Development and application of an ecological monitoring and mapping program for targeted Kerang lakes

"July 2006".

Project Number: Ecological Benchmarking of Targeted Kerang Wetlands - M/BUS/99.

MDFRC item.

The ‘Development and application of an ecological monitoring and mapping program for targeted Kerang lakes’ project aims to enhance our current and future ecological understanding of seven irrigation storage lakes situated near the townships of Kerang and Lake Charm in north-central Victoria. The targeted lakes - Kangaroo Lake, Racecourse Lake, Lake Charm, Little Lake Charm and the Reedy Lakes System (Third, Middle and Reedy or First Lake) - have significant economic, social and conservation value and consequently, the challenge in managing them is to balance the need to maintain or enhance key environmental values within a framework of acceptable and sustainable anthropogenic (economic and social) use. The significant conservation values of the seven lakes, some of which are internationally recognised under the Ramsar Convention, the Japan and Australia Migratory Bird Agreement (JAMBA) and the China and Australia Migratory Bird Agreement (CAMBA), have been the focus of considerable ecological research. There was a clear need to summarise and evaluate this extant information in order to identify key knowledge gaps. These were targeted through baseline monitoring and mapping, and were considered in the development of an ongoing monitoring protocol. The provision of baseline and ongoing data-sets will significantly improve ecological knowledge of the targeted systems. In turn, this will assist environmental decision making, raise awareness of threatened species or values, and form a point of reference against which the effects of management actions and/or ecological change can be judged. This is particularly important in light of the potential impacts of water trading, new irrigation development and changes to the future operation of the lakes as a result of the broader water reforms outlined in the Victorian Government’s White Paper ‘Our Water Our Future’ (see progress report: DSE, 2005a).

Specifically, the purpose of this project was to enhance current and future ecological knowledge of the targeted Kerang lakes through; 1. An assessment of the existing ecological literature. A ‘stop-light’ framework was used to evaluate the quality of the existing ecological data collected for biotic (i.e. fish, birds, macroinvertebrates, wetland vegetation) and abiotic (i.e. surface water) indicators by a diverse range of individuals and organisations, and with varying levels of ecological expertise and sampling rigour. The quality of the ecological data collected was found to be generally high, being collected and reported in a rigorous and appropriate manner. For the purposes of developing a baseline data-set however, much of the data was considered unsuitable given that it was collected outside a timeframe useful for determining current ecological conditions (< 10 years). 2. Baseline ecological monitoring and mapping of a range of indicators. ‘Snapshot’ baseline ecological monitoring and mapping was conducted between November 2005 and April 2006 in order to provide up-to-date ecological information for the following key indicators; fish, turtles, frogs, macroinvertebrates, wetland vegetation and surface water quality. The fish communities in the targeted lakes were relatively diverse compared to those of similar lowland wetlands in Victoria and South Australia (Ellis and Meredith, 2005; Ho et al., 2004; SARDI Aquatic Sciences, 2006) due, in part, to the ongoing stocking programs operating in the Kerang region (DPI, 2006). Eight native and five exotic species were recorded across the surveyed lakes, with native fish being of greater abundance than exotic fish. Three of the native species sampled are considered threatened at a state level (i.e. Murray Cod, Murray or Crimson-Spotted Rainbowfish and Fly-Specked Hardyhead). The Murray Cod is also considered vulnerable at a national level, under the EPBC Act.

Of the two native turtle species sampled, the Murray Turtle was the more widespread and abundant; the Murray Turtle was sampled at each of the lakes but was particularly abundant at Third Lake and First/Reedy Lake. The Eastern Long-Necked Turtle, which is extremely widespread and common throughout south-eastern Australia, was sampled in moderate numbers across five of the seven lakes. The male advertisement calls of seven frog species known to be common in Victoria were recorded during the survey. The Spotted Grass Frog and Peron’s Tree Frog were the dominant species within the lakes. Almost twenty-two thousand birds representative of thirty-five species were observed during the study. Seven of the species identified are considered vulnerable, near threatened or endangered in Victoria (DSE, 2003). Birds from fish and crustacean feeding guilds dominated the communities at most lakes, perhaps due to the scarcity of shallow wading habitats and submerged macrophytes in these deep permanent systems. Approximately 90% of all birds observed were breeding Ibis and Spoonbills located at the Middle Lake rookery. The macroinvertebrate assemblages at the lakes were dominated by freshwater shrimp, except at Lake Charm, where non-biting midge larvae were most abundant. The SIGNAL 2 rapid-assessment system indicated that the macroinvertebrate communities at each lake were dominated by families tolerant to a broad range of physico-chemical stressors, which may be linked to anthropogenic influences. Six wetland Ecological Vegetation Classes (EVCs) were identified in the littoral zones of the targeted lakes. All of the wetlands, with the exception of Middle Lake, were dominated by extensive tracts of Tall Marsh (EVC 821), in which Typha domingensis was commonly occurring, and often colonising. Lignum Swamp Woodland (EVC 823) was dominant at Middle Lake.

In the riparian fringe, exotic species, such as Weeping Willow, represented a large proportion of the vegetation. In the littoral zone, few submerged macrophytes were located which suggests that there has been a significant decline in the abundance of these species over the last few decades (Spencer Lovell, pers comm. April 2006; Tom Lowe, pers comm. April 2006). Dead wood, remnant of historical vegetation patterns and largely constituting Black Box and River Red Gum, provides crucial habitat for a broad range of biota in the littoral, open water and riparian areas of the lakes, particularly in the Reedy Lakes System and in Lake Charm. The water quality conditions at the targeted lakes were generally good as concentrations of most parameters fell within or close to their expected range. While electrical conductivity (EC) levels were much higher at Lake Charm than at the other lakes, this did not appear to limit the diversity or abundance of faunal communities. 3. The development of an ongoing monitoring methodology. Standardised monitoring methodologies were outlined for a range of key indicators in order to facilitate the development of ongoing ecological data-sets. The methodologies outline sampling techniques and frequencies, and the number and position of sites to be targeted, as well as the limitations of the data and suggestions for supplementary monitoring. The recommendations have been developed based on expert experience, as well as from information generated from the baseline ecological monitoring and mapping (outlined above). They are based on a surveillance monitoring program, in that the objectives of the program are broadly; 1. To build ecological data-sets for a range of key indicators, and 2. To identify changes in the targeted ecological values over time.

The standardised monitoring and mapping methodologies will, when collected routinely and compared to the baseline data-sets, facilitate measurement of temporal changes in key ecological indicators. Importantly, future monitoring and mapping needs to occur over a range of conditions, including periods of drought and flooding, in order that the natural variability in ecological responses can be fully understood. The information generated from the implementation of the recommended monitoring methodologies for all indicators should be assessed in conjunction with comprehensive hydrological information. While the baseline data gleaned from monitoring/mapping will impart significant information about the current and future ecological status of the seven Kerang lakes, it is of central importance that consideration is given to how the volume and quality of inflows, the number and volume of extractions, as well as groundwater and catchment functioning contribute to that status.