01 Sep John Koehn
John Koehn, Australia
Dr John Koehn has been working with fish and flows for 35 years. He has undertaken a wide range of research on many of the freshwater fishes of south-eastern Australia, especially in the Murray-Darling Basin. He is currently using new and existing knowledge to assist management decisions for the use of environmental water under the Murray-Darling Basin Plan. This knowledge has been used for the basis of a series of population models that can be utilised to compare the likely outcomes for flow scenarios to be undertaken in water plans.
Presentation Title: How do we manage a long-lived, highly migratory, flow-responding fish at a basin scale?
The Murray-Darling Basin (MDB) covers an area of over 1 million km2 and is subject to the Basin Plan which provides additional water for environmental purposes. Flow management needs to occur at spatial scales that are most appropriate to the species of concern, varying from local, site-based to large landscape scales and there is an immediate need for knowledge and tools to inform watering plans. Golden perch is one of the many MDB native fish species that have suffered severe declines and are perhaps the most enigmatic species in the MDB, being widespread and are highly migratory. Recent advances in understanding their ecology (including movements and recruitment and likely nursery sites) have enabled the development of a general meta-population model to examine the influence of flow on population dynamics. The model has 6 sub-populations and is underpinned by the consultative development of a contemporary conceptual model of their flow related life history. The model is still being refined and results are preliminary; nevertheless, the broad concepts are in place from which numerous insights are gained. Key messages are: this species needs to be managed at a large riverscape scale; there is inter-dependence of the southern basin fish population with northern populations; provision of river connectivity and fish passage is vital; high level flows enhance recruitment and smaller pulses enhance recolonization by juveniles; and efforts must be made to provide access and connectivity to key wetland nursery areas for recruitment pulses.