Coupling ecological and social network models to assess "transmission" and "contagion" of an aquatic invasive species.

Network analysis is used to address diverse ecological, social, economic, and epidemiological questions, but few efforts have been made to combine these field-specific analyses into interdisciplinary approaches that effectively address how complex systems are interdependent and connected to one another. Identifying and understanding these cross-boundary connections improves natural resource management and promotes proactive, rather than reactive, decisions. This research had two main objectives; first, adapt the framework and approach of infectious disease network modeling so that it may be applied to the socio-ecological problem of spreading aquatic invasive species, and second, use this new coupled model to simulate the spread of the invasive Chinese mystery snail (Bellamya chinensis) in a reservoir network in Southeastern Nebraska, USA. The coupled model integrates an existing social network model of how anglers move on the landscape with new reservoir-specific ecological network models. This approach allowed us to identify 1) how angler movement among reservoirs aids in the spread of B. chinensis, 2) how B. chinensis alters energy flows within individual-reservoir food webs, and 3) a new method for assessing the spread of any number of non-native or invasive species within complex, social-ecological systems.

Ulcerative disease outbreak in crayfish Orconectes propinquus linked to Saprolegnia australis in big Muskellunge Lake, Wisconsin.

Crayfish populations in the area of the North Temperate Lakes Long Term Ecological Research (LTER) project, Wisconsin, USA, have been monitored for >25 yr. In 2005, native crayfish Orconectes propinquus from Big Muskellunge Lake were found with ulcerated lesions in the cuticle. In 2006, lesions occurred in 9.5% of sampled crayfish from the lake (n=3146). Ulcers generally occurred on the appendages of affected individuals but varied in location and severity. The prevalence of ulcers varied widely among sites, sample depths, and sampling dates, ranging from < 2% to >20%. The prevalence of ulcers in crayfish increased from a minimum in early June to a maximum in late July and August. In aquarium trials, healthy crayfish representing either O. propinquus or O. rusticus co-housed with ulcerated crayfish did not develop ulcers within 4 wk of exposure. Gross and histopathologic analyses of ulcerated crayfish revealed the presence of filamentous hyphae in the lesions while hemocytic infiltrates, melanotic reactions and silver-stained sections indicated that the ulcers had an oomycete etiology. Excised samples of ulcerated crayfish cuticle grown in culture developed an oomycete that was identified as Saprolegnia australis by PCR amplification and sequence analysis of 2 different DNA fragments. This is the first report of the occurrence of ulcers in wild crayfish associated with S. australis infection in the U.S.A. The advent of the outbreak and its underlying ecological causes are still under investigation.