Refinement of ecological targets for fish condition monitoring in the Pike and Katarapko Anabranch systems.
The Pike and Katarapko systems are two of three major anabranch and floodplain complexes (the other being Chowilla) in the South Australian Riverland. These anabranch systems comprise a mosaic of aquatic habitats, including permanent lotic (flowing) creeks and subsequently, support a diversity of native aquatic biota, including fish species of conservation concern. The associated floodplains of these systems also support significant vegetation communities that include river red gum (Eucalyptus camaldulensis) and black box (Eucalyptus largiflorens) woodlands, lignum (Duma florulenta) shrublands, chenopod shrublands, herblands (incl. flood responsive ephemeral communities) and dunes. Due to the declining condition of long-lived floodplain vegetation, the South Australia Riverland Floodplains Integrated Infrastructure Program (SARFIIP) was undertaken (completed in 2020) to facilitate engineered (managed) floodplain inundation at the Pike and Katarapko anabranch systems with the aim of restoring floodplain condition and function. SARFIIP and the preceding Riverine Recovery Project (RRP) involved a range of on-ground works including: the upgrade, installation and replacement of banks and flow regulating structures, construction of fishways, floodplain groundwater and salinity management, and a range of complementary measures. Together, this infrastructure will be used to promote a hydrological regime at Pike and Katarapko that includes: (1) improved connectivity and extension of lotic habitats under normal operating conditions; and (2) more frequent floodplain inundation owing to managed inundation events. The operation of this infrastructure will be guided by the Pike and Katarapko Floodplain Operations Plans and a Monitoring, Evaluation, Reporting and Improvement (MERI) framework. Fish are a key ecological attribute of the Pike and Katarapko systems that stand to be influenced by future management. As such, a series of draft Ecological Objectives and Targets were established to guide system management. An understanding of fish species diversity, extent, abundance and demography is critical to assess these targets, and ultimately, variability in ecological condition through time. This study aims to refine fish-related Ecological Targets and develop associated indices to assist in quantifying change in ecological condition at the Pike and Katarapko anabranch systems through time. Specific objectives were to: 1. Review current fish-related objectives and ecological targets, and retain or revise as appropriate; and. 2. Use existing empirical data to develop quantitative indices associated with ecological targets to allow future assessment of fish community condition at the Pike and Katarapko anabranch systems. The review and refinement process led to the proposal of seven specific fish-related Ecological Targets related to: (1) species diversity; (2) species extent (distribution); (3) abundance of freshwater catfish (Tandanus tandanus); (4) abundance of Murray cod (Maccullochella peelii); (5) recruitment of Murray cod; (6) recruitment of generalist species; and (7) recruitment of non-native species. Quantitative indices were developed for each target and guided by the approach recently applied at the Chowilla Icon Site under The Living Murray Program. Data collected from past fish surveys at Pike (2009-2020) and Katarapko (2009-2015) using standardised sampling methods (i.e. boat electrofishing) were used to calculate reference values for each index. The refined Ecological Targets and indices will form a framework with which to assess the condition of the fish community at the Pike and Katarapko systems into the future. Monitoring undertaken in 2021 will provide the first opportunity to apply these targets. An effort has been made to ensure consistency with the approach used at Chowilla, ensuring comparability of data across anabranch systems in the Riverland. Nonetheless, it is suggested that targets are reviewed again in three to five years to ensure continued appropriateness.