<< BACK TO CONTENTS Survival Water for the environment “The upstream dispersal of juvenile tupong can allow them to take advantage of additional habitats for feeding, growth and survival, which may be important to growing the population,” Frank said. “There are a couple of mechanisms for this dispersal. First, increases in river flows can stimulate the upstream movement of these fish. Second, maintaining suitable flows enables fish to move to feed and breed. For example, if flows drop to a point where the river becomes a series of disconnected pools, then the fish cannot migrate upstream.” Environmental watering for diadromous fish occurs during autumn and winter to trigger spawning migrations, during spring to attract fish into coastal streams, and during summer to trigger migration. “In addition, summer base flows are maintained in a number of rivers to provide river connectivity, which allows tupong to migrate upstream,” Frank said. “For example, in 2017 in the Thomson River, tupong dispersal upstream was possible during the summer with higher baseflow conditions. Similarly, juvenile tupong migrated to the upstream portion of the middle reaches of the river by early February.” Adult tupong migrate from freshwater downstream to the sea in autumn and winter to breed, triggered by increased river flows. Frank said age verification data and continued sampling under various flow conditions would continue to add to the knowledge of the tupong life cycle and the influence of river flows. “The findings can help inform when environmental flows are beneficial and how much water is required,” he said. “We plan to sample for another two years and will analyse the data to investigate the role of discharge, including environmental flow releases, on the immigration and upstream dispersal of diadromous fish.” Young tupong migrate into freshwater streams from the sea in spring and summer to feed and grow. Reflections – Environmental watering in Victoria 2016–17 | 24
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