Differences in the trophic niche along the gladius of the squids Illex argentinus and Doryteuthis gahi based on their isotopic values

• Published in: Regional studies in marine science 2017-03, Vol.11, p.17-22
• Main Authors: Rosas-Luis, Rigoberto, Navarro, Joan, Martínez-Baena, Francisco, Sánchez, Pilar
• Format: Article
• Language: English
• Subjects: Niche width; South Atlantic Ocean; Squids; Stable isotopes; Trophic ecology
• ISSN: 2352-4855; 2352-4855
• DOI: 10.1016/j.rsma.2017.02.003

The squids Doryteuthis gahi and Illex argentinus coexist in the Patagonian shelf and other oceanic waters of the South Atlantic Ocean. Both species perform movements to and from shallow waters related to their ontogenetic growth. To examine changes in the trophic habitats in both species and across the ontogeny, we analyzed the stable isotopic values of δ13C and δ15N in their gladii. Based on sections of the gladii, we compared the trophic niche in three stages (adult [the newest section], juvenile [middle section], and a near-birth section [near the conus]). δ13C and δ15N values differed significantly between the two species and between gladius segments, revealing interspecific and ontogenetic differences in the trophic niche width. In particular, differences between segments of the gladius concurred with the ontogenetic and spawning migrations of these squids, in the Patagonian Shelf. •δ15N values demonstrated that the trophic width of Doryteuthis gahi and Illex argentinus increases with increases in size.•δ13C values confirmed the in–off shore migration of both squid species in the Patagonian shelf.•Use of feeding sources varied according to the size of the squid and of each segment of the gladius analyzed. [Display omitted]