Trophic Interactions of Common Elasmobranchs in Deep-Sea Communities of the Gulf of Mexico Revealed through Stable Isotope and Stomach Content Analysis

Authors

Diana A. Churchill, Florida International University
Michael Heithaus, Florida International University
Jeremy Vaudo, Florida International UniversityFollow
R. Dean Grubbs, Florida State University
Kirk Gastrich, Florida International University
Jose I. Castro, National Oceanic and Atmospheric Administration

Document Type

Article

Publication Title

Deep Sea Research Part II: Topical Studies in Oceanography

ISSN

0967-0645

Publication Date

5-2015

Keywords

Stable isotopes, Deep-sea, Shark, Feeding behavior, Food web, Trophic structure, Gulf of Mexico

Abstract

Deep-water sharks are abundant and widely distributed in the northern and eastern Gulf of Mexico. As mid- and upper-level consumers that can range widely, sharks likely are important components of deep-sea communities and their trophic interactions may serve as system-wide baselines that could be used to monitor the overall health of these communities. We investigated the trophic interactions of deep-sea sharks using a combination of stable isotope (δ¹³C and δ¹⁵N) and stomach content analyses. Two hundred thirty-two muscle samples were collected from elasmobranchs captured off the bottom at depths between 200 and 1100 m along the northern slope (NGS) and the west Florida slope (WFS) of the Gulf of Mexico during 2011 and 2012. Although we detected some spatial, temporal, and interspecific variation in apparent trophic positions based on stable isotopes, there was considerable isotopic overlap among species, between locations, and through time. Overall δ¹⁵N values in the NGS region were higher than in the WFS. The δ¹⁵N values also increased between April 2011 and 2012 in the NGS, but not the WFS, within Squalus cf. mitsukurii. We found that stable isotope values of S. cf. mitsukurii, the most commonly captured elasmobranch, varied between sample regions, through time, and also with sex and size. Stomach content analysis (n=105) suggested relatively similar diets at the level of broad taxonomic categories of prey among the taxa with sufficient sample sizes. We did not detect a relationship between body size and relative trophic levels inferred from δ¹⁵N, but patterns within several species suggest increasing trophic levels with increasing size. Both δ¹³C and δ¹⁵N values suggest a substantial degree of overlap among most deep-water shark species. This study provides the first characterization of the trophic interactions of deep-sea sharks in the Gulf of Mexico and establishes system baselines for future investigations.

DOI

10.1016/j.dsr2.2014.10.011

Volume

115

First Page

92

Last Page

102

Comments

©2014 Elsevier Ltd. All rights reserved.

NSUWorks Citation

Diana A. Churchill, Michael Heithaus, Jeremy Vaudo, R. Dean Grubbs, Kirk Gastrich, and Jose I. Castro. 2015. Trophic Interactions of Common Elasmobranchs in Deep-Sea Communities of the Gulf of Mexico Revealed through Stable Isotope and Stomach Content Analysis .Deep Sea Research Part II: Topical Studies in Oceanography : 92 -102. https://nsuworks.nova.edu/occ_facarticles/858.