Evaluating invasion risk for freshwater fishes in South Africa

Abstract

Background: South Africa, as a signatory of the Convention on Biological Diversity, has an
obligation to identify, prioritise and manage invasive species and their introduction pathways.
However, this requires knowledge of the introduction pathways, factors influencing
establishment success, invasive potential, current distributions and ecological impacts.
Objectives: To evaluate the Fish Invasiveness Screening Kit (FISK) to predict the invasion risk
posed by fish species proposed for introduction into South Africa.
Method: FISK assessments were compiled for species whose invasion status in South Africa
was known. A Receiver operating characteristic (ROC) analysis was conducted to calibrate the
FISK for South Africa. The calibrated FISK was used to evaluate the risk that three species
recently proposed for importation for aquaculture could become invasive in South Africa.
Results: A FISK score of 14 was identified as the threshold to delineate between species that
could become invasive in South Africa and those that are unlikely to become invasive. Of the
three species evaluated, Silurus glanis had a high risk of becoming invasive in South Africa,
Lates calcarifer was likely to be invasive and Oncorhynchus tshawytscha was unlikely to be
invasive in South Africa.
Conclusion: FISK was demonstrated to be a useful risk assessment tool to evaluate the invasion
risk posed by species proposed for use in aquaculture. For the large number of fish imported
for the pet trade, a rapid screening assessment to flag potentially high risk species was
recommended prior to a full FISK assessment for flagged species.