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Summary Crayfishes and other freshwater aquatic fauna are particularly at risk globally due to anthropogenic demand, manipulation and exploitation of freshwater resources and yet are often understudied. The Ozark faunal region of Missouri and Arkansas harbours a high level of aquatic biological diversity, especially in regard to endemic crayfishes. Three such endemics, Orconectes eupunctus, Orconectes marchandi and Cambarus hubbsi, are threatened by limited natural distribution and the invasions of Orconectes neglectus. We examined how natural and anthropogenic abiotic factors influence these three species across multiple spatial scales. Local and landscape environmental variables were used as predictors in classification and regression tree models at stream segment and segmentshed scales to determine their relation to presence/absence and density of the three species. Orconectes eupunctus presence was positively associated with stream size, current velocity and spring flow volume. Orconectes marchandi presence was predicted primarily by dolomite geology and water chemistry variables. Cambarus hubbsi was associated with larger stream size, with highest densities occurring in deep waters. Stream segment and segmentshed scale models were similar, but there were important differences based on species and response variables (presence/absence versus density). Stream segment scale models consistently performed better than or equal to segmentshed scale models. Anthropogenic abiotic environmental variables were of minor importance in most models, with the exception of O. marchandi being negatively related to road density and human population density. Classification tree models predicting distribution performed well when compared to random assignment, but regression trees were generally poor in explaining variation in density. We found that a range of environmental variables were important in predicting crayfish distribution and abundance at multiple spatial scales and their importance was species‐, response variable‐ and scale dependent. We would encourage others to examine the influence of spatial scale on species distribution and abundance patterns.

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Research on the ecology and impacts of the zebra mussel (Dreissena polymorpha) has developed in parallel with the long history of their spread across Europe and to North America. There is less scientific knowledge however about the quagga mussel (Dreissena rostriformis bugensis). The recent spread of both zebra and quagga mussels to the Western states of the USA, has spurred on dreissenid research. The 17th International Conference on Aquatic Invasive Species (ICAIS), was held in San Diego, California in September 2010. This special edition of Aquatic Invasions includes topical research presented at ICAIS and also extra subsequent papers on ecology, risk assessment and control of various aquatic invasive species in different parts of the globe.

Invasive crayfishes adversely affect fisheries throughout the United States and Canada. Recommended management strategies, such as regulation and education, limit primary introduction pathways (e.g., aquaculture, bait shops, pet trade, educational classrooms). We present a case study of our state agency's approach to collecting data to support regulation development and accompanying educational efforts in Missouri. We studied other agencies’ approaches, industry pathways, and stakeholder groups to develop and support regulations. We found that bait, pet, and aquaculture industries’ crayfish sales only constituted a small portion of their incomes. High school and college educators used crayfishes in lessons, with most being obtained from the wild or biological supply companies; some educators released live crayfishes to the water afterward. The biological supply companies providing specimens to educators often provided species that differed from ones advertised, including invasive species. Biological and survey data‐supported regulations were implemented in 2012, and stakeholder input was used to revise them. A suite of pre‐ and postregulation education was aimed at the general public and targeted stakeholders to describe the problem and process. We believe that we used a science‐informed process to partially close some important introduction pathways.