Potential effects of the invasive ‘killer shrimp’ (Dikerogammarus villosus) on macroinvertebrate assemblages and biomonitoring indices

Abstract

Summary 1. Water quality monitoring data from 10 watercourses and laboratory mesocosm studies were used to assess the potential impacts of the crustacean amphipod invader Dikerogammarus villosus on resident macroinvertebrate assemblage structure in Central European fresh waters. 2. The presence of D. villosus was associated with a decline in the prevalence of many native species, pollution sensitive as well as pollution tolerant, and changes in biotic indices, despite the trends of improved water quality coinciding with the invasion period. A general increase in the prevalence of other invaders was also noted. The potential impacts of D. villosus were substratum dependent, differing between stone, concrete and sand‐dominated sites. 3. Mean Multimetric Macroinvertebrate Index Flanders (MMIF) values were marginally lower when D. villosus was present (P < 0.06), as opposed to when other amphipod species or no amphipods were present, despite the improved water quality. Mesocosm studies showed that several macroinvertebrate taxa were completely eliminated in treatments with D. villosus, oligochaete worms, Caenidae mayfly, chironomids and tipulids being particularly vulnerable to D. villosus predation. Biological Monitoring Working Party (BMWP) scores were lower in mesocosms with D. villosus as opposed to the native Gammarus pulex or no amphipods at all. 4. We predict that resident macroinvertebrate assemblages in both Central Europe and Britain will come under increasing pressure as D. villosus invasions progress. Consequently, macroinvertebrate biotic indices, such as the MMIF or BMWP, may need to be revised to account for changes in taxa sensitivities to water quality as well as increased predation and competition.

The long-term effects of invasive signal crayfish (Pacifastacus leniusculus) on instream macroinvertebrate communities

“…The results of this research clearly demonstrate that the predation and interaction of an invasive species with the receiving ecosystem can significantly modify aquatic community composition. These community modifications may thereby potentially affect the results of widely utilised biomonitoring indices and as a result care should be taken when interpreting routine biomonitoring data (i.e water quality, river flow or fine sediment pressures) where non-native / invasive taxa are known to be present (MacNeil et al, 2013, Mathers et al, 2016. This study highlights the value and need for further multi-scale research to fully understand the wider spatial and temporal implications of historic invasions to complement reach scale and mesocosm studies (Wilson et al, 2004;McCarthy et al, 2006).…”

Size matters: predation of fish eggs and larvae by native and invasive amphipods

“…The 'killer shrimp' D. villosus is spreading across Europe with significant ecological impacts, including declines in resident macroinvertebrate populations attributed to predation by the invader (Dick and Platvoet 2000;Josens et al 2005;van Riel et al 2006;MacNeil et al 2013). Since D. villosus has been observed to feed upon fish eggs and larvae, there is concern over its potential impact on biologically and commercially important fish populations.…”

“…Invasion by D. villosus frequently coincides with the decline or extinction of resident benthic macroinvertebrates such as isopods, tubificids and amphipods (Dick and Platvoet 2000;Dick et al 2002;Kley and Maier 2003;Josens et al 2005;Boets et al 2010;MacNeil et al 2013;Dodd et al 2014;Gergs and Rothhaupt 2015). Thus, once established D. villosus typically dominates the macroinvertebrate community in both number and biomass (Josens et al 2005;van Riel et al 2006).…”

“…Predation by D. villosus may be an important mechanism behind these changes. In the laboratory, D. villosus will consume a wide range of animal prey, including aquatic bugs, leeches, isopods, juvenile crayfish, chironomid larvae, odonate larvae, ephemeropteran larvae and even other amphipods (Dick and Platvoet 2000;Platvoet et al 2009;Boets et al 2010;MacNeil et al 2013). Stable isotope and fatty acid analyses suggest predatory tendencies tend to be retained in the field (van Riel et al 2006;Maazouzi et al 2007; but see Hellmann et al 2015).…”

Baseline histopathological survey of a recently invading island population of ‘killer shrimp’, Dikerogammarus villosus

“…Several life history characteristics of D. villosus are important for its success as an invader; these include a high salinity tolerance (Bruijs et al 2001, an ability to survive and grow in a wide range of temperatures (Maazouzi et al 2011), rapid growth and early maturation, with short interbrood periods (Piscart et al 2003, Devin et al 2004, high fecundity (Kley & Maier 2003, Pöckl 2007, an omnivorous diet (Krisp & Maier 2005) and a capability to compete with, and prey upon, a range of cohabiting taxa, including those se veral trophic levels above itself (Dick et al 2002, Krisp & Maier 2005, MacNeil et al 2013. These attributes have resulted in D. villosus out-competing other gammarids within Europe, including Gamma rus pulex (Boets et al 2010), G. tigrinus and G. due beni (Dick & Platvoet 2000).…”