The tables are turned: an invasive species under potential threat.
This study reviews the current distribution of the native Asian common walking catfish (Clarias batrachus) within Singapore, and compares the present distribution to its historical distribution in the last 90 years based on literature records and museum material. We record a severe decline in the distribution of C. batrachus in Singapore concomitant with a sharp increase in the distribution of the invasive African sharptooth catfish (Clarias gariepinus). We review evidence suggesting that the introduction and the establishment of the African sharptooth catfish in Singapore have adversely affected the Asian common walking catfish. The potential displacement by the African sharptooth catfish of the Asian common walking catfish - itself a widespread invader in other parts of Asia and North America - is particularly interesting as an example of a notorious invasive species becoming threatened by an exotic within its own native range.