Risk of invasiveness of non-native fishes in the South Caucasus biodiversity and geopolitical hotspot

Abstract

Aquatic invasions are one of the major threats for freshwater ecosystems. However, in developing countries, knowledge of biological invasions, essential for the implementation of appropriate legislation, is often limited if not entirely lacking. In this regard, the identification of potentially invasive non-native species by risk screening, followed by a full risk assessment of the species ranked as higher risk, enables decision-makers to be informed about the extent of the threats posed to the recipient (risk assessment) area. In this study, 32 non-native extant and horizon fish species were screened for their risk of invasiveness under current and predicted climate conditions for the South Caucasus – a biodiversity and geopolitical hotspot that includes the countries of Armenia, Azerbaijan and Georgia. Overall, the number of very high-risk species increased from four (12.5%) under current climate conditions to 12 (37.5%) under predicted climate conditions. The highest-risk species under both conditions included the already established gibel carp Carassius gibelio and topmouth gudgeon Pseudorasbora parva, the locally translocated pikeperch Sander lucioperca and the horizon North African catfish Clarias gariepinus. Under predicted climate conditions, a very high risk of invasiveness was predicted also for the translocated three-spined stickleback Gasterosteus aculeatus and Eurasian perch Perca fluviatilis, for the already established eastern mosquitofish Gambusia holbrooki, ruffe Gymnocephalus cernua, sharpbelly Hemiculter leucisculus and Nile tilapia Orechromis niloticus, and for the horizon pumpkinseed Lepomis gibbosus and largemouth bass Micropterus salmoides. Future research on the non-native species in the South Caucasus should be conducted both country- and region-wide and should account not only for the high biodiversity, but also for the critical geopolitical situation affecting the study area.

Synergistic Effects of Climate Change and Alien Fish Invasions in Freshwater Ecosystems: A Review

“…Using AS-ISK, the authors found that one of the species whose invasiveness may be most favored by global warming is Clarias batrachus (Siluriformes: Claridae), a tropical species native to Southeast Asia capable of tolerating extreme environmental conditions (water hypoxia, high salinity and pH values); rising temperatures (up to 35 • C) are expected to provide more suitable habitat availability for the establishment of the species. Mumladze et al [50], using the same tool, identified the highest-invasiveness-risk species, under current and predicted climate conditions, for the South Caucasus biodiversity hotspot, including Armenia, Azerbaijan, and Georgia. They found that in this area, characterized by a continental mesophilic climate and by high endemic freshwater fish species richness, the number of very high-risk species is expected to triple within a climate change context.…”

“…Many authors agree on the need to assess the potential impacts of emerging aquatic invaders under projected climate change scenarios [44,51,52] and to predict which species are likely to become invasive under future warmer climatic conditions [60,75]. Especially in developing regions, there is a knowledge gap concerning biological invasions, in terms of high-quality fish-monitoring data, which are often limited or lacking [50], mainly due to limited resources for research. Providing current inventory, predicting future distributions of alien species, and understanding their impacts on native biodiversity are of crucial importance to implement conservation measures for freshwater ecosystems [50,59].…”

“…Especially in developing regions, there is a knowledge gap concerning biological invasions, in terms of high-quality fish-monitoring data, which are often limited or lacking [50], mainly due to limited resources for research. Providing current inventory, predicting future distributions of alien species, and understanding their impacts on native biodiversity are of crucial importance to implement conservation measures for freshwater ecosystems [50,59].…”