PARENT SESSION
Poster Session 20: Invasive Species
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Effects of the crayfish Orconectes virilis on a recovering acidified lake ecosystem: A reintroduction or an invasion?
Phillips, Iain*,1, Vinebrooke, Rolf1, 1 Department of Biological Sciences, Edmonton, Alberta, Canada
ABSTRACT- Re-introduction of keystone species into stressed ecosystems has been proposed as a strategy for reversing catastrophic shifts and facilitating recovery. However, the sudden reappearance of an extirpated species may have adverse ecosystem impacts that are analogous to the effects of an invasive species. Therefore, we experimentally re-introduced the crayfish species Orconectes virilis into a recovering acidified boreal lake (Lake 302S, Experimental Lakes Area, Canada) to determine the magnitude of its effects on the abundance and composition of zoobenthos and periphyton following a 17-yr absence. A single factor experimental design consisting of two treatment levels (crayfish-less control vs 2 crayfish/m 2) was replicated five times for a total of 10 large (4 m 2) aquaculture cages placed in the littoral area in June 2004. During the 50-day experiment, O. virilissignificantly suppressed total zoobenthos (RM-ANOVA, p<0.05) and periphyton (p<0.001) biomass by 70% and 90%, respectively. Our findings suggest that the re-introduction of O. virilismust be controlled carefully because this omnivore can function as an invader, exerting pronounced negative effects on the productive capacity of boreal lakes in the absence of fish predation.
Key words: crayfish, foodweb, species re-introduction, omnivory