Assessing the diet and trophic level of marine fauna in a fishing ground subject to discarding activity using stable isotopes

Type Article
Date 2022
Language English
Author(s) Lejeune BenjaminORCID1, 2, Kopp DorotheeORCID2, Mehault SoniaORCID2, Mouchet Maud Aline1
Affiliation(s) 1 : Centre d’Ecologie et de Sciences de la Conservation, CNRS-MNHN-SU, Paris, France
2 : DECOD (Ecosystem Dynamics and Sustainability), IFREMER, INRAE, Institut Agro—Agrocampus Ouest, Lorient, France
Source Plos One (1932-6203) (Public Library of Science (PLoS)), 2022 , Vol. 17 , N. 6 , P. e0268758 (17p.)
DOI 10.1371/journal.pone.0268758
WOS© Times Cited 1

Discarding practices have become a source of concern for the perennation of marine resources, prompting efforts of discard reduction around the globe. However, little is known about the fate of discards in marine environments. Discarding may provide food for various marine consumers, potentially affecting food web structure and stability. Yet, quantifying reliance upon discards is difficult because identity and frequency of discards may change according to multiple factors, and most previously used diet assessment techniques do not allow to assume consistency of feeding strategies over time. One currently untested hypothesis is that significant contribution of discards over time should reflect in increased trophic level (TL) of marine fauna, particularly in low TL consumers. Here, we explored this hypothesis by modeling the TL and assimilated diet of consumers living in fishing grounds subject to important discarding activity using stable isotope analysis. We found indications that benthic invertebrates and Chondrichthyes may depict a higher than expected TL, while other fish tend to depict similar to lower TL compared to global averages from the literature. Based on prior knowledge of discard consumption in the same area, stable isotope mixing models congruently revealed that discards may represent substantial portions of the assimilated diet of most benthic invertebrate macrofauna, cephalopods and Chondrichthyes. We highlight limitations and challenges of currently used diet assessment techniques to study discard consumption and stress that understanding their reintegration in marine food webs is crucial in the context of an ecosystem approach to fisheries management and to better understand the functioning of marine ecosystems subject to fishing.

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Publisher's official version 17 742 KB Open access
S1 Table. Raw stable isotope data. 5 446 KB Open access
S1 Fig. Dendrogram of the clustering analysis using the UPGMA method, highlighting the 6 trophic groups identified within the consumers community. 1 19 KB Open access
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