Native freshwater species get out of the way: Prussian carp (Carassius gibelio) impacts both fish and benthic invertebrate communities in North America

Abstract

Prussian carp (Carassius gibelio) are one of the most noxious non-native species in Eurasia. Recently, Prussian carp, a non-native freshwater fish species, were genetically confirmed in Alberta, Canada and have been rapidly expanding their range in North America since establishment. Given their rapid range expansion, there is an increasing need to determine how Prussian carp may impact native species. We assessed the severity of the Prussian carp invasion by (i) determining their impact on fish communities, (ii) assessing their impact on benthic invertebrate communities, (iii) evaluating if Prussian carp alter abiotic conditions, and (iv) identifying where we find higher abundances of Prussian carp. When Prussian carp were established, we found significant changes to the fish community. Correspondingly, the degree of impact to benthic invertebrate communities was related to the stage of invasion (none, early or recent), where changes in fish communities were significantly concordant with changes in benthic invertebrate communities. Finally, we found that higher abundances of Prussian carp were significantly associated with lower abundances of a majority of native fish species. Altogether, using three lines of evidence, we determine that Prussian carp can have wide-ranging impacts on freshwater ecosystems in North America, pressing the need for management intervention.

Keywords: before–after comparison; benthic invertebrates; concordance; freshwater fishes; non-native species; time since invasion.

Figure 1.

(a) The 2014 sampling locations in the Red Deer River watershed (light grey) located within Alberta, Canada. Sites with only samples from 2014 are denoted by white circles and those sites with samples from 2005 to 2014 are denoted by a cross. The dashed black line is the estimated range extent of Prussian carp as of 2014. (b) All confirmed presences of Prussian carp (white triangles) as of 2014 overlaid on the kernel density estimate (number of presences per 0.25 km²).

Figure 2.

Principal components analysis of fish community composition for sites (a) before (2005) and after (2014) the presence of Prussian carp (n = 28) and (b) sites that have not been invaded, experienced an early invasion (4–9 years) or had a recent invasion (1–3 years) by Prussian carp (n = 42). Also shown are 50% confidence ellipses in (a) for before (green) and after (red), and in (b) for none (green), early (red) and recent (yellow) sites, alongside arrows that denote the temporal change in the centroid position of the ellipses. Species codes are listed in electronic supplementary material, table S2.

Figure 3.

Principal components analysis of benthic invertebrate communities at sites (n = 22) that have not been invaded, experienced an early invasion (4–9 years) or had a recent invasion (1–3 years) by Prussian carp. Also shown are 50% confidence ellipses for none (green), early (red) and recent (yellow) sites, alongside arrows that denote the temporal change in the centroid position of the ellipses. Species codes can be found in electronic supplementary material, table S1.

Figure 4.

Comparison of mean differences with 95% CI in environmental characteristics at sites (n = 28) before (white bars) and after (grey bars) the presence of Prussian carp, corresponding to sampling in 2005 and 2014. * denotes significance at p < 0.05 for permuted t-tests.

Figure 5.

Comparison of mean differences with 95% CI in environmental characteristics measured in 2014 sampling at sites (n = 42) that have not been invaded (white bars), experienced an early invasion (light grey bars; 4–9 years) or had a recent invasion (dark grey bars; 1–3 years) by Prussian carp. * denotes significance at p < 0.05 for permuted ANOVAs.