The impact of an invasive predator (Orconectes rusticus) on freshwater snail communities: insights on habitat-specific effects from a multilake long-term study

Abstract

Most studies of the impacts of invasive species are done at small spatial and short temporal scales, greatly limiting generalizations to natural ecosystems. In contrast, we examined the long-term, whole-lake impacts of predation by the introduced rusty crayfish ( Orconectes rusticus ) on snail communities in 10 lakes in northern Wisconsin, USA. In 1987 and 2002, crayfish and snails were surveyed in lakes that initially differed in O. rusticus abundance; during the 15 years between surveys, crayfish abundance changed substantially in four lakes. In the two lakes where O. rusticus populations increased from low to high densities, large reductions occurred in snail abundance. As predicted, snails declined much more in habitats preferred by O. rusticus (sand and cobble) than in habitats that are avoided by the crayfish (muck). In the two lakes where O. rusticus abundance decreased dramatically after 1987, no significant increase occurred in snail densities, illustrating the difference in response time of snail populations to release from predation relative to increasing predation. Contrary to prediction, no consistent difference in snail species composition existed between high and low crayfish density lakes.

Food web consequences of long-term invasive crayfish control

“…5). As expected from previous studies (e.g., Lodge and Hill 1994;Wilson et al 2004;Kreps et al 2012), total gastropod density increased approximately 300-fold in cobble habitat (Fig. 5A).…”

Comparing the effects of introduced signal crayfish and native noble crayfish on the littoral invertebrate assemblages of boreal lakes

“…However, our results differ from those reported by Nilsson et al (2012) who found that macroinvertebrate abundance was negatively affected by invasive rusty crayfish (Orconectes rusticus) in 10 Wisconsin lakes. This discrepancy might be accounted for by the generally low abundance of crayfish in boreal lakes (CPUE typically <<10 individuals; Erkamo et al 2010, Sandström et al 2014, including our study lakes (Table S1), compared to the large catches of O. rusticus typically reported from North American lakes (Kreps et al 2012, Nilsson et al 2012. Signal crayfish were introduced into our study lakes almost 20 y ago, and presumably, noble crayfish have occupied their lakes for a very long time.…”

“…Nevertheless, we urge caution when considering the introduction of signal crayfish to lakes like those in our study because the 2 species can differ in their effects on other ecosystem components, e.g., leaf-litter decomposition (Dunoyer et al 2014, Jackson et al 2014, macrophytes (Hansen et al 2013), fine sediment dynamics (Harvey et al 2014), or macroinvertebrates in other habitats than stony littoral zones. Influence of crayfish on invertebrate prey generally is habitat-specific (e.g., Kreps et al 2012, Hansen et al 2013. For instance, Ruokonen et al (2012) suggested that signal crayfish can exploit prey and have impacts at greater depths than noble crayfish, although this wider foraging range might not be relevant for our smaller, shallower lakes (Table S1).…”

The introduced signal crayfish and native noble crayfish have different effects on sublittoral macroinvertebrate assemblages in boreal lakes

“…Recent field studies and meta-analyses have shown that crayfish effects can be habitat-specific (Kreps et al 2012, Hansen et al 2013, Ruokonen et al 2014 or species-specific (Haddaway et al 2012, Jackson et al 2014. Furthermore, crayfish impacts might change in the long-term (Strayer et al 2006, Kelly et al 2013, and hence it has been stressed that effects should be investigated at large temporal scales to observe changes that develop in native biota over time.…”