Isotope-based inferences of the seasonal foraging and migratory strategies of blue whales in the eastern Pacific Ocean

Tissue selection, preservation, and processing quantitative data on the proportion of feeding that occurs on the summer-fall versus winter-spring foraging grounds is required to better Blue whale skin biopsies and sloughed skin from different regions in understand the physiological strategies and energy requirements of the the eastern Pacific Ocean (Fig. [...] The models for NEP regions (CCE, GC and CRD) only included the blue whale skin strata data and corresponding prey All the data processing, statistical analyses, and graphical represen- data from the CCE, GC and the CRD, because the aim of these models tations of the data were performed in the R language (R Core Team, was to estimate the proportional dietary contribution from these regions 2019). [...] externum, and finally in sloughed skin, depending on the date of arrival For our isotope mixing models, we categorized the CCE as the area and time spent in a specific foraging region, and also on the rate of from British Columbia to the west coast of the Baja California Peninsula consumption of local prey.” because published datasets of potential blue whale prey show consistent δ15N values over d. [...] The integrated primary production in 2 1 months (Busquets-Vass et al., 2017), the mean (±SD) contribution of the GC versus the CRD is similar (~1 gC m− d− ) (Álvarez-Borrego, prey from the CRD (12–19%, Table 3) in the skin strata sampled during 2012; Selph et al., 2016), however, physical characteristics of areas the winter-spring months in the GC indicates that some blue whales within the GC (e.. [...] Given krill and defecating in January (Calambokidis et al., 2009b; Matteson, that our sampling resolution is limited to October and November, 2009), and the photo-recaptures of seven blue whale individuals that additional sampling of blue whales in the southern ETP, especially from were observed in the GC and CRD.