Figure 4.

Otolith oxygen and carbon stable isotopes (δ¹⁸O/δ¹³C values) for age ≥ 2 unknown adult Northwest Atlantic mackerel samples collected in the US shelf waters for 9 year-classes (1998–2000 and 2011–2016) classified based on the binomial generalized linear mixed model. Background colors indicate the probability of each individual assigned to either contingent (0.7 threshold). Different symbols represent different age-classes within each year-class. The proportion of the northern contingent of assigned fish (probability > 0.7) for each year-class is shown in the top left corner of each panel. All isotope values were reported in delta notation with respect to Vienna-Pee Dee Belemnite (V-PDB). Note that classification baselines were developed separately for the older and recent year-classes and the scales of the x- and y-axes differ between those panels.