Data for: Dynamic coastal pelagic habitat drives rapid changes in growth and condition of juvenile sockeye salmon (Oncorhynchus nerka) during early marine migration

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.