Multi-scale Impacts of Climate Change and Human Activities on Salmon Productivity (hosted by AFS)

ROOM: Atlantis, Grand Ballroom 1
Recent decadal-scale declines of salmon populations have consequences for fisheries-dependent communities plus cascading effects on ecosystems. 2019 is the focal year for International Year of the Salmon (IYS) and several IYS workshops have implicated climate variation and change (CVC) impacts in marine ecosystems as major sources for these declines. However, IYS workshop observations and/or projections of CVC impacts have focused on recruitment trends of adult salmon leaving unexplored knowledge gaps at many life-stages, spatial and temporal scales. For example, overarching CVC effects in freshwater (e.g. changes of river discharge, timing, temperature) affect salmon spawning success, growth, survival, and habitat interconnectivity at fine spatial scales, potentially leading to life-stage specific changes in salmon productivity, distribution and total production at broad spatial scales. Consequently, this symposium will examine and integrate knowledge of cumulative effects of climate change and habitat alterations operating on salmon productivity at multiple scales from restricted-area spawning in headwater streams to migration and rearing across vast marine expanses. Participants and a summary panel discussion will identify (1) implications of climate change superimposed on other cumulative impact processes for salmon productivity trends, future fisheries management and (2) key research gaps.

8:20AM Introductory Remarks
  Jim Irvine, Kim Hyatt
8:40AM Exploration of Climate Change Impacts on British Columbia Salmon Via Pathway of Effects Models.
  Kim Hyatt, Howard Stiff, Margot Stockwell, Marc Nelitz, Ogden Athena
An overview of historic climate variation and change patterns plus future climate trends affecting British Columbia’s aquatic ecosystems suggest freshwater trends are already apparent and that climate-induced changes to freshwater and marine ecosystems will become increasingly problematic for salmon between now and 2050. We have developed pathways of effects models (POE) to examine consequences of these changes for Sockeye and Chinook Salmon populations within freshwater and marine ecosystems at local and broader spatial scales to develop insights into future CVC impacts on adult migration and fry recruitment outcomes for these species. Next we have developed serial freshwater & marine POE models to provide additional insights into potential salmon production variations likely to result from cumulative-impacts of climate change from coupled freshwater and marine effects. Common POE models applied to geographically scattered salmon populations reveal a wide range of potential impacts on future production potential of salmon along a south to north and outer coast to interior gradient. Results from coupled POE models for a smaller number of these populations suggest the virtual elimination of some commercially important populations by mid-century absent active stock and habitat management interventions.
9:00AM Endangered Sockeye Salmon (Oncorhynchus nerka) Imperiled By Eutrophication and Climate Change through Degradation of Nursery Lake Critical Habitat
  Daniel T. Selbie, Lucas B. Pon
Cultus Lake, British Columbia is critical freshwater habitat for one of Canada’s most imperiled Pacific salmon populations, the endangered Cultus Lake Sockeye Salmon. Precipitous post-1970’s stock declines have historically been attributed to incidental harvest in the Fraser River mixed-stock fishery, poor marine survival, and pre-spawning adult mortality, yet targeted fisheries management and amelioration of these constraints have not yielded population recovery. We integrate targeted limnological, paleolimnological, lake/watershed modeling, and fisheries studies, revealing significant population mortality arising from freshwater habitat degradation that is being interactively forced by lake eutrophication and climate change. Fall epilimnetic temperatures (r2 = 0.84*) and water column stability (r2 = 0.80*) are linked to reductions in freshwater survival through climatic influences on the intensity and duration of lake stratification. Fall fry-smolt survivals are strongly related to spring deep-water oxygen concentrations (r2 = 0.93*), which set total stratified-period hypolimnetic oxygen availability that is seasonally depleted through aerobic decomposition of eutrophication-enhanced algal productivity (r2 = 0.81*). Hydrodynamic lake models, coupled to downscaled global climate models, predict protracted lake stratification under climate change, which will likely enhance seasonal oxygen deficits and freshwater mortality, highlighting the critical importance of rapid, targeted nutrient loading abatement to conserve endangered salmon.
9:20AM Climate, Competition and Life History Diversity Interact to Shape Pacific Salmon Dynamics across the Northeast Pacific Ocean
  Brendan Connors, Michael Malick, Greg Ruggerone, Peter Rand, Milo D. Adkison, James Irvine, Rob Campbell, Kristen Gorman
Ocean conditions and inter- and intra-specific interactions are well known to influence salmon growth and survival. However, there has been little analysis of the potential mediating effects of ocean conditions on density dependent interactions among salmon at sea. Such mediating effects may occur, for example, as a result of climate induced reductions in growth during early marine life leading to increased sensitivity to density dependent effects later in marine life. Alternatively, favorable ocean conditions during early marine life may mask the detection of density dependent interactions or mediate their potential effects. Using data from over 40 Sockeye salmon populations across the eastern north Pacific Ocean, along with information on ocean climate conditions and indices of potential salmon competitors, we find evidence that ocean conditions may mediate the consequences of competition among salmon at sea and that the magnitude and direction of these effects vary over large spatial scales. Using simulation and empirical analyses we also show that variation in age at ocean entry likely mediates these effects. Our findings provide a macroecological foundation upon which to consider how interactions among a changing ocean, inter-specific competition, and the erosion of life history diversity may shape the dynamics of exploited fish populations.
09:40AM Break
1:10PM Impacts of Fisheries Injuries and Water Temperature on Survival of Migrating Fraser River Sockeye Salmon
  David Moulton, Scott Hinch, David A. Patterson, Brian Hendriks, Kendra A. Robinson, Laura Elmer
Adult Fraser River (BC) sockeye salmon (Oncorhynchus nerka) pass through numerous fisheries while migrating to spawning grounds and are frequently observed with wounds indicative of escape from harvest gear. Climate change may exacerbate the impacts of these injuries from thermal stress and enhanced vulnerability to infectious agents. To examine the cumulative impacts of these stressors, we combined laboratory and field telemetry studies on summer- and late-run sockeye migrating under different thermal regimes. Fish were entangled in gillnets and beach seines for varying durations and their physiology and survival over time assessed. Summer-run sockeye exposed to temperatures greater than 20℃ suffered extremely high levels of mortality in the first week (63%) and over the full migration duration (96%). Gillnet entanglement led to the greatest migration mortality for late-run sockeye (58%), which experienced a maximum water temperature of 15.5℃. Longer entanglement durations resulted in more severe injuries, but not significantly different mortality outcomes. Mortality was highest for females in both studies, which is particularly worrisome because females limit spawning productivity. Additionally, gillnet entanglement and elevated water temperature both led to increased external fungus development. The results indicate that high water temperatures and gillnet injuries result in elevated migration mortality, particularly for females.
1:30PM Deep Enough to Swim? Hydraulic Controls on Coho Salmon Smolt Outmigration in the Russian River Watershed, CA
  Brian Kastl
Anadromous salmonid populations are declining worldwide, including endangered Coho Salmon (Onchorynchus kisutch) in California’s Russian River watershed near the southern extent of the species’ range. Streamflow alterations from land use and climate change may amplify the effects of life-cycle bottlenecks. During juvenile outmigration, shallow stream depths limit downstream smolt movement. However, little is known about the hydraulic conditions that support outmigration. This study investigates how variation in water depth and streamflow affect outmigration timing. We explored the relationships between flow and water depths at the riffle crest thalwegs (RCT), which are the shallowest points along a stream’s longitudinal profile. We measured water depths at 12 RCT sites, spread over 0.5 – 2 km-long reaches, at each of five streams during 2018 and 2019 outmigration seasons. Next, we converted continuous stage data to continuous RCT depths, which we analyzed in relation to observed smolt movement past PIT-tag antennas over seven years. We found that outmigration typically peaks when RCT depths are 4 – 9 cm. Winter rainfall and the duration of suitable water depths among streams are positively correlated with outmigration period duration. As droughts worsen, our results can inform management that builds the resilience of Coho Salmon populations.
1:50PM The Physiological Associations between Infectious Agents and Ocean Migrating Juvenile Chinook Salmon (Oncorhynchus tshawytscha)
  Yuwei Wang, Scott Hinch, Arthur Bass, Shaorong Li, Tobi Ming, Emiliano Di Cicco, Kristi Miller
The role of infectious diseases as a cause in the declining productivity of wild Chinook salmon (Oncorhynchus tshawytscha) in the Pacific Northwest is poorly understood. The early marine life of Pacific salmon (Oncorhynchus spp.) is believed to be a critical part of the declining populations. Our study assessed how infectious agents are associated with the physiology of migrating juvenile Chinook salmon upon their entry to marine waters. It is one of the first to study infectious agents carried by wild salmon through combining molecular, protein, and cellular levels of fish physiology information. We detected 26 assayed infectious agent taxa, including viruses, bacteria, and parasites. Fish from the Columbia River system were found to have higher infection burden than those derived from five other regional groups. We discovered associations between fish physiological conditions and five infectious agents, including Piscine orthoreovirus (PRV). PRV was recently reported in many salmon farms in British Columbia as the suspected causal agent of two related diseases in both Atlantic (Salmo salar) and Chinook salmon, and has potential to be exchanged between farmed and wild populations. We provide the evidence of potential impacts of PRV both on host genes and histopathology in the wild juvenile Chinook salmon.
2:10PM Disturbance, Climate, and Habitat: Understanding the Distribution of Chinook Salmon Redds in a Large River Network.
  Gregory Jacobs, Russ Thurow, John Buffington, Daniel Isaak, Seth Wenger
Habitat conditions, natural disturbances, and demographic variability strongly influence spawning distributions of Pacific salmon in western North America. In addition, short- and long-term climatic variation may alter spawning and rearing habitats through changes in stream temperature and flow regime, and through enhanced sediment inputs from increased fire frequency. Informed species conservation and management requires a better understanding of how reproductive effort is distributed among spawning streams as a function of these factors. We leveraged a spatially continuous, georeferenced, long-term (24 years) database of Chinook salmon redd locations across 760-km of the Middle Fork Salmon River, Idaho, USA, to evaluate spawning site selection relative to contemporaneous variation in habitat conditions, stream temperature, stream size, and fire extent. We tested competing logistic regression models predicting redd occurrence within 1-km reaches as a function of these and other biologically meaningful covariates. Redd site selection was strongly affected by substrate size, stream size, stream temperature, and total redd abundance, but was weakly affected by fire and winter high flows. Therefore, the distribution of spawning salmon may be more sensitive to changes in stream size and stream temperature rather than to increasing fire and winter high flow frequency with future climate change.
2:30PM Evaluation of Fish Rescue Programs across Varying Drought Conditions
  Brittany Beebe, Jonathan Armstrong, Kale Bentley, Thomas Buehrens
Projected intensification of drought conditions in the Pacific Northwest may reduce the capacity of streams to rear fish and exacerbate the challenge of recovering ESA-listed salmon populations. Drought will likely intensify stream drying and fragmentation during the dry summer season in intermittent streams, lowering juvenile salmonid survival during the summer. To combat drought-related mortality of juvenile salmonids, fish rescue and salvage programs have proliferated, whereby juveniles are captured and transferred to offsite rearing facilities. However, the need for and efficacy of these programs as a conservation tool remains poorly understood. We developed a life cycle model to examine the implications of fish rescue on coho salmon abundance across serial life stages. The model operates under the assumption that fish rescue improves juvenile survival but may decrease smolt-to-adult return rates, either through lower marine survival or increased straying as a result of offsite rearing. Our simulation model examines scenarios across various levels of rescue, drought severity, and reduced smolt-to-adult return rates. We compare the intergenerational abundance and extinction risk of each scenario to explore under which conditions fish rescue may be necessary or beneficial.
2:50PM Refreshment Break
3:20PM Gene Transcription Reveals Physiological Response in Chinook Salmon (Oncorhynchus tshawytscha) during Long Migration
  Shannon Waters, Vanessa R. von Biela, Lizabeth Bowen, Stephen D. McCormick, Randy J. Brown, Michael P. Carey, Sean Larson, Amy Regish, Christian E. Zimmerman
Yukon River Chinook Salmon (Oncorhynchus tshawytscha) have an extremely long freshwater spawning migration, with some individuals traveling >3,000 km from the Bering Sea to Canada. Noticeable declines in returning numbers of adult Chinook Salmon began in the late 1990s. Rising temperatures in the Yukon River are thought to be contributing to these declines by increasing prespawn mortality. As molecular responses are known to be good indicators of thermal stress, we compared gene transcript levels of fish caught in 2016 and 2017 at the Emmonak Test Fishery (EMF) (near the Yukon River mouth; low temperatures) and Eagle Test Fishery (ETF) (near the Canadian border; relatively high temperatures). We found indications of thermal stress, elevated levels of HSP70 transcripts, in salmon sampled at ETF, in comparison with transcript levels of salmon sampled at EMF. Additionally, genes associated with response to contaminants, nutritional stress and pathogen pressures reduced transcription in fish sampled at ETF, potentially linked to extended migration. Transcription patterns also differed between years, highlighting variability in environmental stressors. This project provides insight into the likely contributions of thermal stress to the decline of Yukon River Chinook Salmon and could be applied to future studies evaluating intergenerational responses to thermal stress.
3:40PM Managing Gulf of Maine Atlantic Salmon (Salmo salar) in a Changing Climate
  Dan Kircheis, Diane Borggaard, Dori Dick, Dan Tierney
The current range of the Gulf of Maine Distinct Population Segment (DPS) of Atlantic salmon was listed as an Endangered Species in 2009. Climate change was identified as a growing threat to Atlantic salmon, but it was not understood how climate change would affect the species, or to what degree. Since the listing, new science has improved our understanding of the effects of climate change on Atlantic salmon. Until recently, there remained uncertainty on how to manage for it. We will review three proactive tools under NMFS’s Climate Science Strategy to address climate change in lieu of the uncertainties. These include: 1) how a climate vulnerability analysis improved our understanding of Atlantic salmon’s vulnerabilities to climate change; 2) how scenario planning helped identify “no regret” science and management actions to address climate change across a range of plausible, future scenarios; and 3) how implementing identified actions such as mapping climate resilient/vulnerable habitats can show where salmon populations are most likely to succeed in warming conditions. These proactive measures helped inform management to further Atlantic salmon recovery and can serve as model for managing species in a changing climate.
4:00PM Climate Vulnerability Assessment for Pacific Salmon and Steelhead in the California Current Large Marine Ecosystem
  Lisa Crozier, Michelle McClure, Melissa Haltuch, Steven Bograd, Tim Beechie, David Boughton, Mark Carr, Jason Dunham, Correigh M. Greene, Jim Myers, Nate Mantua, Brian Spence, Laurie Weitkamp, Mark W. Nelson, Elliott Hazen
Major ecological realignments are already occurring in response to climate change. Conservation strategies need to account for geographical patterns in traits sensitive to climate change, as well as climate threats to species‑level diversity. We conducted a climate vulnerability assessment that included all Pacific salmon and steelhead (Oncorhynchus spp.) distinct population segments (DPSs) listed under the U.S. Endangered Species Act. Using an expert‑based scoring system, we ranked 20 attributes for 33 DPSs in relation to sensitivity, exposure, and adaptive capacity. The most vulnerable DPSs were Chinook in the California Central Valley, coho in California and southern Oregon, sockeye in the Snake River Basin, and spring‑run Chinook in the interior Columbia and Willamette River Basins. We identified DPSs with similar vulnerability profiles using a hierarchical cluster analysis. Life‑history characteristics, especially freshwater and estuary residence times, interplayed with gradations in exposure from south to north and from coastal to interior regions to generate landscape‑level patterns within each species. Anthropogenic factors, especially migration barriers, habitat degradation, and hatcheries, have reduced the adaptive capacity of most populations. Enhancing adaptive capacity is essential to mitigate for the increasing threat of climate change. These results provide a framework to support recovery planning for West Coast salmonids.
4:20PM Concluding Remarks
  Kim Hyatt, Jim Irvine

Organizers: Kim Hyatt, James Irvine
Supported by: International Year of the Salmon (North Pacific Anadromous Fish Commission, North Atlantic SalmonConservation Organization); AFS Fish Habitat Section

Location: Atlantis Hotel Date: September 30, 2019 Time: 8:20 am - 5:00 pm