This paper provides a series of glimpses into valuable extensive data sets which uniquely display the responses of Australian freshwater fishes and their habitats to changes in river discharge. The perspective is that of an independent practitioner, unconstrained by organisational paradigms, and with a predilection for direct-observation surveying techniques.

The first glimpses of hydro-ecological dynamics arise from a decade of work on freshwater fish from the relatively hydrologically-predictable streams of Kakadu National Park in the Northern Territory. Understandings from these dynamics were, perhaps naively in some cases, then taken south to the far less predictable rivers of north-eastern NSW.

Arrival in NSW coincided with the emerging management and research interest in environmental flows and these have been the primary investigation focus over the ensuing twenty-five years. With an understanding that ‘habitat volume’ was a basic driver, the initial focus was hydro-habitat dynamics and glimpses are given of hydro-physical-habitat relationships based on flow manipulations across a set of rivers. Subsequently, habitat dynamics investigations included aquatic vegetation assemblages in upper estuaries. An example of these dynamics is provided for an eight-kilometre stretch of the Hastings River estuary over fifteen years. Both flood scouring and low-flow-mediated salinity impacts are dramatically demonstrated and detailed knowledge of the latter has considerable utility in refining environmental flows in the system.

An important theme in the physical-habitat investigations has been the availability of fish passage across tidal-barrier riffles in systems where significant water extraction occurs upstream. Such work can be quite challenging in lower river reaches which braid. This is the case in the Manning River where verification effort has focused on developing a better understanding of fish-migration dynamics. This work, undertaken on two spatial and temporal scales over seven years, has provided unique insights into these dynamics and demonstrated the complexity arising from the less-predictable hydrology in this system.  

Understanding hydro-ecological dynamics? – long-term, landscape-scale surveying holds the key! Transferring knowledge between systems? – be cautious!