SALVELII,{US C ONFLUENTU S. A Thesis. Presented to. the Graduate Faculty. Central Washington University. In Partial Fulfillment.

Transcription

1 Er,'o THE EFFECTS OF SEASONAL STREAM DE.WATERING ON THREE AGE CLASSES OF BULL TROUT, SALVELII,{US C ONFLUENTU S A Thesis Presented to the Graduate Faculty Central Washington University In Partial Fulfillment of the Requirements for the Degree Master of Science Biology by William Rogers Meyer February,2002

2 CENTRAL WASHINGTON UMVERSITY Graduate Studies We hereby approve the thesis of William Rogers Meyer Candidate for the degree of Master of Science APPROVED FOR THE GRADUATE FACULTY Paul W. James, Committee Chair David M. Darda Patrick J. Brvan Associate Dean of Graduate Studies ll

3 ABSTRACT THE EFFECTS OF SEASONAL STREAM DE-WATERING ON THREE AGE CLASSES OF BULL TROUT, SALI/ELINUS CONFLUENTUS by William Rogers Meyer February 2002 De-watering occurs during summer in many headwater streams of the yakima River Basin in central Washington, where chronically low populations of the threatened bull trout, Salvelinus confluentus, occur. The influence of historical land management practices on de-watering, and the resulting effect of de-watering on the survival, densities and movement of bull trout, was investigated in the summer and fall of Kachess River and Gold Creek are two headwater streams which persistently de-water near where they flow into reservoirs. Historical evidence suggests these streams have switched to an alternate stable state over the past years due to mining, logging and road building. Reservoir drawdown appeared to have no direct effect on de-watering the streams. Juvenile bull trout have shifted their out-migration from sunmer to fall, because of the swnmer de-watering. Adult migration at Gold Creek was curtailed in August by dewatering, whereas adults at Kachess River seem to have locally adapted to de-watering by r migrating in October, after the lower reaches of the river re-waters. Bull trout populations in these system seem to be at carrying capacity and recovery to greater numbers likely depends upon watershed restoration. lll

4 ACKNOWLEDGMENTS To little Ben for playing in the river and providing lots of inspiration. I would like to thank my advisor, Dr. Paul James, for his advice and discussions during the project. I would also like to thank the rest of my committee members, Dr. David Darda and Dr. Patrick Bryan for their recommendations and assistance. I am especially grateful to Yuki Reiss for her ideas and assistance with field work, her snorkeling skills - in ice cold water at night, and her friendship. I would also like to thank, Mark Tuttle, Cory Straub, Heather Simmons, Gary Lenhart, Brenda James, Charity Hervosma, and Sallie Herman for their assistance carrying out field work. I would like to thank Scott Kline for his skill in mining the Bureau of Reclamation's website to acquire historic precipitation and reservoir data, and for assisting in calculating stream discharge. The following people were quite helpful in gathering historic data or providing assistance with the project, and I would like to express my thanks to: Shan Madden (USFS), for providing historic logging, roading, mining and fire information; Eric Anderson (WDFW), for his ideas and encouragement and providing historic data; Lee Spencer (Plum Creek Timber Co.), for land ownership and logging history information; Larry Brown (WDFW, retired) for historical insights, and finally Judy De La Vergne and Aaron Bosworth (USFWS), for survey data on Kachess River; and Steve Caromile (WDFW), for his support and encouragement. IV

5 TABLE OF CONTENTS Chapter Page I. INTRODUCTION II. STIIDY AREA Kachess River...8 HistoricConditions...9 BoxCanyonCreek...10 LakeKachess...11 GoldCreek...L2 HistoricConditions...13 LakeKeechelus M. METHODS JuvenileSnorkel Surveys...17 Adult Bull Trout Surveys...20 FryStrandingSurveys I PhysicalEnvironment.. "22 HistoriclnformationandData IV RESULTS,,...25 KachessRiver...25 JuvenileBullTrout...25 Timing ofadult Bull Trout Migration and Spawning FryStranding...34 SpeciesComposition Physical Environment: Stream Temperature, Discharge, and Rainfall 37 ReservoirElevations...40 GoldCreek...41

6 TABLE OF CONTENTS (continued) JuvenileBullTrout...,41 Timing ofadult Bull Trout Migration and Spawning FryStranding.,.45 SpeciesComposition Physical Environment: stream Temperature, Discharge, and Rainfall 4g ReservoirElevations...51 V. DISCUSSION 52 ThePhenomenonofDe-watering/Re-watering...53 The Influence of Mining, Logging and Geology onflowpatterns andbulltrout...55 JuvenileBullTroutDensities...59 AdultMigrationandStranding...65 FryStrandingSurveys The Persistence of Bull Trout in Kachess River and Gold Creek...72 \/I. LITERATURECITED..,,,75 VI

7 LIST OF TABLES Table Page 1. Kachess River night snorkel survey data of 1200 m for juvenile and adult bull trout, and cutthroat/rainbow trout......,..., Historical adult bull trout presence and stream conditions at Kachess River......"..., Annual summary of redds from atkachess River. Box Canyon Creek and Gold Creek Kachess River fry stranding pool summary......,..., ' species composition and size ranges at Kachess River by number and percent for all sample dates, Gold creek night snorkel survey data of 1000 m for juvenile and adult bull trout, cutthroat/rainbow trout, and brook trout bv reach and date......:...,42 7. Gold Creek firy stranding pool summary Species composition and size ranges at Gold Creek by number and percent for all sample dates g vll

8 LIST OF FIGURES Figure Page 1. Map of the study areas " Map of the Kachess River study area......".1g 3. Map of the Gold Creek study area Juvenile bull trout and cutthroat/rainbow linear stream densities (# fish/100m) from night snorkel surveys of the upper 600m reference site, for all sampling periods at Kachess River., Juvenile bull trout and cutthroat/rainbow stream densities by surface area (# fish/l00m2), from night snorkel surveys of the upper 600m reference site, for all sampling periods at Kachess River Total number ofjuvenile bull trout from night snorkel surveys in 1000m at Kachess River Juvenile bull trout and cutthroat/rainbow densities (#/100m2) in the upper Kachess River 200m site, above the confluence with Mineral creek......"...2g 8. Total number ofjuvenile bull trout from night snorkel surveys in the upper 200m Kachess River site, above the confluence with Mineral Creek a. Length frequencies ofjuvenile bull trout from night snorkel surveys at Kachess River b, Length frequencies ofjuvenile bull trout from night snorkel surveys at Kachess River......, Average total length ofjuvenile bull trout from night snorkel surveys at Kachess River with a 95Yo confidence interval..." Lake residence (light shading) and timing of migration and spawning (dark bars) from the adfluvial bull trout populations of the Yakima River Basin in vlll

9 LIST OF FIGURES (continued) Figure Page 12. water temperature("c) in Kachess River, just below the trail crossing, from July 20,2000 to November 16, ,...3g 13. Daily temperature ("c) fluctuations at Kachess River from July 20, 2000 and the first of each month thereafter....."...3g 14. Discharge on the main stem of the Kachess River, 300m below the confluence with Mineral creek, and 50m above the confluence on Mineral creek and Kachess River from July 18, 2000 to November 7, ,,Monthly precipitation at Kachess Dam in 2000 compared with a 30-year average ( ) and 95% confidence interval (data from usbr) Kachess and Keechelus reservoir elevations in relation to the de-watering and re-watering of Kachess River and Gold creek..., Juvenile bull trout, cutthroat/rainbow and brook trout densities (# fish/l00m2), from night snorkel surveys of the lower 600m site, for all sampling periods at Gold Creek......" Juvenile bull trout, cutthroat/rainbow, and brook trout densities (# fish/l00m2), from night snorkel surveys of the upper 400m site, for all sampling periods at Gold Creek Total number ofjuvenile bull trout from night snorkel surveys in 1000m at Gold Creek......,., Average total length ofjuvenile bull trout from night snorkel surveys at Gold Creek with a 95Yo confidence interval......,..., I. Water temperature ("C) in Gold Creek 100m below its confluence with the spawning channel, from July 20,2000 to November 30, Daily temperature ("C) fluctuations at Gold Creek from July 20,2000 and the first of each month thereafter tx

10 LIST OF FIGURES (continued) Figure page 23. Discharge at Lower and upper Gold creek from July 19,2000 to October 4, Monthly precipitation at Keechelus Dam in 2000 compared with a 30-year average ( ) and95% confidence interval (data from usbr)..."..50

11 INTRODUCTION Bull trout, Salvelinus confluentus, are classified as char, a subdivision of salmonids which generally inhabit northern latitudes throughouthe world and require cold, clean water to thrive. In North America, bull trout range from northern British Columbia east to Montana and south into northern California, with an isolated population in Nevada (Haas and McPhail 1991; Rieman and Mclntyre 1993;Rieman et al. 1997). Bull trout were not taxonomically separated from the closely related Dolly Varden (Salvelinus malma) until 1978, and genetic work since that time further supports this separation (Cavender 1978;Leary et al. 1993; USFWS 1998b). Historically, bull trout have been regarded with both praise for their beauty, and scom because of their habit of piscivory. The earliest accounts of this genus by Jordan and Evermann (1896) commend them: "The members of this genus (Salvelinus) are by far the most active and handsome of the trout, they live in the coldest, cleanest and most secluded waters. No higher praise can be given to a Salmonid than to say, it is a charr." However, later malaise for the species came from trout fishermen who saw the piscivorous bull trout as a competitor for more desirable specie such as rainbow trout (Oncorhynchus mykiss) or cutthroatrout (On c o r hyn c hus c I arki). Bull trout exhibit four distinct life history patterns primarily based on areas of adult residence and spawning migration. These patterns include: resident fish, which emerge, mature and reproduce in the same tributary stream and grow to a small size relative to the other life history forms; fluvial fish, which emerge and rear as juveniles in a tributary, then emigrate to a mainstem river to mature as large adults prior to returning

12 to a tributary to spawn; adfluvial fish, which emerge and rear as juveniles in a tributary, then emigrate to a lake or reservoir to mature into large adults prior to returning to a tributary to spawn; and finally anadromous fish, which emerge and grow to juveniles in a tributary, and then emigrate to saltwater where they spend some portion of their life, before returning to spawn in the tributary as sizeable adults. Typically, resident fish grow to around 250mm, whereas fluvial and anadromous fish attain lengths of mm and adfluvial fish have been reported growing to 700+mm and can weigh 13kg (Bjornn 1,961; Fraley and Shepard 1989; Pratt 1992). Adult bull trout are iteroparouspawners, meaning they may migrate and spawn several years successively or alternate years. Data from an adfluvial bull trout population in the Flathead Lake system of Montana indicate that between 38 to 69 percent of adults leave the lake each summer to spawn (Fraley and Shepard 1989). All of the above life history patterns, except anadromous bull trout, have been documented in the Yakima River Basin, however this study focused on two adfluvial populations. Currently, bull trout are listed by the U.S. Fish and Wildlife Service as "Thteatened" under the Endangered Species Act due to substantial declines in abundance and distribution across the species range. These declines are primarily attributed to a broad array of factors which generally fall into four categories: habitat degradatron, barriers to movement such as dams or irrigation projects, over-fishing, and competition with non-native species (Thurow et al. 1997; Nakano et al. 1998; USFWS 1998a; Federal Register 1999). Because of their life history requirements, especially the need for cold clean water, bull trout are more vulnerable than many salmonid species to habitat

13 alteration. Landscape altering activities such as logging or farming can result in habitat destruction through increased stream temperature regimes, altered stream flow, and siltation of spawning habitat (Watson and Hillman 1997). The construction of dams or irrigation projects, with or without fish passage, can also alter water temperatures, block migration routes or kill fish passing through these structures. Furthermore, non-native fish such as brook trout, Salvelinus fontinalis, hybidize withbull trout and may also directly compete for food resources (Kitano et al.1994; Bematchez et a1.1995; Kanda and Allendorf 2001). Because most bull trout grow to large size and spawn in small tributaries, they are also highly vulnerable to predation or poaching during spawning, and in some areas have been over-fished (Carl et al. 1989; Ratliff and Howell 1992). In the Yakima River Basin of the Columbia River province, bull trout have been nearly extirpated from many lower fluvial segments of their former range, and they now occur predominantly in headwater streams. Furthermore, these headwater subpopulations within the basin are often isolated from one another on a local and regional scale due to the construction of dams without fish passage in the early part of the 20th century. Many of these adfluvial bull trout populations persist at chronically low levels and therefore are at high risk of local extirpation from both density dependent and density independent disturbances as well as loss of genetic variability (Chapman 1966; Rieman and Allendorf 2001). Therefore, understanding specifically why these small, isolated populations of bull trout remain at chronically low levels is especially importanto improve their long term survival and recovery to healthy population levels. Many of these upper watershed spawning streams exhibit some form of natural or 3

14 land management induced seasonal de-watering, a phenomenon which has been identified by the U.S. Fish and Wildlife Service as one of the factors affecting the long term persistence of bull trout in these systems (USFWS 1998a). Kachess River and Gold Creek are two Yakima Basin headwater bull trout spawning streams which empty into Lake Kachess and Lake Keechelus reservoirs, respectively, and routinely experience dewatering events in their lower reaches during summer. Kachess River frequently dewaters for over two kilometers upstream from its confluence with the reservoir, leaving approximately 1.5'2.5 kilometers of watered habitat available between the de-watered stretch and fish barriers on its upper reaches. Gold Creek stays watered in its lower two kilometers due to a tributary inflow, but approximately 2.5 kilometers of its middle reach routinely de-waters, leaving approximately 5 kilometers of watered habitat above the drv stretch. Fisheries biologists from several agencies in central Washington have regularly noted numerous incidents of stranding and mortality in bull trout fry, juveniles and adults, as well as obstructions to adult fish passage, related to de-watering events on headwater streams in the upper Yakima River Basin (Brown 1992; Craigand Wissmar 1993; Mongillo 1993). De-watering also seems to be a relatively long term phenomenon, as several records occur from over twenty years ago (Parson 1980; Anderson and Cummins 1992; WDFW 1997; Anderson 2001). There has been much speculation as to the cause of de-watering in these systems and severalikely explanations have been put forth, including dropping of reservoir levels, effects of past timber sales, mining, gravel excavations, road building, and past natural events such as deposition of gravel by floods. 4

15 In 1987, the Washington State Department of Fish and Wildlife (WDFW) reported that Kachess River had been de-watering for at least a decade, and suggested the population was in danger of extirpation. They attributed the de-watering to the deposition of massive amounts of cobble/gravel near the mouth of the stream after large rainstorm events, and suggested relocating approximately 500m of the river channel to bypass the area of alluvium deposition. The objectives of this study were to investigate the natural and historical land management influences on the phenomenon of seasonal de-watering at each site, and to examine the effect de-watering has on the survival, density and movement of firy, juveniles and adults" Because of the varied habitat requirements amongst age classes of bull trout, de-watering events in these systems are likely to affect fry, juveniles and adults in a dissimilar manner (Kahler et al. 2001). I developed two hypotheses to test the impacts of de-watering on juveniles and adults. First, I hypothesized that as stream discharge decreased, and de-watering made emigration to the reservoir impossible, available habitat would be reduced, and juvenile bull trout densitie should increase. Secondly I hypothesizedthat the timing of spawning migrations by adults in these dewatering systems would follow the general Yakima Basin pattern of early summer migration, but would be significantly constrained by the de-watering event. 5

16 STUDY AREA The two streams chosen for this study were Kachess River and Gold Creek, both located in the Cascade Mountain Range of central Washington (Figure l). Kachess River and Gold Creek were chosen as study sites because both stream systems routinely exhibit de-watering events in their lower reaches beginning in latter summer as base flows decrease. Likewise, both streams have spawning populations of bull trout, in which fisheries biologists have regularly noted fry stranding and fish passage issues as the sheams recede. Gold Creek and Kachess River currently flow into Lake Keechelus and Lake Kachess reservoirs respectively, however natural lakes existed at these sites in the early part of the 20th century, prior to reservoir construction. Box Canyon Creek is the only other bull trout spawning stream flowing into Lake Kachess, and although this stream was not part of this study, several interesting comparisons can be made to Kachess River. All three streams flow from basins which are fairly poorly developed hydrologically, meaning that water entering these basins tends to be released relatively quickly in comparison to hydrologically well developed systems. This is a feature shared amongst many streams in the upper Yakima River basin, and creates a condition that in concert with underlying geology, and variable rainfall, can bring about the phenomenon of de-watering. The pattem of de-watering is frequently variable between streams and depends upon local conditions. For instance, the lower and upper ends of Gold Creek remain watered, while its middle area de-waters, but at Kachess River, the entire lower stream de-waters and the middle and upper reaches remain watered.

17 7 tn Box Canyon Creek Lake Keechelus Figur$ 1. Map of the study areas.

18 Kachess River The main stem of Kachess River is a third order stream that drains a28.5 kmz watershed into the head of Little Kachess Lake. Kachess River and Box Canyon Creek are the only known bull trout spawning streams flowing into Lake Kachess. The main channel of lower Kachess River is at an elevation of approximately 688m and is composed mostly of riffles with some small pools, a gravellcobble substrate and a gradient averaging approximately I%o. The channel width in this area often exceeds 50 m and is generally devoid of large woody material other than occasional rooted stumps from clearcutting and a couple recent windfalls undermined by the cutbank. Approximately half the riparian zone in this area has been logged and it is now a 50:50 mix of alder (Alnys rubra) thimbleberry (Rubus parviflorus) re-growth along old timber sale boundaries, while the other half of the riparian corridor is composed of typical old growth understory species, such as vine maple (Acer cirinaturi) and Devils club (Oplopanax horrif,us), overhanging stream banks in the remnant forest patches. Kachess River forks apprdximatelyl.8 km upstream from the reservoir as Mineral Creek joins Kachess River from the northwest. Barrier falls occur on both forks approximately I km and 1.5 km upstream of the confluence respectively, at anapproximatelevation of 762m. Gradients steepen to between 2-7Yo in this area and channel widths drop to approximately5-15 m, whilo riparian vegetation consists mostly of typical old growth understory species. High alluvial banks persist along the stream channel for several hundred meters downstream of the confluenee while bedrock is common above the confluence on both forks of the upper strearp. The headwaters of Mineral Creek originate in the Alpine Lakes Wilderness,

19 9 whereas Kachess River headwaters occur on lands managed by Plum Creek Timber Company and the U.S. Forest Service. Interestingly, Kachess River above the confluence with Mineral Creek becomes a significantly smaller tributary carrying approximately 25Yo of the flow of Mineral Creek. However, it is this reach of Kachess River where spawnin gravel is common and not surprisingly, this area contained the majority of bull trout redds in Common surlmer predators of fish along the stream and reservoir include: mergansers (Lophodytespp.), great blue herons (Ardea herodias), kingfishers (ceryle alcyon), garter snakes (Thamnophispp.),black bear (ursus americanus), otters (Lutra canadensis), mink (Mustela vison), and other small mammals. Historic Conditions Kachess River has a varied history of past resource extraction events and natural processes which have contributed to its present state of widened stream channels and dewatering reaches. One of the earliest reports of potentially stream-altering activities is copper mining at the tum of the century in the Kachess system. Copper deposits were discovered on Mineral Creek and a wagon road was built sometime in the early 1900s to extract ore mined from the hillsides adjacent to the creek. Both an ore crusher and extraction mill were constructed at the stream level of Mineral Creek circa It is unclear how much total ore was processed at the site, however even limited operation of these machines probably produced large amounts of tailings, given their capacity of 25 tons per day. These tailings were presumably sluiced downstream to a tailings pile alongside the creek (Hodges 1897;Patly I92l). Remains of the mining operations are still visible from the trail along Mineral Creek.

20 Commercialogging adjacento the study site occured predominantly on USFS land from 1968 thru 1986, with additionalogging of nearby Plum Creek Timber Company lands in the early 1980s. Although the plum creek Timber company operations were more intensive and concentrated, these lands are mostly located at least a kilometer or more from the stream corridor. Logging directly through the Kachess River study site and at its headwaters occurred on a USFS section and took place from 196g- 1971, with several additional cuts in and 1986/87 (Plum Creek Timber Company 2000; USFS 2001). Road building directly adjacent to the study site took place at approximately the same time period and one road crossed through and traveled along the stream channel to a gravel pit and clear cuts on the west side of the River. Severalarge fires burned hillsides around the study sites in the early part of the last century or 1800s (usfs 2001). Box Canyon Creek 10 Box Canyon Creek flows into the main part of Lake Kachess 4.8 km south of Kachess River and is the only other known bull trout spawning stream draining into Kachess Lake. Box Canyon Creek has experienced occasional sporadic de-watering in the past, but because it is steeper in gradient than either Kachess River or Gold Creek it only de-waters when reservoir levels are low and it crosses the reservoir bed. It is a third order stream draining a 316 km2 watershed and has a barrier falls approximately 2 km up Box Canyon that restricts adfluvial adult spawners to the lower portions of the creek. Box Canyon Creek has an abundance of cutthroat trout which are most likely prey for juvenile bull trout.

21 tl Lake Kachess Historically, Lake Kachess consisted of two natural basins, the main lake and Little Kachess Lake, prior to being impounded in l9l2to increase water storage for irrigation. Kachess River is one of the main sources to the lakes and flows from the Alpine Lakes Wildemess area into the head of Little Kachess Lake, which then joins the main lake further down the valley. Before raising the level of the naturalakes, an extensive stand of large, old growth Western red cedar (Thuja plicata) stood at the head of Little Kachess Lake. Western red cedar thrive in boggy wet areas and currently the large stumps of the cut forest now reflect both their historic growing conditions and outline the historic path of the river, which winded its way through the forest to the lake. In the late summer of 2000, once the reservoir had been dropped, there were several upwelling areas in the midst of the cut cedar forest. Currently, when the reservoir is near full capacity in the spring, large volumes of high velocity spring runoff fill all channels of Kachess River' The high energy flow carries excessive alluvium but this drops out once the flow meets the standing water of the reservoir. The result has been that as the reservoir drops, the lower summer stream flow must redefine its channel on the wav to the lake bed and often braids several times due to excessive bed load. Prior to 1980, the reservoir was managed similarly to the current management of Lake Keechelus, where draw-down began in early summer and continued into the fall. However, since 1980 the Bureau of Reclamation keeps Lake Kachess reservoir levels high, into early to mid August, prior to draw-down. Both Little Kachess Lake and Kachess lake are considered to be oligotrophic. The current reservoir has a capacity of

22 9,854,926,000 m3, covers an area of 2r.3 km2, and has a maximum depth of r44 m and is 687m above sea level at full capacity (Goodwin and Westley 1967;Dion et al.1976). Fish passage facilities were not constructed for anadromous or migratory salmonids at the time the reservoir was created. Historically, natural populations of spring chinook, Oncorhynchus tshawytscha, coho, O. kisutch, sockeye salmon, O. nerka, and steelhead trout, O. mykis spawned in the basin above the dam, however these species have been extirpated from the Kachess Lakes (Tuck 1995). Species introduced to the lake since the dam include: Kokanee salmon O. nerka,brook trout, Salvelinus fontinalis and lake ftout, Salvelinus namaycush. Other native species present in the lake system include rainbow trout O. mykiss, cutthroatrout, O. clarki,redside shiner, Richardsonius balteatus,longnose dace, Rhinichthys cataractae, northem pikeminnow, Ptychocheilus oregonensis, burbot, Lota lota, suckers, Catostomas spp., and sculpins, Cottus spp.. Gold Creek Gold Creek flows into the head of Lake Keechelus just below Interstate-90 and is a third order stream draining a35.2 km2 basin. Gold Creek is the only stream flowing into Lake Keechelus where bull trout are known to spawn. The upper portions of the watershed lie in the Alpine Lakes Wilderness area and af,e somewhat pristine, although mining for gold in the early part of the century on the upper portions of the watershed may have impacted the stream. The lower half of the stream, where the study took place, has been impacted by the logging of old growth forest north of Interstate 90 and logging of the old growth cedar foresthat grew on what is now the reservoir lake bed. Additionally, significant gravel excavations from the flood plain of Gold Creek took T2

23 place during the construction of Interstate 90 in the late 1970s (USFS 2001). Gold Creek Pond is one of these excavations and lies directly adjacento the survey sites in this study. The pond is not directly connected to Gold Creek on the upstream end, but siphons some underground stream flow and taps into groundwater. Outflow from the pond retums to lower Gold Creek via an artificial spawning channel constructed for kokanee salmon, thus keeping the lower portion of the creek flowing throughout the summer and fall (Didricksen 2001). The pond has a maximum depth of l8 meters and a base flow of 0.13 m3 sec'r in late fall (wissmar and craig 1997). However a 3-4 kilometer reach of the adjacent stream de-waters as summer base flows drop. The stream channel in this lower reach is composed predominantly of gravel and cobble, and channel widths frequently exceed 60m. Riparian vegetation along the study site is mostly alder and shrubs associated with second growth forest. Coarse woody material is somewhat common, although clumped in log jams and against root wads. De-watering this section coincides with adult bull trout migration and affects both juvenile and fry of several resident fish species. Finally, a barrier falls is located 11.4 km upstream of the reservoir and most bull trout spawning occurs within a2l<n reach below the barrier. Historic Conditions Mining at Gold Creek took place in the late 1800s and early 1900s and predominantly occurred along the upper reaches of the headwater streams, above current bull trout spawning reaches. It is unknown as to how extensive these operations were or what impacthey may have had on the upper reaches of Gold Creek itself (Hodges 1897). Land ownership around the study site on lower Gold Creek is fairly evenly split 13

24 t4 between Plum Creek Timber CompanyiPrivate landowners (section 11) and the USFS (sections 14 & 15). Likewise, commercial logging directly adjacent to the study site occurred fairly extensively on both types of ownership from 1968 thru the mid 1980s. After logging section 11, Plum Creek rimber Company sold the land to private ownership. This land was subdivided and sold in lots adjacento the creek primarily for seasonal cabins, and a series of roads were constructed in the historic flood plain area for access (Plum Creek Timber Company 2000). Lake Keechelus Lake Keechelus was a natural lake prior to being impounded in I9l7 to increase water storage for irrigation. The head of the historic natural lake was once covered with an extensive stand of old growth western red cedar, Douglas fir (Pseudotsugo menziesii) and western hemlock (Tsuga hererophylla) similar to the forest at the head of Lake Kachess. Once the reservoir was created, the same phenomenon of excessive alluvial deposition along the historic stream path began, as described at Lake Kachess. Currently the stream usually flows contiguously to the reservoir for most of the summer, although in places it is so braided and shallow, fish passage is difficult when stream discharge decreases in summer. Curently, the reservoir has a capacity of 308,500,000 m3, covers an area of 10.5 km2, has a maximum depth of 108 m and is767 m above sea level at full capacity (Goodwin and Westley 1967; Dion et al.1976). Fish passage facilities were not constructed at the time the dam was built and thus natural populations of spring chinook salmon, coho salmon, sockeye salmon, and steelhead trout, were extirpated from the upper reaches of this system (Tuck 1995).

25 METHODS The central focus of this study was to understand changes in juvenile density and the movement of adults and juveniles, in relation to de-watering. Measuring shifts in juvenile densities can be useful in inferring mortality, and provides insight into the movement ofjuveniles throughouthe system, in relation environmental change. To test the two main hypothesis of the study, snorkel surveys were conducted every two weeks from 19 July to November 16,2000. These survey dates can be divided into three main ecological periods: the early season watered condition, characteized by relatively stable high flows and total system connectivity; the de-watered condition, a time of low summer base flows and de-watered reacheseparating the upper stream system from the reservoir; and finally, the re-watered fall condition, charucteized by increased unstable flows and often intermittent connectivity. Standardized surveys for firy, juveniles and adults were established in reaches that annually undergo de-watering as sunmer progresses, as well as in areas which remain watered throughouthe summer and fall. In this way, measurements of the physical environment including: water temperature, stream discharge, dissolved oxygen, stream gradient and measurements of woody material were used to assess environmental influence on density shifts and help understand mortality and explain migration patterns. Finally, historical data was used to both establish a reference ofpast vs current conditions and to help define the past disturbance regime at each site, in order to speculate how past management events may have brought about current environment conditions. t6

26 20 snorkelers, beginning downstream and slowly moving upstream, utilizing hand held underwater flashlights to illuminate fish for identification and measurements. Upon entering the downstream portion of each pool or glide, snorkelerscanned the area to track the total number of fish present prior to starting measurements and identification. All fish species beside sculpin were counted and measured, although cutthroat and rainbow trout counts were combined, due to their ecological similarity and difficulty in distinguishing hybrids. Total length measurements were obtained by snorkeling adjacent to each fish with a modified t-square and subsequently recording the length to the nearest centimeter on an underwater writing cuff (Dolloff et al. 1996). Lengths for fish that spooked or were unapproachable due to hiding cover, or depth, were estimated to the nearest 50mm length class (Northcote and Wilkie 1963; Griffrth 1981; Schill and Griffith 1984; Hankin and Reeves 1988). Observers wore fulidry suits and neoprene hoods and gloves due to the cold water temperature. Adult Bull Trout Surveys Both day and night snorkel surveys were used to assess adult bull trout distribution and abundance. Adults were detected in lower Gold Creek and at Kachess River while conducting nighttime juvenile snorkel surveys (Tables I and2). Additionally, two daytime snorkel surveys of the entire stream system at Kachess River were conducted for adult presence on 25 July, on the initial field visit, and9 August, just after de-watering began. Daytime snorkel surveys were also conducted at Gold Creek on 14 and 28 July and 8 and 25 August to determine the timing of migration in relation to de-watering.

27 2002) along with a copy of the Keechelus Dam Safety of Dams Modifications, yakima Project, washington, Final Environmental Impact Statement (usbr 200r). 24

28 RESULTS Kachess River Juvenile Bull Trout Ecologically, the study can be divided into three time periods, the initial watered sample periods (25 July and 9 August), the de-watered sample periods (22 August, 6 and 22 September), and the re-watered fall sampling periods (4 and 18 October, 3 and 16 November). The lower 400m de-watered completely, whereas the middle 600m and upper 200m remained watered throughouthe study. Because of this, the middle and upper areas provided a useful index for measuring juvenile density shifts and changes in number of fish present (Table 1). Densities at Kachess River in the 600m site were plotted in two ways, first, as number of fish per 100 linear meters of stream (Figure 4), and secondly as number of fish per 100 m2 (Figure 5). This was done because flow measurements were not taken during the October sampling periods, and therefore calculations of fish per area were not possible. However, both figures show the same trends. Numbers ofjuvenile bull trout in the 600m sample area also reflect an initial increase, before exhibiting a steady decline (Figure 6). Interestingly, no significant change in densities of cutthroat/rainbow trout were observed at the 600m index site (Figures 4 and,5). Densities in the upper 200m site exhibit a declining trend similar to that of the 600m site, during the de-watered period (Figure 7), Numbers ofjuvenile bull trout in this site also show declines during the de-watered period (Figure 8). Kachess River length frequency diagrams (Figure 9a and 9b) indicate the juvenile population is I composed mostly of three year old (130-2l0mm) and four year old ( mm) fish, 25

29 27 N a (l) 0.6 Date + Bull Trout...r* Cutthroat/Rainbow Figure 5. Juvenile bull trout and cutthroat/rainbow stream densities by surface area (# fish/100m2), from night snorkel surveys of the upper 600m reference site, for all sampling periods at Kachess River a (r. il20 tr C) ls F z ; 1 0!Y - ) Figure 6. Total number ofjuvenile bull trout from night snorkel surveys in 1000m at Kachess River. The Lower 400m de-watered from Aug Oct. 4, whereas the upper 600m remained watered the whole season. Note: Bars are stacked.

30 28 Nd >\ t) c) Jul. 25 Aug.22 Sept. 6 Sept. 20 Date F'igure 7. Juvenile bull trout and cutthroat/rainbow densities (#/100m2) in the upper Kachess River 200m site, above the confluence with Mineral Creek. Arrow indicate start of de-watering. July 25 and August22 stweys are USFWS data. Tu'10 rr. b = A Z T Jut 25 1l;,g.n Sept.6 Sept. 20 Date Figure 8. Total number ofjuvenile bull trout from night snorkel surveys in the upper 200m Kachess River site, above the confluence with Mineral Creek. July 25 andaugust 22 surveys are USFWS data.

31 29 Nlower = 0 Nuppel = 24 August 22,2000 d -.- u) H CH L q) - -t F T - z Nlower = o NuOO.r = 2l September 6,2000 Nlower = o Nuppsl = 17 September 22, r00 ll0 r r r r Size (mm) Figure 9a. Length frequencies ofjuvenile bull trout from night snorkel surveys at Kachess River. Solid bars represent fish present in the upper 600m sample site which remained watered, while striped bars represent the lower 400m site that dewatered August 15 - October 3, Note: Bars are stacked and fish were placed in 1Omm size classes.

32 30 Nlower = 5 Nupper = 8 - H.- U) r-. -t c{- o L C)! de I,l - z Nlower = I Nupper = 7 October Nlower = I Nupper = 4 November 16, ilo t Size (mm) Figure 9b. Length frequencies ofjuvenile bull trout from night snorkel surveys at Kachess River. Solid bars represent fish present in the upper 600m sample site which remained watered, while striped bars represent the lower 400m site that dewatered August 15 - October 3,2000. Note: Bars are stacked and fish were placed in 1Omm size classes.

33 and that the emigration to the reservoir after re-watering is predominantly these same age classes. Furthermore, the decline during the de-watered period appears to be almost exclusively three year old juveniles. Pairwise comparisonshow no significant difference in the average number of juvenile bull trout between the initial watered period and the de-watered period in the 600m reach (f, df :l, P<0,05). However, significantly fewer juvenile bull trout ":0.07 were found in 600m reach after re-watering than were found in the de-watered period (.f df : l,p<0.001). Additionally, there were significantly fewer juvenile bull ":44.04, trout in the lower 400m site after re-watering than were present in the initial watered periods (.f,:4,01, df :1, P=0.05). There was no significant difference in mean length between any of the length frequency distributions ofjuvenile bull trout in the 600m sample area (Figure 10) using Kendal's Coefficient of Concordance (P = 0.09, df =8) d b0 F () Fl c) k!) z Jut 25 Aug. 9 Aug. 22 Sept. 6 Sept. 20 Oct.4 Oct. 18 Nov. 3 Nov. 16 Date Figure 10. Average total length ofjuvenile bull trout from night snorkel surveys at Kachess River with a 95oh confrdence interval.

34 32 Timing of Adult Bull Trout Migration and Spawning I hypothesizedthat the timing of adult migration and spawning at Kachess River would follow the general pattern observed in other Yakima Basin streams, where adults move into the system in early summer and spawn in fall. Furthermore, I predicted that at Kachess River, adult migration would oocur earlier in comparison to streams which do not exhibit de-watering. In order to test this prediction, day snorkel surveys of the entire stream system were conducted before and just after de-watering, although no adults were located. Furthermore, no adults were detecte during summer juvenile night snorkel surveys until October 4,2000 (Table 1), just after the stream re-watered. Only after collecting historic survey records from several agencies (Table 2) did it become evident that no past summer surveys had located adults, and in fact adults were only located twice in the past, both times in early to mid October. Brown (2002) located these fish during electrofishing surveys and no redds were recorded at the time, although the fish were obviously in spawning condition from examining historic photos. Historic redd survey data for Kachess River begins in 1998 with Anderson (personal communication), however no fish were located in the September survey (Table 3). Redd surveys in October and November of both 2000 and 2001 located t5 and 14 redds, respectively. The timing of migration in all adfluvial populations of the Yakima River Basin begins in July or August, except at Kachess River where migration occurs in October (Figure 11).

35 aa JJ Table 2. Historical adult bull trout presence and stream coriditions at Kachess River. Date Observer Stream Condition Adult Presence 5129,616, 9/23180 Brown, L. (WDFW) 2 surv. connected, 1 disconnected 0 adult bull hout: Electrofished t0t7t80 Brown, L, (WDFW) Just connected 4 adult bull trout: Electrofished t0/13t84 Kessler, S. (USFWS) Disconnected 4 adult bull trout 8/31-10/18Brown, L. (WDFW) Disconnected 0 adult bull trout in four visits: 1993 Electrofished 6t25t96 Mongillo, P.(WDFW) Connected 0 adult bull trout: Electrofished 9n996 Lanick, W. (BOR) Disconnected No mention t0/r996 Craig, S. (USFWS) Disconnected No mention 7n7t98 Craig, S. (USFWS) Cormected 0 adult bull hout; Snorkel survey Anderson, E. (WDFW) Disconnected 0 adult bull trout; Redd survey r0t4 - tu Meyer, W., Anderson, E. (WDFW) Connected 12 Adults, plus I predation mortality and 2 mortalities from de-waterins. 917l0l Meyer, W. Disconnected 0 adult bull trout; Table 3. Annual summary of redds from at Kachess River, Box Canyon Creek and Gold Creek. WDFW data, provided by Eric Anderson. YEAR 1984 r t Kachess Lake Box Canyon Creek Kachess River : 4 a J 0 0 : :? : Keechelus Lake Gold Creek 2 2 2I 15 t2 a J 11 t6 I4 YEAR 1993 r t Kachess Lake Box Canyon Creek Kachess River 4 11 : : i T t4 t4 Keechelus Lake Gold Creek ti l 3l

36 34 BoxCanyon Creek lake Keechelus Burrping l^ake Rin:rock Lake Rinrock lake Deep Creek South Fork Tieton River Indian Creek Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 11. Lake residence (light shading) and timing of migration and spawning (dark bars) from the adfluvial bull trout populations of the Yakima River Basin in Fry Stranding Weekly surveys at Kachess River located 6 stranding pools over the course of the study and pools were tracked from their formation until they either dried or re-watered. The maximum total number of bull trout fry stranded in all pools was 47, compared to 100 for cutthroat/rainbow fry. Only a single juvenile cutthroat was located in any of the pools, and no juvenile bull hout were observed stranded in A visit to the site in September 2001, showed all the previous years' pools, except one, were completely dry and the dry zone extended into the previously flowing middle 600m site from Also in 2001, only a single deeper area around a rootwad on the lower end of the 600m site had two large pools containing 13 juvenile bull trout and 9 cutthroat. The stream was still

37 retreating quickly up the 600m section and I found hundreds of sculpins alive on the bare wet rocks along with 2 dead cutthroatrout fry and approximately50 tailed frog tadpoles. Only two small stranding pools were found in the lower river in 2001, and these pools contained a total of 23 cutthroat fry and 12 bull trout fry. Water temperatures in the stranding pools in 2000 and 2001 remained at or below that of flowing parts of the river, while dissolved oxygen levels were typically above 90% saturation, and similar to those of the creek. Species Conrposition The fish community at Kachess River in 2000, was fairly homogenous with only 6 species detected, and the overwhelming majority being bull trout (57%) and cutthroat/rainbow (41%), with only approximately?% brook trout and redside shiner (Table 5). This percentage tally exclude sculpin because of their ubiquitous nature and difficulty in accurately counting the species during snorkel surveys. 35

38 36 Table 4. Kachess River fry stranding pool sunmary. Date Pool I Pool 2 Pool 3 Pool 4 Pool 5 Pool 6 Aug.22 3BT 5 CT/RB 6BT 7 CT/RB Not formed yet Not formed yet Not formed yet Not formed yet Aug.30 Dry 8BT 5 CT/RB 3BT 2 CT/RB 11 BT 42 CT/RB Not formed yet Not formed yet Sept. 6 Dry 6BT 1 CT/RB 5BT O CT/RB 13 BT 56 CT/RB 4BT 26 CT/RB 14 BT 4 CT/RB Sept.13Rain event reconnects all pools to stream, fiy liberated, upper stream flows contiguously for remainder of study. Nov.7 Two dead male bull trout trapped in lower pool as de-watering occurs during out-migration. Table 5. Species composition and size ranges at Kachess River by number and percent for all sample dates. Note: Kokanee salmon and sculpin were excluded. Species ition Species Number Percent Size Range (mm TL) Min, Bull trout C utthro atlrainb ow trout Brook trout Redside shiner t66 n T 4r.'l L 2 <

39 37 Physical Environment: Stream Temperature, Discharge and Rainfall Stream temperature profiles were acquired using two tidbit data loggers at each site for duplicity. Kachess River average stream temperatures over the study period ranged from a low of 1.3"C in November to a high of ll"c in early August (Figure 12). Variation in daily stream temperatures Kachess River ranged from less than loc in November to 4oC in July (Figurel3). Juvenile numbers were negatively correlated with stream temperature Kachess River, (y':0.91, P:0.Q03). Water temperatures Kachess River had low correlation to stream discharge (f :0.47, P :0,52). Stream discharge measurements were generally taken every wepk from 20 July thru September, and whenever feasible thereafter. Three stream dischar$e locations were regularly sampled at Kachess River (Figure 14). Sheam discharge on the main stem of Kachess River ranged from approximately 5 cfs in August and Spptember to approximately4s cfs in the middle of July. Juvenile bull trout numbers were not correlated to stream discharge at Kachess River (f = 0.30, P :0.26). Cumulative monthly precipitation in 2000 was compared to a 30 year monthly average withglo/o confidence intervals (Figure 15). Precipitation in October is notably lower than average and this may have created a longer de-watered period at a time when adults normally migrate upstream at Kachess River.

40 38 16 t sr lo H 8 tr O. Q { o. 6 4 F 2 0 " /.v\ A, -:/"Y1--\iN^h A 'f / u "\;K/ v\:a//p\ A v V"qy' [7\ AN \J V 7\l\^* V^ VV = = b 0 b 0 b A ^ 6 : : r r = 3 8 b " b " b " ; N ( \ l t r r c. r i O \ \ O \ f N \ O c'l N c'l c'l Date!l Y Z Z s..:. o\ Figure 12. Water temperature("c) in Kachess River, just below the trail crossing, from July 20, 2000 to November 16, Temperature was recorded hourly and lines indicate daily minimum, average, and maximum. t6 t4 P 1 2 e 1 0 E! R :v o a. o (.l o 6 6 i t +, s i i 5 o i 6 i 6 o 6 6 i 5 t. 6. i 6 i d # 6 o N 6. i N Time -20-Jul **.**l-aug -l-sep - - l-oct...1-nov Figure 13. Daily temperature ("C) fluctuations at Kachess River from July and the first of each month thereafter.

41 (D bo k 30 d. () a t 10 a 0 t \". % E = b o b o b o b 0 b o ; ; $ $ f s * i N r ) N O \ N N Kachess R. above the Y Mineral Cr above the Y Kachess R. below the Y o o o.t) v) u) \ n s 9 Date F o O O q a? q \ o o o r N I 6 E t Y Y l $ - t i N 6 39 Figure 14. Discharge on the main stem of the Kachess River, 300m below the confluence with Mineral Creek, and 50m above the confluence on Mineral Creek and Kachess River from July 18, 2000 to Novemb er 7,2000. Striped arrow indicates the beginning of de-watering and solid arrow indicates re-watering of the main stem. ii 20 6 '5 l0 6) ti l.o. Mar. Apr. May Jr.nr. Jut Aug. Sept. Oct. Nov. Dec. Month Figure 15. Monthly precipitation at Kachess Dam in 2000 compared with a 30- year average ( ) and 95% confidence interval (data from USBR).

42 40 Reservoir Elevations Reservoir elevations for both Lake Kachess and Lake Keechelus (Figure 16) were plotted on the same graph for comparison by adding 76mto Lake Kachess elevation values. Arows were added to indicate when each stream channel completely de-watered, and initially re-watered. Kachess River de-watered at least twice in the fall after rewatering. However, de-watering was a gradual process at Kachess River beginning in late July and was complete well before the Kachess Reservoir began to be drawn down. Therefore, reservoir drawdown at Kachess River appears to have no affect on the dewatering process. The Keechelus reservoir elevation in early summer is typically approximatelyt6tm, although due to recently discovered structural problems, maximum reservoir elevations in 2000 were approximately765m Reservoir Elevations c) trl Kachess - * Keechelus 2430 l -Jun l-jul l-aug l-sep D ate l-oct l-nov F'igure 16. Kachess and Keechelus reservoir elevations in relation to the dewatering and re-watering of Kachess River and Gold Creek. Striped ilrows indicate de-watering and solid anows indicate re-watering at each site. Note: The plotted elevations for Kachess Reservoir are * 76m actual elevation, for comparing plots.

43 41 Gold Creek Juvenile Bull Trout A summary ofjuvenile bull trout numbers and densities in each reach, for all sample periods, can be found in Table 6. Total numbers ofjuvenile bull trout were frequently only 25-50% of numbers at Kachess River. Similarly, densities at Gold Creek were very low in all sample sites, especially when compared to densities of cutthroavrainbow trout (Figures 17 and 18). Unlike Kachess River, there was no discemable pattern in juvenile bull trout numbers in either the lower 600m site, or the upper 400m site (Figure 19). Sampling visits at Gold Creek can be divided into the same three general ecological time periods of watered, de-watered and re-watered survey periods as at Kachess River. However, the watered state of the upper 400m section at Gold Creek was highly variable, even between visits, making any statistical comparisons biologically inconsequential. The lower 600m area remained watered throughouthe study, and thus can be used to test the idea that densities increase with decreasing flow. However, since this reach remained connected to the reservoir, speculation on what causes any changes (i.e. mortality vs immigration/emigration) is not insightful. Densities ofjuvenile cutthroat/rainbow trout in the lower 600m did show a significant increase between the watered period and de-watered period ((":14.49, df :I,P<0.01). (Zar 1996). Similar to Kachess River, there was no significant difference in mean length between any of the length frequency distributions ofjuvenile bull trout in the 600m sample area (Figure 20) using Kendal's Coefficient of Concordance (P:0.23, df :7).

44 o A..t = = b 0 b 0 o o b t l b o F L 3 3 { { q4 N N c l \ \ O o c ) \ O 6 O F - $ N N 6 d D ate Figure 17. Juvenile bull trout, cutthroat/rainbow and brook trout densities (# fish/l00m2), from night snorkel surveys of the lower 600m site, for all sampling periods at Gold Creek. Striped arrow indicates beginning of dewatering on the upper 400m site, although this site remained partially watered throughouthe study period. Solid arrow indicates re-watering of the stream svstem in the fall. Y -CT/RBT - B ulltro ut E A 6 l l Y = Y 3 Y R ) Z o Z b g 0.6 u.c i fi $ i E fr f, $."H A, q. q B B Y Y \ Z Z = 2 R.! a * q N Figure 18. Juvenile bull trout, cutthroat/rainbow, and brook trout densities (# fish/l00m2), from night snorkel surveys of the upper 400m site, for all sampling periods at Gold Creek. The striped affow indicates the beginning of partial de-watering at this site and the solid arrow indicates re-watering.

45 45 Timing of Adult Bull Trout Migration and Spawning Gold Creek adults were known to migrate in mid-summer and spawn in September, although from historic surveys a few fish had often been detected spawning below the de-watered reach in early fall, suggesting these adults didn't make the summer migration prior to de-watering blocking their passage. In the summer of 2000, adults were first found in the upper creek on 28 July, approximately two weeks prior to the sheam de-watering (Table 6). Gold Creek was still flowing on 1 August, and adults may have been able to migrate to the upper stream, but it had de-watered by 15 August. After de-watering, several adults were seen holding in pools below the de-watered reach. These adults were seen on all surveys until the stream re-watered, and one pair was seen moving upstream as far as possible after a rain event in late September partially reconnected the stream. A single redd was found below the de-watered reach in late September 2000, prior to the re-connection, although the survey was incomplete. In 2001, at least ten adult fish were sighted below the de-watered reach and three redds were located in this area. Historic redd survey data (Table 3) for the past eighteen years shows redd counts have varied from a low of 2 in 1984, to a high of 51 in Fry Stranding The de-watering at Gold Creek happened both in the upper 400m survey area and much higher in the stream. The upper 400m section de-watered in patches and left several relatively deep pools (-20m2 and -2m deep) as refuge areas in between dry sections, and as a result, no fry were found stranded in the 400m sample area, so stranding data is from Gold Creek above the 400m reach (Table 7). The upper pools

46 46 outside the survey area were not located until 25 August on an adult survey, and they appeared further along in the de-watering process than the lower reaches. Six pools containing stranded fish were located in this upper area and they contained both a higher number of fish than Kachess River, and a greater diversity of species and size classes. The maximum total number of fry and juveniles stranded in all pools of this upper area was 97 bull trout/brook trout fry and 4 juvenile bull trout, 64 cutthroat/rainbow fry and, 12 juveniles, a minimum of 50 sculpins, 2 kokanee juveniles, 2 mountain whitefish, and I brook trout juvenile. In the early fry stages it is difficult to distinguish between bull trout and brook trout, and so the above numbers represent the firy of both species. Water temperatures in these pools remained at or below that of lower Gold Creek, while dissolved oxygen levels were typically above 90%6 saturation, and at or only slightly below the flowing portions of the creek.

47 47 Table 7. Gold Creek fiy stranding pool summary. Date Pool 1 Pool 2 Pool 3 Pool 4 Pool 5 Pool 6 Aug25 BT -r0 (1) BRK (1) RB/CT 8 (2) Kok I cot >25 BT -10 RB/CT -20 RB/CT 10 MWF 1 Note: MWF was -250mm RB/CT 3 BT r (1) RB/CT 23 (7) MWF I Not formed yet Aug.30 BT 47 (2) BRK (l) RB/CT 4 (4) Kok 2 cot >25 BT IO RB/CT -20 Dry Dry Dry Not formed yet Sept.6 Br 7 (1) RB/CT 3 Kok 2 cot >25 BT8 RB/CT I7 Dry Dry Dry BT3e (l) RB/CT (l) cot >25 Sept. 13 Rain event reconnects all pools to stream, fry liberated, upper strearn rewaters and de-waters until at least October Note: No adult bull trout mortality observed, but a 300+mm burbot mortality. Species Composition The fish community at Gold Creek in 2000, was relatively diverse, with 12 species detected, although the majority of fish were cutthroat/rainbow (66%), followed by brook trout (160/o), bull trout (8%) and mountain whitefish (6%),leaving less than 5Yo for burbot, redside shiner, suckers, longnose dace and northern pikeminnow (Table 8). Once again, sculpin were excluded due to their ubiquitous nature and difficulty in accurately counting the species. Kokanee salmon were also excluded because other than a few juveniles in the sruruner, the adults only enter the system in September, but by the hundreds.

48 Table 8. Species composition and size ranges at Gold Creek by number and percent for all sample dates. Note: Kokanee salmon and sculpin were excluded. Bull trout Species Cutthroat/Rainbow trout Brook trout Mountain whitefish Burbot Redside shiner, Bridgelip sucker, Longnose dace, Northem pikeminnow Species Composition Number nt Size Range (mm TL) Min t r Physical Environment: Stream Temperatureo Discharge, and Rainfall Average Gold Creek stream temperatures (Figure 21) ranged from a low of 3.5oC in November to a high of t3oc in late July and early August. Variation in daily stream temperatures Gold Creek (Figure 22) were less than loc in November and -3.5oC in July. Stream temperature was significantly negatively correlated to stream discharge at Gold Creek (y' = 0.53, P:0.06). Discharge was sampled at two locations at Gold Creek (Figure 23). Stream discharge at lower Gold Creek ranged from -15cfs in August to cfs in July and October. Juvenile bull trout numbers at Gold Creek were not correlated to either stream discharge (y':0.25, P:0.25), or to stream temperature (y':0.39, P = 0.13). Cumulative monthly precipitation in 2000 was compared to a 30 year monthly average with 95% confidence intervals (Figure 24). A notable pattem at both sites is the unusually low rainfall in October, a factor effecting the emigration of adults to the reservoir.

49 49 t6 t4 g t 2 e 10 H H 8 k o. o, E = b b 0 b o d F l $ S $ $.. l N 6 O r.. + N o 0 o o. o. o - E 6 E : X e B B + $ f r q f i e e q F - r f q O \ a N O \ \ O l ' A. A 6 N 6, r N = i d ; D ate Figure 21. Water temperature ("C) in Gold Creek 100m below its confluence with the spawning channel, from July 20,2000 to November 30, Temperature was recorded hourly and lines indicate daily minimum, average, and maximum. l6 L4 P r z E 8 o 3 6 # o o o ( \ l * t Time $ \ o 6 o c \ t H - c. l N * 20- Jul l-aug -l-sep -*l-oct Figure 22. Dally temperature CC) fluctuations at Gold Creek from July 20,2000 and the first of each month thereafter.

50 50,n o () bo t< a1. Q(r, t-l d C) a \ \ - lswsr Gold - -.UpperGold E 7 E g 0 s 0 s 0 E 0 $ F + * t r l 1 T T 3 N N o \ g R B \ o l R R. + Date Figure 23. Discharge at Lower and Upper Gold Creek from July 19, 2000 to October 4,2000. Lower Gold site was -50m below the confluence with the spawning channel and Upper Gold site was across from the north end of Gold Cr. Pond. Striped alrow indicates beginning of de-watering and solid arrow indicates re-watering of the main stem. o?o 'J3,n o!) d l o Feb. Mar. Apr. Jun. Jul. Nov. Dec. Month Figure 24. Monthly precipitation at Keechelus Dam in 2000 compared with a 30- year average ( ) and 95% confidence interval (data from USBR).

51 51 Reservoir Elevations Reservoir elevations for Lake Keechelus (Figure 16) were plotted on the same graph as those for Lake Kachess for comparison. Arrows were added to indicate when each stream channel completely de-watered, and initially re-watered. The middle section of Gold Creek disconnected from lower and upper Gold Creek on approximately August 15, The Keechelus reservoir elevation in early summer is typically -767m, although due to recently discovered structural problems, maximum reservoir elevations in 2000 were -765m. The reservoir drawdown at Keechelus Reservoir began July 1, 2000, well before Gold Creek began to de-water, so it is unclear if the drawdown influenced dewatering. However, abureau of Reclamation study of the hydrology of Gold Creek and Gold Creek Pond, adjacento the study area, suggests that the pond acts to both channel groundwater to the surface, and draw Gold Creek flow away from the stream channel. The report suggests this probably causes Gold Creek to de-water sooner, and for a longer period, than it might otherwise.

52 DISCUSSION The relatively sudden de-watering of a stream system can play havoc with the aquatic organisms living there, especially less mobile life forms such as aquatic invertebrates or small fish. Because de-watering phenomsnon are consideredensity independent events, all species and size classes of organisms present are usually affected, however the impact on different age classes may vary. Typically, aquatic organisms that are exposed to recurring drought or de-watering events either adapt strategies to endure, speed their metamorphosis development, or emigrate to escape adverse conditions, otherwise high levels of mortality are experienced. Although some organismsuch as aquatic insects frequently have the ability to speed their metamorphosis burrow into moist substrate, fish must generally either find watered areas of refuge within a dewatered zone or emigrate from the de-watering reach (Stehr and Branson 1938; Larimore et al. 1959; Hynes 1972;Power et al. 1988). In many species of trout and char several year classes are usually present within a stream simultaneously, although they usually exploit different microhabitats within the stream. Fry and smaller juveniles frequently occupy the margins of streams which exhibit lower flow rates and presumably provide appropriate forage while allowing them to avoid predation. Because of their small size they are also frequently able to utilize the substrate as hiding cover, in order to avoid cannibalism by juveniles. Juveniles on the other hand, typically occupy areas of higher flow, exploit larger prey items, and are generally more mobile, but often require more complex hiding cover such as rootwads or boulders in deep pools (Pratt 1992;Polacek 1998). Because of these differences in 52

53 habitat use and mobility it is likely that differential rates of emigration, entrapment and mortality occur dependent upon the extent of de-watering. Although adult adfluvial bull trout only migrate into headwater streams in summer and hold until spawning in the fall, they too must pass through areas that de-water and as a result are impacted by this phenomenon. De-watered systems often continue to be perturbed long after re-watering occurs, through alteration of habitat or disruption of food chains, so organisms that were mobile enough to avoid the initial de-watering event still may need to cope with these altered habitats. If the pattem of de-watering is infrequent and sporadic, disruption of the system is minimized and emigration might simply be a response to proximate conditions by individuals. However, if the population has been exposed to recuring events over a longer period, selective forces may help create an evolved response by the population. In particular, traits which confer increased reproductive success, such as the timing of spawning are frequently under stronger geneti control in salmonids and less responsive to short term environmental fluctuations (Legget and Whitney 1972; Quinn and Adams 1996). Therefore, identifying and understanding recurrent long term natural and human caused perturbations to stream systems is critical when interpreting the responses of various organisms to this phenomenon. The Phenomenon of De-watering/Re-watering The Kachess River site de-watered in a fairly predictable manner proceeding from its confluence with the reservoir and slowly creeping upstream as summer progressed and base flows decreased. However, as the creek receded there were several areas of 53

54 54 temporary and long term refuge including: deeper pools formed around root wads and other coarse woody material, a spring channel, and some isolated, but watered side channels in addition to pools at the stream terminus. With the exception of the spring channel, these areas were frequently maintained through hyporheic flow. At Kachess River it was these areas where young-of-year bull trout, cutthroat/rainbow trout firy, sculpins and tailed frog tadpoles were frequently trapped. However, many of these relatively small pools maintained both temperature and oxygen levels similar to the main creek or cooler due to under-gravel flow. A small spring tributary enters Kachess River approximately halfivay between the confluence with Mineral Creek and the reservoir and feeds a small pool which is a refuge for fish in even the driest years. No young of year were found below this point until re-watering occurred in the fall. Interestingly, the only watered point below the spring channel was a single deep rootwad pool 300m downstream of the spring in the summer of 2000, This area was maintained by hyporheic flow and could be used as refuge on the lower half of the stream during de-watering events. This situation is somewhat in contrast to lower Gold Creek where several deep pools remained watered through the dry season to provide areas of refuge (Sedell et al. 1eeO). Understanding both historical land management activities and natural disturbances within and around the study sites is an essential component of interpreting present conditions and stream system dynamics that affect bull trout. Past human activities including road building, logging and mining can couple with natural events such as fires, flood events or windstorms to dramatically alter stream systems (Elliot

55 1986; Baxter et al. 1999; Hauer et al. 1999). Additionally, the geological make-up of a stream system can influence its behavior and state of equilibrium when perturbed by human or natural forces (Baxter et al. 1999; Dunham and Rieman 1999). The Influence of Mining, Logging and Geology on Flow Patterns and Bull Trout Kachess River and Gold Creek both exhibit fairly typical seasonal flow patterns for mountain streams in this region. However, both sites have been impacted by mining and logging, and the effects from these activities work in concert with geologic features at each site to directly affect discharge rates. By examining the synergy of natural processes and human cause disturbance, the phenomena of de-watering and its effect on bull trout become clearer. Mining occurred in the headwater areas of both sites in the early 1900s and at Kachess River tailings were almost certainly sluiced downstream into Mineral Creek. In his work at the site in the early 1980s, Brown (personal communication) noted an excessive amount rough cobble material in the stream channel and speculated that the most likely source was from historic mining operations. High flow events in the past few decades appear to have moved some of this material downstream where it likely worsene de-watering. Clear cut logging and the associated road building around Kachess River and Gold Creek is likely the primary catalyst in shifting the stream stable state, however this is only possible in combination with variation in seasonal precipitation and runoff. The removal of the large old growth trees along the riparian corridor reduced stream sinuosity, thereby increasing stream velocity, and allowing the streams to "mine" their banks during 55

56 56 times of high spring flows. Research by Hauer et al. (1999) suggests logging around streams also alters the delivery, storage and movement of large woody material in streams. These higher energy flows carried away coarse woody material in addition to finer sediments, and deposited excessive cobble and gravel in lower portions of the stream. Photos from the Kachess River Study (Parson 1980), along the middle and lower reaches of the stream, show greater amounts of large woody material in the stream channel than exist today, as well as backwater areas with pools and fine sediments, and thick riparian vegetation. Very little coarse woody material currently exists in these portions of the river, and almost no fine sediment can be found, attesting to the scouring effect of high velocity flows. Furthermore, at the confluence of Kachess River and the reservoir, a massive pile of stumps and logs has accumulated, at a place where only open channels were seen in 1980 photos. The effect of these changes on juvenile and fry bull trout rearing in the stream is to reduce habitat complexity, decrease their favored slow water habitats, and decrease prey availability, Although this appears to be mostly due to human influences at Kachess River, a completely natural series of events on upper Indian Creek, in the Yakima Basin, resulted in an even more dramatic deposition of cobble and a resultant de-watering. The area above Indian Creek is entirely forested wilderness, yet debris flows in years with rain-onsnow events or high water caused the massive deposition of cobble for nearly two kilometers along the stream channel. The portions of Mineral Creek and Kachess River above the confluence are markedly different geologically than the reach from the confluence to the reservoir. The

57 57 most notable features in the stretches above the confluence is a significantly higher gradient and a substrate of bedrock, so that the stream flows above ground even during low summer base flows. This contrasts with the lower reaches, which are wider unbounded alluvial segments and composed solely of deposited cobbleigravel upon which the surrounding forest grows. In these areas, down-welling occurs into the cobble deposited in the valley and de-watering results during low summer base flows. Although reservoir drawdown appears to have no direct effect on the de-watering of either stream, the deposition of alluvium onto the upper reservoir bed from early spring flows seems to effect de-watering later in the fall. This phenomenon is common when high energy stream flow carrying bed load meets a body of standing water such as a lake or reservoir. The energy carrying the bed load is dissipated and the load drops out. The accumulation of this very porous material on the reservoir bed creates a situation where the stream must frequently re-cut its path and often flows through the substrate rather than on the surface, In fact. it was this area at Kachess River where two adult male bull trout were found in a de-watered pool after attempting to emigrate to the reservoir following spawning. Furthermore, several adult kokanee salmon were also found stranded in this area when attempting to migrate upstream to spawn, suggesting that this area could trap juvenile bull trout on their emigration to the resenroir in the fall. By the end of September the reservoir level had dropped considerably and upwelling zones appeared in the upper portions of the reservoir bed, where an extensive stand of large, old growth Western Red Cedar (Thuja plecata) had been cut during the creation of the reservoir. Examination of the pattern of stumps also revealed that large

58 cedar trees once surrounded the up-welling sites and the past stream channel in this part of the stream. It was in this areaa single bull trout redd was located in The situation at Gold Creek is in some ways similar to Kachess River, however, several notable features of the study site alter the de-watering pattern. First, Gold Creek's elevation is slightly above that of the adjacent Gold Creek pond, and as a result, hyporheic flow crosses into the northwest corner of the pond. This appears to cause Gold Creek to de-water at a faster rate than it might if the pond were non-existent. Furthermore, the pond is -20m deep, and taps into the valleys groundwater supply, which upwells and then flows thru an artificial spawning channel, prior to retuming to Gold Creek (Didricksen 2001). This flow supports a continuous, although low flow, of Gold Creek below the pond to the reservoir. Secondly, the middle section of lower Gold Creek contains several deep logiam pools which act as refugia for fish during the de-watering process, however 2.5 km of the upper de-watered stretch are relatively featureless, and it was this reach where fish were trapped and killed. Furthermore, the flood channel is significantly wider than at Kachess River and composed of a large sediment field of cobble. The de-watered reach at Gold Creek (3.2km) is considerably longer than at Kachess River (1.4km) and of lower gradient (Lo/ovs L-3oh), respectively. These features create an uneven and sporadic de-watering pattern, where the middle de-watered reaches flow contiguously at the same time the upper reach is receding. Upon significant drop in base flows the lower gradient of Gold Creek apparently allows a more rapid de-water event to occur on the upper reaches, which in combination with a lack of refugia, causes even larger juveniles and adult mountain whitefish to become trapped. 58

59 59 Juvenile Bull Trout Densities Enumeration ofjuvenile bull trout, rather than fry or adults, can be an important method of indexing populations because juveniles have passed the often harsh survival curve fry experience in their first year. FurtherTnore, usually several age classes of juveniles are present in a stream at the same time, whereas not all adult fish spawn each season, thus requiring the marking or tagging of adults over several years for accurate population estimates (Fraley and Shepard 1989; Bonar et al. 1997). Additionally, juveniles are readily located by night snorkel surveys for density estimates and relatively easy to capture for mark-recapture studies. However, in order to utilize juvenile densities as a meaningful and accurate population index, it is important to understand the environmental and life history traits that influence densities throughout a season. In this portion of the study I was predominantly interested in investigating the influence of flow patterns and stream temperature during a de-watering event on juvenile density. Understanding the general pattem ofjuvenile bull trout rearing and migration in systems which are contiguous throughouthe year, is important before considering dewatered systems"' Juvenile bull trout typically rear in headwater streams for 1-3 years prior to emigrating downstream throughouthe summer and early fall to either larger fluvial systems, or adfluvial lakes or reservoirs. This migration is thought to correspond with an ontological shift from a diet of aquatic insects to piscivory, allowing growing juveniles to exploit a higher energy prey base in conjunction with their developmental needs (Fraley and Shepard 1989; Northcote 1992). Several previous studies have ---.l documented the timing and magnitude of downstream migrations throughout summer and I

60 fall. Fraley and Shepard (1989) report that in the Flathead drainage this out-migration consists predominantly of age 2 (49%) and age 3 (32%) fish with some age I (18%) fish, but only 1olo were age 4. Peak emigration from tributaries to the main stem of the Flathead River occurs from June thru September and further downstream movement in the main stem Flathead immediately thereafter, although movement into Flathead Lake is not well documented. Another study on the main stem of the Flathead by McMullin and Graham (1981) corroborates Fraley and Shepard's work in reporting that juvenile bull trout were captured by electrofishing throughout the year, but their numbers peaked during the late summer and fall months in this section of the river. Further work in Idaho and British Columbia on emigrating juveniles show similar ages and emigration patterns (Bjornn 196l; Oliver L979; McPhail and Murray 1979). Given that many stream systems stay connected throughout the summer, and the same general pattern is observed in several regions, the timing ofjuvenile emigration at Kachess River and Gold Creek would likelv reflect local conditions or constraints related to de-watering or other factors, Little information is available on how bull trout respond to such events, however de-watering appears to be a relatively common phenomenon throughout much of their range. Bonneau and Scamecchia (1998) observed numbers of juvenile bull trout decreasing with summer flow declines in all eight reaches of his study, seven of which remained watered. However, the eighth reach in Rattle Creek, had relatively high juvenile densities in June, but de-watered by early July when he noted young-of-year cutthroat and bull trout stranded in isolated pools. Additionally, Saffel and Scarnecchia (1995) reported that sub-surface flows in the Belt-series geology of northern 60

61 Idaho could readily create barriers to migration and cause subsequent year class failures. Although juvenile bull trout densities in the upper 600m reference site at Kachess River initially increase with decreasing stream discharge, a declining trend begins during the de-watered survey periods, and the trend accelerates with the re-watering of the sheam in the fall and winter. Several plausible explanations of these patterns exist, including: juveniles migrating higher in the system to seek thermal refuge or prey; mortality due to cannibalism, environmental stress, USFWS electrofishing sampling; emigration in the fall; concealment within the reach; or sampling elror. The initial, albeit short, increase densities makes intuitive sense, in that as the same number of fish occupy a smaller available habitat, their densities increase. However, the declining trend in densities during the de-watered periods, as stream flows continue to decrease is somewhat counterintuitive. It is possible that juveniles seeking areas of cooler temperatures or more prey disperse to higher reaches of the stream. Bonneau and Scarnecchia (199S) found juvenile bull trout exhibited a clear preference for the coldest water available in a Granite Creek plunge pool. The pool maintained a temperature gradient from 8oC- 15"C and juvenile bull trout were almost exclusively found in the 8-9oC area. So, a migration upstrea might reflect juveniles seeking cooler temperatures. However, this upstream migration seems unlikely because of a number of observations. First, Selong et al. (2001) report that movement and mortality ofjuvenile bull trout typically occurs when temperatures exceeded 15oC, and maximum stream temperatures on the upper reaches were frequently below I2'C andnever exceed 14oC, therefore temperature seems an unlikely explanation. Secondly, a200m reach in upper 6l

62 Kachess River was snorkeled at night from late July to late September, the period when densities drop the most, and this uppereach also reflecte decreasing densities. Several anecdotal observations also supporthe idea that migration is an unlikely explanation. We frequently observed single bull trout juveniles during daylight resting on the bottom of pools in the 600m section during the summer. Furthermore, no noticeable behavioral change was observed in the fish, for instance, one juvenile with distinguishing scars was seen within a 50m reach on six of the nine survey dates, and its home pool routinely had six juveniles present, suggesting local residence. A second explanation of decreasing densities during the de-watered periods is mortality through cannibalism, environmental stress or electrofishing injury. Juvenile bull trout exhibit piscivory at a remarkably young age (<100mm) in comparison to other salmonids (Cavender 1978; James 1997; Bonneau and Scarnecchia 1998). Bonneau and Scamecchia reported observing several instances of cannibalism amongst juveniles during his study and James reported cannibalism occurring bv fry as small as 65mm in buckets holding captured young-of-year. However, the USFWS reported 16 young-ofyear deaths related to daytime multiple pass electrofishing surveys at Kachess River during the de-watered period, so it is likely that this could account for some of the decline. Furthermore, at least six juveniles were observe during night snorkeling to have suffered injuries from electrofishing, four of which were not marked, indicating some fish were injured but not captured, while concealing themselves during the day. This is understandable given the affinity ofjuvenile bull trout for disappearing under cover during daylight hours, when electrofishing would take place. 62

63 Sampling error is also a possibl explanation for the observedecline in juvenile bull trout densities. However, an underestimation would be expected in the early summer, when water levels are high and fish have a greater area to conceal themselves, but the reverse pattem is observed. The continued decrease in juvenile density in the fall as re-watering occurs, is likely due to a combination of reasons including emigration to the reservoir and concealment to avoid predation by the adults (Cunjak and Power 1986; Griffith and Smith 1993). The most likely explanation for such a sudden decline would seem to be emigration to the reservoir, since it is a pattern frequently documented in populations in several other regions. If so, it would suggest the juvenile out-migration is simply delayed due to de-watering. Further decreases in densities over the last two sampling periods, after adults have emigrated, most likely reflects over-wintering concealment and continued emigration. During winter months, as food becomes more scarce, fish may change microhabitato minimize energy expenditures and/or predation by moving to lower velocity water and closer to cover (Bonneau and Scarnecchia 1998; Thurow 1997). Interestingly, cutthroat juvenile densities during the entire study period remained relatively constant. A gradual increase in cutthroat densities occurred as expected when stream discharge decreased, however no late sufltmer or fall decline occurred. Unlike juvenile bull trout, cutthroat do not exhibit a summer emigration to the reservoir, and frequently rear and mature entirely in the upper portions of watersheds. Likewise, cutthroat occupy open habitat during the day, and as a result are captured quickly when electrofished, resulting in a much lower injury rate than juvenile bull trout. 63

64 The direct effect on fry and juvenile fish of all species during these severe years is obvious, however, the longer term system effects can be somewhat more difficult to quantify. Initial densities and distributions ofjuvenile bull trout are very likely to be directly influenced by previous seasonspawning locations, subsequent suitable rearing habitat, and food availability, all of which depend upon the extent of de-watering events" McPhail and Murray (1979) suggest that limitations in juvenile rearing habitat may form an "ecological bottleneck", greatly affecting overall population levels of bull trout. Juvenile bull trout are known to be opportunistic feeders, and when young, they mainly ingest aquatic invertebrates, especially Diptera and Ephemeroptera, in similar numbers as they occur. Also, because juveniles become piscivorous at a relatively young age, the presence of abundant prey, other salmonid fry or sculpins, would allow quick growth rates (Fraley et al. 1981; James 1997). However, if de-watering dramatically reduced either the aquatic insects or the fish they feed upon, juvenile bull trout production or growth could be severely limited. Even moderate de-watering years may limit growth, for instance, there was no significant difference in juvenile bull trout growth rates at Kachess River through the whole season, perhaps related to the effects of de-watering or simply low sample size. Furtheffnore, degraded conditions might force juveniles to emigrat earlier than they would if conditions were optimal. Severe de-watering events, such as occurred in 2001, directly limit rearing habitat and likely reduce food availability even long after re-watering. For instance, during the drought summer of 2001, the stream receded considerably higher than 2000, and hundreds ofyoung-of-year sculpin and cutthroat fry were observed literally being left dry on the rocks, along with thousands of 64

65 65 aquatic insect larvae (Plecoptera, Diptera and Ephemeroptera). In summary, long term monitoring studies ofjuvenile abundance should consider previou seasons conditions, and account for both time of season and discharge rates when conducting censuses, to avoid misleading results. For example, density estimates would be quite different if taken in early or late summer, or from streams under the influence of disparat environmental conditions. In this way, one might control as much as possible for both important environmental variability and life history shifts. Adult Migration and Stranding Understanding the affects of de-watering on adult bull trout is important because this phenomenon has the potential to alter spawning migrations, and thus affect reproductive success, in addition to directly affecting adult survival. This is especially critical in depressed or isolated stocks such as Kachess River and Gold Creek which typically have fewer than 50 adults spawning each year (Spruell et al. 1999; Rieman and Allendorf 2001). As an example, Craig and Wismar (1993) reported a63%o mortality of the spawning population (n:30) due to de-watering in Furthermore, two adult male bull trout at Kachess River died in 2000 as they were attempting to emigrate through a braided channel in the reservoir bed after spawning and became stranded. Rains temporarily re-watered the stream during spawning, but then rain events were spotty later in the fall, and the stream de-watered and re-watered several times in some reaches. On a broader scale, understanding how these two populations cope with dewatering can provide insight into the patterns of migration and spawning in other headwater sheams in the Yakima Basin and elsewhere.

66 66 Bull trout typically have high spawning site fidelity, a trait that increases the reproductive isolation of a population and also increases the likelihood that site-specific selective factors would affect reproductive timing (Spruell et al, 1999 Kanda and Allendorf 2001; James pers. comm.). As an example, bull trout that spawn in streams which frequently exhibit de-watering events are likely to be more constrained the timing of their migration and spawning and thus more vulnerable to stranding and mortality than are fish in systems which flow continuously throughouthe year. I hypothesized that adult bull trout in these seasonally de-watered systems would follow the general pattern of migrating into the streams during the summer, but their timing of entry into spawning tributaries and then later emigration to the reservoir would be constrained by the de-watering event. Previous research into the proximate cues for migration and spawning in bull trout suggest photoperiod, river discharge, water temperature and possible hormonal influences all may play arole. However, often these cues seem to contradict one another unless correlated closely to the environment of a specific area. For instance, in some stream systems, increases stream discharge and concurrent decreases in water temperature appear to coincide with migration, whereas in other systems increases stream temperature with relatively stable flows appear to cue migration in concert with declining photoperiod (Thiesfield et al. 1996; SwanberglggT; Brenkman et al. 2001). It is quite likely that some hierarchical process including several of these factors operates (Northcote 1984; l9g7). Whatever the pattern, these proximate mechanisms are simply a means to the end of increasing fitness and it is these ultimate evolutionary forces

67 67 that drive the systems. This raises the question of whether differences in the timing of migration and spawning between streams are simply proximate behavioral responses to frequently shifting local conditions, or are due to evolutionary change. The timing of migration and spawning in salmonids is an adaptation to environmental conditions in order to maximize reproductive success, and maintains reproductive isolation between species or stocks. The consequence of migrating or breeding at unfavorable times is reduced relative fitness, and salmonid migration and breeding appear to be under greater genetic control than in most fishes (Legget and Whitney 1972; Hendry et al. 2000; Quinn et al. 2000). Quinn et al. conducted transplantation experiments on chinook salmon introduced to two New Zealand rivers and found there were genetically base differences in the timing of migration. Furthermore, Hendry et al. found evidence for the evolution of reproductive isolation in fewer than 13 generations in a sockeye salmon population introduced to Lake Washington less than 50 years ago. These examples demonstrate the relatively rapid local adaptation of two salmonid species to environmental conditions, however other evolutionary mechanismshould be considered. Genetic drift is more likely in small population such as those studied here" In small populations, any particular genotype represents a much higher percentage of the total genetic diversity than it would in a large population. Therefore, bottleneck events or founder effects can result in particular traits becoming fixed in small populations more quickly than in large populations. For instance, if some Box Canyon Creek bull trout strayed into Kachess River, their strategy of early migrational timing could become

68 established more easily at Kachess River simply due to founder effect. However, if this strategy was being strongly selected against due to de-watering, it would not likely establish itself. This scenario, however, seems unlikely given the extremely low straying rates reported between close populations. Variation in the timing of spawning migrations between and within streams occurs throughouthe Yakima Basin, although peak migration and spawning dates within a stream are often similar between years. However there are exceptions that might indicate some level of flexibility within populations. For example, adult fish at Indian Creek in the Yakima Basin, were blocked from migrating at their usual time when the lower stream became physically disconnected from Rimrock Reservoir in A few early migrating adults made it up the stream prior to the disconnect, but the bulk of the spawning population that year was observed waiting in the reservoir at the mouth of the creek. Once Bureau of Reclamation crews cleared the channel obstructions, fish moved up quickly and redd count numbers jumped dramatically, but were still less than half the previous season. Perhaps the physiological processes leading up to spawning progress at a determined rate, and if spawning is delayed, those processes continue whether or not the fish can reach the spawning grounds. Furthermore, since bull trout are iteroparous spawners, an adaptive strategy during poor conditions, they may be able to re-absorb their gametes and reproduce during following years, thus maximizing lifetime reproductive fitness. This example does seem to indicate that individual fish do have some plasticity in an unpredictablenvironment, but there are undoubtably limits, beyond which reproductive fitness of the individual is lowered. 68

69 Interestingly, no adult bull trout were found holding in the Kachess River system before or after the de-watering event began in mid-summer, despite several sizeable holding pools on the upper end of the system. Furthermore, an assortment of historic surveys at Kachess River from 1980 to present during the summer and fall, also indicate the absence of adults in the system during past summers, thus suggesting a consistent pattern for over twenty years (Table 2). This late migrational pattem contrasts with all other systems in the Yakima Basin, and with Box Canyon Creek, which flows into the same reservoir only approximately four kilometers away. The timing of migration at Kachess River is approximately two months later than average for the basin, and the timing of spawning is a full month later than average dates. Given these observations, the limitations of physiological systems, and the evidence of heritable control of spawning migration timing in salmonids, the pattem observed at Kachess River is likely a result of adaptation to local conditions, rather than simply a phenotypic plasticity of behavior. Kachess River has had a frequent recurring disturbance regime from de-watering for at least years and perhaps as long as a century, as well as natural and management impacts including fires, predation, mining, and logging. Additionally, there is limited summer holding habitat available in the upper stream and de-watering in drought years extends much higher in the system than Gold Creek. Therefore it seems plausible that a combination of repeated catastrophic events over the relatively recent past has eliminated the early migrational strategy at this site. Gold Creek provides yet more insight into the variability of migrational patterns. The majority of adults in Gold Creek follow the typical pattem of migrating in July 69

70 before the de-watering event occurs. However, six adults in 2000 were observed within the lower reaches of the study site that remained watered, holding in deeper pools just below the dry channel. In 2001, approximately ten fish were observed holding in these lower reaches after de-watering began. Several of these fish appeared to be paired up and as the early fall rains began re-watering the channel in September, some of these fish quickly moved upstream as far as the flow would allow. The fact that there have only been 1-2 redds in this lower reach despite 6-10 adults, suggests that perhaps these fish were blocked from migrating by the de-watering event and then spawned in the only channels available. However, it is unclear how spawning lower in these systems effects reproductive success. Fry Stranding Surveys The fry stage in many species of fish is often a time of minimal mobility where young of year are very wlnerable to predation and extreme environmental variability. Salmonid fry employ several strategies to avoid becoming prey, including cryptic coloration, schooling behavior and movement into areas where predation is minimized. In streams, the shallow margins offer both refuge from piscivorous juveniles and provide lower velocity areas to forage, in addition to avoiding accidental dispersal to areas of reduced habitat quality. Interestingly, as Kachess River receded and isolated pools formed along the streambed, only yqung-of-year bull hout, cutthroatrout and sculpins were trapped in the swnmer of This suggests that in this year, juveniles were able to move from these de-watered reaches. Temperature and dissolved oxygen levels in stranding pools 70

71 typically remained close to or below flowing portions of the stream, therefore this seemed an unlikely source of mortality. Hyporheic flow often delivered cool water to the isolated pools, which seemed to support aquatic macro-invertebrates as well (Stanford and Ward 1988). In the early season watered period of 2000, the lowest reaches of fry dispersal were approximately halfivay between the streams confluence with Mineral Creek and the reservoir - a point where a cold spring enters Kachess River from the east. Later in the season, the area below this point de-watered almost completely, except for a single deep rootwad pool, and all stranding pools were above this area. In 2001, a severe drought year, all but one stranding pool from the previou season de-watered by September, and the de-watered reach was rapidly extending into the 600m site which had rernained watered in A deep rootwad pool at the lower end of the upper 600m created a stranding pool with both fry and juvenile bull trout and cutthroatrout. The reach directly upstream of this point was de-watering so quickly that day that fish were literally being left dry on the rocks in this reach. Gold Creek de-watered both within and well above the survey area, however the uppereaches de-watered much quicker and were not located immediately after dewatering. The apparent suddenness of the de-watering event at this site trapped many more juveniles and species than at Kachess River. For instance, a total of seven species and222 fry and juveniles were recorded trapped at Gold Creek. Of this amount, at least 99 fry and juveniles were estimated to have perished, including a 250mm whitefish that was found trapped with several rainbow trout fry one day, and the next day they were found dry on the rocks. 7T

72 The mortality of fry due to de-watering at both sites was lower than the estimate of hundreds per site which some agency biologists had predicted. Unfortunately, no good mortality estimates were available for the 2001 season, during the drought year. To provide perspective in terms of female fecundity, egg production has been estimated to range from approximately eggs per female, depending upon adult size (Fraley and Shepard 1989). Assuming a conservative average of 2000 eggs per female, muttiplied times 15 and 19 redds at Kachess River and Gold Creek, gives approximately 75,000 and 95,000 eggs produced respectively at each site. Assuming a90o/o mortality of eggs reaching the fry stage, provides an estimate of between 15,000 and 19,000 fry produced at each site. However, the mortality at each site is likely a sizeable underestimate, and in these chronically low populations, the cumulative losses of fry from de-watering, in concert with predation and normal attrition, could conceivably create a bottleneck in recruitment into the juvenile and adult age classes. The Persistence of Bull Trout in Kachess River and Gold Creek The frequency and magnitude of disturbancevents at Kachess River and Gold Creek appear to have increasedramatically over the past century. Although some disturbance can be beneficial in maintaining a heterogenous habitat and species richness, too much disturbance can subdivide habitats, increase the likelihood of extinction, and decrease diversity (Connell 1978; Quinn and Hastings 1987; Resh et al. 1988). The cumulative effects associated with the creation of the reservoirs, mining in headwater areas, logging around and through the streams, and road building in each basin, have acted in concert with the natural disturbance regime, to shift portions of these stream 72

73 systems into an alternate stable state. De-watering now seems to be a relatively stable feature of the system. Pearsons et al. (1992), correlated increased habitat complexity with resistence to flooding and the ability of fish communities to remain intact. Elliott (1986) found that the removal of logging debris in Alaska streams was strongly correlated to increased stream velocity, while both macro-invertebrate densities and juvenile Dolly Varden densities and size decreased. Furthermore, Baxter et al. (1999) reported that bull trout redd numbers were negatively correlated to the density of logging roads in spawning tributary basins. The persistence of bull trout at sites with these kinds of disturbance pattems is impressive and attests to the resiliency of the species. However, in reviewing redd survey data from I, it becomes apparent that these populations are likely near their carrying capacity, under the current environmental conditions. Likewise, with fewer than 100 adults estimated in each population, it is likely only a matter of time until these populations are extirpated, especially if no attempts are made to restore their stream habitat or re-establish passage between populations. Observed adult mortality during spawning at Kachess River was approximately I\Yo in2000, due only to de-watering and predation, however this number is almost certainly higher. This is especially likely, given the discovery that the Kachess River population exhibits an adfluvial life history strategy, and spends 80% of the year in the reservoir environment. The slow degradation and transition of a stream environment is not always readily observed and documented by humans, thus underscoring the usefulness of long term 73

74 ecological studies. Habitat restoration in streams affected by natural or management disturbances would increase the likelihood of bull trout persistence over the long term. Lastly, by understanding the influences of environmental change and de-watering on bull trout populations at Kachess River and Gold Creek, further insight may be had into the dynamics of bull trout populations in the Yakima Basin and throughoutheir range. 74

75 LITERATURE CITED Anderson, E fpersonal Communication]. Area Fish Biologist. Washington Department of Fish and Wildlife. Yakima, Washington. Anderson, E., and J. Cummins Yakima Basin bull trout at risk; recovery plan in progress. Yakima Basin Resource News p, Baxter, C.V., C.A. Frissel, and R.F, Hauer Geomorphology, logging roads, and the distribution of bull trout spawning in a forested river basin: implications for management and conservation. Transactions of the American Fisheries Society 128: Bernatchez, L., H. Glemet, C.C. Wilson, and R.G. Danzmann Introgression and fixation of Arctic char (Salvelinus alpinu,s) mitochondrial genome in an allopatric population of brook trout (Salvelinus fontinalis). Canadian Journal of Fisheries and Aquatic Sciences 52(l): Bjomn, T.C Harvest, age structure, and growth of game fish populations from Priesto Upper Priest Lakes. TransacJions of the American Fisheries Society 90: Bonar, S.A, M. Divens, and B. Bolding Methods for sampling the distribution and abundance of bull trout/dolly Varden. Washington State Department of Fish and Wildlife. Research Technical Report. Bonneau, J.L., and D.L. Scarnecchia Seasonal and diel changes in habitat by juvenile bull trout and cutthroatrout in a mountain stream. Canadian Journal of Zoology 76: Brenkman, S.J., G.L, Larson, and R.E. Gresswell Spawning migration of lacustrine-adfluvial bull trout in a natural area. Transactions of the American Fisheries Society 130: Brown, L.G Draft management guide for the bull trout Salvelinus confluentus (Suckley) on the Wenatchee National Forest. Washington Department of Wildlife, Wenatchee, Washington. Brown, L,G fpersonal communication]. Retired Area fish niotogist, Washington Department of Fish and Wildlife. 75

76 76 Bumham, K.P., D.R. Anderson, and J.L. Laake Estimation of density from line transect sampling of biological populations. Wildlife Monographs 17: L-202. Carl, L,M., M. Kraft, and L. Rhude Growth and taxonomy of bull char, Salvelinus confluentus, in Pinto Lake, Alberta. Environmental Biology of Fishes 26: Cavender, T,M Taxonomy and distribution of the bull trout, Salvelinus confluentus (Suckley), from the American Northwest. California Fish and Game 64: Chapman, D.W Food and space as regulators of salmonid populations in streams. The American Naturalist 100 (913): Connell, J.H Diversity in tropical rainforests and coral reefs. Science I99:t Craig, S.D., and R.C. Wissmar Habitat conditions influencing a remnant bull trout spawning population, Gold Creek, Washington. Draft Report. Fisheries Research Institute, University of Washington, Seattle. 43p. Cunjak, R.A., and G. Power. 1986, Winter habitat utilization by stream resident brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta). Canadian Journal of Fisheries and Aquatic Sciences 43: L Didricksen, K.D. 2001, Gold Creek hydrology study. U.S. Bureau of Reclamation. Report UCA-I106, Upper Columbia Area Office. Dion, N.P., G.C. Bortleson, J.B. McConnell, and L.M. Nelson Reconnaissance data on lakes in Washington. Volume 5. Chelan, Ferry, Kittitas, Klickitat, Okanogan and Yakima Counties. Dolloff, A., J. Kershner, and R.F. Thurow Underwater observation. Pages in B.R. Murphy, and D.W. Willis, editors. Fisheries Techniques. American Fisheries Society, Bethesda, Maryland. Dunham, J.B., and B.E. Rieman Metapopulation structure of bull trout: influences of physical, biotic, and geometrical landscape characteristics. Ecological Application s 9 (2): Elliott, S.T Reduction of a Dolly Varden population and macrobenthos after removal of logging debris. Transactions of the American Fisheries Society ll5:

77 77 Federal Register Endangered and threatened wildlife and plants; determination of threatened status for bull trout in the conterminous United States; Final Rule 64. No Fraley, J.J., D. Read, and P. Graham Flathead River fishery study: April Montana Department of Fish, Wildlife and Parks, Kalispell, Montana. Fraley, J.J., and B.B Shepard. 1989, Life history, ecology and population status of migratory bull trout (Salvelinus confluentus) in the Flathead Lake and River system, Montana. Northwest Science 63(4): Goetz, R Distribution and juvenile ecology of bull trout (^9alvelinus confluentus) in the Cascade Mountains. Master's thesis, Oregon State University, Corvallis, Oregon. Goodwin, L.C., and R.E. Westley Limnological survey of Kachess, Keechelus, and Cle Elum Reservoirs. State of Washington, Department of Fisheries, Research Division, Contract No Offipia, Washington. 73p. Griffith, J.S Estimation of the age-frequency distributiln of stream-dwelling trout by underwater observation. The Progressive Fish Cultriralist 43 (1): Griffith, J.S., and R.W. Smith. 1993, Use of winter concealmpnt cover by juvenile cutthroat and brown trout in the south fork of the Snakb River, Idaho. North American Journal of Fisheries Management 13: Haas, G.R., and J,D. McPhail Syurluri.s and distribrltion of Dolly Varden (Salvelinus malma) and bull trout (Salvelinus confluenlus) in North America. Canadian Journal of Fisheries and Aquatic Sciences 48,:2I91-22IL. Hankin, D.G., and G.H. Reeves Estimating total fish albundance and total habitat area in small streams based on visual estimation methoids. Canadian Joumal of Fisheries and Aquatic Sciences 43: Hauer, R.F,, G.C. Poole, J.T. Gangemi, and C,V. Baxter. 199p. Large woody debris in bull trout (Salvelinus confluentus) spawning streams of logged and wilderness watersheds in northwest Montana. Canadian Journal of Fisheries and Aquatic Sciences 56: Helfman, G.S Fish behavior by day, night, and twiligtit. Pages in T.J. Picher, editor. Behavior of teleost fishes. Chapman a4d Hill, New York.

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79 79 Leary, R.G., R.W. Allendorf, and S.H. Forbes Conservation genetics of bull trout in the Columbia and Klamath River drainages. Conservation Biology 7(4):856-86s. Legget, W.C., and R.R. Whitney Water temperature and the migrations of American shad. Fisheries Bulle tin 70 : Lukose, R.L Ontogenetichanges in the foraging ecology of theiwanderingarter snake (Thamnophis elegans vagrans). Master's thesis, Central Washington University, Ellensburg, Washington. Lyons, J.K. and R.L. Beschta Land use, floods, and channel changes: Upper Middle fork Willamette River, Oregon ( ). Water Resources Research 19 (2): McMullin, S.L., and P.J. Graham The impact of Hungry Horse Dam on the kokanee fishery of the Flathead River. Montana Department of Fish, Wildlife and Parks, Kalispell, Montana. McPhail, J.D., and C.B. Munay. 1979, The early life-history and ecology of Dolly Varden (Salvelinus malma) in the upper Arrow Lakes. Department of Zoology and Institute of Animal Resources, University of British Columbia, Vancouver, British Columbia. 113p. Mongillo, P.E. 1993, The distribution and status of bull trout/dolly Varden in Washington state. Washington Department of Wildlife Fisheries Management Division, Report Number Olympia, Washington. 45p, Nakano, S., S. Kitano, K. Nakai, and K.D. Fausch Competitive interactions for foraging microhabitat among introduced brook charr, Salvelinus fontinalis, and native bull charr, S. confluentus, and westslope cutthroatrout, Onchorynchus clarki lewisi, in a Montana stream. Environmental Biology of Fishes 52: Northcote, T.G Mechanisms of fish migration in rivers. Pages 3I7-355 in J.C. McCleave, G.P. Arnold, J.J. Dodson, and W.H. Neill, editors. Mechanisms of migration in fishes. Plenum, New York.

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81 81 Power, M.E., J.R. Stout, C.E. Cushing, P.P. Harper, R.F. Hauer, W.J.Mathews, P.B. Moyle, B. Statzner, and LR. Wais De Badgen Biotic and abiotic controls in river and stream communities. Journal of the North American Bentholosical Society 7(4): Pratt, K.L A review of bull trout life history. Pages 5-9 in P.J. Howell and D.V. Buchanan, editors. Proceedings of the Gearhart Mountain bull trout workshop. American Fisheries Society, Oregon Chapter, Corvallis, OR. Quinn, T.P., and D.J. Adams Environmental changes affecting the migratory timing of American shad and sockeye salmon" Ecology 77(4):LI5T-L162. Quinn, J.F. and A. Hastings Extinction in subdivided habitats. Conservation Biology l: Quinn, T.P., M.J. Unwin, and T. Kinnison Evolution of temporal isolation in the wild: genetic divergence in timing of migration and breeding by inhoduced chinook salmon populations. Evolution 54(4): Ratliff, D.E., and P.J. Howell 1992" The status of bull trout populations in Oregon. Pages in P.J. Howell and D.V, Buchanan, editors. Proceedings of the Gearhart Mountain Bull Trout Workshop. Oregon Chapter of the American Fisheries Societv. Corvallis. Resh, V.H., A.V. Brown, A.P. Covich, M.E. Gurtz, H.W. Li, W.G. Minshall, S.R. Reice, A.L. Sheldon, B.L. Wallace, and R. C. Wissmar The role of disturbance in stream ecology. Journal of the North American Benthological Society 7(4): Rieman, B.E., and F.W. Allendorf Effective population size and genetic conservation criteria for bull trout. Transactions of the American Fisheries Society 2l: Rieman,8.E., D.C, Lee, and R.F. Thurow Distribution, status, and likely future trends of bull trout within the Columbia River and Klamath River Basins. North American Journal of Fisheries Manasement 17:

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83 83 Swanberg, T.R Movements of and habitat use by fluvial bull trout in the Blackfoot River, Montana. Transactions of the American Fisheries Society 126: Thiesfeld, S.L., A.M. Stuart, D.E. Ratlifl and B.D. Lampman Migration patterns of adult bull trout in the Metolius River and Lake Billy Chinook, Oregon. Oregon Department of Fish and Wildlife, Information Reports 96-1, Portland. Thomas, J.A Hydrologic and water temperature investigation of tributaries to Keechelus Reservoir. U.S. Fish and Wildlife Service Mid-Columbia River Fishery Resource Office, Yakima Sub-Office Report. Thurow, R.F Underwater methods for study of salmonids in the intermountain west. General Technical Report INT-GTR-307, Ogden, UT; U.S. Department of Agriculture, Forest Service, Intermountain Research Station. Thurow, R.F Habitat utilization and diel behavior ofjuvenile bull trout (Salvelinus confluentus) at the outset of winter. Ecology of Freshwater Fish Vol. 6,l-7. Thurow, R.F., D.C. Lee, and B.E. Rieman Distribution and status of seve native salmonids in the interior Columbia River Basin and portions of the Klamath River and Great Basins. North American Journal of Fisheries Management 17:1094' Thurow, R.F., and D.J. Schill Comparison of day snorkeling, night snorkeling, and electrofishing to estimate bull trout abundance and size structure in a secondorder Idaho stream. North American Journal of Fisheries Management 16: Tuck, R.L Impacts of irrigation development on anadromous fish in the Yakima River Basin, Washington. Master's thesis, Central Washington University, Ellensburg, Washington. U.S. Bureau of Reclamation (USBR) Keechelus Dam safety of dams modification, Yakima Project. Final Environmental Impact Statement. Yakima, Washington.

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