DOI: 10.5061/dryad.x69p8czn0
title: Data for: Dynamic coastal pelagic habitat drives rapid changes in growth and condition of juvenile sockeye salmon (Oncorhynchus nerka) during early marine migration

description: Migrating marine taxa encounter diverse habitats that differ
 environmentally and in foraging conditions over a range of spatial scales.
 We examined body (RNA/DNA, length-weight residuals) and nutritional (fatty
 acid composition) condition of juvenile sockeye salmon (Oncorhynchus
 nerka) in British Columbia while migrating through oceanographically
 variable waters. Fish were sampled in the stratified northern Strait of
 Georgia (NSoG); the highly mixed Johnstone Strait (JS); and the
 transitional zone of Queen Charlotte Strait (QCS). In 2015, body and
 nutritional condition were high in the NSoG but rapidly declined to reach
 the lowest levels in JS where prey availability was low, before showing
 signs of compensatory growth in QCS. In 2016, juvenile salmon had a
 significantly lower condition in the NSoG than in 2015, although
 zooplankton biomass was similar, condition remained low in JS, and no
 compensatory growth was observed in QCS. We provide evidence that
 differences in juvenile salmon condition between the two years were due to
 changes in the food quality available to juvenile fish. We propose that
 existing hypotheses about fish survival need to be extended to incorporate
 food quality in addition to quantity to understand changes in fish
 condition and survival between years.
description: Zooplankton was collected using a vertical Bong net (250 µm mesh
 size, mouth diameter 0.5 m). The net was deployed from near-bottom depth
 at a maximum of 300 m depth to surface. Zooplankton was preserved in 5%
 buffered formaldehyde-seawater solution. Zooplankton was identified to the
 lower taxonomic level possible. For detailed methods, see the associated
 article. Fish were collected from a 6m motorized vessel
 at distances of 5-60m from shore, using a purse seine designed for manual
 deployment and retrieval (bunt: 27 x 9 m with 13 mm mesh; tow 46 x 9 m 76
 mm mesh). White muscle tissues were collected post-catchment from
 flash-frozen organisms. RNA:DNA ratios were measured at
 the University of British Columbia (UBC) using a VarioSkan Flash
 Microplate Reader (ThermoFisher Scientific). For detailed methods see
 Garzke et al (2022). RNA:DNA ratios were measured in triplicates and
 sample averages were calculated from triplicates not exceeding a
 coefficient of variance above 15%. Fatty acids follow
 the notation C20:5n.3 corresponding to eicosapentaenoic acid (EPA), where
 20 is the number of carbon atoms, 5 is the number of double bonds, and 3
 is the position of the first double bond from the omega end.
 Fatty acids were analyzed at the Fisheries and Oceans Canada
 (DFO) Pacific Science Enterprise Centre. FAs were converted to fatty acid
 methyl esters using a direct transesterification method, separated using
 an Agilent CP-Sil 88 column (50 m, 0.25 mm diameter), and quantified with
 a gas chromatograph (SCION 436) equipped with a flame ionization
 detector. These data represent all chromatogram peaks
 attributed to FAs based on external standards (Nu-Chek Prep GLC-37,
 GLC-463; Cayman Chemical 18:4n-3; Matreya PUFA Mix No. 3) and by comparing
 reference samples analyzed at another lab (M.T. Brett, University of
 Washington). Overall, 81.2 ± 0.08% (mean ± sd) of the chromatogram area
 was identified and attributed to FAs. FAs were quantified based on a known
 quantity of an internal standard, C19:0, that was added to each sample.
 For detailed methods see Garzke et al (2022). For each
 sampling date, fatty acids are presented as μg of total fatty acids of mg
 DW of the analysed muscle tissue. Oceanography data
 (SST and SSS), were collected from CTD profiles using a RBR maestro and
 SeaBird 19plus V2 CTD. Samples represent the average of the upper 10m of
 the water column.
description: No proprietary programs required to use these data.