Risk assessment of the potential invasiveness of Coptodon zillii (Gervais, 1848) in Anzali Wetland using AS-ISK Model

The intentional and unintentional introduction of non-native fish species to the aquatic ecosystems of Iran has occurred with purposes such as enhancing aquaculture, ornamentation, biological control, and research. Some of them cause or have the potential to cause, significant environmental and socio-economic impacts on aquatic ecosystems and/or fish farms. The eradication of non-native fishes is impossible or very costly, especially in large areas. Screening and identifying the potential invasiveness of species are being increasingly used all over the world. The main aim of the present research was to assess the potential invasiveness of redbelly Tilapia Coptodon zillii in Anzali international wetland.

Aquatic Species Invasiveness Screening Kit (AS-ISK) was used to identify redbelly Tilapia Coptodon zillii as a non-native fish that may pose a high potential risk of becoming invasion in Anzali Wetland. The model is able to discriminate between invasive and non-invasive aquatic organisms including non-native fishes by risk area-related threshold value. Also, the Köppen-Geiger climate system and Climatch software were used to match the climate between the native range of redbelly Tilapia and Anzali Wetland. The projected future climate change scenario was taken from relevant studies to carry out Climate Change Assessment (CCA) of the AS-ISK.

The output of the AS-ISK was 44 for redbelly Tilapia that was higher than the AS-ISK threshold value of the risk assessment area, which meant that the species pose a potential risk of becoming invasive in Anzali wetland. There was a high climate-mating between the native range of redbelly Tilapia and the assessed area when the Köppen-Geiger climate system was used. At least one native habitat of redbelly Tilapia in the system was in the same climate category as the studied area. Also, the Climatch model output was 0.87 that shows a high climate matching for the non-native fish. The CCA had an increasing effect on the total score of the AS-ISK. The factors that increased the AS-ISK score were climate-mating, probable climate change, biological attributes, and invasiveness history of other places that the species was introduced. The comparison of the results of this study and other relevant studies that used AS-ISK to assess potential invasiveness of redbelly Tilapia showed that the species had the potential of becoming an invader in Anzali Wetland as well as some other areas around the country.

While non-native fishes are frequently used to enhance aquaculture in the country, a rapid assessment tool is required to avoid nuisance environmental impacts. The AS-ISK can be reliably used as a tool to predict the potential risk of becoming invasive in Anzali Wetland and elsewhere to be used by conservation managers, decision-makers, and policymakers in the aquaculture development plans.