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Abstract

A survey of aquatic macrophytes and macroinvertebrates in Brumbys Creek, the lower Macquarie River and the King River downstream of John Butters power station was conducted twice yearly in spring and autumn for 11 years between 2001/02 and 2011/12, following the requirements of the ‘Downstream Poatina’ component of the Basslink Monitoring Program.

The aim of this program was to:
- Detect changes in key biological variables through time and particularly prior to and following the commencement of Basslink operations;
- Assess any significant departures in these variables during the post-Basslink period relative to the pre-Basslink period.

This aspect of the larger Basslink monitoring program focussed on changes in:
• the cover of aquatic plants in those stream reaches affected by the Poatina power station releases – Brumbys Creek weirs 1 and 3, and the lower Macquarie River in the vicinity of the Brumbys Creek junction;
• the composition and abundance of macroinvertebrate communities in edge habitats of the lower Macquarie River channel in the vicinity of the Brumbys Creek junction, and in riffle habitats in Brumbys Creek and the King River.

This report addresses the aim of identifying relationships between changes in macrophyte and macroinvertebrate variables and aspects of the flow regime. The biological components addressed by this report are:
• % plant cover in Brumbys Creek weirs 1 and 3;
• % plant cover and benthic macroinvertebrate composition along river channel edges in the lower Macquarie river (upstream and downstream of the Brumbys Creek junction);
• Abundance and composition of riffle macroinvertebrate communities in the King River.

In this report no flow-response analysis is reported for mussels in the lower Macquarie River. Inter-annual changes in mussel density and their broad relationship with ‘wet’ and ‘dry’ years are addressed in the main Downstream Poatina Basslink monitoring report (Davies and Cook 2012). Any further interpretation of flow vs. mussel density relationships is precluded by a lack of autecological knowledge for the species with regard to relationships between annual recruitment, habitat conditions and variations in larval host-fish densities.

Biological data collection commenced in 2001/02 for the four years of the ‘pre-Basslink’ phase of the program. Basslink operations commenced across the Hydro Tasmania system just prior to the autumn 2006 sampling, during 2005/06. 2006/07 was the first full year of ‘post-Basslink’ operations and 2011/12 was the sixth and last post-Basslink year of biological monitoring.

Item Type:	Report (Project Report)
Authors/Creators:	Davies, PE
Publisher:	Freshwater Systems
Additional Information:	© Hydro Tasmania 2013, © Freshwater Systems 2013
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