Fish

  Fish
 
Collecting zooplankton samples to determine food availability in wetlands for young fish. Photo: Jessica Davison

Fish Research

The past century has seen declines in the distribution and abundance of native fish within the Murray-Darling Basin. While no native species are believed to have become extinct, more than half of the region’s species are currently listed as threatened or of conservation concern. By contrast, populations of introduced fish have grown rapidly, to the point where today they comprise 80–90% of fish biomass in many rivers in the Basin.

The Basin Plan seeks to protect and restore native fish populations through improvements in their distribution and breeding success. In general terms we understand that native fish respond to stressors such as flow modification, habitat loss and connectivity changes, however there is considerable uncertainty concerning the relationship between specific changes in water flows and fish life cycles. This uncertainty makes effective environmental flow management and habitat restoration difficult. The situation is further complicated because flow modification is believed to interact with a number of other stressors including invasive species, habitat alteration and fragmentation.

To develop environmental water regimes around the needs of native fish, it is vital that we clearly understand the links between key water flow characteristics and potential fish responses.

Research focus

This research will concentrate on understanding the main factors involved in sustaining or limiting the survival of fish through the period when mortality rates are highest (the recruitment phase), and how these factors are affected by water flows.

We are particularly interested in understanding the relative significance of key factors such as food availability and habitat characteristics, and how these factors might interact with flow to affect fish recruitment and population sustainability. We will also be investigating threats to these processes. This information will improve our capacity to predict the outcomes of proposed water management regimes.

Our approach

The research is comprised of a planning and an implementation phase. The planning phase has included development of a management-focussed conceptualisation of fish recruitment. This summary of our current understanding was developed through consultation between the Fish Research team, environmental water managers and scientists, who review existing published knowledge.

The implementation phase will include a range of activities that will generate new knowledge through an integrated program of field sampling and laboratory experiments. The proposed activities will be undertaken in close cooperation with the Food Web Theme and major external projects such as the Commonwealth Environmental Waterholder’s Long-Term Intervention Monitoring.

What will the research be used for?

The most significant output of EWKR’s Fish Research program will be a more refined conceptual model of the relationships between water flow, key drivers of fish recruitment and the response of different types of species. This will ultimately improve the ability of water managers to predict how fish recruitment will be affected by different environmental flow conditions and other stressors.

A publication written for water managers in the Murray-Darling Basin will integrate the outcomes of the research and provide a basis for water management planning.

Research activities

  • Develop conceptual model. There is a large and dispersed pool of existing information that needs to be evaluated. Much of this information comes from correlative studies that are generally short-term and of limited geographic scope. The process will integrate global knowledge with the specific management needs of the Murray-Darling Basin, and will include non-flow-related stressors and threats.
  • Laboratory studies.These will help identify how some of the critical drivers (food and temperature) interact to influence larval survival.

Garth Watson demonstrates a steady hand and a keen eye to determine the density of zooplankton from various riverine habitats. Photo: Rosie Busuttil
  

  • Field surveys. Field data collection will focus on understanding the where in the landscape appropriate conditions (e.g. hydraulic conditions, temperature and food availability) exist to support fish recruitment and how flows affect the ability of young fish to access and be retained within these locations.

Field site Photo: Jessica Davison

 

PDFFact sheet 9. Project update (1180 KB)