Is European catfish a threat to eels in southern France?

Abstract

ABSTRACT1. European eel (Anguilla anguilla) is recognized as a critically endangered species in the northern hemisphere. Threats such as overfishing or pollution are well known as risks for eel populations. However, much less is known about the impact of introduced fish on European eels. In particular, introduced large-bodied predators could become new predators to eels.2. The potential impact of European catfish (Silurus glanis L) on an eel population in the Camargue, southern France was studied using a combination of stable isotope and gut content analyses.3. Only large-bodied catfish (4500 mm) can consume numerous fish prey. However, catfish mostly consumed crayfish (Procambarus clarkii), these prey items being found in 79% of the guts of the largest individuals. Eel was absent from the dissected catfish guts. A mixing model based on Bayesian inference revealed that catfish diet included only 5% (0-8.5%) of marine sources (both eel and mullet).4. While local economic interests prompted ecological studies to assess whether catfish exerted a new and strong predatory pressure on eel, this study found that European catfish behaved as an opportunistic omnivore, and as such was not a direct threat as a predator on eel populations in the Camargue.

Introduction of exotic fish species and decline of native species in the lower Po basin, north‐eastern Italy

“…It is well documented that wels catfish takes advantage of its diet plasticity and ability to prey upon the most abundant available species of a suitable size within its habitat (Carol et al ., ; Syväranta et al ., ; Martino et al ., ). This may have contributed to the sequence of the decline in species.…”

Native European eels as a potential biological control for invasive crayfish

“…European ecosystems have been threatened by a number of non‐native crayfish species, the red swamp crayfish ( Procambarus clarkii ) being one of the most significant (Gherardi et al ., ). P. clarkii represents an important source of prey for several species of birds (Barbraud et al ., ; Poulin, Lefebvre & Crivelli, ), mammals (Beja, ), reptiles (Ottonello, Salvidio & Rosecchi, ) and fish (Martino et al ., ). However, the introduction of P. clarkii may have severe impacts, affecting many ecosystem properties ranging from physical habitat structure to food webs.…”

“…Predators appear to be one of the best biocontrol agents for red swamp crayfish (Gherardi et al ., ). While burbot ( Lota lota ), perch ( Perca fluviatilis ), pike ( Esox lucius ) and wels catfish ( Silurus glanis ) are well‐known predators of P. clarkii (Westman, ; Martino et al ., ), the European eel ( Anguilla anguilla ) is also known to prey on benthic invertebrates and fish, especially when the prey are large (Dörner et al ., ). Eels might prove effective predators of the crayfish because of two morphological advantages: they can detect crayfish by odour (Blake & Hart, ), and their body shape allows them to enter crayfish burrows and consume hidden crayfish (Aquiloni et al ., ).…”

Move or die: change in European catfish (Silurus glanisL.) behaviour caused by oxygen deficiency

“…The European catfish (Silurus glanis L.) is a common inhabitant of rivers, old oxbows and shallow alluvial lakes in the Eurasian temperate zone. Although S. glanis is native to mainland Europe, reaching the Rhine River in the west, it has also been introduced into a number of countries in southern and western Europe, and its possible predation and competitive impact on native species is being increasingly studied and discussed (Copp et al, 2009;Bevacqua et al, 2011;Martino et al, 2011). The European catfish exhibits site fidelity and utilises a stable 'resting place' (Carol et al, 2007).…”