Pages 61-72 of document link. Scroll down to report title on left hand side of page. 

Woodward, G.M. (La Trobe University, Department of Zoology, Bundoora); Malone, B.S. (La Trobe University, Department of Zoology, Bundoora);

Nannoperca obscura (Yarra pygmy perch) and Nannoperca australis (Southern pygmy perch) are endemic to southeastern Australia and are morphologically and ecologically similar. Both species inhabit slow flowing or still water with abundant aquatic vegetation. N. obscura appears to have undergone a much greater decline in abundance and distribution since European settlement than has N. australis. A study to investigate patterns of abundance and habitat use of the species in allopatry and sympatry was conducted at two sites in Deep Creek Vic. The pattern of habitat use by N. obscura was very similar to that of N. australis in allopatry, but was restricted to only a small proportion of habitat and excluded from the floodplain when sympatric with N. australis. Habitats used by N. obscura when sympatric with N. australis were also occupied by large numbers of Perca fluviatilis (Redfin perch). It is speculated that the different patterns in abundance of pygmy perch among sites were largely due to interactions between size-fecundity relationships, habitat use sometimes mediated by interspecific competition, and predation intensity by P. fluviatilis.