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Title: Reconstructing the Migratory Behavior and Long-Term Survivorship of Juvenile Chinook Salmon under Contrasting Hydrologic Regimes

The loss of genetic and life history diversity has been documented across many taxonomic groups, and is considered a leading cause of increased extinction risk. Juvenile salmon leave their natal rivers at different sizes, ages and times of the year, and it is thought that this life history variation contributes to their population sustainability, and is thus central to many recovery efforts. However, in order to preserve and restore diversity in life history traits, it is necessary to first understand how environmental factors affect their expression and success. We used otolith 87Sr/86Sr in adult Chinook salmon (Oncorhynchus tshawytcha) returning to the Stanislaus River in the California Central Valley (USA) to reconstruct the sizes at which they outmigrated as juveniles in a wetter (2000) and drier (2003) year. We compared rotary screw trap-derived estimates of outmigrant timing, abundance and size with those reconstructed in the adults from the same cohort. This allowed us to estimate the relative survival and contribution of migratory phenotypes (fry, parr, smolts) to the adult spawning population under different flow regimes. Juvenile abundance and outmigration behavior varied with hydroclimatic regime, while downstream survival appeared to be driven by size- and time-selective mortality. Although fry survival is generallymore » assumed to be negligible in this system, >20% of the adult spawners from outmigration year 2000 had outmigrated as fry. In both years, all three phenotypes contributed to the spawning population, however their relative proportions differed, reflecting greater fry contributions in the wetter year (23% vs. 10%) and greater smolt contributions in the drier year (13% vs. 44%). In conclusion, these data demonstrate that the expression and success of migratory phenotypes vary with hydrologic regime, emphasizing the importance of maintaining diversity in a changing climate.« less
 [1] ;  [2] ;  [3] ;  [2] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9]
  1. Univ. of California, Santa Cruz, CA (United States). Institute of Marine Sciences
  2. US Fish and Wildlife Service, Lodi, CA (United States)
  3. California Department of Fish and Wildlife, La Grange, CA (United States)
  4. Univ. of California, Berkeley, CA (United States)
  5. Cramer Fish Sciences, Auburn, CA (United States)
  6. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Glenn T. Seaborg Institute
  7. Univ. of California, Davis, CA (United States). Dept. of Animal Sciences
  8. Univ. of California, Davis, CA (United States). Interdisciplinary Center for Plasma Mass Spectrometry
  9. Univ. of California, Davis, CA (United States). Dept. of Animal Sciences; National Marine Fisheries Service, Santa Cruz, CA (United States)
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Additional Journal Information:
Journal Volume: 10; Journal Issue: 5; Journal ID: ISSN 1932-6203
Public Library of Science
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
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Country of Publication:
United States