ASFB Home > The effects of spatial and temporal factors on the abundance of seven key finfish species along south-western Australia.

European Perch (Perca fluviatilis) as a driver of habitat use by Flathead Gudgeon (Philypnodon grandiceps) in the Onkaparinga River, South Australia

Michael Lake, Michael Lake and S Hannon

Sinclair Knight Merz, ARMADALE, AUSTRALIA

THEME: ASFB

In aquatic systems piscivorous fish can greatly influence the community structure of other fish species on which they prey. In Australia European Perch are known to be a significant predator of small fish in freshwater environments where they cohabitate. In the Onkaparinga River in South Australia European Perch populations overlap with those of Flathead Gudgeon. In the gorge section of the river pool habitats become effectively isolated from each for long periods during low flows. Fish surveys have revealed that the distribution pattern of Flathead Gudgeon within these pools was significantly skewed towards shallow habitats with relatively few fish caught in the deep areas. It was hypothesised that this pattern of habitat use by Flathead Gudgeon in the Onkaparinga was influenced by the presence of European Perch. An investigation was carried out to test this hypotheses in using an exclosure experiment and a comparison of Flathead Gudgeon distribution in pools with and without European Perch populations. The interaction between the presence of European Perch and native fish species was investigated in a section of the Onkaparinga River. Preliminary results suggest that European Perch do exert some influence on the habitat use of Flathead Gudgeon, however, several other factors may also be involved. The implications of this interaction is discussed with reference to current methods of environmental flow determinations in Australia.