Assessing ecosystem vulnerability to invasive rusty crayfish (Orconectes rusticus)

Abstract

Despite the widespread introduction of nonnative species and the heterogeneity of ecosystems in their sensitivity to ecological impacts, few studies have assessed ecosystem vulnerability to the entire invasion process, from arrival to establishment and impacts. Our study addresses this challenge by presenting a probabilistic, spatially explicit approach to predicting ecosystem vulnerability to species invasions. Using the freshwater-rich landscapes of Wisconsin, USA, we model invasive rusty crayfish (Orconectes rusticus) as a function of exposure risk (i.e., likelihood of introduction and establishment of O. rusticus based on a species distribution model) and the sensitivity of the recipient community (i.e., likelihood of impacts on native O. virilis and O. propinquus based on a retrospective analysis of population changes). Artificial neural networks predicted that approximately 10% of 4200 surveyed lakes (n = 388) and approximately 25% of mapped streams (23 523 km total length) are suitable for O. rusticus introduction and establishment. A comparison of repeated surveys before vs. post-1985 revealed that O. virilis was six times as likely and O. propinquus was twice as likely to be extirpated in streams invaded by O. rusticus, compared to streams that were not invaded. Similarly, O. virilis was extirpated in over three-quarters of lakes invaded by O. rusticus compared to half of the uninvaded lakes, whereas no difference was observed for O. propinquus. We identified 115 lakes (approximately 3% of lakes) and approximately 5000 km of streams (approximately 6% of streams) with a 25% chance of introduction, establishment, and extirpation by O. rusticus of either native congener. By identifying highly vulnerable ecosystems, our study offers an effective strategy for prioritizing on-the-ground management action and informing decisions about the most efficient allocation of resources. Moreover, our results provide the flexibility for stakeholders to identify priority sites for prevention efforts given a maximum level of acceptable risk or based on budgetary or time restrictions. To this end, we incorporate the model predictions into a new online mapping tool with the intention of closing the communication gap between academic research and stakeholders that requires information on the prospects of future invasions.

Effectiveness of stream sampling methods in capturing non-native Rusty Crayfish (<em>Orconectes rusticus</em>) in Ontario

“…Recent stream surveys in the mid-west and eastern regions of the United States indicate the continuing spread of Rusty Crayfish and concurrent declines in native Orconectes species (Kuhlmann and Hazelton 2007;Kilian et al 2010;lieb et al 2011b;Olden et al 2011). Based on a broadscale survey of the Kawartha lakes region, Berrill (1978) found the Rusty Crayfish to be widespread and common and indicated that it was likely replacing Northern Clearwater Crayfish.…”

“…in other parts of the laurentian Great lakes basin, the major methods of Rusty Crayfish introduction include the release from bait buckets by recreational anglers, the intentional release by aquarium hobbyists, and their introduction by lake users to control nuisance weeds (Olden et al 2011). Where introduced, the Rusty Crayfish has caused dramatic changes to aquatic ecosystems including the replacement of native crayfish, damage to macrophyte beds, and shifts in macroinvertebrate and fish assemblages (Phillips et al 2009).…”

Integrated assessment of biological invasions

“…Step 1.-There is an extensive body of literature on Orconectes; however, for this case study we used information from the data-rich region of the state of Wisconsin (Olden et al , 2011. Detailed demographic data were lacking for this species; thus, in contrast to case study 1 above, this case study illustrates…”

“…Data were also available for native crayfish species presence/absence over time (before and after the invasion of Orconectes). Olden et al (2011) used those data to calculate an index of each lake's vulnerability to invasion: lakes that lost the native species after the invasion have a higher vulnerability index than those where the two native species still persist. We used this vulnerability index as a proxy for the invasive species' competitive ability or potential to spread once it has been introduced in a lake, with more vulnerable lakes indicating the potential for higher population growth of Orconectes.…”

“…Thus, given an ongoing invasion the management approach should be tailored to the pertinent phase of the spread process: dispersal, colonization, or prolifer- 13 E-mail: iibanez@umich.edu ation. In general, common approaches to forecasting invasion generate an overall assessment but do not specify, even if they are included in the calculation, the likelihood of each of the phases of invasion (Olden et al 2011, Leung et al 2012. Hence, we are in need of an analytical approach that integrates all information available to guide management depending on the invasion phase (Lodge et al 2006).…”