Full Title
Effects of turbidity on native fish populations: an ecosystem-scale experiment
Contact Person
Rick Stoffels
Project Team
Rick Stoffels, Matthew Vogel, Daryl Nielsen
Funding Body
Goulburn-Broken Catchment Management Authority
Duration
November 2008 to October 2009
Outcomes
Report to GBCMA
Summary
Many catchment management practices influence the quality of runoff, hence the turbidity of streams and rivers that receive that runoff. However, we have almost no understanding of how turbidity influences native fishes. Turbidity may affect fishes in both direct and indirect ways. For example, turbidity may directly interfere with cues (visual, mechanical) fish utilise to catch prey, whereas it may indirectly affect fishes by reducing levels of primary production, which in turn results in reduced prey productivity. Preliminary data from the Broken River shows that the abundance of certain small fish species may be negatively correlated with turbidity, but an experiment is needed to disentangle the effects of turbidity from the many other factors that covary with turbidity.
The decommissioning of Lake Mokoan presents managers with a rare opportunity to conduct a scientifically rigorous, ecosystem-scale experiment that will improve our understanding of how turbidity influences the productivity of fish populations in lowland rivers. That is, the decommissioning of Lake Mokoan enables a BACI experimental design (before (pre-decomissioning), after (post-decomissioning), control (upstream of Casey's Weir, hereafter CW), implementation/impact (downstream of CW)), one that is known to be particularly powerful when it comes to elucidating the impact of ecological variables, such as turbidity. Here, we aim to determine the impact that the Lake Mokoan decommissioning-hence turbidity reduction-has on the structure of lowland fish communities.
