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.