7:00 – 5:30
7:00 – 8:00
WELCOME SOCIAL – Coffee and light breakfast items available
8:00 – 8:10
Traditional Blessing – Davis Washines/Yakama Nation Fisheries
8:10 – 8:20
Chuck Brushwood/UCSRB Chair & Melody Kreimes/UCSRB Executive Director
Greer Maier/Conference Chair
8:20 – 9:00
The fate of wild salmon across the North Pacific: reports from the Russian Far East to the Pacific Northwest.
Guido Rahr/President & CEO Wild Salmon Center
Under Mr. Rahr’s leadership as President and CEO, the Wild Salmon Center has developed scientific research, habitat protection and fisheries improvement projects in dozens of rivers in Japan, the Russian Far East, Alaska, British Columbia and the US Pacific Northwest, raising over $100 million in grants, establishing eight new conservation organizations, and protecting three million acres of habitat including public lands management designations and eight new large scale habitat reserves on key salmon rivers across the Pacific Rim.
Mr. Rahr earned a BA in English Literature from the University of Oregon and a Masters of Environmental Studies from Yale University. Before coming to the Wild Salmon Center, he developed conservation programs for Oregon Trout, the United Nations Development Programme, the Rainforest Alliance and Conservation International. Mr. Rahr is a member of the World Conservation Union (IUCN) Salmon Specialist Group, and is a passionate fly fisherman and fly tyer. He lives in Portland, Oregon with his wife, Lee, and their three sons.
Abstract: While salmon are a keystone species in river systems that feed the North Pacific, runs are declining on both sides of the Pacific Rim, triggering multibillion dollar restoration efforts. How can we ensure this charismatic and ecologically critical species continues to thrive in the face of human development and climate change? Guido Rahr will describe the status of salmonid fish across the northern Paciifc Rim and major threats to their survival. He will describe place-based efforts to protect salmon strongholds in the Russian Far East, Bristol Bay Alaska, British Columbia and the Washington and Oregon coast.
STATUS OF THE SPECIES
9:00 – 9:30
Plenary Talk: Status of ESA listed Upper Columbia River spring Chinook salmon and steelhead and relationship to southern resident killer whales
Mike Ford/NOAA Northwest Fisheries Science Center
Abstract: In this talk I will provide an overview of the current status of the ESA-listed spring Chinook salmon and steelhead Evolutionarily Significant Units (ESUs) in the Upper Columbia River region and how this status assessment will be updated in the upcoming 5-year ESA status review. These populations have been listed under the ESA for more than 20 years. Over this time there have been some improvements in abundance and some metrics of diversity, but productivity remains low and the ESUs remain far below their recovery goals. Habitat and hydro improvements along with changes to hatchery programs have likely lowered the risk of extinction and hopefully made the populations more robust. Factors outside of the Upper Columbia area, particularly varying ocean conditions and predation, play a dominant role in determining the abundance of these ESUs. The effects of current conservation efforts therefore may become most important and apparent if there is another period of prolonged poor ocean survival. In addition to discussing the ESA status of Upper Columbia salmon, I will also review our current understanding of the importance of these populations and other salmon populations coastwide as prey for endangered southern resident killer whales.
9:30 – 9:45
Termination of a spring Chinook hatchery in the Entiat River and the response of natural-origin spring Chinook a decade later
Greg Fraser/U.S. Fish and Wildlife Service
Co-Authors: Matt Cooper/U.S. Fish & Wildlife Service
Abstract: In 2007, Entiat National Fish Hatchery (NFH) released the last spring Chinook Salmon yearlings of a program that began in 1974. The hatchery switched to summer Chinook Salmon to minimize risk to natural-origin spring Chinook Salmon that are listed as endangered. Since the termination of the program, the abundance of Entiat NFH-origin spring Chinook Salmon found on the spawning grounds decreased to zero, as predicted. However, out-of-basin hatchery-origin Chinook Salmon have persisted, and in recent years hatchery-origin fish have made up nearly half of the spawning population. The delisting criteria for this population is a 12-year mean of 500 individuals. In 2018, less than 100 spring Chinook Salmon returned to the Entiat River to spawn, and half were out-of-basin hatchery-origin fish. Poor returns and a high proportion of hatchery-origin fish raise critical questions about the resilience of the natural-origin population of spring Chinook Salmon and management of both Chinook runs in the Entiat River.
9:45 – 10:15
Estimating the Spawning Escapement of Hatchery- and Natural-Origin Spring Chinook Salmon Using Bias Corrected Carcass Recovery Data
Michael Hughes/Washington Department of Fish and Wildlife
Co-Author: Andrew Murdoch/Washington Department of Fish and Wildlife, Kevin See/Biomark
Abstract: Carcass recoveries are commonly used to generate estimates of the age, sex, and origin compositions of spawning populations. Previous studies have shown that carcass recoveries may not be representative of the spawning population at large; whereby, females have a higher recovery probability than males, and of the males, larger fish have a higher recovery than smaller ones (e.g., jacks and/or mini-jacks spawners). Furthermore, hatchery-origin fish have been shown to return at an earlier age and smaller body size than natural-origin counterparts and, as a result, may negatively bias the proportion of hatchery carcasses recovered on the spawning grounds. We applied the bias corrections generated from our carcass recovery probability model to several years of existing recovery data to develop accurate estimates of spawner demographics and abundances. These results show that correcting for recovery biases in abundance estimates can translate into increased hatchery fish survival while reducing natural-origin survival.
10:15 – 10:30
10:30 – 11:00
BREAK and POSTER SESSION
“STRONGHOLDS” BOOK SIGNING BY GUIDO RAHR
11:00 – 11:15
Status of Bull Trout
John Crandall/Methow Salmon Recovery Foundation
Abstract: In the realm of ESA-listed fish population recovery in the Upper Columbia, bull trout have received noticeably less attention compared to their anadromous counterparts. While it is assumed that much of the anadromous-focused habitat restoration and protection efforts also benefit bull trout, it is necessary to recognize the specific aspects of bull trout life history that differentiate them from other salmonids. Integrating bull trout-centric knowledge into habitat restoration and protection planning is a necessary component of a thoughtful, comprehensive approach to fish recovery in the Upper Columbia region.
Understanding the status and trends of the various local populations inhabiting the Upper Columbia region is an important component of informed species recovery. Yet, only recently have efforts arisen that will more fully support a comprehensive population assessment. This effort will provide information critical to the evaluation of species viability and recovery determination.
11:15 – 11:30
Pacific Lamprey – Translocation Monitoring in the Upper Columbia
Tyler Beals/Yakama Nation Fisheries
Co-Authors: Ralph Lampman & Dave’y Lumley/Yakama Nation Fisheries
Abstract: Pacific Lamprey Entosphenus tridentatus commonly called “eels” by tribal members and others, is an incredibly important species for the Columbia River tribes in terms of food, medicine, and culture. They also serve many roles in the stream ecology, benefiting many, many native species.
Pacific Lamprey numbers have declined throughout the Columbia River Basin, and determining the current distribution and relative abundance is a priority for lamprey conservation. Beginning in 2015 Pacific Lamprey distribution changed as a result of adult translocations conducted by the Yakima Nation (Wenatchee and Methow subbasins) and Colville Confederated Tribes (Okanogan Subbasin). In addition, Grant and Douglas County PUDs have begun translocation starting in 2018 in partnership with others. Yakama Nation Fisheries used several tools to assess Pacific Lamprey presence and relative abundance throughout the Mid-Columbia Region, including targeted electrofishing and eDNA sampling. Initial targeted and occupancy electrofishing surveys in 2012-2015 detected no Lamprey in the Wenatchee River upstream of Tumwater Dam, despite records of historic occupancy. Following multiple translocation releases upstream of Tumwater Dam, PIT tag, eDNA, and electrofishing detections indicate that Pacific Lamprey now occupy many river miles in the Wenatchee River and some of its tributaries (including Nason and Icicle creeks). Pacific Lamprey are now also detected in other new locations, including Upper Methow River (upstream of Chewuch River) and Omak Creek (Okanogan Subbasin) where they have been absent for decades or more. In the Okanogan River, juvenile Pacific Lamprey were last documented in 2010. Numbers of Pacific Lamprey at mainstem Columbia River dams in 2017 were the highest since 2002. This large group of spawners, in combination with contributions from translocated adults, may re-define Pacific Lamprey distribution throughout the Mid-Columbia. Finally, information about how to identify lampreys at various life stages and plans for new monitoring in the region will be shared.
11:30 – 11:45
OCEAN & ESTUARY CONDITIONS
11:45 – 12:00
Mixed Signals: A Report Card from Ocean Surveys in 2019
Brian Burke/NOAA Northwest Fisheries Science Center
Abstract: For the past 22 years, staff from the NWFSC have been studying the ecology of young salmon when they first enter the ocean to better understand marine growth, migration, and survival. Three projects, covering different spatial and temporal extents, contribute to this effort: the Newport Hydrographic Line (NH Line), the coast-wide Pre-recruit survey, and the Juvenile Salmon and Ocean Ecosystem Survey (JSOES). Results from this year’s efforts suggest that ocean conditions for salmon that migrated to sea in 2019 were mixed, with some metrics showing average conditions and others still in an anomalously poor state. Catch per unit effort of juvenile coho and Chinook salmon was in the middle range of observed values in the last 22 years. Off of Newport, OR, the biomass of the northern species of copepods has been low for several years, but has increased over the past several months to levels not seen since mid-2014. In contrast, our data on winter larval fish biomass, which includes just the nearshore species that tend to dominate during years of high salmon survival, was the 3rd lowest in the 22 year time series. During ‘the blob’, fish species such as Pacific pompano and jack mackerel (a potentially important salmon predator) were caught regularly in our trawls; in 2019, these species continued a downward trend towards the low levels observed prior to the blob. Nevertheless, the continued presence of pompano and jack mackerel in our surveys suggests that some ecosystem level effects of the blob still linger. Indeed, California market squid only decreased slightly after the blob, and have significantly increased in the last two years, exemplifying the fact that particular biological responses to warm conditions is difficult to anticipate.
12:00 – 12:15
The Columbia River Estuary: Fish Use, Habitat Status and Restoration Efforts
Catherine Corbett/Lower Columbia Estuary Partnership
Abstract: Research over the past decade or so has documented the importance of the lower Columbia River to juvenile outmigrating salmon and steelhead. In general, we consistently find subyearling smolts using offchannel emergent marsh habitats for days to weeks (even months) while yearling smolts (and late season subyearlings) use the mainstem for much shorter periods, e.g., 6-7 days. Interior stocks of Chinook, steelhead, and sockeye are consistently well represented in our results, and stomach fullness indicate that both subyearling and yearling smolts benefit from prey produced by lower river marsh habitats. However, the lower Columbia River ecosystem has lost 114,050 acres, approximately 50%, of its native historic habitat since the late 1800’s from anthropogenic changes. Over 28,387 acres have been restored or protected by regional partners in the past 20 years, a significant effort to reverse the trajectory of degradation. To ensure our conservation reserve network is protective of common species and provides a basis of recovery for those that are imperiled, we established habitat coverage targets, using generalized conservation biology approaches. The targets include: 1) no net loss of native habitats as of the 2009 baseline and 2) recovery of 40% (i.e., 22,480 acres) of historic extent for priority habitats by 2050. Meeting these targets would increase the overall extent of native habitat to 60% of historic coverage with a range of 45% -88% by river reach. We are presently intentionally integrating climate smart conservation approaches into our restoration program including planning for increased flooding from sea level rise and more intense storms, warming temperatures, and increased summer dry periods. This presentation will briefly touch on conservation biology approaches for integrating shifting climate conditions into conservation reserve networks and how we are integrating climate adaptation measures into individual restoration project designs in the lower Columbia River.
12:15 – 12:30
12:30 – 1:30
LUNCH (on your own)
1:30 – 1:45
Drivers of steelhead migration behavior and survival in the lower Columbia River
Jared Siegel/NOAA Northwest Fisheries Science Center
Co-Authors: Lisa Crozier/NOAA Northwest Fisheries Science Center
Abstract: Many adult summer steelhead encounter high river temperatures in the lower Columbia River during their spawning migration. While some steelhead pass through the lower Columbia River in a matter of days, others use tributary habitats as temperature refuges for periods that can last months. We fit quantitative models to travel time between Bonneville and McNary Dam for each major population group (MPG) in the interior Columbia using PIT tag data from adult return years 2004-2016. The probability of spending weeks to months in the lower Columbia River depended primarily on river temperature and population; for example upper Columbia steelhead were the least likely to delay migration at a given temperature while middle Columbia steelhead were the slowest migrating group. However, migration delay was also associated with dam spill and other fish traits. While upper Columbia steelhead were the least likely to delay migration, their survival to McNary Dam was the most sensitive to high temperatures out of all MPGs. Although high temperatures reduced survival in all populations, survival remained relatively high (73-90%) and consistent from 2004 to 2017, despite record breaking temperatures during this period.
1:45 – 2:00
Abundance and Migration Success of Overshoot Steelhead in the Upper Columbia River Basin
Ben Truscott/Washington Department of Fish & Wildlife
Co-Authors: Andrew Murdoch/Washington Department of Fish & Wildlife
Abstract: The Washington Department of Fish and Wildlife utilizes an instream PIT tag detection site based patch-occupancy model to estimate the abundance of natural and hatchery origin steelhead returning to each population within the Upper Columbia River DPS. Recent improvements to analyses have provided estimates of overshoot adult steelhead from Snake and Mid Columbia River Steelhead DPS populations. Estimates of total steelhead overshoots above Priest Rapids Dam, as well as those that successfully returned to their natal population downstream, are now generated on an annual basis. Additionally, overshoot distribution within the Upper Columbia River DPS, and the relationship between distribution and successful downstream migration will be discussed. Given the prevalence and magnitude of overshoot behavior within steelhead populations, it is critical for overshoot estimates to be incorporated into status and trend monitoring programs, as well as identifying and implementing measures to facilitate downstream movement of adult steelhead in order to minimize impacts to downstream populations.
2:00 – 2:15
Juvenile Salmon and Steelhead Passage and Survival through the Snake and Columbia River Hydrosystem during Spring Gas Cap Spill, 2018
Ryan Harnish/Pacific Northwest National Laboratory (PNNL)
Co-Authors: Kenneth Ham, Tao Fun, Xinya Li /PNNL, John Skalski, Rich Townsend, Jim Lady/Columbia Basin Research University of Washington
Abstract: A court ruling ordered federal dams on the Snake and Columbia rivers to spill at the maximum level that achieved 115% total dissolved gas (TDG) in the forebays and 120% TDG in the tailraces (i.e., gas cap spill) in 2018. This study was conducted to evaluate the effects of gas cap spill on the passage and inriver survival of yearling Chinook salmon (CH1) and juvenile steelhead (STH) migrating through the Snake and Columbia River hydrosystem.
Run-of-river CH1 and STH were collected from the juvenile fish facility at Lower Granite Dam (LGR) and McNary Dam (MCN), implanted with acoustic and PIT tags, and released at multiple locations in the Snake and Columbia rivers. Dead acoustic-tagged hatchery smolts were released at LGR, Little Goose Dam (LGS), MCN, and Bonneville Dam (BON) to estimate dam passage survival using the ViRDCt release-recapture model. Acoustic receiver arrays were deployed to identify route of passage at LGR and LGS and to estimate survival from LGR to MCN, MCN to BON, and LGR to BON.
Spill discharge generally met or exceeded gas cap spill targets throughout the study period. Dam passage survival probability exceeded 0.96 for CH1 and STH at all projects at which that metric was estimated. From LGR to BON, CH1 had an estimated survival probability of 0.5549 (SE = 0.0251) and a median travel time of 9.7 days. STH had an estimated survival of 0.5677 (0.0217) and median travel time of 8.5 days. Comparisons to dam passage, reach, and system-wide survival estimates from past acoustic telemetry studies indicate smolts migrated through the hydrosystem more quickly during the high flow and spill conditions of 2018 than past years. However, the available evidence does not indicate that inriver survival was appreciably higher or that powerhouse passage rates were appreciably lower in 2018.
2:15 – 2:30
A Multistate Model to Estimate Upper Columbia River Spring Chinook Life Cycle Survival from Passive Integrated Transponder Tagging and Detection
Daniel Rawding/Washington Department of Fish and Wildlife
Abstract: The Upper Columbia River spring Chinook Evolutionary Significant Unit (ESU) was listed for protection under the US Endangered Species Act in 1999 and a recovery plan was developed to rebuild the spring Chinook Salmon in the ESU. Despite over 15 years of efforts, in the last status review NOAA Fisheries concluded this ESU remained at a high extinction risk. We developed an integrated population life cycle model that uses Passive Integrated Transponder (PIT) tagged parr and smolts in the Methow, Entiat, and Wenatchee rivers to estimate survival from tagging to adult return in each of these rivers. We present the juvenile and adult reach survival estimates for Upper Columbia spring Chinook Salmon from this model.
2:30 – 2:45
Salmon Were Made To Move: Downstream Rearing in Interior Stocks of Chinook Salmon and Steelhead
Timothy Copeland/Idaho Department of Fish and Game
Abstract: The classic view of stream-type salmon was that early emigrants were viewed as poor competitors that did not contribute appreciably to the population, whereas successful individuals resided in their natal reaches until smoltification. Recent work has shown there is more diversity in successful juvenile rearing patterns than previously thought. These patterns are important considerations for effective conservation and restoration. Conceptually, there are several reasons why individuals would take advantage of suitable habitat downstream, especially for steelhead. I present selected case studies of Chinook Salmon and steelhead populations to illustrate the extent and contrast in patterns of downstream rearing in Idaho. In general, most juvenile spring/summer Chinook Salmon leave their natal reaches before winter and smolt the following spring. Significant winter mortality has been observed for these fish but they often survive to adult return better. Seasonal patterns are more ambiguous for steelhead but successful smolts have been documented spending up to three winters in downstream habitats. The importance of downstream rearing to steelhead populations seems to depend on elevation and hydrology. The foregoing patterns have implications for restoration strategies. Restoration in natal reaches provides stability, which is important to preserve the target population. Natal reach restoration can increase productivity by reducing movement costs to the population because individuals are less exposed to risk. Alternatively, it could produce more robust emigrants that perform better when they go downstream. Restoration downstream can provide greater opportunities for population growth, which is important for recovery. Downstream restoration effectively increases connectivity and allows the population to expand the resources it can access. Downstream restoration may decrease winter mortality or address known or suspected constraining reaches. These examples show that a robust conservation program should consider multiple strategies in order to protect and recover target populations.
2:45 – 3:00
3:00 – 3:30
BREAK & POSTER SESSION
3:30 – 3:45
Plenary Talk: Reintroduction of Salmon to the Upper Columbia River
John Sirois/Upper Columbia United Tribes
Co-Authors: Conor Giorgi/Spokane Tribe, Casey Baldwin/Confederated Colville Tribes, Thomas Biladeau/ Couer D’Alene Tribe
Abstract:The Upper Columbia United Tribes (UCUT) member tribes and their partners have completed the first Phase of the reintroduction of salmon into the upper Columbia River Basin; investigating potential donor stocks of salmon, risks of reintroduction, habitat conditions within the U.S. portion of the blocked area, life-cycle modeling of reintroduced stocks and potential fish passage facilities across Chief Joseph and Grand Coulee hydroelectric projects. These assessments provide a foundation upon which the reintroduction process can build, highlighting management actions that are likely to be successful for reintroducing anadromous fish into the upper Columbia River watershed. Results from these assessments suggest the UCUT, in coordination with appropriate action agencies, proceed to Phase II of the reintroduction process where hypotheses generated from model results can be tested through experimental salmon releases.
3:45 – 4:00
ISAB Review of Predation Impacts and Management Effectiveness for the Columbia River Basin
Stan Gregory/NWPCC Independent Scientific Advisory Board
Co-Authors: Dr. Steve Schroder, Fisheries Consultant and former Fisheries Research Scientist at the Washington Department of Fish and Wildlife
Abstract:The Independent Scientific Advisory Board (ISAB) recently reviewed the biological and economic impacts of native and non-native predators, effectiveness of control efforts, and potential impacts of northern pike. We recommended development of an ecosystem-wide, multi-predator, multi-prey approach for understanding predation impacts.
The current efficacy of the pikeminnow control program is unknown and needs to be updated and do more than count pikeminnow removed. Large numbers of Caspian terns and double-crested cormorants are believed to be one of the greatest sources of mortality for emigrating juvenile steelhead and yearling Chinook salmon from the upper Columbia River. Lethal removal of sea lions may provide relief at Bonneville Dam and Willamette Falls, but its efficacy must be assessed as part of a Basin-wide predation evaluation.
Northern pike are likely to substantially reduce salmonid abundance, especially in low-gradient river segments with wide floodplains. Even with the best predator management, pike likely will invade lower anadromous reaches eventually. Nevertheless, reducing the numbers of fish emigrating from Lake Roosevelt is likely to reduce the chances that pike will establish new populations downstream and hence delay the invasion. It is essential to develop an early detection monitoring program and a rapid eradication response program. Control efforts will need to be extensive and continuous to successfully reduce mortality of salmonids.
Evaluation of predator control programs must do more than simply count the number of predators removed. Compensatory mortality is the most important uncertainty to address when developing predation management plans. Predation evaluation must monitor responses from other predators to the predator removals and evaluate responses of the salmon over the remainder of its life cycle. A basin-wide, ecosystem-based approach for assessing and managing predators collectively is needed to create more effective predator-control actions.
4:00 – 4:15
Using eDNA to determine the distribution of an invasive species at broad scales in the Columbia River Basin
Erika Rubenson/Four Peaks Environmental Science & Data Solutions
Co-Authors: Julian Olden/University of Washington, Joshua Murauskas, Joseph Miller/Four Peaks Environmental Science & Data Solutions
Abstract: Nonnative species are a leading threat to native salmonid species throughout the Columbia River Basin, and climate change, illegal introductions, and habitat alteration are contributing to increases to many nonnative species distributions. Protecting critical salmonid habitat from invasion can be greatly enhanced by predictive models that highlight regions most at risk, especially when paired with tools that enable early detection. Unfortunately, management-relevant distribution data are largely lacking for most invasive species and early detection is complicated by the scale of the problem. To address this, we combined species distribution modeling with environment DNA (eDNA) to locate range boundary regions of smallmouth bass (Micropterus dolomieu), a widespread nonnative predator in the Columbia River Basin, and evaluate its overlap with native salmonids throughout the entire Columbia River Basin. We predicted that smallmouth bass is currently distributed across approximately 18,000 river kilometers and overlaps with 3-62% of rearing habitat of salmonids (species dependent). Under a moderate climate change scenario, smallmouth bass is predicted to expand its range by two-thirds, totaling approximately 30,000 river kilometers by 2080. Basin-wide models were sufficiently accurate to identify upstream invasion extents to within 15 km of the eDNA-based boundary and including eDNA data improved model performance at critical range boundary regions. Our research highlights how eDNA approaches can supplement large geospatial datasets to result in more accurate modeling predictions and can also provide rapid detection of small populations in large streams throughout the Columbia River Basin. These techniques could easily be transferred to other species of interest, including northern pike, walleye, or channel catfish, guiding future nonnative species management efforts.
4:15 – 4:45
Plenary Talk: Stream-and Lake Rearing Strategies of Spring Chinook in the Lake Wenatchee Basin
Matt Polacek/Washington Department of Fish Wildlife
David Beauchamp is interested in advancing a mechanistic understanding for how the behavior, bioenergetics, and sensory capabilities of individual organisms scale up to determine the structure and function of aquatic ecosystems and how food web interactions are mediated by natural and human induced changes in environmental conditions. To this end, he is active in the development and application of bioenergetics models for salmonids, their predators and competitors.
Carlos Polivka is a researcher with the Land and Watershed Management Program at the Pacific Northwest Research Station (USDA Forest Service). Based out of the laboratory in Wenatchee, WA, for the past 17 years, he has done research focusing on ecological interactions across the terrestrial-aquatic ecotone, fish habitat selection behavior with respect to in-stream habitat restoration, and fish behavioral responses to the interaction between habitat quality and predation risk. He holds a Ph. D (2002) in Ecology and Evolution from the University of Chicago and his overall research extends into non-aquatic systems as well.
Co-Authors: David Beauchamp/USGS Western Fisheries Research Center, and Carlos Polivka/U.S. Forest Service PNW Research Station
Abstract: Spring Chinook Oncorhynchus tshawytscha spawn in the White and Little Wenatchee Rivers and express two life history strategies prior to migrating out of the lake in the spring as smolts; 1) rear in their natal river and 2) migrate into the lake to overwinter. Both strategies offer unique survival and potential growth trade-offs. Northern Pikeminnow Ptychocheilus oregonesis and Bull Trout Salvelinis confluentus are the apex fish predators in Lake Wenatchee. High densities of juvenile Sockeye Salmon Oncorhynchus nerka and littoral fishes provide annual forage in the lake. The extent of predation on juvenile Spring Chinook Salmon is unknown. The objectives were to 1) estimate the predatory impact on Spring Chinook Salmon as they rear and migrate through the lake, 2) estimated the relative contribution and fate of different life history strategies to smolt production, and 3) examine patterns consistent with the prediction that predators modulate the vigilance behaviors of sub-yearling Chinook. Northern Pikeminnow and Bull Trout occupied similar habitats and depth strata as sub-yearling Chinook, and their numbers increased near the outlet as salmon migration peaked. Bull Trout consumed primarily Sockeye with 4% of their diet consisting of Chinook salmon, while no Chinook were detected in Northern Pikeminnow diets. Seasonal and habitat-specific scale growth comparisons suggested strong size selective mortality against Chinook that reared primarily in nearshore lake habitats during summer-fall. First year growth for juvenile Chinook was slower in the Little Wenatchee River than in the White River, and nearshore lake-rearing juveniles were significantly smaller than in the streams. Growth trajectories of outmigrating smolts in spring were significantly larger than the smolts migrating down the White River during spring, suggesting that these larger individuals overwintered in the lake. The most common growth strategy contributing outmigrating smolts from the lake system appeared to be the faster-growing White River juveniles that grew primarily in the stream then overwintered in the lake. Based on stable isotope signatures, 5% of Spring Chinook smolts reared primarily in pelagic lake habitat. They exhibited similar mean size to other Spring Chinook smolts but weighed nearly twice as much as the concurrently outmigrating Sockeye smolts that had co-occurred in pelagic habitats the previous growing season. In addition to lethal effects, non-lethal effects of predators can determine the behavior and habitat use of prey. Time and energy invested in predator detection instead of foraging affects life history traits that may be correlated with future fitness. This conceptual framework describes both how the allocation of risk-taking may affect among-individual variation in body condition and how that variation may have consequences at the population level. Preliminary data from sub-yearling Chinook in Lake Wenatchee and the tributaries were consistent with these predictions.
4:45 – 5:00
5:30 – 9:00