DOI: 10.5061/dryad.5mkkwh78j
title: Data for Contrasting life-history responses to climate variability in eastern and western North Pacific sardine populations

description: Massive populations of sardines inhabit both the western and eastern
 boundaries of the world’s subtropical ocean basins, supporting both
 commercial fisheries and populations of marine predators. Sardine
 populations in western and eastern boundary current systems have responded
 oppositely to decadal scale anomalies in ocean temperature, but the
 mechanism for differing variability has remained unclear. Here, based on
 otolith microstructure and high-resolution stable isotope analyses, we
 show that habitat temperature, early life growth rates, energy
 expenditure, metabolically optimal temperature and, most importantly, the
 relationship between growth rate and temperature were remarkably different
 between the two subpopulations in the western and eastern North Pacific.
 Varying metabolic response to environmental changes partly explain the
 contrasting growth responses. Consistent differences in the life-history
 traits are observed between subpopulations in the western and eastern
 boundary current systems around South Africa. These growth and survival
 characteristics can facilitate the contrasting responses of sardine
 populations to climate change.
description: Otolith Increment Width data (JP_Otolith_IW_YYYY.xlsx (YYYY:
 2006-2010, 2014, 2015), CA_otolith_increments.xlsx)
 Extracted sagittal otoliths were cleaned to remove the attached
 tissue in freshwater and then air-dried. Otoliths of JP sardine were
 embedded in epoxy resin (Petropoxy 154, Burnham Petrographics LLC) on
 slide-glass, while those of CA were glued to slide-glass using enamel
 resin and then ground and polished with sandpaper to expose the core.
 Using an otolith measurement system (RATOC System Engineering Co. Ltd.),
 the number and location of daily increments were examined along the axis
 in the postrostrum from the core.  Otolith Isotope data
 (Otolith_isotope_ratios.csv) The otolith portions
 deposited during hatch-30, 31-45, 46-60, 61-75, 76-90, 91-105, and 106-120
 dph for the JP sardine and hatch-30, 31-60, 61-90, 91-120, and 121-150
 dph for CA sardine, were milled out sequentially using a high-precision
 micromilling system Geomill 326. The milling depth was set to 50 um for
 the area near the core and 100 um for the rest. After each milling, the
 otolith was observed under a microscope to check for otolith fractions
 that had cracked outward from other milling area, and these were removed
 using a needle if present. The milled powders were then collected using a
 needle and a stainless-steel cup and poured into response vials. After
 each collection of powder, the otolith was cleaned with an air duster to
 avoid cross-contamination between the milling paths. The d18O and d13C
 values of collected otolith powder were determined using the micro-volume
 analysis system MICAL 3c at the National Institute of Technology, Ibaraki
 College, for the area nearest to the core, and the automatic system DELTA
 V + GAS Bench for the rest at the Atmosphere and Ocean Research Institute,
 the University of Tokyo. The otolith powders were reacted with phosphoric
 acid at 25 deg C, and the released CO2 was purified before being
 introduced into the mass spectrometer for the MICAL3c system. The response
 with phosphoric acid was performed at 72 deg C for DELTA V. 
 Seawater Isotope data (Seawater_d18O_California.csv)
 Surface and sub-surface seawater samples for the isotope analysis
 were collected during the 1708SR CalCOFI cruise survey conducted by the
 California Cooperative Oceanic  Fisheries Investigations in August 2017.
 At every two stations on three line transects extending offshore from the
 Southern California Bight, seawater samples for d18O analysis were taken
 from 10m and 50m depths using CTD-attached Niskin bottles and preserved in
 sealed glass vials to prevent evaporation. After membrane-filtration (pore
 size: 0.45 um, Toyo Roshi Kaisha, Ltd.), d18O values were measured at the
 National Institute of Technology, Ibaraki College using the Picarro
 L2130-i system with a precision better than 0.05 permil. The cruise
 information and temperature and salinity data were obtained from CalCOFI
 database (https://calcofi.org/data/oceanographic-data/).
description: All data can be opened by Microsoft Excel.