North American Journal of Fisheries Management 23:1215±1224, 2003 ᭧ Copyright by the American Fisheries Society 2003

In¯uence of Fishway Placement on Fallback of Adult Salmon at the Bonneville on the

TAMI S. REISCHEL* AND THEODORE C. BJORNN Idaho Cooperative Fish and Wildlife Research Unit, Department of Fish and Wildlife Resources, University of Idaho, Moscow, Idaho 83844-1141, USA

Abstract.ÐUsing radiotelemetry, we observed and quanti®ed the behavior of upstream migrating adult Chinook salmon Oncorhynchus tshawytscha and sockeye salmon O. nerka exiting the Bradford Island ®shway at the on the Columbia River in 1997 and 1998. Nearly all of the ®sh that exited the ®shway migrated upstream along the Bradford Island shoreline. Those ®sh that took the route nearest to the spillway were most likely to fall back over the spillway. From 14.5% to 21.3% of the ®sh tracked along the Bradford Island shore fell back over the spillway of the dam. The combined effects of spill, water temperature, and Secchi disk visibility were associated with route patterns and fallback behavior during each year. High spill was signi®cantly and pos- itively correlated with fallback behavior for Chinook salmon in 1998. Most of the ®sh we tracked that fell back reascended the ®shway and migrated upstream (Ն95% in 1997; Ն70% in 1998). We suggest that modifying the con®guration of this ®shway's exit would decrease the proportion of ®sh that fall back, perhaps reduce the risk of injury and fatigue, and improve the precision of counts of ®sh migrating upstream.

At some hydroelectric adult Paci®c salm- way (Monan and Liscom 1973; Gibson et al. 1979; on Oncorhynchus spp. and steelhead O. mykiss oc- Turner et al. 1984). In 1996, Bjornn et al. (2000) casionally deviate from their upstream migration determined that 14% of the radio-tagged Chinook to spawning areas and move downstream through salmon O. tshawytscha that passed over the Bon- turbines, juvenile bypass facilities, navigation neville Dam fell back one or more times, and that locks, ®sh ladders, or over spillways in an event 82% of the fallbacks were ®sh that had used the termed fallback. Although fallback behavior has Bradford Island ®shway. been documented at all lower Columbia and Snake In this study we used radiotelemetry with aerial river dams, it occurs most frequently at the Bon- and underwater antennas to monitor the move- neville Dam (Bjornn and Peery 1992), possibly ments of adult radio-tagged salmon in the area caused by the con®guration of the ®shways at the surrounding and within the two ®shways of the dam. At the Bonneville Dam there are two ®sh- Bonneville Dam. Our objectives were to determine ways: the shore ®shway (which exits the routes followed by the radio-tagged adult Chi- on the river's north shore) and the south ®shway nook and sockeye salmon O. nerka exiting the (which exits on Bradford Island; Figure 1). Falling Bradford Island ®shway, and to evaluate the ef- back over the dam may result in injury or fatigue, fects of dam spill, water temperature, and Secchi and ®sh that reascend are counted twice (resulting disk visibility on the observed ®sh behavior. in in¯ated ®sh counts). Fish have been observed moving downstream not only at dams but in res- Study Area ervoirs as well. Gowans et al. (1999) observed The Bonneville Dam is located at river kilo- Atlantic salmon Salmo salar returning downstream meter (rkm) 235.1 on the lower Columbia River after migrating to the head of the Loch Faskally approximately 64 km east of Portland, Oregon reservoir in Scotland. (Figure 1). It is the ®rst dam adult salmonids en- Adult Paci®c salmon and steelhead have been counter during their upstream migration from the observed migrating along shorelines. As they Paci®c Ocean. Two ®shways at the Bonneville leave the exit of the Bradford Island ®shway, some Dam provide access for the upstream migration of of the ®sh migrate upstream along the island and anadromous ®sh species including Chinook salm- then proceed directly into the forebay of the spill- on, coho salmon O. kisutch, sockeye salmon, steel- head, American shad Alosa sapidissima, and Pa- ci®c lamprey Lampetra tridentata. Fish enter the * Corresponding author: [email protected] Bradford Island ®shway below powerhouse I and Received July 17, 2002; accepted February 10, 2003 at the southern end of the spillway, and exit at the

1215 1216 REISCHEL AND BJORNN

FIGURE 1.ÐBonneville Dam study area, lower Columbia River, and routes of radio-tagged adult sockeye and Chinook salmon after they exited the Bradford Island ®shway: (1) BF, ϭ Bradford Island shore to spillway forebay and fell back; (2) BWA, ϭ Bradford Island shore across spillway forebay to Washington shore; (3) BOR, ϭ Bradford Island shore across to the Oregon shore; and (4) POR, ϭ across powerhouse I to the Oregon shore. The hatched area in route 2 represents the area in which ®sh crossed to the Washington shore. FISHWAY PLACEMENT AND ADULT SALMON FALLBACK 1217 south shore of Bradford Island (Figure 1). Fish movements were monitored at ®xed receiver/an- enter the Washington-shore ®shway below pow- tenna sites set up in the tailrace, in the ®shways, erhouse II and at the north end of the spillway, and upstream from the dam. and exit on the north shore. Immediately upstream Analysis of migration behavior.ÐWe classi®ed from the dam, the Columbia River channel narrows ®sh behavior into one of four migration routes: (1) from 900 to 400 m. the ®sh swam upstream along the Bradford Island shore to the forebay of the spillway and fell back; Methods (2) the ®sh swam along the Bradford Island shore Tagging.ÐIn 1997 and 1998, adult Chinook and then moved across the spillway forebay to the sockeye salmon were diverted from the Washing- Washington shore and upstream; (3) the ®sh swam ton shore ®sh ladder into a large tank at the Adult along the Bradford Island shore to the upstream Fish Facility (AFF). After passing over a false end of the island, then crossed the channel to the weir, the ®sh slid down a chute and were diverted Oregon shore and moved upstream; or (4) the ®sh by the trap operator into a holding tank containing swam across powerhouse I to the Oregon shore anesthetic (MS-222). Once immobile, the ®sh were then moved upstream. The ®sh that were tracked transferred to a trough where they were measured into the spillway and did not fall back but had an and inspected for sex and overall clinical health. undetermined route out of the spillway were not A Lotek radio transmitter (MCFT-7A [83 ϫ 16 included in the analysis (n ϭ 67). For sockeye mm, 7 V] or MCFT-3B [43 ϫ 14 mm, 3 V] on salmon, route 4 was not included in the analysis frequency 149 MHz, New Market, Ontario) was due to the small sample size (n ϭ 3). placed in glycerol and then inserted into the ®sh's We used multivariate analysis of variance esophagus and stomach (Eiler 1990; Winter 1996). (MANOVA) to examine the dependence of dam The ®sh were then placed in a 2,271-L recovery spill, water temperature, and Secchi disk visibility tank for an average of 1.5 h and transported to one on the routes (MANOVA model: dam spill ϩ water of two release sites about 10 km downstream from temperature ϩ Secchi disk visibility ϭ route ϩ the dam: Dodson Landing at rkm 225.6 (Oregon error). We used Wilk's lambda as the test statistic shore), or Skamania Landing at rkm 224 (Wash- in the MANOVA and conducted a posteriori, pair- ington shore). We released 577 adult sockeye wise multiple comparisons using least-squares es- salmon and 991 spring/summer Chinook salmon timates of marginal means (SAS 1996). We veri- in 1997, and 957 spring/summer Chinook salmon ®ed MANOVA assumptions with residual plots in 1998. and used log or square root transformations (Zar Radio tracking.ÐThe paci®c salmon out®tted 1996). To explore the effects of each of the three with radio transmitters were tracked as they left variables in models we used a canonical analysis the Bradford Island ®shway exit from the forebay of powerhouse I and across the top of the spillway (with ␣ Յ 0.10 as the signi®cance level in statis- forebay at the Bonneville Dam. The ®sh were tical tests). Because ¯ow and spill were signi®- tracked 8 h/d in daylight from April through July cantly correlated in 1997 (r ϭ 0.99, P Ͻ 0.001) using a boat out®tted with a six-element Yagi an- and 1998 (r ϭ 0.73, P Ͻ 0.001), only spill was tenna and a Lotek SRX 400 receiver. The timing used in the analysis. The data for river conditions of observations coincided with the passage of the used in the analysis (hourly spill, hourly water majority of radio-tagged ®sh that exited the ladder temperature, and daily Secchi disk visibility) were throughout the day. If several ®sh exited the ®sh- downloaded from the U.S. Army Corps of Engi- way at the same time, the ®rst ®sh moving upriver neers Technical Management Team internet site was tracked, and in some instances multiple ®sh (U.S. Army Corps of Engineers 1998). were tracked if ®sh movements allowed us to mon- We examined fallback behavior (route 1) and itor more than one ®sh. From the Bradford Island de®ned fallback as a ®sh that was tracked in the ®shway exit, ®sh were tracked until they moved forebay and was later recorded in the tailrace of 2±3 km upstream of the forebay. the dam. Fish that fell back more than 24 h after The channel, code, exit time, and points along exiting the Bradford Island ®sh ladder were not the route of each ®sh were recorded on a map of used in the analysis (n ϭ 21) because the fallback the forebay area. The precision of tracking was event was likely not related to the ladder of pas- based on the power of the radio signal; the distance sage or to the environmental conditions. For ®sh from a ®sh during tracking ranged between 10 and that fell back and were tracked twice (n ϭ 9), we 30 m. In addition to mobile boat tracking, ®sh used the records of the ®rst passage in the analysis. 1218 REISCHEL AND BJORNN

and near average in 1998. In 1997, ¯ow (April± July) averaged 10,960 m3/s and peaked at 15,746 m3/s; in 1998, ¯ow averaged 7,052 m3/s and peak- ed at 11,894 m3/s. Spill, water temperature, and Secchi disk visibility averaged 5,183 m3/s, 14ЊC, and 0.6 m, respectively, in 1997, and 2,591 m3/s, 15ЊC, and 1.0 m, respectively, in 1998 (Figure 2).

Routes Adult Chinook (122 in 1997; 129 in 1998) and sockeye (110 in 1997) salmon with transmitters were tracked in the forebay of the Bonneville Dam. Ninety percent of all tracked ®sh moved upstream along the Bradford Island shore after exiting the ®sh ladder. The majority of tracked salmon in both years followed one of four routes after leaving the Bradford Island ®shway (Table 1; Figure 1). When 1997 and 1998 Chinook salmon route data were combined, we found a signi®cant difference between years in spill (P Ͻ 0.001) and Secchi disk visibility (P Ͻ 0.001). Spill was higher and Secchi disk visibility was lower in 1997; therefore, we analyzed the routes for each year separately. In 1997, we found a signi®cant effect (P ϭ 0.085) of combined spill, water temperature, and Secchi disk visibility on the Chinook salmon routes (Table 2; FIGURE 2.ÐRadio-tracking of adult sockeye and Chi- Figure 3). Chinook salmon fell back and crossed nook salmon in relation to spill volume, water temper- to the Oregon shore from Bradford Island during ature, and Secchi disk visibility and incidence of fallback signi®cantly lower water temperatures (P ϭ 0.023; within 24 h after exiting the Bradford Island ®shway, 2 Bonneville Dam, from April to July 1997 and 1998. r ϭ 0.13) than ®sh that crossed to the Washington shore or moved across powerhouse I to the Oregon shore. We found standardized canonical coef®- We ran the same model procedures for evaluating cients highest for water temperature (1.12). fallback behavior as described above. In 1998, we found a signi®cant effect (P ϭ 0.006) of combined spill, water temperature, and Results Secchi disk visibility on Chinook salmon routes Over the 2 years the study was conducted, river (Table 2). Chinook salmon fell back during sig- ¯ows were above the long-term average in 1997 ni®cantly higher spill (P Ͻ 0.001, r2 ϭ 0.20) than

TABLE 1.ÐThe number and percent of radio-tagged adult sockeye and Chinook salmon in 1997 and Chinook salmon in 1998 that used one of four routes in the forebay of the Bonneville Dam, Columbia River.

1997 1998 Route Sockeye Chinook Chinook 1. Bradford Island shore to spillway forebay Fell backa 16 (14.5%) 26 (21.3%) 20 (15.5%) Did not fall backb 14 (12.7%) 33 (27.0%) 20 (15.5%) Total 30 (27.3%) 59 (48.4%) 40 (31.0%) 2. Bradford Island shore across spillway to Washington shore 29 (26.4%) 24 (19.7%) 59 (45.7%) 3. Bradford Island shore across to Oregon shore 46 (41.8%) 20 (16.4%) 19 (14.7%) 4. Bradford Island ®shway across powerhouse I to Oregon shore 3 (2.7%) 12 (9.8%) 8 (6.2%) 5. Other routes 2 (1.8%) 7 (5.7%) 3 (2.3%) Total 110 122 129 a Includes all ®sh that fell back. b Did not fall back and had an undetermined route out of the spillway forebay. FISHWAY PLACEMENT AND ADULT SALMON FALLBACK 1219

TABLE 2.ÐResults of multivariate analysis of variance (MANOVA) of the effect of spill, water temperature, and Secchi disk visibility on routes of radio-tagged adult sockeye and Chinook salmon in the forebay of the Bonneville Dam, Columbia River. Variables with P-values with an asterisk are signi®cant at P Յ 0.10.

MANOVA Wilk's ␭ Salmon species Year Source df FP Chinook 1997±1998 Route ϫ year 9 1.11 0.352 Routea 9 1.90 0.041* Yeara 3 61.87 Ͻ0.001* Chinook 1997 Route 9 1.73 0.085* Chinook 1998 Route 9 2.62 0.006* Sockeye 1997 Route 6 2.32 0.035* a Main effects model results without the interaction term.

FIGURE 3.ÐBox plots with the means (horizontal dashed lines), interquartile ranges (boxes), and ranges (vertical lines) of spill, water temperature, and Secchi disk visibility at the Bonneville Dam for radio-tagged adult sockeye and Chinook salmon routes in 1997 and 1998. Routes with the same letters are not signi®cantly different. Abbre- viations are as follows: BF ϭ Bradford Island shore to spillway forebay and fell back; BWA ϭ Bradford Island shore across spillway forebay to the Washington shore; BOR ϭ Bradford Island shore across to the Oregon shore; and POR ϭ across powerhouse I to the Oregon shore. Note that the box plot showing spill for Chinook salmon in 1998 has a different scale. 1220 REISCHEL AND BJORNN

TABLE 3.ÐResults of multivariate analysis of variance (MANOVA) of the effect of spill, water temperature, and Secchi disk visibility on radio-tagged adult sockeye and Chinook salmon that fell back at the Bonneville Dam. Variables with P-values with an asterisk are signi®cant at P Յ 0.10.

MANOVA Wilk's ␭ Salmon species Year Source df FP Chinook 1997±1998 Fallback ϫ year 3 1.16 0.325 Fallbacka 3 1.22 0.302 Yeara 3 96.91 Ͻ0.001* Chinook 1997 Fallback 3 1.52 0.213 Chinook 1998 Fallback 3 4.85 0.003* Sockeye 1997 Fallback 3 0.55 0.649 a Main effects model results without the interaction term.

®sh that crossed to the Washington and Oregon was due to spill (P Ͻ 0.001), Secchi disk visibility shores from Bradford Island (Figure 3). We found (P Ͻ 0.001), and water temperature (P ϭ 0.041). standardized canonical coef®cients highest for Therefore, we analyzed fallback events for each spill (1.12). year separately. No signi®cant effect was found For sockeye salmon in 1997, we found a sig- from the combined spill, water temperature, and ni®cant effect (P ϭ 0.035) of combined spill, water Secchi disk visibility on the fallback behavior of temperature, and Secchi disk visibility on routes. Chinook salmon (P ϭ 0.213) or sockeye salmon Sockeye salmon crossed to the Washington shore (P ϭ 0.649) in 1997 (Table 3; Figure 4). from Bradford Island during signi®cantly lower In 1998, we found a signi®cant effect (P ϭ spill (P ϭ 0.058, r2 ϭ 0.06) than ®sh that crossed 0.003) of combined spill, water temperature, and to the Oregon shore from Bradford Island (Figure Secchi disk visibility on the Chinook salmon that 3). Sockeye salmon also fell back and crossed to fell back versus ®sh that did not. Spill (P Ͻ 0.001, the Oregon shore from Bradford Island during sig- r2 ϭ 0.10) was signi®cantly higher and Secchi disk ni®cantly lower Secchi disk visibility (P ϭ 0.013, visibility signi®cantly lower (P ϭ 0.044, r2 ϭ 0.03) r2 ϭ 0.09) and lower water temperatures (P ϭ for the Chinook salmon that fell back compared 0.014, r2 ϭ 0.14) than ®sh that crossed to the with that of the ®sh that did not (Table 3; Figure Washington shore from Bradford Island (Figure 3). 4). We found standardized canonical coef®cients We found standardized canonical coef®cients highest for spill (1.07). highest for water temperature (0.98). Discussion Fallback Behavior The fallback behavior at the Bonneville Dam is In both years ®sh fell back over the spillway at observed most frequently at the Bradford Island the Bonneville Dam. In 1997, 21.3% (26 of 122) ®shway because ®sh exit the ladder and follow the of Chinook salmon and 14.5% (16 of 110) of sock- shoreline of the island into the forebay of the spill- eye salmon fell back and in 1998, 15.5% (20 of way. The migration patterns we observed in both 129) of the tracked Chinook salmon fell back. years at the Bonneville Dam were similar to those Reascension rates were high in both years of the reported in previous studies (Monan and Liscom study, and the majority of fallback events occurred 1973; Gibson et al. 1979; Ross 1983; Turner et al. within 24 h after exiting the Bradford Island ®sh- 1984). Eighty percent or more of the tracked ®sh way. Ninety-six percent (25 of 26) of the Chinook in both years initially followed the Bradford Island salmon in 1997, 100% of the sockeye salmon in shoreline from the ®shway exit. From 14.5±21.3% 1997, and 70% (14 of 20) of the Chinook salmon of the ®sh migrated along the Bradford Island in 1998 reascended and passed over the dam a shore into the forebay of the spillway and fell back. second time. Sixty-two percent (16 of 26) of the Several factors were associated with the fallback Chinook salmon in 1997, 81% (13 of 16) of sock- behavior at the Bonneville Dam. Our study found eye salmon in 1997, and 50% (10 of 20) of Chi- dam spill, Secchi disk visibility, and water tem- nook salmon in 1998 that fell back did so within perature were signi®cant factors associated with 24 h after exiting the Bradford Island ®shway. migration route, but they explained little of the When we combined data for 1997 and 1998 Chi- variation. At the Bradford Island ®shway, reverse nook salmon fallback behavior, we found a sig- currents ¯ow upstream along the spillway side of ni®cant difference between years (P Ͻ 0.001) that Bradford Island and continue around the tip of the FISHWAY PLACEMENT AND ADULT SALMON FALLBACK 1221

FIGURE 4.ÐBox plots with the means (horizontal dashed lines), interquartile ranges (boxes), and ranges (vertical lines) of spill, water temperature, and Secchi disk visibility at the Bonneville Dam for radio-tagged adult sockeye and Chinook salmon that did and did not fall back in 1997 and 1998. Fell back ϭ Bradford Island shore to spillway forebay and fell back. Note that the box plot showing spill for Chinook salmon in 1998 has a different scale. island. However, personnel at The Waterways Ex- We feel our tagging procedures had little effect on periment Station (Vicksburg, Mississippi) found fallback behavior. The majority of ®sh passed the no relationship between the reverse currents (from dam within the same day of tagging and we ob- project operations) in the forebay of the Bonneville served little downstream movement from the re- Dam and fallback behavior in 1997 and 1998 (M. lease sites. The regurgitation of transmitters in Langeslay, U.S. Army Corps of Engineers, per- both years for tracked ®sh was less than 1%. Thor- sonal communication). stad et al. (2000) found no differences in the en- In this study, we assumed that handling and tag- durance or physiological factors of Atlantic salm- ging did not affect the behavior of the ®sh. Bernard on with small or large external tags and small im- et al. (1999) observed handling delay and the planted transmitters at any swimming speed. downstream movement of adult Chinook salmon Because adult Paci®c salmon tend to migrate that were caught in a net and externally tagged along shorelines, ®shway placement can be vital without anesthetic. Haynes and Gray (1980) spec- in adult passage at dams or river obstacles (John- ulated that their tagging procedures might have son 1960; French and Wahle 1965). Prior to the affected ®sh falling back over the dam. However, construction of the second powerhouse at the Bon- they observed similar migratory rates to the dam neville Dam in 1982, the Washington shore ®sh- as other studies and concluded that delays and fall- way exited into the forebay of the spillway and back were likely not due to handling and tagging. fallback rates were higher for ®sh exiting the 1222 REISCHEL AND BJORNN

Washington shore ®shway than for those exiting to the area, and only one of seven ®sh that were the Bradford Island ®shway (Liscom et al. 1977). released upstream of their capture site moved back However, after the completion of the second pow- downstream. erhouse, smaller numbers of ®sh fell back after Fallback behavior has a direct effect on the man- exiting the Washington shore ®shway compared agement of adult Chinook salmon and steelhead, with the ®sh that exited the Bradford Island ®sh- and ultimately on spawning success. Dauble and way (Bjornn and Peery 1992). Due to safety re- Mueller (2000) described the dif®culties in esti- strictions we did not track ®sh that exited the mating adult Chinook salmon survival due to dam Washington shore ®shway. However, Bjornn et al. counts, delay at dams, fallback, and straying. Fish (2000) found 94±95% of radio-tagged Chinook counts at dams are vital to run size estimation and salmon that fell back within 24 h in 1997 and 1998 provide information for ®shery harvest limits. had exited the Bradford Island ®shway. Correction factors have been estimated for Chi- Adult upstream-migrating salmon can encounter nook salmon fallbacks at the Bonneville Dam. dif®cult areas of passage in free-¯owing rivers as Bjornn et al. (2000) estimated an overcount of Chi- well as at hydroelectric projects. In the Vefsna nook salmon at Bonneville to be 8,853 ®sh in 1996 River (Norway), a ®sh ladder was built to allow (15.1%), 22,923 ®sh in 1997 (19.3%), and 7,063 the passage of Atlantic salmon upstream of a 16- ®sh in 1998 (13.5%). m-high waterfall (Jensen et al. 1986). In the Fraser Fallback can cause injury or mortality, and delay River, Hell's Gate was identi®ed as an area of dif- upstream passage. Although fallback rates were ®cult passage due to high ¯ows even though a ®sh high for both years of our study, a high percentage ladder had been built (Hinch et al. 1996). Through of ®sh that fell back reascended the ®shways and electromyogram studies, Hinch et al. (1996) found passed over the dam a second time. However, ®sh sockeye salmon exerted more energy and took lon- that did not reascend may re¯ect injuries or mor- ger to pass through the Hell's Gate area than ®ve talities, or may have wandered too far upstream other areas of the river. In the Tana River (Nor- while their true destination was a tributary down- way), Atlantic salmon migration was occasionally stream from the Bonneville Dam. We did not es- delayed during low river ¯ows in the lowest rif¯e timate mortality rates because we could not de- area of the river (Erkinaro et al. 1999). The move- termine if ®sh that did not reascend either suc- ments of Atlantic salmon were monitored with cessfully spawned downstream of the dam or re- sonic tags as they migrated the Loch Faskally res- gurgitated the radio transmitter. In 1996, 94 ervoir in which ®sh were found to have reached radio-tagged spring/summer Chinook salmon that the head of the reservoir only to return downstream fell back one or more times (8.5% fell back Ͼ1) (Gowans et al. 1999). Haynes and Gray (1980) took 8.3 d from tagging to pass the Bonneville documented 1.6 fallbacks per ®sh on average at Dam for the last time, compared with 2.1 d for the Little Goose Dam on the Snake River during 704 ®sh that did not fall back (Bjornn et al. 1999). spill. Haynes and Gray (1980) noted delay times per While migrating upstream to spawn, adult salm- fallback ranged up to 4.2 d. on occasionally move back downstream. ékland Since the energy reserves Paci®c salmon have et al. (2001) identi®ed three migration phases of for completing migration and spawning are ®nite, Atlantic salmon migrating in a free-¯owing river. there is concern that fallback behavior may di- The ®rst phase was migratory (moving upstream rectly affect spawning success. The use of elec- rapidly), the second and most common phase was tromyogram telemetry has been used for estimat- search (moving upstream or back downstream), ing energy expenditure in fall Chinook salmon and ®nally a holding phase near the spawning area. (Geist et al. 2000). Jonsson et al. (1997) estimated In our study, we observed the majority of ®sh fall- total energy loss with tissue samples and found ing back over the Bonneville Dam within 24 h after that between 60% and 70% of energy reserves are exiting a ®shway. We also observed ®sh moving lost during migration and spawning for Atlantic upstream several kilometers and then moving salmon. Through modeling and the use of physical downstream and falling back over the dam. Fish parameters, Rand and Hinch (1998) found Fraser that moved upstream ®rst and then fell back may River sockeye salmon used 84% of their energy have been confused in their homing behavior and through swimming activity. Bjornn et al. (1999) moved too far downstream. Heggberget et al. estimated percent survival to major tributaries or (1988) found 71% of Atlantic salmon that were to the on the mid-Columbia released downstream of their capture site returned River for radio-tagged Chinook salmon in 1996. FISHWAY PLACEMENT AND ADULT SALMON FALLBACK 1223

Fish that fell back at the Bonneville Dam had a and equipment for a safety boat. This manuscript 5.2% lower survival rate than ®sh that did not fall contributed to a portion of the master's thesis re- back. Fish that fell back at a Columbia or Snake search conducted by T. Reischel and is contribu- river dam had a 3% lower survival rate than ®sh tion 964 of the Forestry, Wildlife, and Range Ex- that did not fall back at any dam. Because spawn- periment Station. We would like to dedicate this ing ground survey information was limited, Bjornn manuscript to the memory of Theodore C. Bjornn. et al. (1999) could not determine if ®sh that fell back and reascended spawned successfully. References Information on fallback behavior is important Bernard, D. R., J. J. Hasbrouck, and S. J. Fleischman. in understanding the dynamics of adult salmon be- 1999. Handling-induced delay and downstream havior at dams. Several populations of adult Chi- movement of adult chinook salmon in rivers. Fish- nook salmon that pass the Columbia and Snake eries Research 44:37±46. Bjornn, T. C., M. L. Keefer, C. A. Peery, K. R. Tolotti, river dams are listed under the Endangered Species R. R. Ringe, and L. C. Stuehrenberg. 1999. Mi- Act. There is concern that ®sh that fall back at gration of adult chinook salmon past Columbia and dams may incur lower rates of survival than ®sh Snake river dams, through reservoirs and distribu- that do not fall back; if this is so, then a better tion into tributaries, 1996. Bonneville Power Ad- understanding of the factors that contribute to fall- ministration and U.S. Army Corps of Engineers, back will assist in developing measures to reduce Portland, Oregon, and Walla Walla, Washington. fallback and improve systemwide survival rates Bjornn, T. C., M. L. Keefer, C. A. Peery, K. R. Tolotti, R. R. Ringe, and L. C. Stuehrenberg. 2000. Adult for returning adult salmon. Reducing fallback will chinook and sockeye salmon, and steelhead fallback also reduce the bias associated with in¯ated ®sh rates at Bonneville Dam, 1996±1998. Bonneville counts and will improve the quality of the infor- Power Administration and U.S. Army Corps of En- mation used to make management decisions. gineers, Portland, Oregon, and Walla Walla, Wash- Clearly, the shoreline swimming behavior of ington. Chinook and sockeye salmon exiting the Bradford Bjornn, T. C., and C. A. Peery. 1992. A review of lit- erature related to movements of adult salmon and Island ®shway leads ®sh around Bradford Island steelhead past dams and through reservoirs in the and within close proximity to the spillway. Moving lower Snake River. U.S. Fish and Wildlife Service or extending the Bradford Island ®sh ladder exit and Idaho Cooperative Fish and Wildlife Research to the Oregon shore may be the best option for Unit for U.S. Army Corps of Engineers, Walla Wal- reducing fallback behavior and should be inves- la, Washington. tigated. Dauble, D. D., and R. P. Mueller. 2000. Dif®culties in estimating survival for adult chinook salmon in the Acknowledgments Columbia and Snake rivers. Fisheries 25(8):24±34. Eiler, J. H. 1990. Radio transmitters used to study salm- The use of product names in this publication on in glacial rivers. Pages 364±369 in N. C. Parker, does not imply endorsement. We thank Bob Dach A. E. Giogi, R. C. Heidinger, D. B. Jester, Jr., E. and Mike Langeslay (U.S. Army Corps of Engi- D. Prince, and G. A. Winans, editors. Fish-marking neers) for assisting in the project, and the U.S. techniques. American Fisheries Society, Sympo- Army Corps of Engineers Portland District and the sium 7, Bethesda, Maryland. Erkinaro, J., F. ékland, K. Moen, E. NiemelaÈ, and M. Bonneville Power Administration for funding the Rahiala. 1999. Return migration of Atlantic salmon project. Kirk Steinhorst (University of Idaho) pro- in the River Tana: the role of environmental factors. vided advice on statistical analyses. We thank Journal of Fish Biology 55:506±516. Christine Mof®tt (University of Idaho) and three French, R. R., and R. J. Wahle. 1965. Study of loss and anonymous reviewers for providing valuable sug- delay of salmon passing Rock Island Dam, Colum- gestions for this manuscript. The following people bia River, 1954±56. U.S. National Marine Fisheries Service Fishery Bulletin 65:339±368. participated in ®eldwork and coordination of this Geist, D. R., C. S. Abernethy, S. L. Blanton, and V. I. project from the Idaho Cooperative Fish and Wild- Cullinan. 2000. The use of electromyogram telem- life Research Unit: Travis Dick, Michelle Feeley, etry to estimate energy expenditure of adult fall Megan Heinrich, Mike Jepson, Matt Keefer, Pat chinook salmon. Transactions of the American Fish- Keniry, Steve Lee, Chris Peery, Dennis Queampts, eries Society 129:126±135. Rudy Ringe, Ken Tolotti, and Clifford Shippen- Gibson, G., R. Michimoto, F.Young, and C. Junge. 1979. Passage problems of adult Columbia River chinook tower. Lowell Stuehrenberg and Alicia Matter (Na- salmon and steelhead, 1973±1978. Oregon Depart- tional Marine Fisheries Service) provided database ment of Fish and Wildlife, Portland. management and assistance in processing of data. Gowans, A. R. D., J. D. Armstrong, and I. G. Priede. The Bonneville Dam Rangers provided personnel 1999. Movements of adult Atlantic salmon through 1224 REISCHEL AND BJORNN

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