Non-native species risk analysis

In 2017, a new non-indigenous crayfish species was found established in Europe. The captured individuals were identified as an orange morph of the Mexican dwarf crayfish Cambarellus patzcuarensis Villalobos, 1943. Fifteen adults (including three ovigerous females) and 26 juveniles were collected in a thermal pond in Budapest, Hungary. Two additional adults were caught below the pond's outflow in the adjacent Danube River. To our knowledge, this is the first record of a C. patzcuarensis population outside North America, which is also true for the rest of dwarf crayfish (family Cambaridae, subfamily Cambarellinae). With this finding, indigenous crayfish species in Europe are now more than twofold outnumbered by non-indigenous species. An analysis of the probability of establishment of C. patzcuarensis in continental Europe revealed that specific regions in the south of the continent are suitable areas for the establishment of the species. Moreover, as a confirmed carrier of the crayfish plague pathogen, this species should be treated with caution and eradicated if possible.

Invasive non‐native species (NNS) are internationally recognised as posing a serious threat to global biodiversity, economies and human health. The identification of invasive NNS already established, those that may arrive in the future, their vectors and pathways of introduction and spread, and hotspots of invasion are important for a targeted approach to managing introductions and impacts at local, regional and global scales. The aim of this study was to identify which marine and brackish NNS are already present in marine systems of the northeastern Arabia area (Arabian Gulf and Sea of Oman) and of these which ones are potentially invasive, and which species have a high likelihood of being introduced in the future and negatively affect biodiversity. Overall, 136 NNS were identified, of which 56 are already present in the region and a further 80 were identified as likely to arrive in the future, including fish, tunicates, invertebrates, plants and protists. The Aquatic Species Invasiveness Screening Kit (AS‐ISK) was used to identify the risk of NNS being (or becoming) invasive within the region. Based on the AS‐ISK basic risk assessment (BRA) thresholds, 36 extant and 37 horizon species (53.7% of all species) were identified as high risk. When the impact of climate change on the assessment (CCA) was considered, the combined risk score (BRA + CCA) increased for 38.2% of all species, suggesting higher risk under warmer conditions, including the highest‐risk horizon NNS the green crab Carcinus maenas, and the extant macro‐alga Hypnea musciformis. This is the first horizon scanning exercise for NNS in the region, thus providing a vital baseline for future management. The outcome of this study is the prioritisation of NNS to inform decision‐making for the targeted monitoring and management in the region to prevent new bio‐invasions and to control existing species, including their potential for spread.