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RESEARCH ARTICLE

Trophic ecology of Humboldt squid (Dosidicus gigas) in the oceanic waters off Ecuador: insight from isotopic signature analysis on beaks

Guan Yu Hu A B , Jian Hua Li B , Bi Lin Liu https://orcid.org/0000-0002-0701-0741 B C D E * , Na Liu B and Xin Jun Chen https://orcid.org/0000-0001-6311-6842 B C D E *
+ Author Affiliations
- Author Affiliations

A State Key Laboratory of Marine Geology, Tongji University, Shanghai, 200092, P.R. China.

B College of Marine Sciences, Shanghai Ocean University, Shanghai, 201306, P.R. China.

C The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources, Ministry of Education, Shanghai, 201306, P.R. China.

D National Engineering Research Center for Oceanic Fisheries, Shanghai, 201306, P.R. China.

E Key Laboratory of Oceanic Fisheries Exploration, Ministry of Agriculture and Rural Affairs, Shanghai 201306, P.R. China.


Handling Editor: Haseeb Randhawa

Marine and Freshwater Research 73(4) 469-477 https://doi.org/10.1071/MF21183
Submitted: 23 June 2021  Accepted: 15 November 2021   Published: 22 December 2021

© 2021 The Author(s) (or their employer(s)). Published by CSIRO Publishing.

Abstract

The sclerotised beaks of cephalopods have emerged as useful material to track their habitat and trophic ecology by using stable isotope analysis, because beaks grow continuously throughout their life without replacement. Here, stable isotopes of δ13C and δ15N in five continuous sections along the crest were measured to investigate the potential ontogenetic habitat shift and foraging-ecology change of Dosidicus gigas from the oceanic waters off Ecuador. In total, 90 sections from 18 upper beaks were examined with δ13C values of −18.99 to −17.49‰ and δ15N values of 0.69 to 7.09‰. Kruskal–Wallis test showed that there were significant differences in both isotopes between sections. The result of generalised additive models showed a significant overall decrease in both δ13C and δ15N values across the beak crest. The corrected standard ellipse area (SEAc) of the beak sections was 0.48 to 0.93‰2, with no high overlap between the two sections, with values ranging from 0.00 to 0.57. High individual variation of δ15N values in most beak sections indicated that D. gigas in our study area appears to have a generalist food spectrum in most of its life history, except for the stage just before being captured.

Keywords: beak, Dosidicus gigas, δ13C, δ15N, feeding, habitat, ontogenetic, isotopic niche.


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