Temporal variability in lotic macroinvertebrate communities associated with invasive signal crayfish (Pacifastacus leniusculus) activity levels and substrate character

Abstract

Invasive signal crayfish (Pacifastacus leniusculus) are considered to be the most prevalent non-native crayfish species in Europe. Where large populations become established they have significant and long-term effects on benthic macroinvertebrate communities. However, much less is known about how community effects associated with crayfish invasion change in the short-term as a function of varying activity levels during the summer months. We examined the macroinvertebrate community composition of two lowland UK rivers, one which supported a well-established non-native crayfish population (invaded) and one in which crayfish had not been recorded (control). Colonisation cylinders were deployed which recorded community composition over a 126-day time period. Results indicate that once the activity period commences, invasive crayfish consistently altered macroinvertebrate community structure regardless of substrate character. Invaded communities displayed reduced beta-diversity compared to control sites. However, effects on the macroinvertebrate assemblage varied over the period when crayfish were active probably reflecting the behavioural activity of crayfish (which intensifies with increasing water temperature and during the spawning season) and life histories of other macroinvertebrates. The results indicate that crayfish invasions modify macroinvertebrate community composition, but over shorter timescales, the effects vary associated with their activity levels.

Flow regimes control the establishment of invasive crayfish and alter their effects on lotic macroinvertebrate communities

“…where populations are often well-established (Crawford, Yeomans, & Adams, 2006;Mathers et al, 2018;Ruokonen, Karjalainen, & Hämäläinen, 2014; but see Mathers, Chadd, Dunbar, et al, 2016;Ruokonen et al, 2016). In general, invasion by P. leniusculus results in modifications to macroinvertebrate communities associated with selective predation of certain Hirudinea, Gastropoda and Bivalvia taxa, which display limited locomotion and predator avoidance trait affinities (Dorn, 2013;Stenroth & Nystrom, 2003;Weber & Lodge, 1990).…”

“…A number of crawling ephemeroptera taxa are preferentially predated on by P. leniusculus (e.g. Caenis sp., Habrophlebia fusca) reducing their densities in invaded rivers (Mathers, Chadd, Dunbar, et al, 2016;Mathers et al, 2018) which may leave them highly vulnerable to local extirpation during high spring flows (Adámek, Konečná, Podhrázská, Všetičková, & Jurajdová, 2016;Wood et al, 2000). A reduction in functional evenness may have considerable repercussions in controlling future invasion resistance with an even distribution of traits enabling higher invasion resistance (Dukes, 2001) and may therefore make waterbodies supporting invasive species more susceptible to future invasions.…”

“…As such, where they successfully establish, ecological effects can cascade throughout the food web associated with their polytrophic feeding habits. Modifications have been reported in detrital processing rates and algal composition (Carvalho, Pascoal, Cássio, & Sousa, 2016;Creed, 1994) through to reductions in the density and richness of macroinvertebrates (Mathers, Rice, & Wood, 2018;Stenroth & Nystrom, 2003) and macrophytes (Lodge & Lorman, 1987;Roessink, Gylstra, Heuts, Specken, & Ottburg, 2017). The ecological consequences of crayfish invasion can be temporally persistent (decadal) and spatially extensive (regardless of biogeographical context), with modifications in macroinvertebrate community composition representing significant and long-term ecological perturbations (Mathers, Chadd, Dunbar, et al, 2016;Ruokonen, Ercoli, & Hämäläinen, 2016).…”

Behavioral Interactions and Trophic Overlap between Invasive Signal Crayfish Pacifastacus leniusculus (Decapoda, Astacidae) and Native Fishes in Iberian Rivers

“…These findings indicated a foraging strategy more "generalist" for crayfish (e.g., [40]), whereas fish species followed a more "predatory" feeding tactic on invertebrates. This would be related to an ecological role for signal crayfish as a wide omnivorous species, affecting different levels of the freshwater trophic web [60,61]. As it was stated in the Methods section, the present study used dietary data from different years (see above).…”

“…In particular, summer drought can be ecologically "severe" in northern rivers of the Iberian Peninsula under partly Mediterranean climate conditions [62]. Moreover, signal crayfish populations can reach high densities in the study rivers [70], with the pressure on benthic invertebrates being increased accordingly [61]. However, the relationship between competition and niche overlap is highly complex and difficult to evaluate in field studies.…”