Feeding behaviour, predatory functional responses and trophic interactions of the invasive Chinese mitten crab (Eriocheir sinensis) and signal crayfish (Pacifastacus leniusculus)

Paula J Rosewarne,Christopher Grocock,Robert J.G Mortimer,Robert J Newton,Christopher D Wing,Alison M Dunn

doi:10.1111/fwb.12717

Paula J Rosewarne, Christopher Grocock + Show 4 more

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https://doi.org/10.1111/fwb.12717

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Abstract

Summary Freshwaters are subject to particularly high rates of species introductions; hence, invaders increasingly co‐occur and may interact to enhance impacts on ecosystem structure and function. As trophic interactions are a key mechanism by which invaders influence communities, we used a combination of approaches to investigate the feeding preferences and community impacts of two globally invasive large benthic decapods that co‐occur in freshwaters: the signal crayfish (Pacifastacus leniusculus) and Chinese mitten crab (Eriocheir sinensis). In laboratory preference tests, both consumed similar food items, including chironomids, isopods and the eggs of two coarse fish species. In a comparison of predatory functional responses with a native crayfish (Austropotamobius pallipes), juvenile E. sinensis had a greater predatory intensity than the native A. pallipes on the keystone shredder Gammarus pulex, and also displayed a greater preference than P. leniusculus for this prey item. In outdoor mesocosms (n = 16) used to investigate community impacts, the abundance of amphipods, isopods, chironomids and gastropods declined in the presence of decapods, and a decapod >gastropod >periphyton trophic cascade was detected when both species were present. Eriocheir sinensis affected a wider range of animal taxa than P. leniusculus. Stable‐isotope and gut‐content analysis of wild‐caught adult specimens of both invaders revealed a wide and overlapping range of diet items including macrophytes, algae, terrestrial detritus, macroinvertebrates and fish. Both decapods were similarly enriched in 15N and occupied the same trophic level as Ephemeroptera, Odonata and Notonecta. Eriocheir sinensis δ13C values were closely aligned with macrophytes indicating a reliance on energy from this basal resource, supported by evidence of direct consumption from gut contents. Pacifastacus leniusculus δ13C values were intermediate between those of terrestrial leaf litter and macrophytes, suggesting reliance on both allochthonous and autochthonous energy pathways. Our results suggest that E. sinensis is likely to exert a greater per capita impact on the macroinvertebrate communities in invaded systems than P. leniusculus, with potential indirect effects on productivity and energy flow through the community.

Highlights

Freshwaters are vulnerable to humanmediated introduction of invasive species due to their physical connectivity and high levels of human disturbance (Dudgeon et al, 2006), biological invasions are currently one of the most widespread and deleterious pressures on freshwater ecosystems (Leprieur et al, 2009; Ricciardi & Macisaac, 2011)
In outdoor mesocosms (n = 16) used to investigate community impacts, the abundance of amphipods, isopods, chironomids and gastropods declined in the presence of decapods, and a decapod >gastropod >periphyton trophic cascade was detected when both species were present
Eriocheir sinensis affected a wider range of animal taxa than P. leniusculus

Summary

Introduction

Freshwaters are vulnerable to humanmediated introduction of invasive species due to their physical connectivity and high levels of human disturbance (Dudgeon et al, 2006), biological invasions are currently one of the most widespread and deleterious pressures on freshwater ecosystems (Leprieur et al, 2009; Ricciardi & Macisaac, 2011). Understanding and quantifying the impacts invasive species have on the communities and ecosystems they invade is crucial for effectively targeting the limited resources available for management and control (Parker et al, 1999; Keller et al, 2011). The potentially complex interactions between invaders can mediate ecological outcomes, for example, by facilitating subsequent establishment of introduced species in an ‘invasion meltdown’ (Simberloff & Von Holle, 1999; Ricciardi, 2001), or modifying structural and functional impacts on the invaded community through additive or counteractive effects (Strayer, 2010; Preston, Henderson & Johnson, 2012; Jackson et al, 2014). Invaders can reduce the abundances of native species by direct predation and, through a variety of mechanisms, may exert a stronger predation pressure than functionally equivalent native predators (Noonburg & Byers, 2005; Salo et al, 2007). To disentangle the effects of multiple invaders in an ecosystem, it is necessary to quantify impacts (e.g. predation) for each species separately, and in combination to detect potential niche shifts and behavioural plasticity when invasive predators occur in sympatry

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