Shark predation on cephalopods in Mexico and EcuadorPublished online on 09. April 2013
Shark predation on cephalopods in the Mexican and Ecuadorian Pacific Ocean
Felipe Galván-Magaña, Carlos Polo-Silva, Sandra Berenice Hernández-Aguilar, Alejandro Sandoval-Londoño, Maria Ruth Ochoa-Díaz, Nallely Aguilar-Castro, David Castañeda-Suárez, Alejandra Cabrera Chavez-Costa, Álvaro Baigorrí-Santacruz, Yassir Eden Torres-Rojas, Leonardo Andrés Abitia-Cárdenas
Pelagic predators such as sharks have been shown to be effective cephalopod samplers, because they have high consumption rates and swimming speeds. The stomach contents of these predators allow us to determine the distribution and abundance of cephalopods, considering the scarcity of biological information and the difficulty of catching squids and octopi using traditional methods. The stomach contents of the silky shark (Carcharhinus falciformis), blue shark (Prionace glauca), scalloped hammerhead (Sphyrna lewini), smooth hammerhead (S. zygaena), pelagic thresher shark (Alopias pelagicus), and bigeye thresher shark (A. superciliosus) were caught off both coasts of Baja California Sur, Mexico and in the Ecuadorian Pacific Ocean. Cephalopod sizes (mantle lengths, ML) were calculated based in the beak measurements to determine the size of cephalopods consumed by the sharks. We identified 21 cephalopod species based on beak items found in the shark stomachs. The most abundant cephalopods consumed by sharks in both areas were Dosidicus gigas, Ancistrocheirus lesueurii, Onychoteuthis banksii, Sthenoteuthis ovalaniensis, Argonauta spp., Abraliopsis affinis, and Mastigoteuthis dentata. The cephalopod’s habitat provides information about the depth at which these sharks capture their prey. The blue shark feeds on cephalopods in epipelagic, mesopelagic, and bathypelagic waters; the silky shark feeds on cephalopods in epipelagic waters; and the scalloped hammerhead shark preys on cephalopods in neritic (bottom) and oceanic waters (epipelagic and mesopelagic). The pelagic thresher shark consumed epipelagic and neritic species; whereas the bigeye thresher shark feeds mainly on epipelagic and mesopelagic squids in Ecuadorian waters. The smooth hammerhead preys on epipelagic and mesopelagic squids off Mexico and Ecuador.
Deep Sea Research Part II: Topical Studies in Oceanography
In Press, Accepted Manuscript