Unexpected prey of juvenile spotted scat (Scatophagus argus) near a wharf: The prevalence of fouling organisms in stomach contents.

Xianzhi Lin,Simin Hu,Sheng Liu,Hui Huang

doi:10.1002/ece3.4380

Abstract

A knowledge of fish diets can contribute to revealing the trophic role and ecological function of species in aquatic ecosystems. At present, however, there are no efficient or comprehensive methods for analyzing fish diets. In this study, we investigated the diets of juvenile Scatophagus argus collected near a wharf in Daya Bay, China, by dissection and high‐throughput sequencing (HTS) using the 18S rDNA V4 region. Microscopy disclosed large amounts of bryozoans and unrecognizable detritus. In contrast, HTS analysis indicated that the fish diets were considerably more diverse than visual inspection suggested. After eliminating fish sequences, approximately 17,000 sequences from taxa in nine phyla (Ciliophora, Bryozoa, Annelida, Bacillariophyta, Chlorophyta, Arthropoda, Dinoflagellata, Tunicata, and Phaeophyta) were identified from the analysis of stomach contents. Twenty‐one food categories were identified, most of which (95.2%) were benthic fouling organisms that could easily be collected around wharfs. These consisted of bryozoans (31.9%), ciliates (45.7%), polychaetes (14.6%), and green algae (3.0%). Therefore, to adapt to anthropogenic habitat modification, the fish had probably shifted from planktonic to benthic feeding. The prevalence of fouling organisms in the stomachs of juvenile S. argus indicates that the fish have responded to habitat changes by widening their food spectrum. This adaptation may have increased their chances of survival. The fouling organisms that inhabit highly perturbed coastal ecosystems could represent a food source for animals at higher trophic levels. Our results accordingly suggest that human activity might significantly influence fish feeding behavior and material transfer along the food chain.

Highlights

high-throughput sequencing (HTS) was applied in an in situ dietary analysis of juvenile Scatophagus argus(Linnaeus 1766) collected from Daya Bay, Guangdong, China, a region that is under severe threat from human activity (Huang et al, 2015)
Some postdigestion stomach contents that were difficult to distinguish microscopically could be accurately identified using molecular methods, which require no special skills in anatomy, morphology, or taxonomy
HTS could produce a sufficient number of sequences for diet analysis even when it over-represented predator DNA

Summary

Introduction

KEYWORDS 18S rDNA, dietary analysis, high-throughput sequencing, juvenile fish 1 | INTRODUCTION The sequence data generated by HTS significantly expands existing knowledge on the food spectra of different predators because this technique can detect very rare prey species (Deagle et al, 2009). HTS was applied in an in situ dietary analysis of juvenile Scatophagus argus(Linnaeus 1766) collected from Daya Bay, Guangdong, China, a region that is under severe threat from human activity (Huang et al, 2015).

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Conclusion