Diet of European Catfish in a Newly Invaded Region

Abstract

Biological invasions are considered to be one of the leading causes of biodiversity loss worldwide. Freshwater ecosystems are amongst the most biodiverse, containing about 50% of the world’s known fish species but, ironically, are the most invaded ecosystems. In Portuguese freshwaters, there are currently 20 identified non-native fishes, arriving at an unprecedented rate of a new species every two years. A recent non-native is the European catfish Silurus glanis, a top predator native to Central and Eastern Europe, that arrived at the Lower Tagus (Portugal) circa 2006. This study compares the dietary habits of this top predator in two different habitats of the Lower Tagus in order to evaluate its potential impact. The stomach contents of 96 individuals were analyzed, 61 from the lotic environment and 35 from the lentic systems. A total of 66 stomachs contained prey items, 38 from the lotic and 28 from the lentic. Diet varied considerably between habitats, with shrimp and crayfish being the most abundant prey items in the lentic systems and shrimp and fish the most abundant prey items in the lotic section. Tendency to piscivory was observed in large-sized individuals. Overall, the findings in this study provide the first evidence of the potential impacts of European catfish through predation on the fish communities.

Variation in Diet Patterns of the Invasive Top Predator Sander lucioperca (Linnaeus, 1758) across Portuguese Basins

“…According to previous studies, see [64], a high species richness was described in the Tagus mainstem which is consistent with the higher prey diversity found in S. lucioperca in this site, observed as "Other Fish" (generally native fish). Finally, a similar pattern of increasing proportions of Atyidae in the diet has been observed in another top predator, the European catfish (Silurus glanis), in the lotic Tagus that exhibited lower fish prey richness and higher proportions of Crustaceans, see [65].…”

“…These findings are important for our efforts to maintain the integrity of the highly endangered native fish existing in Iberian watersheds, where native fish communities, originally devoid of any native predator, are highly vulnerable to new predators. In fact, it is urgent to evaluate the impact of these predators in riverine fish communities, generally dominated by natives, especially during their initial colonization (but see [65]). Describing the dietary traits of top predators, understanding their behavior and knowing their potential feeding preferences, are essential pieces of information to evaluate the predator impacts on our endemic fishes and enable a better conservation strategy focusing on these unique freshwater ecosystems.…”

Spoiled for Choice during Cold Season? Habitat Use and Potential Impacts of the Invasive Silurus glanis L. in a Deep, Large, and Oligotrophic Lake (Lake Maggiore, North Italy)

“…For the stomach content analysis, the catfish were divided into two size classes (Class I < 100 cm; Class II > 100 cm) following a previous work on catfish diet and corresponding to possible diet transitions according to body size [26]. To compare the feeding intensity and the amount of food ingested by catfish of different size classes and caught at different sites and habitats, the vacuity index (V I ) and fullness index (F I ) were calculated, where: V I is the proportion of empty stomach found with respect to the number of stomachs analyzed and is expressed as a percentage [52]; F I is the percent ratio between the total weight of a certain prey and the total weight of the predator [53].…”

“…European catfish is a top-predator, but, compared to other piscivorous fishes, it has a wider trophic niche [20,21,25] and its diet is unpredictable, especially in the invaded range, where the species adapts its diet to novel and available resources. For example, it has developed a new feeding behavior (i.e., "beaching behavior" [24]) to prey upon semiaquatic or terrestrial organisms, or it tends to feed upon other exotic species such as the invasive shrimp Dikerogammarus villosus (Sowinsky, 1894) or the invasive red swamp crayfish Procambarus clarkii Girard, 1852 [25,26]. Moreover, the diet of invasive catfish populations can vary from the earliest to the latest stages of the invasion [16] and with seasons [27].…”

An allometric niche model for species interactions in temperate freshwater ecosystems

“…We examined the inferred diets for three species not used in the calibration and whose actual diets have been widely described: the European catfish ( Silurus glanis ), the whitefish ( Coregonus lavaretus), and the gammarid shrimp ( Gammarus pulex ). The gammarid shrimp can feed on diverse food resources ranging from fragments of decaying terrestrial organic matter, fungi, bacteria, and algal biofilms (Graça et al 1993, MacNeil et al 1997, Maltby et al 2002, Franken et al 2005), the whitefish is zooplanktonophagus with a diet mainly composed of cladocerans and chironomids (Amundsen et al 2010, Anneville and Hamelet 2018), and the European catfish is omnivorous, feeding on various prey from invertebrates to fish (Carol et al 2009, Copp et al 2009, Ferreira et al 2019). We explored their inferred prey characteristics (i.e., identity, body size, prey preferences, and habitats) to complementarily evaluate how the aNM inferences would provide plausible trophic niches in relation to previous diet studies.…”