Abstract
We review a model we developed in 2007 to predict the invasion potential of an introduced population, based on the relationship between juvenile growth (mean total length at age 2) and mean age-at-maturity, and test the model with data from 75 non-native populations of pumpkinseedLepomis gibbosusin nine countries of Europe and western Asia. The database used to construct the model was derived from a mix of primary and secondary data collected between 1981 and 2016. Based on number of specimens collected or catch-per-unit-effort data, and/or comments by the original authors, populations were classifieda priorias “invasive” or “non-invasive.” The plot of the proposed model placed populations in three invasiveness categories (non-invasive, transitional, invasive). Of those predicted by the model to be invasive, only 57% were correct with regard to theira prioriclassification, a result that was not statistically significant. For populations predicted by the model to be non-invasive, 70% were correct with regard to theira prioriclassification when “transitional” were grouped with non-invasive (P= 0.0024), and 64% were correct when “transitional” were excluded from the test (P= 0.12). Applications of the model to two other non-native freshwater fishes (black bullheadAmeiurus melasand crucian carpCarassius carassius) are also discussed. The lack of stronger statistical support for the model may have been the result of using life-history traits from the populations after they were introduced, as the source populations were unknown, as well as to shortcomings in the dataset that could affecta prioriand modeled classifications. We conclude that such life-history models can be useful for predicting invasiveness status in non-native freshwater fishes, though the basis of the predictions, statistical or heuristic, will depend on the size and quality of the underlying life-history database.
Highlights
A major challenge confronted by environmental managers and policy makers in the development and implementation of strategies to avoid or mitigate bioinvasions is the identification of nonnative species likely to become invasive and exert adverse impacts on native species and ecosystem services (Williams and Grosholz, 2008; Zengeya et al, 2017)
Studies that assess adverse impacts by freshwater fish species are in general limited to a few prominent species, e.g., common carp Cyprinus carpio Linnaeus, 1758, so risk analysis considers a non-native species’ attributes, which include invasion history, the propagule pressure associated with the species’ introductions, population traits, and life-history traits
The underlying purpose of risk analysis is to inform decision makers as to the threats posed by non-native species so that measures may be taken to avoid the introduction of potential pest species, or to control the spread as well as to limit the impacts of existing non-native species
Summary
A major challenge confronted by environmental managers and policy makers in the development and implementation of strategies to avoid or mitigate bioinvasions is the identification of nonnative species likely to become invasive and exert adverse impacts on native species and ecosystem services (Williams and Grosholz, 2008; Zengeya et al, 2017). We chose pumpkinseed as a test (or “model”) species because: (a) the relationship between juvenile growth and mean ageat-maturity had already been assessed in populations of this species in part of its native range (Fox, 1994); (b) an increasing amount of growth and life-history data was being acquired for pumpkinseed populations introduced to European waters with which to evaluate the use of these traits in a model to predict invasiveness; (c) many of the populations for which these data are available have been evaluated for invasiveness by one or more of the criteria listed, though with regard to definitions of the term “invasive,” the most commonly reported aspects were high density and/or prolific reproduction; and (d) population expansion is facilitated in environments with a species initially not present with “r-selected traits” like early maturity. Briefly discussed are two applications of this model to predict the invasiveness of the North American ictalurid catfish, black bullhead Ameiurus melas (Rafinesque, 1820) in European waters and that of the European cyprinid Carassius carassius (Linnaeus, 1758), which is not native to Great Britain (Copp et al, 2016; Tarkan et al, 2016)
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