The South American cichlid fish, Acarichthys heckelii, is one of many exotic species established in Singapore's artificial freshwater habitat; forming the only recorded population outside its native distribution. The discovery of an A. heckelii individual in a sensitive natural waterway (Nee Soon Swamp Forest) prompted this study, which aimed to investigate the distribution, diet, growth and reproductive ecology of the fish, as well as its possible route of introduction. We found that A. heckelii is largely restricted to artificial freshwater bodies, although a sizable established population occurs in a modified waterway connected to Nee Soon Swamp Forest. Gut contents revealed that the fish fed mainly on benthic algae and macroinvertebrates, the latter occurring in higher frequencies in larger individuals. While unable to ascertain clear seasonality in its breeding, we observed a peak in reproductive investment coinciding with the Northeast monsoon, indicating possible life history adaptations. Genetic comparisons of the cytochrome b mitochondrial marker between individuals from South America, Singapore and the ornamental fish trade shows that the A. heckelii populations in Singapore's fresh waters are more closely related to fishes in the ornamental fish trade than the native population in South America, corroborating anecdotal evidences identifying aquarists as the source of local releases. Our findings also demonstrate the viability of the ornamental trade as an avenue of species introduction and the potential invasiveness of A. heckelii.
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Acknowledgments The National Parks Board of Singapore and the Public Utilities Board of Singapore are gratefully acknowledged in granting permission to conduct surveys in areas under their jurisdiction. We thank Rudolf Meier for his support and use of his laboratory facilities; Ng Heok Hee, Ng Ting Hui, and Paul Chen Zijian for logistical support and field assistance; Kho Zi Yi for help with figures used in this paper; and members of the Freshwater and Invasion Biology Laboratory. We also acknowledge financial support from the National Research Foundation and the Economic Development Board (SPORE, COY-15-EWI-RCFSA/N197-1), and NUS grant number R-154-000-465-133. This study was conducted under protocols approved by the National University of Singapore Institutional Animal Care and Use Committee of the National University of Singapore (Protocol No.: S09/09).
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- Introduced species
- Nee Soon swamp forest
- Ornamental fish trade