Figure 1.
Sperm whales are distributed year-round in offshore deep waters (∼>150 km off the US west coast [29]).
Skin samples (○) from free-ranging sperm whales were collected together with skin from stranded individuals. Tissue samples were used for bulk (in black) and amino acid (in red) stable isotope analysis.
Figure 2.
Time series of isotopic data from sperm whale skin.
(A) δ15N values from bulk skin, average source-AAs and average trophic- AAs (± SD); and (B) δ13C values from bulk skin and average essential-AAs (±SD). Bulk isotope data are plotted with a square symbol (□), filled grey squares indicate the samples that were also analyzed for amino acid stable isotope analysis. The corresponding linear regression equations are provided in Table 1, as are the amino acids included within each AA-group.
Table 1.
Temporal variation in δ 15N and δ 13C values from the offshore California Current System in sperm whale skin samples.
Figure 3.
Time series data of sea surface temperature anomaly (SSTA) from the offshore California Current (inset map) and the Pacific Decadal Oscillation (PDO).
Monthly SSTA was computed in 0.5-deg fields from the Simple Ocean Data Assimilation version 2.2.4 reanalysis (http://coastwatch.pfeg.noaa.gov/erddap/griddap/hawaii_d90f_20ee_c4cb.html), and then averaged in the offshore area (the plot shows ±1sd). Monthly SSTA (°C) and PDO values were smoothed with a 25-month lowess smooth. The linear fit is for 1992–2006 (red line, slope −0.044°C y-1). Sample periods are indicated along the time axis.