Abstract
Shark-cephalopod interactions have been documented in trophic ecology studies around the world. However, there is little information about the encounters between white sharks Carcharodon carcharias and squids in the eastern North Pacific Ocean. Here we provide evidence of interactions between white sharks and large squids in the waters of Guadalupe Island, Mexico. Through the use of non-invasive techniques, we found the presence of evident scars made by large squids on the body of the white sharks, mainly on the head and trunk, of at least 14 sharks recorded during August–December in the years 2008, 2012, 2013, 2017 and 2019. The mean length of the white sharks was 3.7 m (SD ± 0.6; total length), although the majority of the sharks with scars were adult and subadult males (n = 9; 64%). One of these males was photographically recaptured during the same season in which the individual showed new scars, confirming that the squid-white shark interaction likely occurs near Guadalupe Island. Our results highlight the importance of the twilight zone for white sharks and the use of shared habitat and trophic interactions between squid and white sharks, in which future ecosystem studies should consider both species for management and conservation purposes.
Highlights
Shark-cephalopod interactions have been documented in trophic ecology studies around the world
In the eastern North Pacific Ocean, the white sharks evidence migratory patterns that involve their presence in an oceanic zone known as the Shared Offshore Foraging Area (SOFA) from February through June[6,7], and in the waters surrounding Guadalupe Island from July to F ebruary[8,9], with some sharks moving to Hawaii, the coast of Baja California and the Gulf of C alifornia[10,11]
A few weeks later, this shark was registered with new scars that were first recorded in September, October and November (Fig. 1a,b), which indicates that this interaction likely occurred in Guadalupe Island between September 9–21 (Table 1)
Summary
Shark-cephalopod interactions have been documented in trophic ecology studies around the world. Cephalopods can represent up to 98% of the diet biomass of species such as the blue shark Prionace glauca, the scalloped hammerhead Sphyrna lewini (68%), or the pelagic thresher Alopias pelagicus (69%), because they provide nutrients in terms of proteins, carbohydrates and fatty a cids[3,4] In some species such as the white shark Carcharodon carcharias, previous studies have suggested that cephalopods are an important component of their diet, since large amounts of squids have been found in their s tomachs[2,4], and are reflected in the isotopic values of their m uscle[5]. Code WS01 WS02 WS03 WS04 WS02 WS05 WS06 WS07 WS08 WS09 WS10 WS11 WS12 WS11 WS11 WS11 WS11 WS13 WS11 WS14
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