Will they stay or will they go? Movement and recruitment dynamics of an iconic Australian freshwater fish in a cold-water impacted River

The construction of large water storages and subsequent alteration of flow regimes and thermal pollution have had devastating impacts on native freshwater fish populations globally. Native fish populations in the lower reaches of the Mitta Mitta River have declined substantially since the construction (in the 1970’s) and operation of Dartmouth Dam. Self-sustaining populations of Trout cod and Murray cod were reported to have substantially declined or become locally extinct in the river by the early 1990’s, attributed largely to the largely annual release of cold water during spring and summer. In more recent times, recreational fishing reports and fish surveys have detected Murray cod again occupying this reach of river. This prompted managers to reconsider the general view that the reach is unsuitable for native fish populations. Here we present outcomes of a research project aimed at improving the knowledge of the Murray cod population in the lower Mitta Mitta River with the aim of guiding improved river operations and management. We investigate patterns of recruitment dynamics, movement and hydrological records to understand the role of water operations in influencing population dynamics of Murray cod in the lower reaches of the River. We then use this information in a population modelling framework to explore long-term trajectories of the population under a variety of management scenarios

Using Adaptive Management to Meet Multiple Goals for Flows Along the Mitta Mitta River in South-Eastern Australia

In this chapter we reflect on a relatively small but influential example of adaptive management which seeks to enhance the environmental benefits of the flow regime in the highly regulated Mitta Mitta River in Australia's Murray-Darling Basin. In 1999 an operational review recommended the reintroduction of greater in-stream flow variability in the Mitta Mitta River in an attempt to improve river health. The river managers have worked towards this through managed variable releases from Dartmouth Dam. These variable releases have been trialled four times from 2001-2008, with the explicit intention of learning more about the ecological impacts of variable flows while still achieving operational goals for the River Murray System overall. The ecological impact of the variable releases was studied via a series of consultancies by a University freshwater ecology team. They concluded that variable flow improved ecological condition compared with the condition after periods of relatively constant flow for greater than 1 month, although the benefits of it are relatively short-lived. Principles were developed over time through discussions between river managers and the research team. These principles are being progressively refined and incorporated into the current operational plan for the river, and learning continues. We suggest that three key ingredients enabled and supported adaptive management in this particular case; aspects of the operational context, the people involved and the trusting relationships that developed

Re-operation of large dams to improve the condition of regulated rivers: An integrated adaptive management approach (Mitta Mitta River, south-eastern Australia)

Flow regulation and water extraction have significantly modified the flow regimes of rivers throughout the world and have contributed to the decline in the biophysical condition of these rivers (Ward & Stanford 1995). To ameliorate this decline, environmental flows have been implemented, or are being considered for implementation in many rivers (Arthington et al 2006). However, in most regulated rivers only a small proportion of water is allocated for environmental purposes. To achieve a significant improvement in the condition of regulated rivers it is essential that consumptive water is also released from dams in a way that achieves environmental benefits at the same time as meeting supply requirements. The challenge for river managers is to alter the operation of dams and weirs to deliver environmental benefits at the same time sustain the industries and communities that rely on water from these systems

Will they stay or will they go? Movement and recruitment dynamics of an iconic Australian freshwater fish in a cold-water impacted River

The construction of large water storages and subsequent alteration of flow regimes and thermal pollution have had devastating impacts on native freshwater fish populations globally. Native fish populations in the lower reaches of the Mitta Mitta River have declined substantially since the construction (in the 1970’s) and operation of Dartmouth Dam. Self-sustaining populations of Trout cod and Murray cod were reported to have substantially declined or become locally extinct in the river by the early 1990’s, attributed largely to the largely annual release of cold water during spring and summer. In more recent times, recreational fishing reports and fish surveys have detected Murray cod again occupying this reach of river. This prompted managers to reconsider the general view that the reach is unsuitable for native fish populations. Here we present outcomes of a research project aimed at improving the knowledge of the Murray cod population in the lower Mitta Mitta River with the aim of guiding improved river operations and management. We investigate patterns of recruitment dynamics, movement and hydrological records to understand the role of water operations in influencing population dynamics of Murray cod in the lower reaches of the River. We then use this information in a population modelling framework to explore long-term trajectories of the population under a variety of management scenarios