Within the Murray-Darling Basin (MDB) many species undertake extensive downstream migrations as eggs, larvae, juveniles or adults and passage through river infrastructure has been shown to impact on their survival. The relative contribution that different stresses (such as rapid decompression and fluid shear) make to overall injury and mortality remains poorly understood, and this in turn makes it difficult to assess the risk associated with infrastructure projects or to develop engineering and operation guidelines to manage the downstream fish passage risks.

This presentation details laboratory experiments that were used to determine the tolerance of various species and life stages of fish from the MDB to rapid decompression (in hypo/hyperbaric chambers) and elevated fluid shear (in a shear flume). Fish were exposed over a wide range of conditions so that the probability of injury and/or mortality could be modeled. In doing this, the ultimate goal was to determine critical thresholds for injury and mortality and develop criteria that if applied would protect downstream migrating fish at river infrastructure. We present criteria in an attempt to better inform policy relating to the development and management of mini-hydropower and irrigation infrastructure for the protection of downstream migrating fish.