Predation by the plague minnow (Gambusia holbrooki) - key threatening process listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list Predation by Gambusia holbrooki (Plague Minnow) as a KEY THREATENING PROCESS on Schedule 3 of the Act. Listing of Key Threatening Processes is provided for by Division 2 Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Gambusia holbrooki Girard, 1859 (previously known as Gambusia affinis) (Plague Minnow, also known as Mosquito Fish) is a small freshwater fish originally introduced into Australia in the 1920s. The fish was imported as an aquarium fish but some were released into creeks around Sydney, Melbourne and Brisbane.

2. During the Second World War a government sponsored campaign was initiated to spread Gambusia holbrooki into as many east coast waterways as possible, as a control agent for mosquitoes.

3. Gambusia holbrooki is an aggressive and voracious predator. Overseas research has documented its impact on fish, invertebrates and frogs. (Grubb, J.C. 1972. American Midland Naturalist 88, 102-8; Hurlbert, S.H., Zedler, J. & Fairbanks, D. 1972. Science 175, 639-41)

4. Recent research has documented that Gambusia holbrooki preys upon eggs and tadpoles of the Green and Golden Bell Frog, Litoria aurea (Morgan, L.A. & Buttermer, W.A. 1996. Australian Zoologist 30, 143-149, White, A.W. & Pyke, G.H. 1998 unpublished manuscript submitted to Australian Zoologist).

5. Other studies have demonstrated that Gambusia also preys upon Litoria dentata (Morgan & Buttermer op.cit), Litoria lesueuri (White & Pyke, op.cit) and Limnodynastes peronii (Webb, C. & Joss, J. 1997. Australian Zoologist 30, 316-26).

6. Presence of Gambusia holbrooki has been linked to the decline of Litoria aurea, the New England Bell Frog Litoria castanea, Southern Bell Frog Litoria raniformis, and the Southern Tablelands Bell Frog (Litoria sp.)

7. Breeding by Litoria aurea is almost completely restricted to water bodies lacking Gambusia holbrooki.

8. In view of 3, 4, 5, 6 above the Scientific Committee is of the opinion that Predation by Gambusia holbrooki is a serious threat to the survival of Litoria aurea and Litoria castanea, both species listed as threatened under the Threatened Species Conservation Act, and to other species of frog, and that predation by Gambusia holbrooki is therefore eligible to be listed as a key threatening process because it adversely affects two or more threatened species and it could cause species that are not threatened to become threatened.

Proposed date to be Gazetted: 29/1/99
Exhibition period: 29/1/99 - 12/3/99