Using Sensorfish to Predict Impacts of Water Infrastructure on Freshwater Fish

The operation of large-scale river development projects is leading to worldwide declines in fisheries productivity. Little information is available on mechanisms influencing fish welfare and most knowledge of impacts is limited to downstream movements of salmonids. Many other species require downstream dispersal pathways and technology now exists to help identify potential sources of injury to fish during passage. We used sensorfish technology to quantify specific hydraulic conditions that likely caused injury during downstream passage. Regulated river systems usually have water delivered via bottom-releasing undershot gates or fixed crest overshot weirs and each has contrasting hydraulic conditions. We subsequently used sensorfish to model pressure, shear and strike probability for fish passing through each design. Sensorfish reported rapid decompression through undershot gates and the rate of change was dependent on upstream approach depth and render fish susceptible to barotrauma-related injuries. Probability of physical contact was high and likely increased injury probability during high volume undershot releases. Overshot weirs had different hydraulic profiles and compression was greatest when impacting the downstream apron during low tailwater depths. The work was a useful mechanism to identify potential sources of injury to fish and could be readily applied to other water infrastructure project such as hydro or offtake design.