Small fish….big problem! Gambusia

Female Eastern gambusia collected during the MD1043 sampling. Photo credit: Zeb Tonkin

Female Eastern gambusia collected during the MD1043 sampling. Photo credit: Zeb Tonkin

Eastern gambusia (Gambusia holbrooki) is an alien fish present in all 23 river valleys in the Murray-Darling Basin (MDB), and in some locations is the most abundant fish species. Eastern gambusia is also a problem species elsewhere in Australia, as well as in other parts of the world, where there is a growing body of research being undertaken on this species. Despite being little, Eastern gambusia can have significant impacts on small and juvenile native fish species.

To learn more about Eastern gambusia a forum was convened by the MDBA to facilitate the sharing of current knowledge and experiences with this fish. The forum brought together presenters from USA, New Zealand and six states of Australia deliver papers to an audience of over 60 attendees. The 22 presentations covered topics including the biology and, impacts of Eastern gambusia, both in its native range in North America and as an introduced fish in New Zealand and Australia, on native fishes and amphibians. A number of practical control options were discussed including community engagement and participation in control exercises.

Mature female Eastern Gambusia. Photo credit: Tarmo Raadik

Mature female Eastern Gambusia. Photo credit: Tarmo Raadik

The forum identified a number of knowledge gaps relating to Gambusia with scientists reporting that though Eastern gambusia is an easy species to study, there is still much to learn of the biology and ecology. Others highlighted the need for greater clarity around legislative and managerial responsibilities. All groups were interested in control measures, and agreed that sharing of information via electronic media was critical with the creation of a central database of information a valuable tool to facilitate communication.

Implications for native fish

Eastern gambusia is now widespread in the MDB and has negative effects on many small and juvenile native fish species (and amphibians), including threatened species. An improved understanding of their biology and ecology, together with an understanding of the effects of control measures, may help reduce the numbers of this alien species at priority locations which will ultimately result in a reduction in the impact of this alien species on native fishes.


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