Pathways and places associated with nonindigenous aquatic species introductions in the Laurentian Great Lakes

Abstract

Propagule pressure (i.e., the frequency and abundance of introductions) is a common indicator of the likelihood of nonindigenous aquatic species (NAS) establishment success. Evaluating propagule pressure associated with multiple introduction pathways relative to present NAS distribution patterns may identify which pathway presents the greatest risk. Our objective was to develop and evaluate three geospatial metrics for the Laurentian Great Lakes as proxies of propagule pressure associated with three major introduction pathways: maritime commerce, organisms in trade, and water recreation. Logistic and linear regression analyses were conducted between NAS presence and introduction pathway intensity (e.g., number of vessel trips received by a port) for 23 NAS over a five-decade period (1970-2013). Notably, city population size was the best predictor of NAS presence, even for NAS introduced through ballast water discharge. Moreover, through time, city population size was an increasingly significant predictor of the presence of organisms in trade, signaling a change in both the types of organisms introduced and places where introductions are occurring. Nonetheless, all three metrics are reasonable proxies for propagule pressure and as such are applicable for risk assessment, monitoring, and control strategies.

Historical distribution and current drivers of guppy occurrence in Brazil

“…Nonetheless, studies on different organisms and at different spatial and temporal scales indicate that invasion success is idiosyncratic, with individual species or assemblages supporting different hypotheses (Fitzgerald et al ., ; O'Malia et al . ; Skóra et al ., ). If such idiosyncrasy holds, case‐by‐case studies such as the present one, identifying key determinants of individual species, are important to understand the distribution of invasive species and to develop major conservation efforts to prevent such invasions.…”

“…Another source of introduction in aquatic systems is the direct release of aquarium specimens, which increases the propagule pressure of non-native species (Copp et al, 2005;Dawson et al, 2017;Ferraz et al 2019;Leprieur et al, 2008;Magalhães & Jacobi, 2010). If the total number of releases is linked to the size of the human population in a given area, then one would expect to find especially numerous records of non-native species in areas with high densities of human population (Dawson et al, 2017;O'Malia et al, 2018). Non-native populations also have high establishment success in degraded freshwater habitats (Vörösmarty et al, 2010) because they often harbour simplified native assemblages (Casatti et al, 2006;Leitão et al, 2018) and thus have more available niches (Catford et al, 2009).…”

Urban Biodiversity and the Importance of Scale

“…Conversely, large cities may play a disproportionate role in the spread of invasive species or pathogens, due to their transport and trade networks [22].…”

Hobbyists acting simultaneously as anglers and aquarists: Novel pathways for non‐native fish and impacts on native fish

“…Such routes cannot be tracked or controlled by targeting the official market, such as through changing customs regulations. Current risk assessment models frequently use commerce schemes and organisms in trade as a proxy for propagule pressure (O'Malia, Johnson, & Hoffman, 2018). However, based on this study, we suggest that these models could be amended by incorporating the non‐market flows of fish species.…”