Results from linear regression of fraction of days white sharks engaged in diving behaviors over distance (degrees of longitude) from the center of the Café.

*<p>_All refers to male, female and unknown sex.</p

The fraction of time each month that male (A) and female (B) white sharks engaged in ‘ROD’ (black) and ‘DVM’ (grey) behavior.

<p>The bars represent median values, while the error bars show the upper inter-quartile range among individuals.</p

Dendrogram of white shark behavior, determined from clustering analysis of differences in diving patterns.

<p>Each column represents a 24-hour depth histogram (n = 5571 days from 53 sharks) and is colored by fraction of time. Distinct vertical distribution patterning is evident in the grouping of days with similar depth distributions. The size of each cluster, is indicated by the number of days (n), and percent of total days (in parentheses). The density variable is expressed as a fraction of each day spent in depth bins defined along the y-axis.</p

White shark seasonal and spatial patterns corresponding to each behavioral mode for males and females.

<p>The dotted lines represent the coast of California (red; near 122°W), the Café (green; near 135°W) and Hawaii (blue; near 156°W) respectively. All longitude estimates for the entire male (left panels) and female (right panels) dataset are shown in grey in the background with only the relevant data for each cluster and sex highlighted in black.</p

Daily median white shark position estimates from 53 tracks, Each position estimate is colored according to behavioral cluster; cluster 1 (yellow; ‘ROD’), cluster 2 (purple; ‘Cluster 2’), cluster 3 (green; ‘Travel’), cluster 4 (magenta; ‘DVM’), cluster 5 (orange; ‘Coastal’).

<p>The distinct diving behaviors, distinguished by each cluster, generally differed in the locations where they most commonly occurred. The ‘Coastal’ behavior occurred primarily along the North American coast, ‘ROD’ primarily at the ‘white shark Café’, while ‘DVM’ occurred throughout the offshore area (the Café, Hawaii, and in between) and ‘Travel’ connected North America and the offshore core areas (the Café and Hawaii).</p

Spatial dependence of white shark ‘ROD’ (A) and ‘DVM’ (B) behavior in the Café.

<p>The regression shows that for ‘ROD’ the fraction of time (days) white sharks were engaged in ‘ROD’ declined steadily and linearly as a function of distance from the center of the Café region. In contrast no clear spatial relationship was evident for ‘DVM’.</p

Differences in white shark behavior categorized as ‘ROD’ (rapid oscillatory diving) in the Café (a) and in Hawaii (b).

<p>High-resolution time and depth data were corrected for local time and aggregated by cluster over a 24-hour period. The relative density of data (log scale) is shown on a gridded surface. Clustering analysis placed most ROD in the Café, but some occurred in Hawaii. However, the high vertical swimming speed characteristic of ROD in the Café was not present in Hawaii. While the overall depth distribution was similar there were clear differences apparent at time-scales below the cluster data bin size (24 hrs) including a strong daytime density band around 50 m in Hawaii. These differences illustrate that the ROD behavior in the Café is unique.</p

Using Stable Isotope Analysis to Understand the Migration and Trophic Ecology of Northeastern Pacific White Sharks (<em>Carcharodon carcharias</em>)

<div><p>The white shark (<em>Carcharodon carcharias</em>) is a wide-ranging apex predator in the northeastern Pacific (NEP). Electronic tagging has demonstrated that white sharks exhibit a regular migratory pattern, occurring at coastal sites during the late summer, autumn and early winter and moving offshore to oceanic habitats during the remainder of the year, although the purpose of these migrations remains unclear. The purpose of this study was to use stable isotope analysis (SIA) to provide insight into the trophic ecology and migratory behaviors of white sharks in the NEP. Between 2006 and 2009, 53 white sharks were biopsied in central California to obtain dermal and muscle tissues, which were analyzed for stable isotope values of carbon (δ¹³C) and nitrogen (δ¹⁵N). We developed a mixing model that directly incorporates movement data and tissue incorporation (turnover) rates to better estimate the relative importance of different focal areas to white shark diet and elucidate their migratory behavior. Mixing model results for muscle showed a relatively equal dietary contribution from coastal and offshore regions, indicating that white sharks forage in both areas. However, model results indicated that sharks foraged at a higher relative rate in coastal habitats. There was a negative relationship between shark length and muscle δ¹³C and δ¹⁵N values, which may indicate ontogenetic changes in habitat use related to onset of maturity. The isotopic composition of dermal tissue was consistent with a more rapid incorporation rate than muscle and may represent more recent foraging. Low offshore consumption rates suggest that it is unlikely that foraging is the primary purpose of the offshore migrations. These results demonstrate how SIA can provide insight into the trophic ecology and migratory behavior of marine predators, especially when coupled with electronic tagging data.</p> </div

White shark focal areas from satellite tag data from Jorgensen et al. [<b>4</b>].

<p>Regions used in the mixing model are indicated (California, Pelagic, Hawaii), see text for details. White shark aggregation sites in central California where tissue collection occurred are designated with the star. Mean chlorophyll-<i>a</i> concentration for 2006 (Aqua MODIS, <a href="http://oceanwatch.pfeg.noaa.gov" target="_blank">http://oceanwatch.pfeg.noaa.gov</a>) showing productivity gradients which isotopic gradients generally follow. Inset shows conceptual diagram showing how the seasonal migration of white sharks take them between regions with isotopically distinct prey.</p

Relationship between white shark length (TL) and δ¹³C and δ¹⁵N of white shark muscle.

<p>The two ellipses contain the δ¹³C and δ¹⁵N values of two of the smallest sharks that had the highest δ¹³C and δ¹⁵N values.</p