The Nonindigenous Aquatic Species Alert Risk Mapper (ARM) Active

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The Science Issue and Relevance: The Nonindigenous Aquatic Species (NAS) Database and Alert System provides a framework for the rapid dissemination of new aquatic plant and animal invasions as they are incorporated into the NAS Database. The system notifies registered users of new sightings of >1,330 non-native aquatic species as part of national-scale early detection and rapid response systems. The NAS group has developed a new tool, the NAS Alert Risk Mapper (ARM), to characterize waterbodies in the conterminous U.S. and Hawaii at potential risk of invasion from a new nonindigenous species sighting. The ARM tool uses a nonindigenous species’ current range to assess a species’ short-term, within six months, risk of possible invasion of new waterbodies and to develop credible scenarios of its potential movement within a drainage based on the species mobility and drainage barriers (e.g., dams and waterfalls). Maps produced by ARM indicate lakes, river reaches, and other water bodies potentially at risk of invasion by a nonindigenous aquatic species and accompany the NAS Alert emails sent to subscribers and managers.

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Methodology for Addressing the Issue: The information for the NAS Alert (species, location, date, and alert level) is added to the ARM map in ArcGIS in an easy-to-access table (Figure 1). The sighting location and previous NAS records for the species are added to the two ARM map views (regional and specimen) through database queries. On the maps, the orange star marks the new sighting location and previous NAS records for the species are characterized by orange diamonds. The ARM maps utilize the National Hydrography Dataset Plus (NHDPlusV2) layer for information on locations of stream reaches, lakes, and swamps. The at-risk locations within a drainage are determined by two steps: species-specific mobility and locations of barriers. The species-specific mobility is determined by coupling a species dispersal potential (an estimated distance a species could move in six months) and dispersal type. The dispersal types include: passive movers (e.g., plants and Dreissena spp.) that are a risk to only downstream waterbodies, active movers (e.g., fishes and crayfishes) that can move up and downstream, and terrestrial movers (e.g., frogs and turtles) that have the potential to invade in all directions. Barriers include large dams (generally > 2 m in height) which are treated as hard barriers to all movement, and waterfalls which are treated as upstream barriers. The at-risk waterbodies or stream reaches are determined based on the location of the sighting of the nonindigenous species, and include the continuous areas that species could reach from barrier to barrier, headwater to a barrier, or barrier to the ocean and used in concert with the species-specific distribution to determine direction and distance (Figure 2). All stream reaches, waterbodies, and swamps that are determined to be at risk are indicated in purple on the specimen view (Figures 3 & 4).

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Future Steps: In the near future, the NAS group intends to create and integrate a national boat ramp database into the ARM maps. Boat ramps represent a potential distribution vector for both nonindigenous plants and animals. By integrating public boat ramp location information, the maps created by ARM could account for the risk of spread of invasive species via boat between drainages. For example, an at-risk lake with a nonindigenous plant or invertebrate (e.g., Eurasian watermilfoil, Myriophyllum spicatum or quagga mussel, Dreissena bugensis) and a public boat ramp would represent an additional risk to surrounding drainages with boat ramps. This vector would be species-specific focusing on species known to be dispersed by boats. The national boat ramp database would be the first of its kind, and would make use of existing location information for public boat ramps but linked to a common GIS layer (National Hydrography Dataset Plus).

These maps will provide management agencies information on the spatial extent of a possible rapid response action. This may help them decide if such an action is feasible. Such information can also be used to determine the area at risk if no action is taken.

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