Invasiveness Risk Assessment of Non-native Freshwater Fish Species (Order: Siluriformes)for Lake Taal, Philippines

Abstract

Biological invasions caused by the introductions of non-native species (NNS) into their non- native ecosystems have long been a global environmental concern. In the Philippines large-scale importation of non-native freshwater fish species for the aquarium and aquaculture industry have been documented as early as 1940s. However, little invasiveness assessment has been done in the past, which resulted to the invasion of some of these exotic species. Thus, in this paper, 25 NNS (Order: Siluriformes) were assessed using the Aquatic Species Invasiveness Screening Kit (AS-ISK) to determine their potential for becoming invasive in the chosen risk assessment (RA) area, as well as their ecological and socioeconomic potential impacts on the Philippines. Based on the comprehensive ROC Curve, with the use of the Youden-J index, overall threshold values of ≥ 35 for basic risk assessment (BRA) and ≥ 47 for BRA + climate change assessment (CCA) were established to categorize the potential invasiveness of each species as low-, medium-, or high-risk. According to BRA, 10 (40%) NNS were screened as highly invasive, 14 (56%) with medium risk, and one (4%) with low risk. For BRA + CCA, 10 (40%) NNS were categorized as highly invasive, 12 (48%) with medium risk, and three (12%) with low risk. These findings highlight the need for more RAs of the non-native fish species that enter the country through the ornamental industry, as well as improved public educational campaigns and comprehensive regulatory and management policies to prevent their future invasion.