Spatial and temporal variation in the composition of riverinefish communities
|Spatial and temporal variation in the composition of riverinefish communities
Non Technical Summary
Fish communities are routinely used to monitor the health of aquatic ecosystems in New South Wales. An understanding of spatial and temporal variation, over small and large scales, is necessary when designing such monitoring programs. Biological monitoring programs are necessary to establish the outcomes of management actions taken to ensure sustainable use of natural resources.
NSW Fisheries is involved in two large scale fish monitoring programs, the Integrated Monitoring of Environmental Flows and the Sustainable Rivers Audit, both co-ordinated by the Department of Infrastructure, Planning and Natural Resources. An assessment of the likely spatial and temporal variation in the structure of fish communities was considered necessary in order to design an effective fish monitoring protocol for these, and possible future large-scale, fish monitoring programs.
This study showed that there was small-scale spatial variation and short-term temporal variability in fish community structure in the Macquarie and Namoi Rivers in the Murray-Darling Basin. The biggest differences found in the fish communities were between the two rivers. Although the fish communities within each river changed over a three-month period, the underlying differences between rivers were still detectable over this time. These results suggest that sampling at any time within a single season will be sufficient to show spatial differences that occur over large spatial scales, such as comparisons between rivers, between geographical regions, or across the entire Murray-Darling basin.
Monitoring programs intended to evaluate changes in fish communities at large spatial scales, such as entire river basins, between regions within a basin or between individual rivers, need only sample at the scale immediately below the level of interest. For example, where the management focus is among rivers, then replicate samples could be drawn from representative reaches within rivers without the necessity of having replicated sites within those reaches.