DOI: 10.5061/dryad.c56rk
title: Data from: Reconstructing the migratory behavior and long-term survivorship of juvenile Chinook salmon under contrasting hydrologic regimes

description: 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 generally
 assumed to be negligible in this system, &gt;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%). 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.
description: Otolith Sr isotope
 values for Chinook salmon spawning in the Stanislaus
 RiverThe data file contains
 87Sr/86Sr values measured in the otoliths of adult Chinook salmon sampled
 in the Stanislaus River, California, between 2001 and 2006. Fish age was
 estimated using scale annuli, and individuals that outmigrated in 2000 and
 2003 were retained for the current analysis (see "Outmigration
 year"). Each otolith contains multiple 87Sr/86Sr values, representing
 spot analyses sampled along a standardized 90° transect from the otolith
 core towards the otolith edge. The average isotopic value of the natal
 region (post-exogenous feeding check) was used to assign river or hatchery
 of origin, and for individuals that originated in and returned to the
 Stanislaus River, the distance to the last natal spot (see "Distance
 from core") was used to estimate size at outmigration. The data file
 also includes the instrument error ("2SE"), strontium signal
 ("Sr (V)") and laser operating conditions associated with each
 spot analysis. See accompanying "README" file for additional
 information on each fish, including natal assignments.Stanislaus_2000_2003_Sr_spot_data_PLOS_ONE_DRYAD.xlsxDaily abundance of fry, parr and smolt outmigrating from the Stanislaus River in 2000 and 2003Daily passage estimates of juvenile salmon outmigrating from the Stanislaus River in 2000 and 2003, alongside measurements of turbidity, temperature and flow. Passage estimates were extrapolated from rotary screw trap captures and classified by fork length (fry ≤55mm, parr &gt;55 to &lt;75mm, and smolts &gt;75mm).Daily_N_fry_parr smolt_2000 2003_DRYAD.xlsx