Abstract
Simple SummaryNeogobius melanostomus is a highly invasive fish that has colonized most major European rivers and is dispersing into their tributaries. Its foraging behaviour does not show particular prey preferences, which makes predicting its interactions with endangered members of the macrozoobenthic community in tributaries a challenge. We observed the interaction of N. melanostomus and crayfish juvenile or A. aquaticus in single- and multiple-prey systems to better predict its ecological impact. The results suggest an impact of N. melanostomus on crayfish similar to that on A. aquaticus, potentially making it a threat to crayfish population stability. Destabilization of a keystone species such as crayfish in river tributaries may lead to a trophic cascade in the ecosystem with irreversible consequences.Despite the spread of round goby Neogobius melanostomus into freshwater streams, there is a lack of information with respect to its effect on macroinvertebrate communities, especially crustaceans. We studied foraging efficiency of N. melanostomus on Procambarus virginalis and Asellus aquaticus, using a functional response (FR) approach. Stocking density of the prey species was manipulated to determine its effect on consumer utilization, with prey offered separately or combined at 1:1, 3:1, and 1:3 at each tested density. For both prey species, N. melanostomus exhibited type II FR, occasionally with a high proportion of non-consumptive mortality. Procambarus virginalis suffered a significantly higher attack rate compared to A. aquaticus. Neogobius melanostomus killed significantly more of the most prevalent prey, regardless of species. In trials with prey species of equal proportions, a difference in the number of each species killed was observed only at the highest density, at which P. virginalis was preferred. Neogobius melanostomus may be an important driver of population dynamics of prey species in the wild. The non-selective prey consumption makes N. melanostomus a potential threat to macrozoobenthic communities of river tributaries.
Highlights
Crayfish have an impact at multiple trophic levels through predation, shedding, burrowing, and competition [1,2,3] and are considered keystone species influencing stability and functionality of ecosystems, in tributaries to major streams [4,5,6]
We used two hard-bodied benthic invertebrate prey species of similar body mass differing in escape strategy: The native water louse Asellus aquaticus (L.) (W = 5.56 ± 1.94 mg) is representative of isopods that form a component of the N. melanostomus diet [58,59]
Type II functional response (FR) was previously observed in N. melanostomus towards amphipods [49,51,73], A. aquaticus [49], and common carp Cyprinus carpio L. larvae [52] under experimental conditions
Summary
Crayfish have an impact at multiple trophic levels through predation, shedding, burrowing, and competition [1,2,3] and are considered keystone species influencing stability and functionality of ecosystems, in tributaries to major streams [4,5,6]. Crayfish populations worldwide are threatened by multiple stressors: Climate change, water pollution, habitat modification, invasive species, and disease [5,7]. One third of crayfish species worldwide are threatened with extinction [7]. Throughout the world [9,10] aim to improve the ecological status of freshwater lotic ecosystems, the threat presented by non-indigenous species is ever-increasing [11]. In addition to interactions with non-indigenous crayfish, native crayfish interact with small benthic fishes, including non-native species [1]. The round goby Neogobius melanostomus (Pallas 1814), among the most invasive of freshwater fish species [12], has expanded substantially beyond its native range the PontoCaspian region. It poses a serious threat to freshwater and brackish ecosystems [13]
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