Abstract
Carbon and nitrogen isotope profiles constructed from the upper beaks of four giant squid Architeuthis dux from the Bay of Biscay and Namibian waters provided a time-integrated record of their diet. Values of delta N-15 ranged from 5.5 to 13.4% and of delta C-13 from 214.4 to 217.8%. Nitrogen isotope profiles differed significantly in shape among the four animals analysed, but delta N-15 increased along each profile, with lowest values around the rostral tip. The difference between the lowest and the highest delta N-15 values was similar to 5.8%, slightly less than a two-level difference between the trophic position of small and large A. dux. The increase in delta C-13 values was not as pronounced as for the delta N-15 profiles, but the changes suggest an ontogenetic shift in diet early in life from smaller prey of relatively low trophic status to larger prey of higher status. Fluctuations in delta C-13 values observed near the rostral tip may be associated with a greater intrinsic variability in the carbon isotope composition of relatively small prey, and/or transient migratory behaviour early in life. The relative stability of the delta C-13 profiles over the remainder of their lifespan is consistent with the hypothesis that adult giant squid inhabit relatively small, well-defined, and productive areas, where food resources have a constant carbon isotope composition.
Original language | English |
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Pages (from-to) | 1425-1431 |
Number of pages | 7 |
Journal | ICES Journal of Marine Science |
Volume | 67 |
Issue number | 7 |
Early online date | 4 Aug 2010 |
DOIs | |
Publication status | Published - Oct 2010 |
Keywords
- beak
- cephalopods
- giant squid
- stable isotopes
- trophic relationships
- nitrogen isotopes
- including giant
- Southern-Ocean
- fatty-acid
- carbon
- diet
- ratios
- ecology