Do non-native ornamental fishes pose a similar level of invasion risk in neighbouring regions of similar current and future climate? Implications for conservation and management

1. Global trade in non-native ornamental species coupled with high connectivity among countries is well known to result in worldwide biological invasions, which pose challenges for the conservation and management of biodiversity.
2. There are few studies aimed at implementing management strategies that have examined differences in the potential invasiveness of non-native species between neighbouring political regions within the same ecoregion.
3. To compare the potential risk of invasiveness of non-native ornamental fishes with high commercial value in the river basins of two neighbouring regions of East and Southeast Asia, 32 extant and horizon species were screened with the aquatic species invasiveness screening kit (as-isk ) for the lower Pearl River basin (South China) and the Chao Phraya River basin (Thailand). Both regional (i.e. basin level) and combined risk-ranking thresholds were determined by receiver operating characteristic curve analysis.
4. Of the 32 species screened, 14 were categorized as posing a high risk and seven were categorized as posing a medium risk of being invasive in both regions, under current and future climate conditions. These species have a history of invasiveness and the climate of their native ranges is similar to that of the two study regions. Pterygoplichthys pardalis received the highest risk score in both regions. The risk ranks of 11 species differed between the two regions, based on either the combined or regional thresholds, and this was partly related to the different risk of invasiveness between the two regions, coupled with cognitive subjectivity among the assessors.
5. The results of the present study suggest that the invasion of non-native ornamental fish species could pose similar threats to biodiversity in neighbouring regions. This will serve to inform policy makers of neighbouring countries in the development of coordinated, mutually beneficial regulations and management strategies to enhance the conservation of native species.