Australian Centre for Ecological Analysis and Synthesis (ACEAS)
Dr Nick Bond (Griffith University) (Principal Investigator). ILWS members involved are Dr Paul Humphries, Dr Nicole McCasker and Dr Keller Kopf . Other project team members are from CSIRO Land and Water, Monash University, Charles Darwin University, Texas A & M University, CSIRO, Tasmania, DEPI, Victoria & NSW DPI
Native freshwater fish populations in many parts of southern and eastern Australia have undergone extensive declines since European settlement. This includes iconic native species such as Murray cod and Queensland lungfish, and popular angling species such as Golden perch. A range of measures has been suggested to rehabilitate populations (eg. Murray-Darling Basin Native Fish Strategy) but to date, most actions have focused on top down pressures such as demographic bottlenecks associated with barriers to movements, limited habitat or angling pressures. Coincident with native fish declines has been a growth in populations of introduced fish species such as Common carp.
Although their potential effects are widely recognised, "bottom-up" processes that result in energetic limitations have not been explored in detail. One widely held, but currently unsubstantiated, view is that feeding lower in the food chain by detritivoruous species such as carp has effectively redistributed (or 'locked away') energy once available to predatory native fish such as cod. Similarly, altered flooding regimes may have reduced the total pool of energy available to drive fish production in many lowland rivers. Such ecosystem-type impacts on production and food chain energetics are fundamental to our understanding of ecosystem function, but rarely can be considered in 'operational' type funding arrangements.
This group brings together ecologists with expertise in fish and floodplain ecology and NRM managers responsible for actions to restore native fish populations, to explore the potential for these different but overarching mechanisms to constrain the recovery of native fish stocks. The group is combining early historical and current data on fish stocks with simple demographic and bio-energetic models to help quantify the relative merit of different hypotheses regarding the competing mechanisms. The working group outputs will help to better understand the merits of targeting different drivers in restoring native fish populations.
The group will produce two peer-reviewed papers and one briefing note relevant to government agencies responsible for the management of native fish populations. The first peer-reviewed paper (arising from Workshop 1, North Stradbroke Island, QLD in November 2012) will summarise alternative hypotheses regarding what factors now constrain the recovery of native fish populations. The team will then produce a second paper (Workshop 2, North Stradbroke Island in April 2013) based on a case study, in which it will use basic semi-quantitative models of population growth and energy demands, to evaluate the competing hypotheses identified in the first workshop. A goal of this analysis will be to determine the type and level of intervention/restoration required to overcome current constraints on population growth, and the likely timescales involved. The group will also identify and catalogue available data on changes in native fish abundance that spans the period of major impact from European settlement.
The working group outputs will help to better understand the merits of targeting different drivers in restoring native fish populations. It will recommend an alternative approach to river management; one that will have a lasting, and hopefully, a significantly positive, effect on river ecosystems in general, and fish in particular.
Dr Paul Humphries
Charles Sturt University – Albury