Abstract
Abstract Impacts of invasive signal crayfish Pacifastacus leniusculus on native species and ecosystems are widely recognised, but mostly through small‐scale studies and laboratory experiments that may not always reflect impacts in nature. Recorded effects of signal crayfish on fish populations are equivocal. In this study, using the before–after/control–impact and control–impact approaches, the effects of signal crayfish invasion on native fishes, particularly benthic fishes and young‐of‐year (YoY) salmonids, and macroinvertebrate communities, were determined on several spatial and temporal scales through three correlated study elements (S1–S3), in upland streams of the River Tees, England. In S1, we sampled fish and benthic macroinvertebrates of 18 streams identically in 2011 and 2018. These streams were categorised into two groups: (1) uninvaded (without signal crayfish in both sampling years; n = 7); and (2) invaded (with signal crayfish) streams, comprising pre‐invaded (invaded before 2011; n = 8) and newly invaded (invaded between 2011 and 2018, n = 3). Despite similar habitat conditions in both years (all variables p > 0.05) fish and macroinvertebrate communities changed over time in pre‐invaded streams and by comparison to uninvaded streams. A decline in the abundance of benthic fish and YoY salmonids was observed in pre‐invaded and newly invaded streams. Complete disappearance of bullhead Cottus perifretum following signal crayfish invasion was recorded in two pre‐invaded streams. In the second study, S2, we assessed within‐stream differences in fishes and macroinvertebrates in two Tees streams by comparing sections with (invaded) and without (uninvaded) signal crayfish. Compared to uninvaded sections, taxonomic richness and abundance of fish and macroinvertebrates were significantly lower in invaded sections, and the overall communities also differed significantly. In S3, long‐term data series (since 1990) of water quality and macroinvertebrates of six Tees streams comprising those invaded by signal crayfish (n = 3) and uninvaded (n = 3) were analysed. Water quality showed little change, or an improvement, over time but significant changes in the macroinvertebrate taxonomic richness and community structure occurred following signal crayfish invasion. Long‐term changes in macroinvertebrate communities in invaded streams tended to be due to declines in more sedentary taxa such as molluscs and cased trichopterans. Widespread and long‐term ecological disruption is occurring because of signal crayfish invasion in upland streams of the Tees catchment that may lead to a complete disappearance of some benthic fish species, as well as reduced densities of YoY salmonids and a shift towards less diverse macroinvertebrate communities, dominated by more mobile, crayfish‐resistant taxa.
Highlights
Among the reasons for declining biodiversity worldwide, biological invasion plays a key role (Dudgeon et al, 2006; Naeem, Duffy, & Zavaleta, 2012; Simberloff et al, 2013)
We show the effects of crayfish on native communities in invaded streams, compared to uninvaded habitats, on several spatial and temporal scales
Pairwise comparisons showed that the macroinvertebrate communities of invaded and uninvaded streams did not differ before signal crayfish invasion (PERMANOVA: p = 0.070), but differed significantly after invasion (p < 0.001; Table S1)
Summary
Among the reasons for declining biodiversity worldwide, biological invasion plays a key role (Dudgeon et al, 2006; Naeem, Duffy, & Zavaleta, 2012; Simberloff et al, 2013). Crayfish are among the largest and longest-lived freshwater invertebrates and where they occur they often form a major part of benthic biomass (Lodge & Hill, 1994; Sousa et al, 2013) They are omnivorous and their diet may include invertebrates, macrophytes, periphyton, detritus, fish, and other crayfish (Lirås et al, 1998; Momot, 1995; Nyström et al, 1996). They are commonly considered as ecosystem engineers, partly because of their role in the alteration of detrital processing rates (Carvalho et al, 2016; Creed & Reed, 2004), and by grazing plants (Creed, 1994; Matsuzaki et al, 2009; Nyström et al, 2001) and so are considered keystone consumers (Gheradi et al, 2011; Reynolds, 2011)
Sign-in/Register to view highlights & summary 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 callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
