The rise and rise of Gambusia holbrooki in Australia – Serious threat or scapegoat for poor environmental management?

Ivor Stuart¹, Jarod Lyon¹ and Shanaugh McKay¹

¹Arthur Rylah Institute for Environmental Research, 123 Brown Street, Heidelberg VIC 3084 Australia.

Email: Ivor.Stuart@dse.vic.gov.au

Since their introduction into Sydney’s Royal Botanic Gardens in 1925, Gambusia (Gambusia holbrooki) have spread rapidly throughout Australia, assisted by human dispersal and an amazing ability to cope with a range of extreme environmental conditions. Gambusia are now the most widespread freshwater fish in Australia, occurring in all states and territories on the mainland, as well as recently being discovered in the Tamar River region of Tasmania. Gambusia show a preference for warm, slow flowing waters amongst aquatic vegetation at the edge of waterbodies with depths of 10 cm or less. This habitat preference puts this species in direct competition with many small bodied native fish, and although no local extinctions have been directly attributed to Gambusia, they are thought to have played a role in the decline of species from six genera (Mogurnda, Ambassis, Melanotaenia, Pseudomugil, Craterocephalus and Retropinna). While competition with native species can occur in a variety of forms, it is the aggressive nature of Gambusia, and their tendency to nip at the fins of other species, which often receives the most attention, with several recent studies quantifying this deleterious trait. Although a nation-wide approach to Gambusia control is yet to be implemented, a recent report to the Murray-Darling Basin Commission has recommended the formation of a Gambusia task force to tackle the problem. This presentation will attempt to shed light on the current status of Gambusia in Australia, as well as discussing evidence of actual impacts on freshwater fauna and potential management techniques.

Room 1 Monday 3.50 pm