). Three collection methods were used: fixed-site traps (all years), portable traps (2009 only) and dip-netting (all years) (see Moser et al for trap details). A total of 276 lampreys were captured of which 157 were from the two fixed-site traps located in the Oregon-shore fishway or in portable funnel traps fished behind the Oregon-shore picket lead near the count station and 119 were dip-netted from behind the Oregon-shore fishway viewing window. Between 15 and 39% of the annual sample were captured by dipnet in In 2009, a very small lamprey run reduced the efficacy of the fixed-site traps and we relied on intensive dip netting. Personnel located inside the Oregon-shore fish viewing facility used a two-way radio to communicate the location of lamprey in the fishway viewing area to personnel on the catwalk above who then attempted to dip-net lampreys as they swam past. Dipnetted lampreys were transferred to a holding tank at the McNary Dam Juvenile Fish Facility (JFF). The stationary traps were checked each morning and all lampreys were transported to the tagging station for transmitter implantation and recovery. Study animals were then transported by truck about 1 km downstream of the dam and released. Tagging Procedures All study lampreys were anesthetized using 60 ppm eugenol for 5-8 min and were weighed and measured (length and girth). Lampreys were then placed head first into a 10 cm diameter polyvinyl chloride (PVC) pipe with a sealed T-end. A portion of the pipe was cut away to allow access to the ventral surface of the lamprey for surgery. During surgery, the head and gills of the fish were submerged in a 60 ppm concentration of eugenol. An incision approximately 3 cm long was made just left of the ventral midline directly below the anterior-most portion of the first dorsal fin. At this point, if the animal was receiving both a radio transmitter and an HD PIT tag, the PIT tag (23 mm 3.8 mm, 0.6 g in air) was inserted into the body cavity. A catheter was then placed inside the body cavity and pushed through the musculature and skin approximately 5 cm posterior to the incision. The radio transmitter antenna was threaded through the catheter and the catheter was removed by pulling it through the body wall, leaving the antenna protruding through a small hole in the skin. The radio transmitter was then inserted into the body cavity and the incision was closed with two or three simple interrupted Monocryl 3-0 sutures. Most radio transmitters were model NTC-4-2L (Lotek Wireless Inc., Newmarket, Ontario), which weighed 2.1 g in air ( mm) and had a 5 sec burst rate. In , some lamprey received larger transmitters (model NTC-6-2; 4.5 g in air; mm; 5 sec burst rate). Tagged lampreys were randomly released approximately one km downstream from McNary Dam at two sites on opposite sides of the river 2

8 ( N, W; N, W) in all years but 2010 when lamprey were released only at the Oregon-shore site. McNary Dam Exit Exit m Forebay Spillway Powerhouse North-shore fishway entrance North-PH fishway entrance South-PH fishway entrance Lock LM GO GR Figure 1. Diagram of McNary Dam that shows locations of underwater radiotelemetry antennas ( ) used to monitor adult Pacific lamprey. Aerial radiotelemetry antennas located ~1 km downstream were used to monitor the tailrace, and HD-PIT detectors were located near ladder exits and near the first overflow weirs in the fishway (not shown, but located near radiotelemetry antennas). Insets show the locations of main stem dams (BO = Bonneville, TD = The Dalles, JD = John Day, MN = McNary, PR = Priest Rapids, IH = Ice Harbor, LM = Lower Monumental, GO = Little Goose, GR = Lower Granite) and tributaries (1 = John Day River, 2 = Umatilla River, 3 = Yakima River) mentioned in the text. Monitoring Sites In all study years, two aerial Yagi antennas located on opposite sides of the Columbia River approximately 2.5 km downstream from McNary Dam monitored fish movement in the tailrace (Figure 1). Multiple underwater antennas monitored fish behavior outside and inside McNary fishway openings, in fishway transition pools, and at top-of-ladder fishway exits (Figure 1). Radiotelemetry monitoring at Ice Harbor Dam consisted of antennas at tailrace sites (Yagi) and at fishway entrances, transition pools, and top-of-ladder exits. Monitoring at Priest Rapids Dam consisted of underwater telemetry antennas located near fishway exits. Additional radiotelemetry sites were located in the Columbia River Hanford Reach and at Lower Monumental, Little Goose, and Lower Granite dams in some years. In all years, HD-PIT detectors at McNary Dam monitored 3

9 lamprey passage at fishway weirs (typically at the first weir that was never inundated regardless of tailwater elevation) and at fishway exits. Monitoring of the Oregon-shore fishway exit and the two auxiliary juvenile passage channels located inside the fishway pier wall that connected to the forebay was added in At Ice Harbor Dam, HD-PIT coverage included detectors at fishway entrances, at fishway weirs, and at fishway exits in all years except 2005, when only the south fishway exit was monitored. At Priest Rapids Dam, HD-PIT detectors were installed in both fishway ladders in Detectors were installed at Wanapum Dam in 2009 (maintained by the Public Utility District). (Note: starting in 2008, additional Yagi radiotelemetry antennas were installed to monitor the areas adjacent to fishway openings at McNary and Ice Harbor dams. The primary objective for these antennas was to estimate the number of fish that approached a fishway but were not close enough to be detected on underwater antennas. At McNary Dam, data from these aerial antennas were used in place of data from underwater antennas at fishway openings in 2008 only. Because the aerial antennas detected only a very small number of fish that were not detected by underwater antennas, we used only the underwater antennas data in so that radiotelemetry data would be most comparable across years.) Data analyses Fishway and dam passage metrics were estimated by calculating ratios between numbers of lampreys released and/or detected at each site. For example, the return to McNary Dam metric was defined as the number detected at McNary fishway antennas divided by the number released. Similarly, fishway passage metrics were defined as the number that passed the dam divided by the numbers that approached or entered fishways. Pearson s χ 2 tests were used to test for differences in efficiency metrics among years and among sub-groups of the tagged fish (i.e., for those that used different fishway openings. We used generalized linear models (GLM) to test for among-year and among-fate differences in lamprey size and release dates. Logistic regression models were used to examine the relationships among a variety of predictor variables (i.e., lamprey size, release date, river discharge) and both lamprey return to McNary Dam and dam passage. Similar models were used to evaluate the behavior of lampreys HD PIT-tagged at Bonneville Dam and subsequently detected at John Day and McNary dams (see Keefer et al for description of the Bonneville studies). The latter analyses were used to evaluate potential negative effects of handling at McNary Dam. Lamprey passage times were calculated between pairs of antennas. Metrics at McNary Dam included time from release to first fishway approach, from approach to first fishway entry, from fishway entry to transition pool entry, from transition pool entry to exit into the forebay, and from fishway entry to fishway exit into the forebay. Additional passage times were calculated from time of McNary passage to detection upstream at antennas in the Columbia River Hanford Reach and at Priest Rapids and Ice Harbor dams. 4

10 Results River Environment and Dam Operations Mean Columbia River discharge at McNary Dam during the lamprey migration seasons (15 June to 15 September) ranged from kcfs in 2009 to kcfs in 2008 (Figure 2). Five out of six years were below the previous 10-year (1994 to 2004) average of kcfs. River discharge in 2008 was significantly lower (ANOVA, P 0.013, Tukeys tests) than in 2005 and Discharge (kcfs) Spill (kcfs) Temperature ( o C) Jun 1 Jul 15 Jul 1 Aug 15 Aug 1 Sept 15 Sept Figure 2. Columbia River discharge, dam spill, and water temperature recorded at McNary Dam during the adult Pacific lamprey migrations in

11 Spill occurred at McNary Dam in all study years through 1 September (Figure 2). Mean spill during the lamprey migrations ranged from 66.1 kcfs in 2009 to 87.3 kcfs in 2008; these two years were the only two years where spill level differed significantly (ANOVA, P = 0.022, post hoc Tukey tests). Before 2005, summer spill typically ended before 1 September, precluding direct comparisons with long term means. Mean water temperatures during the lamprey migrations ranged from 18.8 C in 2008 to 19.8 C in 2009 (Figure 2). Mean water temperature from 1994 to 2004 for this date range was 20.0 C. Mean water temperature in 2008 was significantly (ANOVA, P 0.020, Tukey tests) cooler than in Temperatures in 2009 were significantly (ANOVA, P = 0.02) warmer than in 2008 and Lamprey count June 1 July 1 Aug. 1 Sept. 1 Oct. Figure 3. Daytime counts of adult Pacific lampreys (thin solid lines) at McNary Dam in Whisker plots show tag dates, including median ( ), quartile (vertical lines) and 5 th and 95 th percentiles (horizontal lines). Lamprey Runs and Samples Collected Daytime counts of adult lamprey at McNary Dam were 4,158 (2005), 2,456 (2006), 3,453 (2007), 1,530 (2008), 676 (2009), and 825 (2010) (Figure 3). An additional 345 lampreys were counted at night in 2010 using video (archived at Based on the daytime counts, the date that the first 10% of the run passed the dam ranged from 6 6

12 July in 2005 to 22 July in both 2008 and 2010 (Figure 3). Median passage dates ranged from 5 August in 2005 to 20 August in All years Weight (g) All years Length (cm) All years Girth (cm) Figure 4. Distributions of weight (g), length (cm) and girth (cm) measurements for adult Pacific lamprey captured at McNary Dam in Box plots show median, quartile, 5 th, 10 th, 90 th, and 95 th percentiles. (Note: weights were not collected for 28 of 40 lampreys in 2006.) Lamprey trapping was initiated at McNary Dam when sufficient numbers of lampreys were counted passing count stations. This date ranged from 22 June in 2006 to 26 Jul in 2010 (Figure 3). In total, 276 lampreys were radio-tagged, with annual samples of 40 (2005), 40 (2006), 60 (2007), 34 (2008), 84 (2009), and 18 (2010). Median tag dates ranged from 26 July in 2006 to 7 August in Mean tag date was significantly earlier (ANOVA F 5,270 = 4.0, P 0.002, Tukey tests) in 2006 than in 2008 and

13 Mean weights for tagged lampreys ranged from 425 g in 2008 to 486 g in 2006 (Figure 4) and differed among years (ANOVA F 5,241 = 2.3, P = 0.048; note: weights were not collected for all fish in 2006). Pairwise differences were not significant Tukey s tests. Mean lamprey length ranged from 64.6 cm in 2007 to 67.8 cm in 2005 (F 5,270 = 3.5, P = 0.004; 2005 > 2007 in pairwise tests). Mean lamprey girth ranged from 10.5 cm in 2007 and 2008 to 10.9 cm in 2005 and 2006 (F 5,270 = 2.7, P = 0.037; no pairwise comparisons were significant). Lamprey Detection and Passage Efficiencies at McNary Dam With all years combined, 57% of the lampreys released were subsequently recorded at McNary fishway openings or were known to have passed openings based on upstream records (Table 1). This return-to-dam metric (i.e. tailrace passage efficiency) ranged from 23% in 2007 to 81% in 2009 and differed significantly among years (χ 2 = 60.7, P < 0.001). A total of 46% of the released fish entered a McNary fishway (range = 17-72%) and estimates differed among years (χ 2 = 38.1, P < 0.001). Thirty-seven percent of the released fish eventually passed McNary Dam (range = 12-56%; χ 2 = 32.2, P < 0.001). The latter metric describes total passage efficiency from release, through the tailrace, and through fishways. Table 1. Numbers of radio-tagged lampreys released in , and numbers that approached, entered, and passed McNary Dam fishways. Ratios show passage efficiencies through various combinations of tailrace, fishway entrance, and full fishway reaches. Year Total (mean) Released (n) Approached (n) Entered (n) Passed (n) Approached:Released (0.58) Entered:Released (0.49) Passed:Released (0.37) Entered:Approached (0.84) Passed:Approached (0.64) Passed:Entered (0.76) Of the fish detected at the dam, 81% subsequently entered a McNary fishway (Table 1). This metric ranged from % and did not significantly differ among years (χ 2 = 8.9, P = 0.114). A total of 65% of the fish that approached a fishway eventually passed the dam (range = 54-80%) and this metric also did not differ among years (χ 2 = 5.2, P = 0.393). Lastly, passage efficiency from fishway entry to pass the dam was 80% (range = 70-89%) and did not differ among years (χ 2 = 5.1, P = 0.398). In univariate logistic regression models, migration date and lamprey length were significant predictors of lamprey return to McNary Dam following release (Figure 5). Return to the dam was 8

14 more likely for early than late migrants (n = 276, χ 2 = 10.4, P = 0.001, odds ratio = 0.974, 95% confidence interval = 0.959, 0.990) and more likely for larger than smaller fish (n = 276, χ 2 = 7.0, P = 0.008, odds ratio = 1.086, 95% confidence interval = 1.022, 1.154). When date, lamprey length, river discharge, and McNary spill were included in a multivariate model, the date, length, and discharge terms were significant (P < 0.05) but spill was not. The probability of dam passage for the subset of lampreys that returned to McNary Dam was higher for early migrants (n = 156, χ 2 = 7.2, P = 0.023, odds ratio = 0.977, 95% confidence interval = 0.958, 0.997) and for larger fish (n = 158, χ 2 = 3.6, P = 0.059, odds ratio = 1.095, 95% confidence interval = 0.997, 1.204). In the multivariate model, only the length term was significant (P < 0.05) but both length and date were significant (P < 0.05) when discharge and spill terms were dropped from the model. Logistic regression models of other efficiency metrics (i.e., Entered:Released, Passed:Released, and Passed:Entered) showed similar overall size and migration timing patterns. 1.0 P (return to dam) P (dam passage) Jun 15 Jul 15 Aug 15 Sept 15 Oct 15 Nov Date Lamprey length (cm) Figure 5. Top panels show the probability (and 95% confidence intervals) of detection at a McNary Dam fishway after lampreys were released downstream, predicted using logistic regression models with release date and lamprey length as independent variables. Bottom panels show the probability of McNary Dam passage for lampreys that were detected approaching fishways, predicted using logistic regression models with fishway approach date and lamprey length as independent variables. 9

15 Lamprey Use of McNary Fishways A total of 158 lampreys were known to have approached McNary Dam fishways after release. On average, these fish approached the monitored fishway openings 2.1 times per fish (median = 2, maximum = 10). The 128 that entered fishways did so 1.3 times on average (median = 1, maximum = 6) and the 40 that exited into the tailrace did so 1.3 times on average (median = 1, maximum = 5). These estimates should all be considered minimums, as it was possible for lampreys to approach, enter, and exit via unmonitored fishway openings in all years along the powerhouse collection channel. The largest numbers of first and total fishway approaches (40-43%) and entries (50-51%) were at the south-shore fishway opening (Table 2). Another 22% of first approaches and total approaches were at the north-shore and north powerhouse openings. A similar proportion approached the North PH entrance, but very few (3-4%) lampreys entered the opening. Because lamprey could enter the south fishway via unmonitored openings, 13-25% of first and total approaches and entrances were coded as unknown because detections occurred inside the fishway without corresponding records at fishway openings (Table 2). Most of these fish presumably entered via orifice gates. Table 2. Fishway openings radio-tagged Pacific lampreys approached and entered in Percentages show the distributions of activity among sites, while proportions indicate those that eventually passed the dam. PH = Powerhouse. Fishway First fishway approach First fishway entry Opening n % Passed:Approached n % Passed:Entered North shore 35 22% % 0.75 North PH 34 22% % 0.33 South shore 68 43% % 0.79 Unknown PH 20 13% % 0.94 Total Total fishway approaches Total fishway entries North shore 73 22% % 0.59 North PH 81 25% % 0.17 South shore % % 0.65 Unknown PH 42 13% % 0.73 Total Fish with completely unknown passage routes (i.e., detected upstream but not passing McNary) were excluded Where lamprey approached and entered McNary fishways was associated with subsequent dam passage success (Table 2). Dam passage percentages by first fishway approach site were 72% (south shore), 41% (south powerhouse), 57% (north shore), and 95% (unknown powerhouse). 10

16 These estimates differed with (4 2 χ 2 = 9.6, P = 0.022) and without (3 2 χ 2 = 6.9, P = 0.032) the unknown first approaches included. Dam passage percentages by first fishway entry location also differed among sites, with low passage success for those that first entered the north powerhouse opening (33%) and relatively high passage for those that entered at the north- and south shore openings (74-75%). Differences were significant when unknown entries were included (4 2 χ 2 = 8.6, P = 0.036) but not when unknowns were excluded (3 2 χ 2 = 3.4, P = 0.179). Patterns were similar for total fishway approaches and entries (Table 2). (Note: dam passage percentages were lower for total approach and entry estimates because individual fish made multiple attempts). We also estimated dam passage percentages for lampreys recorded at each radiotelemetry antenna at McNary Dam (Figure 6). In the north fishway, all lampreys recorded at antennas in the upper transition pool and ladder eventually passed the dam. Mean passage percentages were 60% for those recorded at the north shore fishway opening and 75% for those recorded inside the north shore fishway below the main transition area. The lowest passage percentages (means = 13-40%) were for lampreys recorded at antennas at the north powerhouse antennas, though relatively few fish were recorded in this portion of the south fishway (Figure 6). Mean passage percentages for those recorded in the south entry, collection channel, and transition pool ranged from 69-88% and were 96% for those recorded in the upper south ladder. A total of 54 fishway exit events were recorded or inferred as lamprey moved from a McNary fishway into the tailrace. About a quarter of these could not be conclusively assigned to a site, all from the south fishway where there were unmonitored openings along the face of the powerhouse. Of the 54, 12 (22%) were from the north shore fishway opening, 23 (43%) were from the south shore opening, 6 (11%) were from the north powerhouse opening, and the remaining 12 (22%) were from unknown sites in the south fishway Mean (se) percent past dam All fish recorded at dam: 65% Total lampreys detected (n) 0 E I T T T T L L L E I I I E I I T T T T T T T L L L North-shore North-PH South-PH Figure 6. Mean annual percent (, +/- se) of radio-tagged Pacific lampreys detected at each antenna site (in ascending order) that eventually passed McNary Dam. Vertical bars represent the total numbers of lampreys detected at each antenna, summed across years. E = entrance, I = inside fishway, T = transition pool, L = ladder. The most downstream transition pool antennas were always at submerged weirs whereas 0 11

17 upstream pool antennas were in overflow-weir sections of the lower ladders at high tailwater elevation. (Note: some fish passed individual antennas undetected and there were three routes into the south transition pool, which explains some of the variability at adjacent antennas.) In general, lampreys turned around in lower reaches of fishways prior to exiting to the tailrace. The most upstream point reached prior to the 12 north shore exit events was just inside the fishway opening (17%) and in the downstream end of the transition pool (83%). In the south fishway, lamprey turned around in the collection channel (14% of 42 exit events), inside the south shore opening (43%), in the transition pool (40%, distributed throughout the pool), and in the upper ladder (2%). Of 128 unique lampreys that entered a McNary fishway, 26 (20%) never passed the dam. Turnaround locations for these fish were similar to those described above. A total of 101 known lamprey passage events occurred at McNary Dam, of which 81 (80%) were via the south fishway and 20 (20%) were via the north fishway. One fish passed undetected by either radiotelemetry or HD-PIT sites (identified by upstream records). Five lampreys fell back at McNary Dam, and all subsequently reascended fishways. Lamprey activity at all fishway sites was predominantly nocturnal (Figure 7), with nocturnal defined as h (between sunset and sunrise on all days except for 4 min/d near the summer solstice). Among the coded telemetry records that marked first lamprey passages at individual antennas and movements between antenna sites, 80-89% of fishway approaches, entries, exits to the tailrace, and exits to the dam forebay occurred at night. The only exception to this behavior was that 64% of movements inside fishways (i.e., inside the collection channel and transition pools) were at night. This was presumably because some lampreys that entered fishways at night remained inside during the following day. 80 Percent of coded movements (%) Approach Entry Exit to tailrace Inside fishway Top of ladder Time of day Figure 7. Distributions of the times (binned by hour) that radio-tagged lampreys were detected approaching (n = 287) and entering (n = 123) fishways, exiting fishways to the tailrace (n = 39), moving inside fishways (n = 1,702), and passing top-of-ladder sites (n = 146), Includes only coded records indicating movement and excludes movements with ambiguous times (i.e., when lampreys entered a fishway undetected). 12

18 Lamprey Passage Times Lamprey passage times through the McNary tailrace and McNary fishways were quite variable within and among years (Table 3). Median times to pass the tailrace, from release to first detected fishway approach, ranged from 1.6 to 7.6 d (means = d). Several lampreys took more than a month to pass the tailrace (Figure 8). Median tailrace passage times differed significantly among years (P < 0.05, Kruskal-Wallis tests). Lampreys entered fishways relatively quickly after their first fishway approach (median 0.15 d (~3.6 h), mean = d; Table 3). Similarly, they quickly entered transition pools after entering fishways (median 0.01 d (~15 min), mean = d). The longer passage times in the fishway entry transition pool segment were at the south-shore fishway, where some lamprey had to move longer distances to reach the pool. Table 3. Numbers of radio-tagged lampreys and their median and mean passage times (d) through the McNary tailrace and fishways in Year Release - fishway approach n Median Mean Fishway approach - entry n Median 0.15 <0.01 < <0.01 <0.01 Mean Fishway entry transition pool n Median < <0.01 <0.01 <0.01 <0.01 Mean Transition pool ladder exit n Median Mean Fishway entry ladder exit n Median Mean Median passage times from transition pool exit to the top of a ladder ranged from d (Table 3). This segment included overflow-weir sections of the ladders and count window areas. Sample sizes were small, but medians differed among years (P < 0.05). Median times to pass the entire fishway, from first entry to exit from the top of a ladder ranged from d (means = d; Table 3, Figure 8). This metric included time lampreys spent in 13

19 the tailrace if they moved in and out of fishways, and the longest passage times were almost exclusively by fish that exited to the tailrace Release - first fishway approach First fishway approach - past dam First fishway entry - past dam Passage time (d) Figure 8. Distributions of adult Pacific lamprey passage times (d) from release to first approach a fishway opening, from first fishway approach to pass the dam, and from first fishway entry to pass the dam in Box plots show median, quartile, 5 th, 10 th, 90 th, and 95 th percentiles. Last Recorded Sites for All Radio-Tagged Lampreys Across years, 63% (174/ 276) of the radio-tagged lampreys were last recorded downstream from McNary Dam or in a fishway below the top-of-ladder exit (Table 4). The largest number in this group (106, 38% of the full sample) was last recorded at a release site. Most of the release-group lampreys likely moved downstream after release, though only one fish was recorded entering the Umatilla River and none were recorded at John Day Dam or in the John Day River. A total of 102 lampreys passed McNary Dam (37% of the 276 released). Of the 102, the largest number (n = 57, 56% of those that passed the dam) was last detected at the top-of-ladder exit sites. A total of 9 lampreys (9%) were last detected at Snake River Dams and 34 (33%) were last recorded at Priest Rapids or Wanapum dams. We note that HD-PIT detectors at Wanapum Dam were not deployed in early study years. Two lampreys (2%) were last detected at the Hanford Reach radiotelemetry antenna, a site that was not operated in later study years. As described previously, larger and earlier-timed lampreys were more likely to be detected at McNary Dam after release and were more likely to pass the dam. These effects carried over into the final distribution of tagged fish. In general, early migrants were more likely to be recorded in the Snake River and at upper Columbia River dams, while those tagged late in the migrations were likely to be last detected at the release site or in the McNary tailrace (Figure 9). Differences in 14

20 release dates were significant among the six groups shown in Figure 6 (ANOVA F 5,267 = 2.3, P = 0.046). Similarly, larger lampreys were most likely to be last recorded at the upriver sites (ANOVA F 5,267 = 3.3, P = 0.006). Table 4. Last locations radio-tagged lampreys were recorded in , including detections at HD-PIT antennas for double-tagged fish. (Note: HD-PIT sites were installed at dams in different years: see Methods.) Site Total Percent Number released Umatilla River % Release site % McNary tailrace % McNary fishway % McNary ladder exit % Ice Harbor Dam % Lower Monumental Dam % Lower Granite Dam % Hanford Reach % Priest Rapids Dam % Wanapum Dam % Evidence for Constraints on Upstream Migration Distance The seasonal and lamprey-size effects associated with upstream movement by the radio-tagged fish (see Figures 5 and 9) raised the possibility that handling and/or tagging lampreys at McNary Dam negatively affected fish performance. We used independent datasets to test whether the sizeor migration timing effects were an artifact of collection. First, we used the relatively large samples of HD PIT-tagged lampreys collected at Bonneville Dam in to test for both size and timing effects on escapement from John Day Dam past McNary Dam. Second, we used daytime lamprey counts at John Day and McNary dams to estimate approximate escapement through this reach in relation to environmental factors. In logistic regression models using the Bonneville-tagged lampreys, larger and earlier-timed lampreys that passed John Day Dam were significantly (P 0.002) more likely to pass McNary Dam than smaller and later migrants (Figure 10). Similarly, the lamprey count data at the two dams indicated that lamprey in warm, low-discharge years were more likely to pass through the John Day to McNary reach than were lampreys in cold, high-discharge years (Figure 11). We tested a variety of mean monthly and seasonal temperature and discharge variables and most supported this overall pattern: Figure 11 shows environmental variables that had relatively higher correlation coefficients. The combined Bonneville HD PIT tag results and the count data strongly suggest that adult lamprey passage at McNary Dam is constrained by seasonal environmental conditions and/or 15

21 lamprey size or energetic status. We think it is likely that the failure of many radio-tagged lampreys to return to McNary Dam following release was related to these migration-scale constraints, though tag effects may also play a role. Release site McNary tailrace McNary fishway McNary ladder exit Snake River Priest Rapids / Wanapum 15 Jun 1 Jul 15 Jul 1 Aug 15 Aug 1 Sept 15 Sept Release date Release site McNary tailrace McNary fishway McNary ladder exit Snake River Priest Rapids / Wanapum Length (cm) Figure 9. Distributions of the dates that adult Pacific lampreys were radio-tagged at McNary Dam (top panel) and lamprey fork lengths (bottom panel) based on the last recorded locations of each fish. Box plots show median, quartile, 5 th, 10 th, 90 th, and 95 th percentiles. Fish last recorded in the Umatilla River (n = 1) and the Hanford Reach (n = 2) are not shown. Discussion This series of adult Pacific lamprey studies is unique in the Columbia River basin in that lampreys were collected in mid-migration, more than 450 kilometers from the ocean and upstream from three main stem dams. Previous research has shown that very few adult lampreys that enter the Hydrosystem subsequently reach McNary Dam, and those that do are among the largest in the population that passes Bonneville Dam (e.g., Keefer et al. 2009a). The McNary sub-population is therefore both phenotypically distinct and critically important in terms of escapement to interior spawning sites in the Snake River and upper Columbia River basins where populations have precipitously declined. A key finding across study years was that many radio-tagged lampreys did not return to McNary Dam after release just one kilometer downstream. About 38% of the tagged fish were last detected at the release site and another 24% were detected at a McNary fishway, but did not pass. Annual 16

22 percentages that did not return to the dam varied four-fold among years (from 19-77%), which was among the most variable passage efficiency metrics evaluated. We have no definitive explanation for these results and the fate of the fish last detected below the dam remains an important uncertainty. However, several lines of evidence suggest that many adult lampreys reach some type of threshold condition during their passage from John Day Dam to McNary Dam. We found that smaller lampreys and those arriving late in the migration were consistently and significantly less likely to be detected at McNary Dam. Results from lampreys PIT tagged at Bonneville Dam and from the daytime lamprey count ratios (at John Day and McNary dams) clearly paralleled results from the radio-tagged group, with later-timed and smaller fish showing significantly lower passage efficiency. Probability of McNary passage Probability of McNary passage Jun 1 Jul 15 Jul 1 Aug 15 Aug 1 Sept 15 Sept 1 Oct 15 Oct 1 Nov John Day Dam passage date Lamprey weight at tagging (g) Figure 10. Predicted probability that PIT-tagged lampreys detected passing John Day Dam subsequently passed McNary Dam, based on the date that tagged fish passed John Day Dam (top panel) and lamprey weight when collected at Bonneville Dam (bottom panel), Probabilities were generated using logistic regression models and included 675 lampreys that passed John Day Dam (all years combined, P = for both models). This convergence of results suggests that adult lampreys respond to environmental cues (e.g., water temperature, day length), or to physiological cues (e.g., diminished energetic reserves) that result in stopped or slowed migration in the John Day McNary reach. In particular, the pattern of lower John Day McNary escapement in years with high discharge and low water temperature 17

23 point to some external controls on lamprey migration distance (also see Keefer et al. 2009b). We hypothesize that both the failure of radio-tagged lampreys to return to McNary Dam after release and the continued decline in adult lamprey escapement to the upper basins may be to related the condition of individuals as they arrive at dams. Specifically, adults that are earlier and larger may be in better physiological or energetic condition, and may be more motivated to expend the resources required to pass the dam. We note that such a threshold model is more likely in a taxon such as lamprey with little evidence of natal homing than salmonids, which have strong natal homing. McNary lamprey count / John Day lamprey count r 2 = July 29 July 2 Aug. 7 Aug. 12 Aug. 17 Aug. 22 Aug Median passage date at McNary Dam 0.1 r 2 = Mean May discharge (m 3 s -1 ) at McNary Dam 0.1 r 2 = Mean August water temperature ( o C) at McNary Dam Figure 11. Relationships between the ratio of McNary:John Day adult lamprey counts (daytime only) and median lamprey passage date at McNary Dam (top panel), mean Columbia River discharge in May 18

24 (middle panel), and mean August water temperature (bottom panel). Lines are linear regression (each significant at P < 0.05). While return-to-mcnary behavior varied considerably among years, radiotelemetry data collected at McNary Dam indicated that lamprey behaviors near and inside fishways were quite consistent across years. More than 70% of the tagged fish detected outside fishways entered a fishway in each year and fishway passage efficiency ranged from 69-89% (mean = 76%). These values are high when compared to lamprey fishway passage efficiency at Bonneville Dam and comparable to values recorded at The Dalles Dam (e.g., Clabough et al. 2010). The most used fishway opening at McNary Dam was at the south end of the Powerhouse, but many lampreys also used the north-shore fishway and some fish used both fishways. The north powerhouse entrance adjacent to the spillway had relatively limited use. A shortcoming of the fishway monitoring effort in all years was that orifice gates were open but unmonitored. By inference, many lampreys used these openings to enter and exit the south fishway, but the spatial distribution of these behaviors and the efficiency of these openings were unknown. The lack of monitoring likely resulted in underestimates of fishway approach, fishway entry, and fishway exit metrics and caution should be used when comparing these result to those from other sites (i.e., at downstream dams). Problem areas for lampreys inside the McNary fishway appeared to be concentrated in the transition pools (both fishways) and in the south fishway collection channel. The north powerhouse entrance adjacent to the spillway also appeared to present passage problems, though relatively few lampreys were detected there. Turn around locations for fish that exited a fishway into the tailrace were highest in the transition areas where confusing attraction cues, hydraulic conditions, or other factors may have impeded passage (e.g., Naughton et al. 2007; Clabough et al. 2010; Johnson et al. in press). Unlike at Bonneville Dam, there was no direct evidence that lampreys had undue difficulty passing the McNary count stations or through the overflow-weir sections of fish ladders. However, these sites were not monitored in any year and the lack of passage difficulty was largely inferred from the relatively rapid passage times from transition pool exit to top-of-ladder antennas. In general, the likelihood that lampreys would pass McNary Dam steadily increased the further up the fishway they were detected. Among all monitored sites, lamprey passage likelihood was lowest for fish recorded at the north powerhouse fishway opening and at the north-shore fishway opening. Results from the two-year ( ) fishway velocity experiment were inconclusive. Entrance use and entrance efficiency estimates in 2009 did not notably differ among reduced velocity and normal operating conditions (Boggs et al. 2010). The modest sample size in 2009 (n = 84) and the very small 2010 sample (n = 18) did not provide enough statistical power to determine whether the reduced velocity condition was beneficial as a priori power analyses suggested required sample size of Likewise, there was no evidence for a negative effect. Given the successful application of this operational modification at Bonneville Dam (Johnson et al. 2009a; in press) and evidence that lampreys move upstream more efficiently when fishway velocity is lower (Keefer et al. 2011), reduced velocity operations at McNary fishway openings presumably provide some lamprey passage benefit. A total of 34 lampreys were detected at Priest Rapids and/or Wanapum dams and nine were detected at Snake River dams. These fish were significantly larger and earlier migrants than those that did not move upstream. We did not identify any traits or behaviors that were associated with Snake River versus upper Columbia River migrants. It is possible that environmental conditions such as temperature or flow differences at the Columbia-Snake confluence affected behavior, but 19

25 small samples (particularly of Snake River fish) made it difficult to directly assess possible environmental drivers. Hypothetically, water velocity from the Hanford Reach arm may have been higher than from the Snake River, providing stronger rheotactic cues for fish in the confluence area. Alternately, pheromones or other olfactory cues may have attracted more lampreys to the Columbia versus the Snake River. In conclusion, the behavioral information collected in this study has provided a good foundation for identifying sites where structural or operational changes to fishways may benefit adult lampreys. We recommend that future studies evaluate fine-scale behaviors near fishway entrances and in transition pools as many passage failures occurred in these areas. To adequately assess lamprey behaviors at these sites, a combination of passive monitoring and tagging studies may be needed. Passive monitoring, including acoustic (e.g., DIDSON) and/or optical underwater video, may provide important, local-scale observations that will clarify how lampreys move or fail to pass through difficult areas. Most importantly, these technologies may help identify specific mechanisms associated with passage failure events. Particular attention should be given to sites where water velocity and turbulence are high (e.g., Johnson et al. in press) and where there are structural impediments like diffuser grating, steps, and sharp-edged corners (e.g., Keefer et al. 2010b, 2011). Additional monitoring of tagged fish may be necessary to address several lingering information gaps. Tagging with acoustic transmitters would help identify the distribution and fate of lampreys in reservoirs both up- and downstream from McNary Dam, particularly if transmitters are programmed to extend battery life into the spring when lampreys move to spawning sites. Such studies could help to determine the fate of the group of adults that was unaccounted after release in this study. Acoustic or radio studies may also be needed to evaluate lamprey response to operational or structural modifications at the dam. Continued HD PIT monitoring would improve our understanding of lamprey passage through the upper Columbia and Snake rivers, as all main stem dams now have (or will soon have) HD PIT detectors in fishways. References Boggs, C., M. Keefer, C. Caudill, C. Peery, and M. Moser Evaluation of adult Pacific lamprey migration and behavior at McNary and Ice Harbor dams, Technical Report of Idaho Cooperative Fish and Wildlife Research Unit to U.S. Army Corps of Engineers, Portland District. Boggs, C. T., M. L. Keefer, C. C. Caudill, and M. L. Moser Evaluation of adult Pacific lamprey migration and behavior at McNary Dam with effects of night-time fishway flow reduction, 2009 and detection and behavior of transported adult Pacific lamprey. Technical Report to U.S. Army Corps of Engineers, Walla Walla District. Clabough, T. S., E. L. Johnson, M. L. Keefer, C. C. Caudill, and M. L. Moser 2010b. General passage and fishway use summaries for adult Pacific lamprey at Bonneville, The Dalles and John Day dams, Technical Report of Idaho Cooperative Fish and Wildlife Research Unit to U.S. Army Corps of Engineers, Portland District. 20