Seasonal and ontogenetic variation of whiting diet in the Eastern English Channel and the Southern North Sea.

Charles-André Timmerman,Pierre Cresson,Paul Marchal,Margaux Denamiel,Clémence Couvreur,Takefumi Nakazawa

doi:10.1371/journal.pone.0239436

Abstract

An accurate description of trophic interactions is crucial to understand ecosystem functioning and sustainably manage marine ecosystems exploitation. Carbon and nitrogen stable isotopes were coupled with stomach content analyses to investigate whiting (Merlangius merlangus, Linnaeus, 1758) feeding behavior in the Eastern English Channel and Southern North Sea. Whiting juveniles and adults were sampled in autumn and winter to investigate both ontogenetic and seasonal changes. In addition, queen scallops (Aequipecten opercularis) samples were collected along with fish to be used as isotopic benthic baseline. Results indicated an ontogenetic diet change from crustaceans to fish and cephalopods. In autumn, δ15N values generally increased with fish size while in winter, a decrease of δ15N values with fish size was observed, as a potential result of spatial variation in baseline δ15N values. In winter, a nutrient-poor period, an increase in feeding intensity was observed, especially on the copepod Temora longicornis. This study provides further insights into whiting trophic ecology in relation to ontogenetic and seasonal variations, and it confirms the importance of combining several trophic analysis methods to understand ecosystem functioning.

Highlights

Since trophic interactions shape communities’ structure, determining fish diet is a key prerequisite for a better understanding of ecosystem functioning [1, 2] and a sustainable management of marine ecosystems [3, 4]
Trophic interactions play a central role on ecosystem functioning, implying transfer of energy and nutrients between species [7] and trophic cascades [1, 8], the understanding of which is necessary to gain knowledge on food webs structure and eventually inform ecosystem-based management [3, 4, 9]
Average size was similar at both seasons for both the whole dataset (246 ± 89 mm in autumn, 257 ± 76 mm in winter) and the subsample considered for stable isotopes (252 ± 83 mm in autumn, 262 ± 76 mm in winter)

Summary

Introduction

Since trophic interactions shape communities’ structure, determining fish diet is a key prerequisite for a better understanding of ecosystem functioning [1, 2] and a sustainable management of marine ecosystems [3, 4]. Ecosystem functioning refers to biotic and abiotic processes that occur within an ecosystem and determine its structure and stability [5, 6]. Trophic interactions play a central role on ecosystem functioning, implying transfer of energy and nutrients between species [7] and trophic cascades [1, 8], the understanding of which is necessary to gain knowledge on food webs structure and eventually inform ecosystem-based management [3, 4, 9].

Objectives

Methods

Results

Conclusion