2.1 | Sample collection and processing
Young-of-the-year (YOY) POP were collected during NOAA oceanographic
surveys in the summer of 2014 and 2015 (Figure 1). POP larvae and YOY
were distinguished from congenerics (Kendall et al., 2007) using
diagnostic SNPs (Garvin et al., 2011) prior to inclusion in this study.
The resulting sample size of identified YOY POP was 399 fish in 2014 and
108 in 2015.
Fish length, weight, and lipid content for each identified POP fish were
measured at Auke Bay Laboratories in Juneau, AK. Lipid content was
extracted using the Folch method (Folch et al. 1957) and quantified
using the colorimetric sulpho-phospho-vanillin (SPV) method (Chabrol and
Charonnet, 1937). Condition index was calculated as the residual value
from a log(weight)~log(length) linear regression. This
index accounts for the different lengths due to age of the YOY fish
where a positive residual indicates better body condition than expected
(Froese, 2006). Finally, for DNA analysis, a small tissue plug was
extracted through an incision in the abdominal wall that included the
heart tissue and stored in 95% ethanol.