High-throughput sequencing outperforms traditional morphological methods in Blue Catfish diet analysis and reveals novel insights into diet ecology.

Heather K Evans,Kara B Carlson,Joseph D Schmitt,Aaron J Bunch,Frederick J Hoogakker

doi:10.1002/ece3.7460

Abstract

Blue Catfish Ictalurus furcatus are an invasive, yet economically important species in the Chesapeake Bay. However, their impact on the trophic ecology of this system is not well understood. In order to provide in‐depth analysis of predation by Blue Catfish, we identified prey items using high‐throughput DNA sequencing (HTS) of entire gastrointestinal tracts from 134 samples using two genetic markers, mitochondrial cytochrome c oxidase I (COI) and the nuclear 18S ribosomal RNA gene. We compared our HTS results to a more traditional “hybrid” approach that coupled morphological identification with DNA barcoding. The hybrid study was conducted on additional Blue Catfish samples (n = 617 stomachs) collected from the same location and season in the previous year. Taxonomic representation with HTS vastly surpassed that achieved with the hybrid methodology in Blue Catfish. Significantly, our HTS study identified several instances of at‐risk and invasive species consumption not identified using the hybrid method, supporting the hypothesis that previous studies using morphological methods may greatly underestimate consumption of critical species. Finally, we report the novel finding that Blue Catfish diet diversity inversely correlates to daily flow rates, perhaps due to higher mobility and prey‐seeking behaviors exhibited during lower flow.

Highlights

Blue Catfish Ictalurus furcatus (Figure 1) are an invasive species found in high abundance throughout the Chesapeake Bay (Bunch et al, 2018; Fabrizio et al, 2018)
The trophic ecology of invasive Blue Catfish has been investigated in several tidal rivers in Virginia (MacAvoy et al, 2001; Schloesser et al, 2011; Schmitt et al, 2019) and elsewhere in Chesapeake Bay (Aguilar et al, 2017; Iwanowicz et al, 2019) with high spatial and temporal resolution
Federally endangered Atlantic Sturgeon predation was not detected through morphological identification or DNA barcoding of unidentified diet tissues

Summary

| INTRODUCTION

Blue Catfish Ictalurus furcatus (Figure 1) are an invasive species found in high abundance throughout the Chesapeake Bay (Bunch et al, 2018; Fabrizio et al, 2018). We sought to gain a holistic view of diet behavior and of the potential impact of invasive Blue Catfish predation in a Chesapeake Bay tidal river ecosystem using high-throughput sequencing methods. To accomplish this objective, we conducted HTS of 134 Blue Catfish representing multiple life stages that were collected in the fall of 2016 from the Pamunkey River, Virginia. We sought to quantitatively compare our results using HTS methods to a Blue Catfish diet study that employed a hybrid approach using visual observations of stomach content coupled with barcoding of single, yet unidentifiable tissues (Schmitt et al, 2018)

| METHODS

Findings

| DISCUSSION