The objectives of the present work were to determine whether:
• Southern pygmy perch (Nannoperca australis) preferentially select structured habitats over open ones and if so, whether they show a preference for macrophyte habitats over woody habitats
• observed patterns of habitat selection vary when a predator (Redfin perch - Perca fluviatilis) is visible
• the activity levels/metabolic rate of Southern pygmy perch differs in the presence or absence of structure (artificial macrophytes)
• observed patterns in activity levels/metabolic rate among habitats vary when a predator (Redfin perch) is visible.
The anticipated outcomes of this project were to provide managers with an improved ability to:
• manage habitat in order to better support existing populations
• identify suitable translocation sites based on structural habitat availability.
• Southern pygmy perch demonstrated a statistically significant preference for structured habitats (macrophytes and wood) as compared to unstructured habitats.
• Macrophyte habitat patches were selected by a significantly greater number of Southern pygmy perch than woody habitat patches.
• Habitat selection was not influenced by the presence of Redfin perch.
• Metabolic rates were significantly higher when macrophytes were present than when they were absent.
• Metabolic rates were not influenced by the presence of Redfin perch.
Implications for management of existing Southern pygmy perch habitats and the selection of translocation sites:
• The results from this project strongly suggest that whilst Southern pygmy perch may use non-macrophyte habitats such as those containing wood, macrophytes represent their preferred habitat type. Consequently, management of existing Southern pygmy perch sites should focus on maintaining or creating significant areas of aquatic vegetation. Similarly, in the event that Southern pygmy perch are translocated to new sites, site selection should be strongly based on the presence of aquatic vegetation, as well as other habitat features such as low velocities and relatively shallow depths.
o Knowledge need: There is a need to determine whether macrophyte type, architecture and density, location within the water body (e.g. fringing) and total area of macrophyte cover influence habitat suitability for Southern pygmy perch.
• Contrary to our predictions, the metabolic rates of Southern pygmy perch were higher when macrophytes were present than in open habitat. Given that the explanation for this is unlikely to be related to elevated stress levels, these results are indicative of reduced routine movement when macrophytes are absent. This suggests that processes essential for survival and growth (e.g. foraging movements) as well as reproduction may be negatively impacted if structured habitat is not available.
o Knowledge need: Whilst we have established the importance of structured habitat, particularly macrophytes, as important habitat for Southern pygmy perch, it is not clear what the implications of little or no macrophytes are for the species. For example, how does the presence or absence of macrophytes affect foraging rates, reproductive output and success? What are the implications for growth and carrying capacity for this species?
• Southern pygmy perch are highly susceptible to predation by introduced species that also utilise macrophyte habitats (e.g. Redfin perch). This is based on the fact that habitat selection and metabolic rates did not vary in the presence or absence of Redfin perch. We suggest that these results are a consequence of: