Climate Change Across the Salmon Life-Cycle (hosted by AFS)

Symposium
ROOM: Atlantis, Grand Ballroom 1
SESSION NUMBER: 8073
 
Climate change is affecting salmon throughout their life cycle in different and sometimes unexpected ways. Individual life stages are impacted—from ocean climate variability driving large shifts in survival and growth to warming streams causing mortality in adult migrants. Yet, the population-level impacts of climate change will be a function of cumulative impacts of climate change across life stages. Importantly, climate impacts in one life-stage may carryover to the next. Experiences/conditions from the freshwater environment can be carried over to the early ocean environment and this may affect early ocean survival, and population growth. Likewise, changes in ocean conditions could change en-route mortality, pre-spawn mortality and influence the next generation through intergenerational effects. This symposium will bring together researchers studying salmonids across life-stages including carryover and intergenerational effects. We will begin with the juvenile life-history stage and work through the life stages of salmon ending where we began, at the juvenile life-history stage. The end of the symposium will include a panel discussion on next steps for research. For this symposium we welcome studies that examine climate change in the context of individual, population and species-level effects on salmonids that cut across one or more life stages.

8:20AM Critical Windows in Chinook Salmon Development: Differential Sensitivity to Warming and Hypoxia during Development and Long-Term Effects of Developmental Exposure
  Annelise Del Rio, Gabriella Mukai, Rachel Johnson, PhD, Benjamin Martin, Nann Fangue, Joshua Israel, Anne E. Todgham
Conditions within salmon redds, or nests, can be highly variable. With the progression of global climate change, high temperatures and hypoxia may occur more frequently within the gravel rearing environment. We examined how elevated temperature and hypoxia as single and combined stressors affected the survival and physiology of developing Chinook salmon. Exposures lasted either from fertilization through hatching or for short periods during embryonic development to test the effect of exposure timing. Upon hatching all treatments were returned to control conditions of cold normoxic water and tested as post-hatch alevins and fry to investigate persistent and latent effects of developmental exposure to stressors on growth, physiology, and behavior. Hatching success was lowest in the chronic warm hypoxia exposure and the late warming and hypoxia exposure, suggesting the combination of stressors is most detrimental to survival, with greater sensitivity during later stages in embryonic development. Embryos reared in hypoxia also developed more slowly and took longer to hatch compared to normoxic treatments. Determining developmental windows of increased sensitivity to stressors can inform effective and efficient water management policies to support salmon embryo survival.
8:40AM Climate Change, Fry Emergence Timing and Subsequent Variation in Chinook Salmon Life History
  Brian Beckman, Abby Furrman, Deborah Harstad, Dina Spangenberg, Donald Larsen
Salmon spawn their eggs in the autumn, eggs hatch and alevins incubate in river gravels over the winter, emerging as fry into the water column during the spring. At emergence, salmon fry first experience daily photoperiod cycles. Climate change certainly will change the magnitude and frequency of seasonal temperature fluctuations, inevitably altering seasonal spawn timing, egg and alevin incubation temperatures and the subsequent seasonal timing of fry emergence. We have conducted several experiments exploring how variation in the daily photoperiod cycle when salmon fry emerge results in subsequent variation in timing of smolting (seawater entry) and prevalence of early male maturation. We’ve found that when fry emerge under a short-day photoperiod (December – January) juvenile chinook tend to smolt as sub-yearlings and age-1 male maturation is common. In contrast, when fry emerge under a long-day photoperiod (May) juvenile Chinook salmon generally smolt at yearlings and age 1 male maturation is totally absent. Thus, increased winter water temperatures, through the acceleration of fry emergence timing, may have pronounced actions on subsequent life history variation in Chinook Salmon.
9:00AM The Ricker Model and Size-Dependent Survival Emerge from a Framework of Juveniles Growing through a Field of Gape-Limited Predators
  James Anderson
Many studies demonstrate both freshwater and marine conditions affect the survival of salmon between juvenile and adult stages. The observations are often explained by qualitative models or statistical relationships that involve a number of processes such as bottoms-up vs. top-down population control, density dependence, critical or compensatory growth, size-selective predation and freshwater carryover effects. In this paper I present a model that integrates these concepts through first principles involving growth, predator-prey interactions and the frequency distribution of predator gapes. A special case of the model produces a Ricker spawner-recruit equation in which the carrying capacity depends in part on the marine entrance size of juveniles and the size distribution of predator gapes. Because the six model parameters have mechanistic foundations the effects of climate change on salmon might be linked through the effects of climate on the parameters.
9:20AM Exploring the Potential for Freshwater Carry-over Effects and Their Interaction with Climate Change in Steelhead Trout
  Colin Bailey, Jonathan W. Moore
Steelhead trout display more life-history variation than any other Pacific salmon; up to 36 distinct life-histories have been recorded across two watersheds. Steelhead life-histories include variation in the number of years spent as juveniles in a stream, the number of years spent as adults in the ocean, and the number of spawning migrations an adult completes. While we know that genetics and environment play strong roles in steelhead life-history expression, we still understand relatively little about the effects of multiple simultaneous environmental factors on life-history variation. The Keogh River salmonid monitoring and enumeration program has been running for 4 decades, and provides an excellent opportunity to explore the environmental drivers of life-history variation and survival across the steelhead life-cycle. For this presentation, I will summarize the effects of the freshwater environment on juvenile life-history variation in the Keogh River, show preliminary results on how juvenile life-history and ocean climate combine to influence marine survival and adult life-history variation, and discuss the results in the context of climate change. Understanding the drivers of marine survival and life-history variation in steelhead can improve our understanding of how environmental variation may affect their population stability, productivity, and persistence.
09:40AM Break
1:10PM Size-Dependent Estuary Use in Juvenile Coho Salmon: Implications for Linkages across Life Stages
  Alexandra Sawyer, Karl Seitz, Willam Atlas, Jonathan Moore
Juvenile salmon rear in freshwaters and transition to estuaries before migrating seaward to a hungry ocean. This continuum of habitats may vary in growth opportunity as well as mortality risk. For example, in marine ecosystems salmon face strong size-dependent mortality risk coupled with increasingly uncertain ocean conditions. Here we consider the role of estuaries in mediating patterns of size-selective ocean survival. We have performed several years of mark-recapture life-cycle monitoring of coho salmon in the Koeye River system on the remote Central Coast of British Columbia, using passive integrated transponders and estuary seining. Mark-recapture analysis of tagged coho salmon pre-smolts and returning spawners indicated that larger juveniles tended to have higher ocean survival rates than smaller individuals. On average, juveniles sampled at marine entrance were substantially larger than those exiting freshwater, and daily growth rates in the estuary were high. Yet, pre-smolts that were small at freshwater exit exhibited longer estuary residence times and greater estuary-associated growth than their larger counterparts. These results suggest that estuaries support pre-smolt coho salmon growth, with potential to boost watershed-level productive capacity and buffer size-selective survival in a changing marine environment.
1:30PM Linking Ecosystem Change, Growth, and Survival of Penobscot River Atlantic Salmon
  Miguel F. Barajas, Katherine E. Mills, Timothy F. Sheehan, Ruth E. Haas-Castro
Beginning in the 1980s, return rates of Atlantic salmon to the Penobscot River, Maine U.S.A. declined and have persisted at critically low levels. The timing of this decline coincided with similar widespread declines of North American and European Atlantic salmon stocks as well as with major physical and biological shifts in the Northwest Atlantic ecosystem. Prior studies using scale pattern increment analysis suggest that the declines of European stocks are related to decreased post-smolt growth whereas declines of North American stocks have not shown the same relationship, suggesting that marine survival of North American salmon stocks is somewhat growth-independent. We constructed a time series of growth data based on scales of Atlantic salmon returning to the Penobscot River for smolt-years spanning four productivity periods—1978-1980, 1986-1988, 1998-2000, and 2010-2014. The growth data were analyzed to determine if and how growth patterns have changed over the four productivity periods and to identify seasons during which the changes have occurred. Preliminary results indicate that the declining growth during late marine stages and the loss of slow-growing fish are associated with reduced marine survival in this population.
1:50PM Climate Change Effects on Juvenile Chinook Salmon Migratory Phenotypes
  Travis Apgar, Benjamin Martin, Joe Merz, Eric Palkovacs
A species that expresses a wider range of phenotypes for a given life-history trait can usually survive better under fluctuating environmental conditions, as this buffers populations against extinction when conditions are not favorable. In salmonids, a wide range of migratory life-histories have arisen from different environmental selective pressures, and Chinook salmon are one species that express a wide range of juvenile migratory phenotypes. The main segregation in Chinook juvenile migratory life-histories are usually Ocean-type and Stream-type. Within each of these groups there are also a variety of migratory phenotypes that may be present depending on the different environmental conditions each cohort face in a given stream or year. Shifting temperature and flow regimes due to climate change have the potential to shift the frequencies and timing of the migratory traits. Using Chinook outmigration datasets from California to Washington we analyzed the effects of climate change on these phenotypes. Our findings suggest that changes in flow, temperature, and juvenile density play a major role in the frequency and timing of these traits and that climate change may fundamentally alter their expression.
2:10PM Phenological Mismatch, Carryover Effects, and Marine Survival in a Wild Steelhead Trout Population
  Samantha Wilson, Thomas Buehrens, Jennifer Fisher, Kyle Wilson, Jonathan Moore
The match/mismatch hypothesis may be a useful tool for predicting recruitment of marine fishes, particularly in the face of climate-driven changes in ocean productivity. For example, the temporal matching of young salmon outmigrating from freshwater to the ocean relative to their prey could influence their marine survival. To determine whether mismatches between juvenile salmon and their prey could contribute to low ocean survival, we analyzed the migration timing and ocean survival of 22,116 tagged juvenile steelhead trout over 12 years from the Wind River, Washington State, USA. We used a multilevel modelling approach to determine which individual (e.g. size) or yearly (e.g. biological spring transition date (day that cold-water zooplankton first appeared near the Columbia River estuary)) factors contributed to survival. Larger fish had higher ocean survival, providing further evidence that freshwater growing conditions have carryover effects on marine survival. Survival was higher when fish migrated after the biological spring transition date, which varied widely across years. Thus, in years when the biological spring transition date was earlier, more steelhead trout survived. Collectively these findings indicate that freshwater growing conditions and timing of food availability in the nearshore coastal environment work in concert to determine individual survival.
2:30PM Direct and Carryover Effects of Freshwater, Marine and Fish Conditions on Juvenile, Ocean, and Adult Survival of Snake River Chinook Salmon
  Jennifer L. Gosselin, Eric R. Buhle, Nicholas Beer, Lisa Crozier, Chris Van Holmes
Understanding freshwater-marine carryover effects in anadromous salmonids can help to inform river management and forecast ocean survival. We examine how freshwater and marine conditions, migration timing, and smolt length can affect survival across life stages: 1) downstream-migrating smolt, 2) ocean, and 3) upstream-migrating adult. Explanatory variables (including snow-water-equivalent index, river temperature, flow, smolt length, migration timing, sea surface temperature [SST], and NPGO) are tested for “direct” effects occurring in the same life stage as survival response. Smolt-life-stage explanatory variables are also tested for “carryover” effects on ocean survival. We examine these relationships using a Bayesian Cormack-Jolly-Seber mark-recapture model that also includes random interannual variation in survival and detection probabilities. We utilize individually passive-integrated-transponder tagged (ptagis.org) wild spring/summer Snake River Chinook salmon (Pacific Northwest, USA) outmigrating 2002–2015. We found that migration timing, river temperature and SST had negative direct and carryover effects on survival. Smolt length was also a key biological trait with positive carryover effects on ocean survival. To assess potential climate change effects, we simulate survival from the posterior predictive distribution given scenarios of potential future migration timing and temperature. These results provide future ranges of cross-life-stage salmon survival influenced by migration timing, freshwater and marine temperature indices.
2:50PM Refreshment Break
3:20PM Effects of Warming Climate and Competition in the Ocean for Life-Histories of Pacific Salmon
  Timothy Cline, Jan Ohlberger, Daniel Schindler
The life-histories of exploited fish species, such as Pacific salmon, are vulnerable to a wide variety of anthropogenic stressors including climate change, selective exploitation, and competition with hatchery releases for finite foraging resources. However, these stressors may generate unexpected changes in life-histories due to developmental linkages when completing their migratory life cycle in different habitats. We used multivariate time-series models to quantify changes in the prevalence of different life-history strategies of sockeye salmon from Bristol Bay, Alaska, over the last half-century—specifically, how they partition their lives between freshwater habitats and the ocean. Climate warming has decreased the time salmon spend in their natal freshwater habitat, as climate-enhanced growth opportunities have enabled earlier migration to the ocean. Migration from freshwater at a younger age and increasing competition from wild and hatchery-released salmon tended to delay maturation toward spending an additional year feeding in the ocean. Models evaluating the effects of size-selective fishing on these patterns had only small support. These stressors combined to reduce the size-at-age of fish vulnerable to commercial fisheries and have increasingly favored a single age class, potentially affecting the age class complexity that stabilizes this highly reliable resource.
3:40PM Early-Season Reproductive Failure of Chinook Salmon: Limited Behavioral Plasticity in Warming Rivers?
  Michael Hellmair, Matt Peterson, Tyler J. Pilger, Doug Demko, Andrea Fuller
Monitoring of populations near the margins of a species’ natural distribution, which often occur in habitats approaching their thermal limits and may be susceptible to even modest temperature increases, can provide insights on the effects of climate stressors expected to affect more northerly populations in the future. Annual monitoring activities track the escapement, document spatial and temporal spawning distribution and estimate juvenile production and outmigration characteristics of fall-run Chinook salmon, Oncorhynchus tshawytscha, in California’s Stanislaus River. Monitoring during the recent record-breaking drought revealed only minor migration- and spawning delays for returning adults, despite water temperature conditions considered detrimental to egg incubation. Results from degree-day analyses to estimate fertilization dates of emigrating juvenile salmon suggests diminished reproductive success of early spawners. While peak timing of reproduction might shift over time resulting from poor fitness of early spawners, this reduces in-river rearing opportunities of juveniles, which must emigrate before thermal connectivity to the marine environment is lost in spring. Long-term air temperature data indicates that cooling below certain temperature thresholds occurs progressively later in fall, while the same thresholds are exceeded earlier in spring, reducing the window for emigration of juvenile fall-run Chinook salmon and, by extension, further diminishing population resilience.
4:00PM Multi-Species Regime Shifts in Productivity of Anadromous Pacific Salmonids in a Small Watershed
  Kyle Wilson, Colin Bailey, Trevor Davies, Jonathan Moore
Pacific salmon population dynamics can exhibit frequent and large fluctuations over time driven by combinations of intrinsic (e.g., density-dependence) and extrinsic factors (e.g., climate changes and/or species interactions). These ‘regime shifts’ change population productivity, which can impact population resilience and sustainable fishery targets. Many Pacific salmon populations have declined from apparent regime shifts but understanding mechanisms causing these shifts remains poor. Here, we assessed temporal trends in productivity using stock-recruitment data on five species of Pacific salmonids since 1976 including: Steelhead, Coho Salmon, Pink Salmon, anadromous Dolly Varden, and anadromous Coastal Cutthroat Trout. We used a multivariate autoregressive state-space modelling appraoch to examine whether shifts in productivity were caused by marine climate oscillations, freshwater climate, or species interactions and whether these trends were similar across species. In general, we identified an apparent productivity regime shift in the early 1990’s with similar declines observed across Steelhead, Dolly Varden, and Cutthroat Trout – neither Coho nor Pink Salmon experienced this shift. We explore how changing climates, competitive interactions in early life, and species’ life cycles may affect how species responded to this regime shift. Lastly, we discuss how patterns from the Keogh River generalize to salmonid populations throughout the Pacific Northwest.

 
Organizers: Colin Bailey, Daniella LoScerbo, Samantha Wilson
 
Supported by: AFS Fish Habitat Section

Symposium
Location: Atlantis Hotel Date: October 3, 2019 Time: 8:20 am - 5:00 pm