Biological control of invasive populations of crayfish: the European eel (Anguilla anguilla) as a predator of Procambarus clarkii

Abstract

The red swamp crayfish, Procambarus clarkii, is a paradigmatic invader of freshwater systems. Several attempts have been made to mitigate its multiple impacts but none was successful. Among the different methods proposed, the use of the European eel (Anguilla anguilla) as an indigenous predator is promising but the available information about its predatory ability on crayfish is to date scanty. To fill this gap in knowledge, we ran three experiments in wetlands and irrigation ditches in Italy. The first experiment, in the laboratory, was aimed at quantifying the extent of predation by eels on crayfish, the second, in enclosures, the size classes of crayfish mainly preyed and the possible effect of the eels on P. clarkii behaviour, and the third, in the field, its ability to effectively reduce crayfish populations. Results showed that eels prey on small-sized or soft crayfish, attacking them from the back; an indirect effect was to reduce crayfish trophic activity, which in turn might increases crayfish mortality due to starvation and decreases impact on the community. However, as shown in the field, the use of eels should be appropriately calibrated to the context of application. Taken together, our results show that eels might be used as a complement to the traditional trapping method. However, additional studies are necessary to understand the adequate number of eels to be introduced and to develop appropriate methods for quantifying such effects.

A New Threat to Groundwater Ecosystems: First Occurrences of the Invasive Crayfish Procambarus clarkii (Girard, 1852) in European Caves

“…This successful invader, that can cause a large variety of impacts (see Savini et al, 2010), was first introduced in Portugal in the 1970s and then in Italy in the 1980s, and it has now colonized most of the surface freshwater systems of both countries (Correia, 2003;Aquiloni et al, 2010). Here we report the first occurrences of this invasive crayfish in some cave waters of Portugal and Italy and briefly discuss the implications of this discovery for this unique and complex aquatic environment.…”

Red swamp crayfish: biology, ecology and invasion - an overview

“…Furthermore, P. clarkii is one of the vectors of the crayfish plague, which is mostly asymptomatic in North American crayfish species such as P. clarkii, Orconectes limosus (Rafinesque, 1817) and Pacifastacus leniusculus (Dana, 1852), but lethal to crayfish from other regions (Souty-Grosset et al, 2006;Aquiloni et al, 2010;Longshaw, 2011). This disease, caused by Aphanomyces astaci, constitutes a remarkable threat to indigenous crayfish species, thus being one of the leading causes of native crayfish population decline in Europe (Gutiérrez-Yurrita et al, 1999;Souty-Grosset et al, 2006;Holdich et al, 2009).…”

“…Biological control methods were also employed worldwide, including the use of fish predators, disease-causing organisms and microbes that produce toxins (Holdich et al, 1999;Frutiger and Müller, 2002) but the only method that has been successful so far is the use of predaceous fish like eels, burbots, perches and pikes (Westman, 1991;Aquiloni et al, 2010;Freeman et al, 2010). Nevertheless, biocontrol might be risky since it may lead to new species introductions and it is not specific to the target organism, possibly also affecting native organisms as well.…”

Estimating age composition in Alpine native populations of Austropotamobius pallipes complex

“…The populations of the freshwater crayfish Austropotamobius pallipes (Lereboullet, 1858) species complex have undergone a remarkable contraction and decline on a widespread basis in Europe (Holdich, 2002;SoutyGrosset et al, 2006;Holdich et al, 2009), including Italy (Aquiloni et al, 2010). This decline is due to causes frequently linked to direct human action, such as habitat fragmentation, deforestation and water deterioration (Nardi et al, 2005;Trouilhe et al, 2007;Favaro et al, 2010).…”