EFFECTS OF ZERO VERSUS NORMAL FLOW AT NIGHT ON PASSAGE OF STEELHEAD IN SUMMER AND FALL

Transcription

1 EFFECTS OF ZERO VERSUS NORMAL FLOW AT NIGHT ON PASSAGE OF STEELHEAD IN SUMMER AND FALL Part VII of Final Report for MIGRATION OF ADULT CHINOOK SALMON AND STEELHEAD PAST DAMS AND THROUGH RESERVOIRS IN THE LOWER SNAKE RIVER AND INTO TRIBUTARIES By T.C. Bjornn, P.J. Keniry, K.R. Tolotti, J.P. Hunt, and R.R. Ringe U.S. Geological Survey, Biological Resources Division Idaho Cooperative Fish and Wildlife Research Unit University of Idaho, Moscow, ID for U.S. Army Corps of Engineers Walla Walla District and Bonneville Power Administration Portland, Oregon 1998

2 EFFECTS OF ZERO VERSUS NORMAL FLOW AT NIGHT ON PASSAGE OF STEELHEAD IN SUMMER AND FALL Part VII of Final Report for MIGRATION OF ADULT CHINOOK SALMON AND STEELHEAD PAST DAMS AND THROUGH RESERVOIRS IN THE LOWER SNAKE RIVER AND INTO TRIBUTARIES by T.C. Bjornn, P.J. Keniry, K.R. Tolotti, J.P. Hunt, and R.R. Ringe U.S. Geological Survey, Biological Resources Division Idaho Cooperative Fish and Wildlife Research Unit University of Idaho, Moscow, ID for U.S. Army Corps of Engineers Walla Walla District and Bonneville Power Administration Portland, Oregon 1998

3 Preface A study of adult salmon and steelhead migrations past dams, through reservoirs, and into tributaries of the Snake River began in 199 with planning, purchase, and installation of radio telemetry equipment. Adult spring and summer chinook salmon were outfitted with transmitters in , and adult steelhead were outfitted in Progress reports have been issued periodically (Bjornn et al. 1992, 1994, 1995) and final reports as listed below. Part I of the final report includes a general introduction, methods that apply to all segments of the work, and information on passage of chinook salmon. Other parts of the final report include an introduction and methods section specific to the topic covered. Part I - Passage of chinook salmon through the lower Snake River and distribution into tributaries Part II - Passage of steelhead through the lower Snake River and distribution into tributaries Part III - Entrances used and passage through fishways for adult chinook salmon and steelhead at Snake River dams. Part IV - Turbine priority and its effects on passage of steelhead at Snake River dams. Part V - Movements of steelhead in fishways in relation to transition pools. Part VI - Evaluation of fishway fences and spill for adult salmon and steelhead passage at Snake River dams. Part VII - Effects of zero versus normal flow at night on passage of steelhead in summer and fall. Page i

4 Table of Contents - Part VII of Final Report Preface...i Abstract...iii Introduction... 1 Methods... 1 Steelhead tagged with spaghetti-loop tags... 5 Steelhead outfitted with transmitters...13 Results...16 Migration rates of steelhead with spaghetti-loop tags...16 Passage success of steelhead with spaghetti-loop tags...28 Recoveries at Lower Granite trap of steelhead with spaghetti-loop tags...33 Returns to hatcheries and fisheries of steelhead with spaghetti-loop tags...38 Migration rates of steelhead outfitted with transmitters...4 Passage success of steelhead with transmitters...52 Discussion...56 References...61 Acknowledgments Many people assisted in this project and its successful completion was made possible by Teri Barila, the Corps of Engineers project officer. Michelle Feeley, Brian Hastings, Jay Nance, and Matthew Keefer played important roles in the study. Page ii

5 Abstract Tests were conducted from 1991 to 1993 to determine if operation of the four lower Snake River dams for peaking-power generation during the fall (low-flow conditions) would affect the upstream migration of steelhead. Two treatment conditions were tested at the upper three of the four dams: zero flow and normal operational flow (11.5 kcfs) at night. Treatments were run in 2-week blocks from September to November each year, when adult salmon and steelhead are normally migrating upstream. The exact starting dates of the treatments were determined by fish movements and water temperatures. Approximately 7 adult steelhead were outfitted with radio transmitters during the migration season in both 1991 and 1992 at Ice Harbor Dam. A number of steelhead were outfitted during each treatment segment. During the 1993 season, 884 steelhead were trapped at John Day Dam and outfitted with transmitters. In addition, approximately 2, (2,3 in 1992) steelhead were tagged each season with spaghetti-loop tags at Ice Harbor Dam. Different tag colors were used for each treatment, and approximately 5 fish were tagged at the beginning of each 2-week segment. Steelhead with transmitters were monitored at receiver sites as they passed dams and migrated into tributaries. Fish with transmitters and those with spaghetti-loop tags were also counted as they passed up the ladders at each dam or were recaptured in the adult trap at Lower Granite Dam or at hatcheries or by anglers. Mean and median passage times of steelhead were calculated from Ice Harbor Dam to the Lower Granite trap. Passage times were also calculated separately for steelhead passage through the Ice Harbor, Lower Monumental, and Little Goose reservoirs. Mean and median travel times for steelhead from different treatment segments were compared using analysis of variance; fish included in the analysis were those exposed to only one flow regime for the entire time they were in the reservoirs. Results of the passage time analysis were consistent from year to year for spaghetti-loop tagged steelhead and for fish outfitted with transmitters. There was no clear evidence that reducing flows to near zero at night affected migration rate, proportion of fish passing the dams, proportion of fish captured in the fishery, or proportion of fish returning to hatcheries. No statistically significant differences were found between mean or median travel times for groups of steelhead released during periods of zero or normal nighttime flow, or for groups of steelhead released during the early portion of the run versus the latter portion of the run. There was also no statistically significant difference between years in travel time through the Little Goose pool, but differences were found between years for travel times through Ice Harbor and Lower Monumental pools. Page iii

6 While there were no statistically significant differences in migration rates, there was a consistent pattern of steelhead migration rates each year. Steelhead released at the end of September and early October migrated at a slightly faster rate than those released in early September, late October, or November. We believe the seasonal differences were related to water temperatures (high early in September then declined) and not flow at night from the three upper dams. Page iv

7 Introduction Tests were conducted in to determine if operation of the four lower Snake River dams in an electrical power-peaking mode during the fall would affect the upstream migration of steelhead. From an electrical power production view, it was desirable to match flow through the powerhouses with power demand, which was high during the day and low at night. The tests were conducted in the fall because that is normally the period with low flows and adult salmon and steelhead migrating upstream. Two treatment conditions were tested, near zero and normal (11.5 kcfs) flow at night from the upper three of the four dams (Figures 1 and 2). The primary null hypotheses tested were that there was no difference in time to migrate or proportion of steelhead migrating from Ice Harbor to Lower Granite dams with the two nighttime flow conditions. Secondary null hypotheses were that the two nighttime flows did not affect the returns of steelhead to fisheries and hatcheries in or upstream from the lower Snake River. Steelhead were chosen for study because most of the fish entering the Snake River in the fall migrate past all four dams in the fall, and, thus, they would provide an opportunity to assess the cumulative effects of the treatment conditions through the entire lower Snake River reach. Chinook salmon migrating in the fall were not studied because of the small number of fish available, and because significant numbers of the salmon passing over Ice Harbor Dam returned back downstream or entered a hatchery midway through the reach and thus impaired our ability to measure effects for the full reach of river. In previous studies of reduced flows at night and adult salmon and steelhead migration in the lower Snake River, McMaster et al. (1977) could not detect an effect of reduced flows at night between Ice Harbor and Little Goose dams on adult migration based on counts of fish at the dams and movements of fish outfitted with radio transmitters. Liscom et al. (1985) studied adult salmonid migrations between Lower Monumental and Little Goose dams, using radio transmitters, and reported that zero flows at night at the two dams delayed the migration of steelhead and fall chinook salmon. In the study by Liscom et al. (1985) the investigators apparently considered individual fish with transmitters as the experimental units and replicates that could be used to test the effects of the treatment conditions (zero versus normal flows at night). In our view, the experimental units, to which the treatments were applied, were the periods of time the section of river (reservoir) between the two dams was subjected to the two flow regimes. Because this is a correct assessment, then Liscom et al. had four replicates of each treatment rather than to 42 if the fish with transmitters were thought to be replicates. With the smaller number of replicates per treatment, the finding of delayed migration might not be warranted. Methods Assessing the effects of two different flow patterns at night in a section of river like the lower Snake was a special challenge because the treatments could Page 1

8 6 5 Lower Monumental Dam Little Goose Dam Discharge (kcfs) Lower Granite Dam Sep 1 Sep 15 Sep 2 Sep Figure 1. Hourly flows at the lower Snake River dams during the first 2-week period of the 1993 zero-flow test when flows were reduced to near zero kcfs at night. Tick marks are located at 24 hours. Page 2

9 6 5 Lower Monumental Dam Little Goose Dam Discharge (kcfs) Lower Granite Dam Sep 25 Sep 3 Sep 4 Oct Figure 2. Hourly flows at the lower Snake River dams during the second 2-week period of the 1993 zero-flow test when flows were maintained at a minimum of 11.5 kcfs at night. Tick marks are located at 24 hours. Page 3

10 not be easily and cleanly replicated. There was only one river, that could not be duplicated, so the replicates were obtained over time. Experimental units that were replicated were the periods of time that treatment conditions (zero or normal flow at night) were imposed on the section of river of interest. Fish migrating through the river during each of the treatment periods were not replicates that can be used to test for treatment effects, because the treatments were not assigned to the fish. The fish were merely the sampling units of observation on which we obtained information on time to pass and proportion that passed through the section of river of interest. The same line of reasoning would apply if we were to study the effects of the two flows on a bottom dwelling invertebrate that was relatively immobile. The number of sampling units (fish in this case) is important because we had to observe enough fish passing through the river section to get reliable estimates of the variables of interest. In previous years, the effects of flows at night were studied in limited sections (between two or three dams) of the lower Snake River. In this study, there was an interest in assessing the effects of zero flows at night on the entire section of river impounded by dams, and carry-over effects that might be evident in time and proportion of fish captured in fisheries or at hatcheries upstream from the impounded section. The section of river of direct interest was from Ice Harbor Dam upstream to the upper end of Lower Granite Reservoir; a section containing four reservoirs and four dams. Flow was reduced to near zero at the three upper dams during the periods of zero flow at night, but normal minimum flows at night (11.5 kcfs) were maintained at Ice Harbor Dam because of the free-flowing stretch of river downstream from that dam. When flows from the three upper dams were reduced to zero at night (11 to 5 hours), water velocities in the reservoirs were theoretically reduced to near zero, except at the upper end of Lower Granite Reservoir where the inflowing rivers maintained some current and in the immediate forebay of Ice Harbor Dam where water was withdrawn to maintain downstream flows. The period of time to maintain the treatment flows was primarily dependent on the time required for fish to pass through the section of river from Ice Harbor Dam to the upper end of Lower Granite Reservoir. From previous studies (McMaster et al. 1977; Turner et al. 1983, 1984; Liscom et al. 1985) we estimated that most steelhead could migrate through the lower Snake River in less than 2 weeks. In 1992, the median time for steelhead to migrate from Ice Harbor to Lower Granite dams was 6.1 d, so half the fish released had migrated through three reservoirs and passed three dams in about 6 d (Bjornn et al. 1994). Median times of passage from release to passage at the receiver sites in the lower Clearwater River and the Snake River upstream from Lower Granite Reservoir were longer (15.1 to 46.5 d) and are an indication of the overwintering by steelhead in the Lower Granite pool and section of the two rivers downstream from the receiver sites. The experimental units then for this study were 2-week periods of time when discharges from the upper three dams were reduced to zero or maintained at normal (11.5 kcfs) from 23 to 5 Page 4

11 hours each night (Figures 1 and 2). To ensure interspersion of experimental units within each fall season of steelhead migration, the period of migration was divided into two blocks with 2-week periods of zero and normal flows at night within each block (Figure 3). The treatment conditions were thus replicated twice each fall migration season and the study was conducted for 3 years, thereby providing six replicates of each treatment. The treatment assigned to the first 2-week period in the first year of the study was selected at random (zero flow), but from then on the assignment of treatments was systematic because we believed interspersion of the treatments during the migration season was more important than randomly assigning the treatments to each block. During 1991, the first period had zero flow at night, the second had normal flows, the third had zero flow, and the last period had normal flows (Figure 3). The same alternating assignment of treatments was carried out in the second and third years of the study, except that normal flows were discharged from the dams in the first 2-week period in 1992 and the zero-flow treatment was assigned to the first period again in We used systematic assignment of treatments because we were aware of seasonal differences in migrations of steelhead that might affect the outcome of the test if we relied entirely on random assignment of treatments to a small number of experimental units. During late August and early September temperatures of the Snake River are often high enough (>2 o C) to retard, if not cause a cessation, of migration of steelhead. Few steelhead enter and migrate up the Snake River in the fall until water temperatures begin to decline and fall below about 2 o C (Strickland 1967). We were concerned that during the early portion of the migration period steelhead might migrate at slower rates than later in the season. The second seasonal change in migration that we needed to watch for was the cessation of migration and overwintering that occurs late in the season. If, by randomly assigning the treatments to the periods, we ended up with the same treatment assigned to the first and last periods of each year of study, we believed the result would likely be biased toward longer times to migrate and fewer fish passing a dam or through the reach, not because of the flow at night during those periods, but because of the seasonal differences in migration. By systematic assignment of treatments to the 2-week periods, we ensured that neither of the treatment conditions occurred only in the first and last periods when fish might migrate at slow rates, or in the two middle periods of each season when fish might migrate at maximum rates. Steelhead were marked in two ways, those outfitted with transmitters and those tagged with spaghetti-loop tags (jaw or visual implant tags were used as secondary tags). Steelhead were monitored to assess the time to pass through each segment of the lower Snake River and the proportion of those released that successfully migrated through each segment during each of the treatment periods. Steelhead tagged with spaghetti-loop tags At the beginning of each 2-week period, steelhead were captured at Ice Page 5

12 Flow Steelhead tagged Flow at Lower Monumental Dam at 1 hours (kcfs) Number of steelhead tagged Sep 15 Sep 1 Oct 15 Oct 1 Nov 15 Nov 1 Dec Figure 3. Flows at Lower Monumental Dam at 1 hours during the zero-flow study with number of spaghetti-loop tagged steelhead released at the start of each 2-week period of zero or normal flow at night. Page 6

13 Harbor Dam, tagged with spaghetti-loop tags, released at Charbonneau Park 1.7 km upstream from the dam, and then counted as they passed up the ladders at each dam or were recaptured in the adult trap at Lower Granite Dam and at hatcheries and by fishermen. Observations made on these tagged steelhead allowed us to calculate mean and median times to migrate from release to passage at each of the dams and through the entire reach, and to estimate the proportion of fish that migrated successfully through the segments and were recaptured after being subjected to the treatment flow conditions for 2 weeks following their release. At the beginning of each 2-week block, approximately 5 adipose-clipped adult steelhead were captured in a trap at the top of the south-shore fish ladder at Ice Harbor Dam, anesthetized with tricaine methane sulfanate (MS-222) at a concentration of 5 mg/l, and transported by truck to Charbonneau Park approximately 1.7 km upstream from Ice Harbor Dam for tagging and release. Approximately 1 fish were trapped and tagged per day for the first 4 to 6 d of each period (Figure 3). Releases were spread out over 4 to 6 d because it was impossible to trap and tag more than 1 fish per day. Fish of all sizes were trapped and retained for tagging with spaghetti-loop tags (Figures 4, 5, and 6). Only adipose-clipped fish were used to insure sufficient returns to hatcheries and the fisheries when evaluating the effects of zero-nighttime flow. Fish were tagged with a spaghettiloop tag (different color for each period) inserted under the dorsal fin and secured by either a knot or a metal clip. In 1991 and 1992 a numbered aluminum band was placed around the lower jaw as a secondary tag. In 1993, the jaw tag was replaced with a 1 x 3 mm numbered visual implant (VI) tag injected into the transparent adipose tissue posterior to the left eye. The switch from jaw to VI tags was made because the aluminum band caused damage to the lower jaw of some steelhead. Otherwise, the jaw tag was a good secondary tag, which can be considered for use when the time between tagging and recapture is less than several months and angler recognition of tagged fish is important. A 1- mm piece of magnetic wire (coded wire tag) was injected into the muscle at the base of the dorsal fin on each fish to facilitate recapture in the adult trap at Lower Granite Dam. After tagging, fish were placed in a fiberglass trough (38 L) to recover from the anesthetic. The trough was perforated to allow water circulation and suspended in the river with the lip of the trough several inches below the water's surface. Recovery of fish could be monitored in the trough and the fish were able to swim out into the river when recovered, usually within 2 or 3 min. Passage of steelhead with spaghettiloop tags was recorded, by color, on an hourly basis as a part of regular fish counting activities at each of the four dams on the lower Snake River. Mean and median travel times from release at Charbonneau Park to each of the three dams upstream and the proportion of fish passing each dam from each release group for groups of steelhead released during periods of zero- or normal-night time flow were analyzed using analysis of variance. Since it wasn't possible to identify individual fish as they passed the counting windows, mean and median Page 7

14 5 4 Orange tags - zero flow 471 tagged 16-2 Sep Green tags - normal flow 52 tagged 3 Sep - 4 Oct Number of steelhead Yellow tags - zero flow 53 tagged Oct Blue tags - normal flow 5 tagged 28 Oct - 2 Nov Length (cm) Figure 4. Length frequency distribution of steelhead that were tagged with spaghetti-loop tags in Page 8

15 5 4 3 Orange tags - normal flow 51 tagged 8-13 Sep Green tags - zero flow 51 tagged Sep 2 1 Number of steelhead Yellow tags - normal flow 531 tagged 6-1 Oct Blue tags - zero flow 55 tagged 2-25 Oct Red tags - normal flow 34 tagged 3-5 Nov Length (cm) Figure 5. Length frequency distribution of steelhead that were tagged with spaghetti-loop tags in Page 9

16 5 4 3 Green tags - zero flow 48 tagged 6-11 Sep White tags - normal flow 499 tagged 2-24 Sep Number of steelhead Red tags - zero flow 51 tagged 4-8 Oct Yellow tags - normal flow 55 tagged Oct Length (cm) Figure 6. Length frequency distribution of steelhead that were tagged with spaghetti-loop tags in Page 1

17 travel times were calculated as if all fish were released on the first day of tagging for each release group. One of the assumptions that must be made when using analysis of variance is that the populations being sampled share a common variance. The variance of proportions can be quite variable when proportions are high, as in this study, so we transformed count and recapture data using y t = arcsin (square root of y) to stabilize the variances (Ott 1988). At Lower Monumental Dam, the fourth release group in 1991 and the fifth release group in 1992 were not counted as the counting window closed for the season prior to the release of those groups. Data from Lower Monumental Dam for the third release group in 1991 were not included in statistical tests since inclusion of these data would have created an unbalanced design and biased test results. The second release group in 1991 was counted at Lower Monumental Dam for 31 d. The fourth release groups in 1991 and 1993 were counted for 11 and 43 d, respectively, at Lower Monumental Dam. Since fish from all release groups were counted for at least 11 d at Lower Monumental Dam, statistical analysis for data collected at Lower Monumental Dam was based on the first 11 d following release for all release groups. Data from Little Goose Dam for the fifth release group in 1992 were not included in statistical tests for two reasons. Fish in the fifth release group appeared to move slower than fish in the preceding groups and were likely beginning the overwintering behavior observed by McMaster et al. (1977). Also, inclusion of these data would have created an unbalanced design and biased test results. The fourth release group in 1991 was counted at Little Goose Dam for 33 d. The fourth release groups in 1992 and 1993 were counted for 41 and 43 d, respectively. Since fish from all release groups were counted for at least 33 d at Little Goose Dam, statistical analysis for data collected at Little Goose Dam was based on the first 33 d following release for all release groups. Data from Lower Granite Dam for the fifth release group in 1992 were not included in statistical tests for the same reasons that they were not included in analysis at Little Goose Dam. Fish in the fifth release group appeared to move slower than fish in the preceding groups and were likely beginning the overwintering behavior observed by McMaster et al. (1977). Also, inclusion of these data would have created an unbalanced design and biased test results. The fourth release groups were counted at Lower Granite Dam for 48 d in 1991, 56 d in 1992, and 58 d in Since fish from all release groups were counted for at least 48 d at Lower Granite Dam, statistical analysis for data collected at Lower Granite Dam was based on the first 48 d following release for all release groups. At the adult trap at Lower Granite Dam, fish were measured and checked for condition, the jaw- or VI-tag number was recorded and the spaghetti-loop tag was removed. Spaghetti-loop tags were removed to minimize possible tissue erosion caused by tag movement. Jawor VI-tag numbers were matched with release date to determine travel time from release to the Lower Granite trap for each individual. Mean and median travel times from release to the Lower Granite trap and proportion of fish Page 11

18 from each release group that arrived at the Lower Granite trap were analyzed statistically using analysis of variance. In 1991, the Lower Granite trap was operated 45 d following release of the fourth and final release group. In 1992, the trap was operated 29 d following release of the fifth group. In 1993, the trap was operated 27 d following release of the fourth group. Since the minimum period of trapping was 27 d following release for any of the release groups in any of the three study years, statistical analysis for travel times from release to Lower Granite trap was based on the first 27 d after release for all release groups. As with data from counting windows, data from the fifth release group in 1992 were not included in statistical analyses for migration rates and passage success from release to Lower Granite trap because of the probability that fish from that group were beginning overwintering behavior as well as the problems associated with unbalanced statistical designs. Tagged steelhead that returned to hatcheries were noted by hatchery workers during sorting and spawning activities. Jaw- or VI-tag numbers, presence and color of spaghetti-loop tags (Lower Granite trap was not 1% effective), and approximate date of recapture were recorded by hatchery personnel on forms provided by project personnel. Completed forms were either mailed to the University of Idaho or were picked up at the hatcheries by project personnel. Jaw- or VI-tag numbers were matched to release groups and associated flow regimes. Proportions of fish released during zero- or normal-nighttime flow periods that returned to hatcheries were compared using analysis of variance. To maximize tag returns from fisheries, a $5 reward was offered to private individuals for information on capture of tagged fish. The reward was not available to employees of state, federal, or tribal agencies who recovered tags during the course of their official duties. Angler awareness of the presence of tagged steelhead in the Snake River basin was increased by placing posters describing the tags, position of the tags on the fish, purpose of the study, and the reward program at popular river access points and boat ramps. Creel census workers and biological staff from state, federal, and tribal agencies were also asked to watch for and report to us information on tagged steelhead caught in fisheries. Anglers who caught tagged steelhead were asked to send tags or tag numbers and date and location of recapture to the address stamped on jaw tags and listed on posters. Anglers could also give recapture information to state, federal, or tribal creel census workers who forwarded it to the University of Idaho. Upon receipt of recapture information from an angler, project staff would check the information and, if necessary, contact the angler for verification or clarification of any discrepancies. Once the recapture information was complete, a check for $5 along with a letter explaining the purposes and objectives of the study and thanking the angler for their participation was sent to the angler. Records of fish that were recaptured in the fisheries were matched with tagging information to determine release group and associated flow regime. Page 12

19 Proportions of fish released during zeroor normal-nighttime flow periods that were captured in the fisheries were compared using analysis of variance. Steelhead outfitted with transmitters During 1991 and 1992, steelhead were captured at Ice Harbor Dam almost daily, outfitted with transmitters, and released either at Hood Park 12.4 km downstream from the dam or at Charbonneau Park upstream from the dam to evaluate steelhead migrations past the dams, through the reservoirs, and into the tributaries. In 1993, steelhead were captured, outfitted with transmitters, and released at John Day Dam. Steelhead with transmitters were monitored at receiver sites as they passed each of the dams and migrated into the tributaries. The use of radio transmitters in conjunction with automated radio receiver/data-loggers made it possible to accurately measure and record the passage time of individual steelhead through the lower Snake River reservoirs. In 1991 and 1992, steelhead that were outfitted with radio transmitters were trapped using the same methods that were used for steelhead marked with spaghetti-loop tags with the exception of the selection process. Only adipose-clipped (hatchery origin) steelhead were tagged with spaghetti-loop tags. Fish trapped for the portion of the study using radio transmitters were not restricted to adipose-clipped fish. Approximately 5% of the steelhead intended for outfitting with radio transmitters were lacking an adipose fin and were assumed to be of hatchery origin, and 5% possessed an adipose fin and were probably naturally produced. Due to the size of the radio transmitter used in 1991, we did not place transmitters in steelhead smaller than 66 cm in length. In 1992, a smaller transmitter was available and we were able to use steelhead down to 61 cm in length (Figure 7). Trapping, tagging, and release of steelhead was performed as described in Part I of the final report. Approximately 7 steelhead were outfitted with transmitters and released in both 1991 and During 1993, 884 steelhead were outfitted with transmitters and released at John Day Dam. Releases were conducted throughout the migration season (Figure 8). Two or three receiver sites were used at each dam. The downstream receiver sites were located 1 to 3 km downstream from the dams and consisted of a SRX-4 receiver scanning two nine-element yagi antennas oriented up and downstream to give maximum area of coverage. The second receiver site at each dam was located at the top of each fish ladder. At dams with two fish ladders, a receiver was located at the top of each of the two ladders. In 1991, receiver sites at the tops of fish ladders consisted of a SRX-4 hooked to an underwater antenna. In 1992 and 1993 a DSP-5 scanner was added to the SRX-4 at the top of each ladder. Analysis of movements of fish with transmitters was conducted on a reservoir by reservoir basis. Fish included in the analysis of migration through a reservoir had to be exposed to only one flow regime for the entire period of time that it was in the reservoir. Fish that entered a reservoir under Page 13

20 Number of steelhead Length (cm) Figure 7. Length frequency distribution of steelhead outfitted with radio transmitters during 1991, 1992, and Page 14

21 5 7, Zero flow Normal flow Fish counted Fish tagged 6, 5, 4, 2 3, 1 2, 1, 5 7, Steelhead tagged , 5, 4, 3, 2, 1, Steelhead counted 5 7, , 5, 3 4, 2 3, 1 2, 1, 1 Jul 15 Jul 1 Aug 15 Aug 1 Sep 15 Sep 1 Oct 15 Oct 1 Nov Figure 8. Number of steelhead released with radio transmitters at Ice Harbor Dam and the number of steelhead counted at the counting window at Ice Harbor Dam in 1991, 1992, and 1993 during periods of zero and normal flow at night. Page 15

22 one nighttime-flow regime but did not arrive at the next upstream dam before the beginning of the alternate flow regime were not included in the analysis of travel time through that reservoir. Data on travel times for fish that were exposed to two or more flow regimes during passage through a reservoir were discarded. Travel times through reservoirs for fish with transmitters were calculated by subtracting the date and time for the last record for a fish at the top of a fish ladder at one dam from the date and time for the first record for that fish at the tailrace receiver site at the next dam upriver. Mean and median travel times for steelhead migrating under each flow regime were compared for Ice Harbor, Lower Monumental, and Little Goose pools using analysis of variance. The proportion of steelhead with transmitters successfully migrating though each lower Snake River reservoir during periods of zero- or normal-nighttime flow is another potential measure of the effects of reduced flow at night. Steelhead with transmitters that entered reservoirs during the first week of a 2-week flow period were monitored to determine the proportion of fish that were recorded arriving at the next dam upstream prior to the end of the 2-week flow period. Limiting the analysis to fish that entered the reservoir during the first half of the 2-week flow period insured that passage success was analyzed rather than migration rate by allowing ample time for even slow moving fish to traverse the reservoir. Proportions of steelhead that were exposed to either zero or normal flow at night were compared using analysis of variance. Data were transformed using y t = arcsin (square root of y) (Ott 1988). Results We could not find evidence that reducing the discharges to zero at night from the upper three of four dams in the lower Snake River had any effect on the time for steelhead to migrate or the proportion of steelhead migrating through any segment or the entire impounded reach of the river. The effects of zero flow at night on steelhead were assessed by analyzing travel time from the release site to the dams on the lower Snake River, proportions of fish migrating past each dam in the lower Snake River, and proportions of fish recaptured at hatcheries and in fisheries from each group of tagged fish. Migration rates of steelhead with spaghetti-loop tags Steelhead with spaghetti-loop tags moved upstream through the system and past the lower Snake River dams in a fairly consistent pattern in all three years of the study. Most of the fish in the first three groups released each year passed the upper three dams in the lower Snake River within the 1-d period following release and the start of a flow regime (Figures 9, 1, and 11). In 1993, the fourth group moved past the lower Snake River dams with a pattern similar to that observed in earlier groups, but in 1991 and 1992 groups released in late October or early November moved upriver at a noticeably slower rate without a well defined peak. Page 16

23 Orange tags - zero flow 471 tagged, 16-2 Sep 91 LMO LGO LGR n = 424 n = 414 n = 385 Steelhead counted Green tags - normal flow 52 tagged, 3 Sep - 4 Oct 91 LMO LGO LGR n = 45 n = 42 n = 38 Yellow tags - zero flow 53 tagged, Oct 91 LMO LGO LGR n = 387 n = 383 n = Blue tags - normal flow 5 tagged, 28 Oct - 2 Nov 91 LMO LGO LGR n = n = 288 n = Days after release Figure 9. Frequency distribution of spaghetti-loop tagged steelhead released during each time period (flow regime) and counted at Lower Monumental (LMO), Little Goose (LGO), and Lower Granite (LGR) dams in Page 17

24 Orange tags - normal flow 51 Tagged, 8-13 Sept 92 LMO LGO LGR n = 428 n = 366 n = Green tags - zero flow 51 Tagged, Sept 92 LMO LGO LGR n = 482 n = 358 n = 362 Steelhead counted Yellow tags - normal flow 531 Tagged, 6-1 Oct 92 LMO LGO LGR Blue tags - zero flow 55 Tagged, 2-25 Oct 92 LMO LGO LGR n = 48 n = 376 n = 391 n = 242 n = 267 n = Red tags - normal flow 34 Tagged, 3-5 Nov 92 LMO LGO LGR n = n = 124 n = Days after release Figure 1. Frequency distribution of spaghetti-loop tagged steelhead released during each time period (flow regime) and counted at Lower Monumental (LMO), Little Goose (LGO), and Lower Granite (LGR) dams in Page 18

25 Green tags - zero flow 48 tagged, 6-11 Sept 93 LMO LGO LGR n = 347 n = 279 n = 299 Steelhead counted White tags - normal flow 499 tagged, 2-24 Sept 93 LMO n = 414 LGO LGR n = 355 n = 366 Red tags - zero flow 51 tagged, 4-8 Oct 93 LMO LGO LGR n = 325 n = 374 n = Yellow tags - normal flow 55 tagged, Oct 93 LMO LGO LGR n = 342 n = 322 n = Days after release Figure 11. Frequency distribution of spaghetti-loop tagged steelhead released during each time period (flow regime) and counted at Lower Monumental (LMO), Little Goose (LGO), and Lower Granite (LGR) dams in Page 19

26 At Lower Monumental Dam steelhead with spaghetti-loop tags were first counted 1 to 3 d following release in all three years of the study (Figures 12, 13, and 14). In 1991, the median day of passage for all groups counted at Lower Monumental Dam was the fifth day after release (Table 1, Figure 15). In 1992, the median day of passage was the fourth day for steelhead in the second group (zero flow), the fifth day for fish in the first group (normal flow), the sixth day for fish in the third group (normal flow), and the seventh day for steelhead in the fourth group (zero flow). In 1993, the median day of passage was the fourth day for fish in the second and third groups (normal and zero flow, respectively) and the sixth day for steelhead in the first and fourth groups (zero and normal flow, respectively). No statistically significant differences were found between the median days of passage observed for steelhead migrating during zero- versus normal-nighttime flows (Table 2). Mean travel times from release to Lower Monumental Dam in 1991 were 4.7 d for steelhead in the second release group (normal flow), 5.2 d for fish in the first group (zero flow), and 5.4 d for fish in the third group (zero flow) (Table 1). In 1992, mean passage times ranged from 4.5 d for fish in the second release group (zero flow) to 7. d for fish in the fourth release group (zero flow). Fish in the first and third release groups (normal flow) had mean travel times of 6.3 d. In 1993, mean travel times from release to Lower Monumental Dam ranged from 4.4 to 6.5 d for fish in the third and first release groups, both of which were released under zero flow conditions. Fish in groups two and four (normal flow) had mean travel times of 4.6 d and 5.4 d, respectively. Mean travel times were compared using analysis of variance. No statistically significant differences were found between years or flow regimes for steelhead passage times (Table 2). The first steelhead from each release group were counted at Little Goose Dam 2 to 6 d after release (Figures 12, 13, and 14). In 1991, the median day of passage ranged from day 7 for steelhead in the second group (normal flow) to day 12 for fish in the fourth group (normal flow). Steelhead in groups one and three (zero flow) had median passage times of 8 d (Table 1, Figure 16). In 1992, the median day of passage ranged from day 7 for fish in the second group (zero flow) to day 12 for fish in the fourth group (zero flow). Fish in the first and third release groups (normal flow) had a median passage time of 1 d. Fish in the fifth release group (normal flow) had a median passage time of 11 d. In 1993, fish in groups two and three (normal and zero flow respec tively) both had median passage times of 7 d. Fish in group four (normal flow) had a median passage time of 8 d. The median day of passage for steelhead in the first release group (zero flow) was day 12. No statistically significant differences were found between median passage times for steelhead released during zeroor normal-nighttime flows (Table 3). Mean passage times from release to Little Goose Dam in 1991 ranged from 7.9 to 13. d for steelhead in the second and fourth release groups (normal flow). Steelhead in the first and third release groups (zero flow) had mean passage times of 9. and 8.9 d (Table 1). In 1992, mean passage times ranged from 8.8 d for fish in the second release group (zero flow) to 14. d for fish in the fourth Page 2

27 15 Lower Monumental Dam 1 5 Orange - zero flow Green - normal flow Yellow - zero flow Blue - normal flow n = 48 n = 43 n = 387 n = Little Goose Dam Steelhead counted 1 5 n = 398 n = 4 n = 377 n = 288 Lower Granite Dam 1 n = 384 n = 38 n = 336 n = Days after release Figure 12. Frequency distribution by dam of spaghetti-loop tagged steelhead counted at Lower Monumental, Little Goose, and Lower Granite dams in Page 21

28 15 Lower Monumental Dam 1 5 Orange - normal flow Green - zero flow Yellow - normal flow Blue - zero flow Red - normal flow n = 428 n = 482 n = 48 n = 242 n = Little Goose Dam Steelhead counted 1 5 n = 366 n = 358 n = 376 n = 267 n = 124 Lower Granite Dam 1 5 n = 322 n = 362 n = 391 n = 265 n = Days after release Figure 13. Frequency distribution by dam of spaghetti-loop tagged steelhead counted at Lower Monumental, Little Goose, and Lower Granite dams in Page 22

29 15 Lower Monumental Dam 1 5 Green - zero flow White - normal flow Red - zero flow Yellow - normal flow n = 347 n = 414 n = 325 n = 342 Little Goose Dam Steelhead counted 1 5 n = 279 n = 355 n = 374 n = 322 Lower Granite Dam 1 n = 299 n = 366 n = 41 n = Days after release Figure 14. Frequency distribution by dam of spaghetti-loop tagged steelhead counted at Lower Monumental, Little Goose, and Lower Granite dams in Page 23

30 Table 1. Mean and median days to pass the three Snake River dams upstream from Ice Harbor Dam and percentage of fish released that were counted, based on counts of tagged steelhead passing the counting window for the four groups of spaghetti-loop tagged steelhead released for the zero-flow study in Estimates based on 11 d of counting after release for Lower Monumental Dam, 33 d of counting at Little Goose Dam, and 48 d at Lower Granite Dam. Group number Flow Lower Monumental Dam Little Goose Dam Lower Granite Dam Release dates at Mean Median Percent Mean Median Percent Mean Median Percent night (d) (d) (d) (d) (d) (d) Sep Zero Sep-4 Oct Normal Oct Zero Oct-2 Nov Normal Sep Normal Sep Zero Oct Normal Oct Zero Nov Normal Sep Zero Sep Normal Oct Zero Oct Normal Page 24

31 Proportion of steelhead Group 1 - zero flow Group 2 - normal flow Group 3 - zero flow Group 4 - normal flow Day after release Figure 15. Cumulative frequency distribution of spaghetti-loop tagged steelhead counted at Lower Monumental Dam in 1991, 1992, and Page 25

32 Table 2. Analysis of variance tables for median and mean passage time from release to Lower Monumental Dam for steelhead tagged with spaghetti-loop tags. Source df Sum of squares Mean Square F value P>F Median passage time Year Nighttime flow Season Year*flow Year*season Error 2 5. Total Mean passage time Year Nighttime flow Season Year*Flow Year*Season Error Total release group (zero flow). Fish in the first, third, and fifth release groups (normal flow) had mean passage times of 1.8, 11.3, and 12.1 d, respectively. In 1993, mean travel times from release to Little Goose Dam ranged from 7.4 d for steelhead in the third release group (zero flow) to 15.2 d for fish in the first release group (zero flow). Steelhead in the second and fourth release groups (normal flow) had mean passage times of 8.3 and 8.7 d. No statistically significant differences were found between mean passage times for steelhead released during zero- or normal-nighttime flows (Table 3). The pattern of movement observed at Lower Granite Dam was similar to that seen at Little Goose Dam (Figures 13 and 14). The first steelhead from each release group were counted at Lower Granite Dam 4 to 6 d after release. In 1991, the median day of passage for steelhead counted at Lower Granite Dam ranged from day 1 for fish in the second group (normal flow) to day 18 for fish in the fourth release group (normal flow). Steelhead in groups one and three (zero flow) had median passage times of 11 d (Table 1, Figure 17). In 1992, median passage times ranged from 1 d for steelhead in the second release group (zero flow) to 17 d for steelhead in the fifth group (normal flow). Steelhead in the first (normal flow), third (normal flow), and the fourth groups (zero flow) had median passage times of 12, 13, and 16 d, respectively. In 1993, the median day of passage was day 1 for fish in the second (normal flow) and third (zero flow) groups, day 12 for fish in the fourth group (normal flow) and day 15 for fish in the first group (zero flow). No statistically Page 26

33 Proportion of steelhead Group 1 - zero flow Group 2 - normal flow Group 3 - zero flow Group 4 - normal flow Group 5 - zero flow Day after release Figure 16. Cumulative frequency distribution of spaghetti-loop tagged steelhead counted at Little Goose Dam in 1991, 1992, and Page 27

34 Table 3. Analysis of variance tables for median and mean passage time from release to Little Goose Dam for steelhead tagged with spaghetti-loop tags. Source df Sum of squares Mean square F value P Median passage time Year Nighttime flow Season Year*flow Year*season Error Total Mean passage time Year Nighttime flow Season Year*flow Year*season Error Total significant differences were found in median passage times for steelhead released during zero- or normal-nighttime flows (Table 4). Mean travel times from release to Lower Granite Dam in 1991 ranged from 1.7 d for steelhead in the second release group (normal flow) to 2.2 d for steelhead in the fourth release group (normal flow). Mean travel times for fish in the first and third release groups (zero flow) were 12.4 and 14.6 d, respectively (Table 1). In 1992, mean travel times from release to Lower Granite Dam ranged from 11.8 d for steelhead in the second release group (zero flow) to 19.3 d for steelhead in the fifth release group (normal flow). Steelhead in the first (normal flow), third (normal flow), and fourth (zero flow) release groups had mean travel times of 14.1, 14.9, and 17.9 d. In 1993, the pattern was slightly different. Mean travel times ranged from Page d for fish in the third release group (zero flow) to 18.8 d for fish in the first release group (zero flow). Fish in the second and fourth release groups (normal flow) had mean travel times of 11.1 and 12.8 d. Mean travel times for steelhead released under either zero- or normal-nighttime flows were compared using analysis of variance. No statistically significant differences were found (Table 4). Passage success of steelhead with spaghetti-loop tags The proportion of steelhead successfully migrating past the dams is also a potential measure of the effects of reduced flow at night. The proportion of spaghetti-loop tagged steelhead migrating past each of the lower Snake River dams was calculated for all three

35 Proportion of steelhead Group 1 - zero flow Group 2 - normal flow Group 3 - zero flow Group 4 - normal flow Group 5 - zero flow Days after release Figure 17. Cumulative frequency distribution of spaghetti-loop tagged steelhead counted at Lower Granite Dam in 1991, 1992, and Page 29

36 Table 4. Analysis of variance tables for median and mean passage time from release to Lower Granite Dam for steelhead tagged with spaghetti-loop tags. Source df Sum of squares Mean square F value P Median passage time Year Nighttime flow Season Year*flow Year*season Error Total Mean passage time Year Nighttime flow Season Year*flow Year*season Error Total years of this study. As with migration rates, analysis of the proportions of steelhead migrating past the dams was based on the minimum number of days that fish in any of the groups were counted at a particular dam. The proportion of spaghetti-loop tagged steelhead that passed Lower Monumental Dam in 1991 was.84 for the first group of fish released (zero flow at night) and declined with each subsequent group released that year, with.76 of the second group (normal flow) and.74 of the third group (zero flow) successfully passing Lower Monumental Dam (Table 1, Figure 18). In 1992, the pattern observed at Lower Monumental Dam was slightly different. The proportion of fish that successfully passed the dam ranged from.48 for fish in the fourth release group (zero flow) to.86 for fish in the second release group (zero flow). The first and third release groups (normal flow) were intermediate at.77 and.68. In 1993, the proportion of fish from each release group that successfully migrated past Lower Monumental Dam ranged from.56 for fish in the first group to.78 for fish in the second group. Fish in the third and fourth release groups (zero and normal flows, respectively) were inter- mediate at.61 and.63. No statistically significant differences were observed between proportions of fish that successfully passed Lower Monumental Dam after being exposed to either zero- or normal-nighttime flows (Table 5). At Little Goose Dam in 1991, the pattern of proportions of steelhead that successfully passed the dam from each release group was similar to the pattern seen at Lower Monumental Dam (Figure 18). Proportions ranged from.58 for fish in the fourth release group (normal flow) to.85 for fish in the first release group (zero flow) (Table 1). The second (normal flow) and third (zero flow) Page 3