Construction and analysis of risk assessment system for ichthyotoxic fishes — a case study of the Jailing River

Toxic organisms are widely distributed in natural environment and receive much attention from researchers. Ichthyotoxic fishes are one of the largest groups of toxic vertebrates, which refers to fish whose organs or tissues contain toxins or whose tissues can secrete toxins. However, the existent researches on ichthyotoxic fishes have been rather limited for a long time, especially for the freshwater ichthyotoxic fishes. Up to now, the risk assessment system for freshwater ichthyotoxic fishes is scarce at home and abroad, This would greatly hinder the development and utilization of ichthyotoxic fishes. Given that, to increase people’s awareness of freshwater ichthyotoxic fishes, enhance public awareness of prevention, reduce unnecessary losses, and lay a foundation for in-depth research on ichthyotoxic fishes, this study has preliminarily established a risk assessment system for ichthyotoxic fishes and it was applied to 18 known ichthyotoxic fishes in the Jialing River. This risk assessment system was focused on toxic property, population property, and social property of ichthyotoxic fishes. A total of three first-level indexes, eight second-level indexes, and 26 third-level indexes were included in the risk assessment system. By assigning values to the indices of each ichthyotoxic fishes, the score of risk assessment for each ichthyotoxic fishes was calculated according to the determined weight of each index. Finally, the risk grade was confirmed by the score for risk assessment of each ichthyotoxic fish. Results showed that Cyprinus carpio gained 36 points, which is the highest score. On the contrary, Glyptothorax fukiensis obtained 21 points, which is the lowest score. Acrossocheilus yunnanensis acquired 25 points. Among other 15 ichthyotoxic fish species, 7 of them scored between 26 to 30 points and 8 of them scored range from 31 to 35 points. Results of risk grade indicated that four fish species belonged to high risk grade among 18 ichthyotoxic fishes in the Jialing River, and they are Ctenopharyngodon idella, C. carpio, Silurus asotus, and Siniperca chuatsi, respectively. The other 14 ichthyotoxic fishes were divided into medium risk grade. This study has also made effort to examine the intrinsic connection between risk levels and the ecological factors of ichthyotoxic fishes in the Jialing River. Nevertheless, Chi square test (χ²) result showed that there were no significant difference between different risk grades of ichthyotoxic fishes in the Jialing River in respect to feeding habits, distribution water layer, and distribution range. More work could be done in the next research to explore the relationship between ichthyotoxic fishes risk level and their ecological factors. In summary, the risk evaluation system for the freshwater ichthyotoxic fishes we proposed in this study has certain practical value. However, due to limited knowledge for ichthyotoxic fishes, this risk assessment system will inevitably have deficiencies. In the future, the research on ichthyotoxic fishes should be strengthened and the risk assessment system should be constantly improved. Generally, this study has enriched the basic knowledge of freshwater ichthyotoxic fishes, and strengthened people's understanding of ichthyotoxic fish, and provided support for the management of ichthyotoxic fishes. At the same time, it has laid a foundation for further research.