Contrasting effects of an invasive crayfish (Procambarus clarkii) on two temperate stream communities

Abstract

1. The effects of omnivorous exotic species on native communities are often difficult to predict because of the broad diets and behavioural flexibility of the omnivore, and the diverse abiotic and biotic characteristics of invaded systems. We investigated experimentally the effects of a gradient of density of the introduced, omnivorous red swamp crayfish Procambarus clarkii (Decapoda: Cambaridae) on two stream communities in southern California, U.S.A. 2. The Ventura River is a clear, flowing stream with a cobble substratum, with abundant algae but low densities of large invertebrates, small herbivores and snails. The Santa Ynez River at the time of the study consisted of a series of drying pools underlain by sand, with abundant charophytes, large predatory invertebrates and herbivores, including snails. 3. In the Ventura River, periphyton biomass and inorganic sediment decreased with increasing crayfish abundance, but in the Santa Ynez River, periphyton and sediment were unrelated to crayfish densities. 4. In the Ventura River, the biomass and density of all benthic invertebrates combined, chironomids, micropredators, the meiofauna (chydorid cladocerans, copepods and ostracods), and specific predatory and herbivorous taxa, as well as taxon richness, were negatively related to crayfish density. In the Santa Ynez River, the biomass and average body size of benthic invertebrates, predatory invertebrates, herbivores and chironomids, but not total invertebrate density or taxon richness, were negatively related to crayfish density. 5. Fewer large predatory invertebrates and snails (Physella gyrina) in both streams, and baetid mayflies in the Ventura River, were visible at night in channels where crayfish were abundant. Snails responded to crayfish by moving above the water line in the Santa Ynez River, but not in the Ventura River. 6. We suggest that the same omnivore had different effects on these neighbouring streams because of crayfish predation on large invertebrates in the Santa Ynez River and the scarcity of such prey in the Ventura River, leading to increased crayfish grazing on periphyton, and reductions in periphyton-associated invertebrates, in the Ventura River.

Temporary pond ecosystem functioning shifts mediated by the exotic red swamp crayfish (Procambarus clarkii): a mesocosm study

“…3). On the other hand, the observed macro-invertebrate richness reduction was similar to the reduction found at Ventura River, with twice the crayfish density as in D3 tanks (Klose & Cooper, 2012). Our results agreed with published studies showing that crayfish in general, and the red swamp crayfish in particular, preferentially prey on slow moving large prey, grazers, shredders and detritivores being the most strongly affected guilds (Lodge et al, 1994;Mccarthy et al, 2006;Correia & Anastácio, 2008;Klose & Cooper, 2012;Jackson et al, 2014).…”

“…We randomly assigned each tank to one of the crayfish density treatments (1 or 3 crayfish/tank, hereafter D1 and D3, respectively) or alternatively to control treatment (without crayfish, hereafter C), making a total of 10 replicates for each treatment. We chose the highest experimental density (D3) with the aim of stocking a reasonable density based on visual estimations in a temporary marsh in the area (5-6 ind/m 2 ) and on published densities (Nyström et al, 1996(Nyström et al, , 1999Gherardi & Acquistapace, 2007;Klose & Cooper, 2012), but downgrading it to take into account the possibility that confinement might enhance the impact of the crayfish. We randomly introduced crayfish individuals in the tanks with a total carapace length (measured from the tip of the rostrum to the telson) of ca.…”

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

“…However, in the Finnish study lakes the two species had different effects on some macroinvertebrate taxonomic groups. For example, signal crayfish had negative effects on snail species richness, as has been widely demonstrated in previous studies (Lodge et al 1994, Dorn and Wojdak 2004, Klose and Cooper 2012, Ruokonen et al 2014, but in the Finnish study lakes signal crayfish effects were stronger than those of noble crayfish. Similar negative effects were obtained from IV, where the presence of signal crayfish substantially reduced the species richness, especially of snail taxa, compared to non-crayfish and crayfish introduction sites, where the value was generally higher.…”

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

“…Nyström et al (1999) argued that prey activity would be an important influence on crayfish consumption. Mollusks are slow moving and probably are the taxa most vulnerable to predation by crayfish, which can greatly reduce mollusk population size and species richness (Lodge et al 1994, Dorn and Wojdak 2004, Klose and Cooper 2012. We found significantly lower abundance of Sphaeriidae and a tendency for lower abundance of Gastropoda in crayfish lakes than in control lakes.…”