Abstract
A wide trophic niche and high trophic plasticity are often invoked to explain the successful establishment of many aquatic invaders, but there is little information regarding the diet of most invasive fish in European waters. We combined stomach content and stable isotope analysis (SIA) of 13C and 15N to examine the trophic niche of the highly invasive topmouth gudgeon (Pseudorasbora parva) in four contrasting ponds and reservoirs in South Wales. Marked differences in diet and trophic position were found among neighbouring systems only a few kilometres apart. The most diverse diet was found in ponds with the fewest number of inter-specific competitors, and resulted in topmouth gudgeon having the highest condition factor, the widest variation in δ13C and δ15N values, and the highest carbon content, typical of generalist feeders. In contrast, topmouth gudgeon that coexisted with other cyprinids, were much more likely to have empty stomachs and relied almost exclusively on plant seeds, resulting in fish having a poor condition factor and low trophic position. Comparisons with other trophic studies indicate that variation in isotope values among neighbouring sites can exceed variation across continents, making it difficult to predict the diet or trophic impacts of the invasive topmouth gudgeon. Given the importance of obtaining reliable data on trophic position for risk assessment, our study shows that the use of SIA could be used to prioritize control and eradication measures that take into account trophic plasticity.
Highlights
The topmouth gudgeon (TMG, Pseudorasbora parva) is a highly invasive fish native of Asia that has become one of the worst aquatic invaders in Europe due its potential impact on native biodiversity (Pinder et al, 2005; Britton et al, 2007)
We analyzed 118 topmouth gudgeon originating from four contrasting water bodies in South Wales (Figure 1 and Table 1) that differed greatly in size, use, and fish community composition: two small decorative ponds with few or no fish species other than eel (Turbine Pond, TUR, n = 27; Dyfatty pond, DYF, n = 29), a eutrophic pond used for recreational fishing regularly stocked with eight species of coarse fish (Sylen Lake, SYL, n = 30), and a larger, cooler reservoir used for water supply and stocked with salmonids (Upper Lliedi Reservoir, LLI, n = 32)
There were no significant differences between ponds in the length or weight after Tukey’s HSD correction (Figures 2A,B) but there was a significant difference in condition factor [F(3,114) = 5.05, P = 0.003; Figure 2C] with fish in Turbine Pond having a better condition than those in Dyfatty pond (P = 0.006) or the Upper Lliedi Reservoir (P = 0.003)
Summary
The topmouth gudgeon (TMG, Pseudorasbora parva) is a highly invasive fish native of Asia that has become one of the worst aquatic invaders in Europe due its potential impact on native biodiversity (Pinder et al, 2005; Britton et al, 2007). Topmouth gudgeon has been found to compete for food with native species in Great Britain (Britton et al, 2010), Belgium (Declerck et al, 2002), and Poland (Witkowski, 2002) which can lead to depressed growth rates, reduced reproduction outputs and shifts in the trophic position of native fish (Britton et al, 2010). When other invasive species are present, the topmouth gudgeon’s plasticity in food selection allows it to shift its trophic niche and co-exist with other invaders (Jackson and Britton, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
