Risk assessment of the ornamental fish trade in Mexico: analysis of freshwater species and effectiveness of the FISK (Fish Invasiveness Screening Kit)

Aquarium trade has been recognized as one of the major pathways of introduction of non-native fishes into new regions. Nearly 43 million freshwater ornamental fish of different species and varieties are annually commercialized in Mexico and there is a high probability for the establishment of some of these species because of their invasive attributes and the diverse climatic zones existing in the country. Within this context, the identification of high-risk species is of paramount importance considering the potential threat to Mexico's great biological diversity. In the present study 700 freshwater aquarium fish species commonly imported and produced in the country were filtered for synonyms/varieties, resulting in 368 species, which where submitted to revision for invasive reports using specialized invasive species databases. This allowed ranking the main invasive species and the top 30 were subjected to risk analysis using the Fish Invasiveness Screening Kit (FISK). Calibration of FISK was carried out after generating the reports. A receiver operating characteristic curve was made to determine the FISK ability to discriminate between invasive and non-invasive species in Mexico. Thereafter, Youden's index was calculated and a threshold of 24 was obtained, representing the cut-off value for defining high-risk species. A total of 17 species out of 30 were classified under a high-risk category, among them several species of the genus Xiphophorus, Pterygoplichthys and Poecilia. Most of the species were native to Asia, Central and South America. Some of these species are already invasive in Mexico.