Abstract
The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium- and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a ‘very high risk’ of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate ‘rapid’ management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement.
Highlights
The threat posed by invasive non-native species (NNS) worldwide to native species and ecosystems requires a global approach to identify species that pose a high risk of becoming invasive across varied geographies and climates (Gordon et al, 2008)
As a taxon-generic toolkit, the Aquatic Species Invasiveness Screening Kit (AS-ISK) is applicable to any aquatic species in virtually any climatic/marine ecoregion zone (Copp et al, 2016b; Table 1), and allows the screening of 27 groups of aquatic organisms in total: mammals, birds, reptiles, amphibians, fishes, tunicates, lancelets, invertebrates, ‘other’ animals, plants, protists, fungi, and bacteria
Fishes and invertebrates represented the largest proportion of screened aquatic species, reflecting the composition of introduced animal species recorded for e.g. European waters (Alcaraz et al, 2005; Gherardi et al, 2009; Katsanevakis et al, 2013) and the relative number of experts in the various aquatic organismal groups
Summary
The threat posed by invasive non-native species (NNS) worldwide to native species and ecosystems requires a global approach to identify species that pose a high risk of becoming invasive across varied geographies and climates (Gordon et al, 2008). Aquatic species that are likely to carry a high risk of becoming invasive, posing a threat to native species, usually possess life-history traits including frequent reproduction with a high incidence of ovoviviparity, large body size and a long life span, the ability to exploit opportunistically available food resources, a history of invasion success, and a close climate matching with the RA area (Statzner et al, 2008; Chan et al, 2021) These species often tolerate higher salinity, broader environmental temperatures and higher levels of organic pollution than native species (Leuven et al, 2009). The identification of species posing a high risk of being (or becoming) invasive in a certain RA area provides a basis for advice to policy, decision-makers and other stakeholders regarding management options for existing and potential future invasive NNS (Copp et al, 2005b, 2016b; Mumford et al, 2010; David et al, 2013; David and Gollasch, 2018, 2019)
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