Go with the flow: are environmental flows in the Murray-Darling Basin making fish move?

By Luke Carpenter, Australian Rivers Institute PhD candidate

Across the planet, more than 50% of the global river volume is estimated to be moderately to severely impacted by flow regulation and/or fragmentation due to dams, weirs, hydropower plants, canals and water extraction, to name a few.

With all of these disruptions, water cannot run down the river at its natural rate or course. Although this provides benefits for people (to have a predictable, uniform and controlled flow of water down the river), unfortunately it can have severe negative consequences for freshwater biodiversity. For example, many riverine animals like fish depend on the natural patterns of river flow, such as seasonal high flow pulses, to disperse, feed and breed.

: Luke Carpenter (left) and Helder Espírito-Santo (right) with a Murray cod in the Mehi River, NSW. Credit: Mark Kennard

In the Murray-Darling Basin, water managers are currently releasing water with the intention of emulating parts of the natural flow regime. However, potential ecological benefits of these flow releases are not well understood.

Of particular interest to scientists and local fishermen alike, is whether these environmental flows are stimulating fish to migrate, and eventually breed, as they would under natural conditions.

In a joint collaboration between Griffith University, Commonwealth Environmental Water Office and NSW Department of Primary Industries (Fisheries), my PhD project will quantify the environmental and life history determinants of movement of the threatened freshwater catfish (Tandanus tandanus) and Murray cod (Maccullochella peelii) in response environmental water flows within the Gwydir and Mehi Rivers, NSW.

To do this, I have surgically implanted a number of fish with acoustic tracking devices and set up a series of listening station throughout the rivers to pick up the fish’s locations as they move about. These recorded movements will then be compared to the timing and magnitude of flow releases and other environmental factors, the outcomes of which will contribute to effective environmental flow, habitat and fisheries management for these species.

With this sort of study being such a costly venture, I am greatly appreciative to have recently received a Holsworth Wildlife Research Endowment from the Equity Trustees Charitable Foundation. This endowment will be used to cover the costs of data processing, travel and field supplies.


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