A piecewise regression approach was used to objectively quantify barotrauma injury thresholds intwo physoclistous species, Murray cod Maccullochella peelii and silver perch Bidyanus bidyanus, following simulated infrastructure passage in a barometric chamber. The probability of injuries such asswimbladder rupture, exophthalmia and haemorrhage, and emphysema in various organs increased asthe ratio between the lowest exposure pressure and the acclimation pressure (ratio of pressure change,R(NE:A)) reduced. The relationship was typically non-linear and piecewise regression was able to quantify thresholds in R(NE:A) that once exceeded resulted in a substantial increase in barotrauma injury.Thresholds differed among injury types and between species but by applying a multispecies precautionary principle, the maintenance of exposure pressures at river infrastructure above 70% of acclimationpressure (R(NE:A) of 0·7) should protect downstream migrating juveniles of these two physoclistousspecies sufficiently. These findings have important implications for determining the risk posed by current infrastructures and informing the design and operation of new ones.
Boys, C., Robinson, W., Miller, B., Pflugrath, B., Baumgartner, L., Navarro Cuenca, A., Brown, R., & Deng, Z. (2016). A piecewise regression approach for determining biologically relevant hydraulic thresholds for the protection of fishes at river infrastructure. Journal of Fish Biology, 88(5), 1677-1692. https://doi.org/10.1111/jfb.12910