The role of omnivorous crayfish in littoral communities

Abstract

Large omnivorous predators may play particularly important roles determining the structure of communities because of their broad diets and simultaneous effects on multiple trophic levels. From June 2001 to June 2002 we quantified community structure and ecosystem attributes of six newly establishing freshwater ponds (660 m2 each) after populations of omnivorous crayfish (Orconectes virilis) were introduced to three of the ponds. Crayfish preyed heavily on fish eggs in this experiment, which reduced recruitment of young-of-year fish. This effect indirectly enhanced zooplankton biomass in crayfish ponds. Phytoplankton abundance exhibited a more complex pattern and was probably influenced by non-trophic (e.g., bioturbation) effects of crayfish. Peak dissolved oxygen levels were lower in the crayfish ponds indicating that they had lower primary production: respiration ratios. Metaphytic algae were strongly affected by crayfish presence; filamentous greens quickly disappeared and the blue-green Gleotrichia (a less preferred food item) eventually dominated the composition in crayfish ponds. Chara vulgaris and vascular macrophytes established 34% cover in control ponds by June 2002, but were not able to establish in crayfish ponds. Two important periphyton herbivores (tadpoles and gastropods) were absent or significantly reduced in the crayfish ponds, but periphyton differences were temporally variable and not easily explained by a simple trophic cascade (i.e., crayfish-snails and tadpoles-periphyton). Our results indicate that crayfish can have dramatic direct and indirect impacts on littoral pond communities via feeding links with multiple trophic levels (i.e., fish, invertebrates, and plants) and non-trophic activities (bioturbation). Although the effects of omnivorous crayfish on littoral communities can be large, their complex effects do not fit neatly into current theories about trophic interactions or freshwater community structure.

The Within-Catchment Invasion of the Non-Indigenous Signal Crayfish Pacifastacus Leniusculus (Dana),in Upland Rivers

“…Through a combination of large size, broad feeding habitats and high densities attained, their introduction to new habitats can have a significant impact on the aquatic environment (NYSTRÖM and STRAND, 1996;NYSTRÖM, 2002;DORN and WOJDAK, 2004). The introduction of North American crayfish species into Europe has been partially responsible for severe declines in indigenous European species (HENTTONEN and HUNER, 1999;HOLDICH, ROGERS and REYNOLDS, 1999) through a combination of transfer of crayfish plague Aphanomyces astaci and competitive displacement of native European species.…”

A review of ecological interactions between crayfish and fish, indigenous and introduced

“…Abrahamsson, 1966;Lorman and Magnuson, 1978;Momot et al, 1978). For example, in a range of North American ponds, crayfish had both direct and indirect community effects on the biomass of zooplankton and phytoplankton assemblages and peak levels of dissolved oxygen, also strong negative effects on macrophyte establishment, metaphyton abundance and composition, gastropod biomass, and the density of bullfrog tadpoles (Dorn and Wojdak, 2004). These and other studies suggest that lakes and ponds with abundant crayfish will be structurally comparatively simple, with few macrophytes and gastropods.…”

“…These and other studies suggest that lakes and ponds with abundant crayfish will be structurally comparatively simple, with few macrophytes and gastropods. In such systems some species of amphibians and fish will perform poorly, while other organisms may benefit (Dorn and Wojdak, 2004). Freshwater decapods often coexist with fish in streams and lakes, although other situations where crayfish live, including swamps and temporary wetlands, may not support fish.…”

Predation of invasive crayfish on aquatic vertebrates: the effect of Procambarus clarkii on fish assemblages in Mediterranean temporary streams

“…Further, most bass and pumpkinseed sunfish concentrate their nests in shallow littoral zones, which make eggs more vulnerable to crayfish predation. In experimental ponds, Dorn and Mittlebach (2004) and Dorn and Wojdak (2004) observed virile crayfish preying heavily on fish eggs and found that a crayfish presence significantly affected the successful reproduction of bluegill sunfish, Lepomis macrochirus Rafinesque, reducing the recruitment of young-of-the-year. Fitzsimons et al (2002) estimated a crayfish (O. virilis) consumption of 82% of the potential egg numbers at lake trout spawning reefs based on both the published literature (Miller et al 1992) and experimental work, concluding that high crayfish density and low egg abundance (<100 eggs m À2 ) may also limit natural recruitment of trout in Lake Ontario.…”

“…In the temporary ponds of Doñ ana Natural Park, red swamp crayfish had a strong effect on the reproductive success of Bufo calamita (Laurenti), the survival of its embryos being strikingly reduced when they were directly exposed to crayfish (Cruz et al 2006a). Dorn and Wojdak (2004) studied the effects of the virile crayfish, Orconectes virilis (Hagen), on the development and structure of littoral communities in newly established freshwater ponds in south-western Michigan (USA) and found no bullfrog (Rana catesbiana Shaw) tadpoles in any of the crayfish ponds although tadpoles were abundant in the control ponds.…”