A manipulative field experiment reveals the ecological effects of invasive mosquitofish (Gambusia affinis) in a tropical wetland

Alphonse Hin Fat TSANG*, David DUDGEON

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)peer-review

8 Citations (Scopus)


1. The mosquitofish (Gambusia affinis: Poeciliidae) is one of the world's most widespread invaders, but our ability to predict the consequences for native species in the tropics is limited by a paucity of research and a lack of knowledge of how environmental factors influence mosquitofish impacts.

2. We undertook a field experiment using cages to manipulate mosquitofish densities in a Hong Kong wetland during the warm wet season and the cool dry season. We measured fish effects on invertebrates and periphyton, and tested whether the results were affected by vegetation type (sedge vs. water lily).

3. Mosquitofish reduced abundance and richness of invertebrates, and altered assemblage composition, but had no effect on periphyton biomass. Effects on invertebrate abundance were consistent between seasons, but mosquitofish reduced invertebrate richness only during the wet season, when effects on assemblage composition were more obvious. Vegetation type had no influence on the experimental results.

4. This study adds to the few tropical, or Asian, field studies of the ecological impacts of mosquitofish, and is, as far as we are aware, the only such study measuring their seasonal variability. While we detected some cage effects during our field experiment, they were insufficient to obscure the strong influence of mosquitofish on invertebrate abundance and composition.
Original languageEnglish
Pages (from-to)869-883
Number of pages15
JournalFreshwater Biology
Issue number5
Early online date1 Feb 2021
Publication statusPublished - May 2021
Externally publishedYes

Bibliographical note

We thank Prof. Belinda Robson, Prof. Angus McIntosh, and the two anonymous reviewers for providing suggestions and help improve the manuscript. We are grateful to Lily Ng for technical support, and Jiahuan Liew for providing suggestions on statistical analysis. Moreover, we are thankful to Ivan Lam, Nicole Kit, Martin Li, Kestrel Lam, Andal Chen, and Will Lee for field assistance, Yee Lai and Banson Leung from WWF for helpful discussions and permit arrangements, and the Director of Agriculture, Fisheries and Conservation Department for allowing the conduct of work in Mai Po [(72) in MP4 Pt.7].


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