Figure 1.
Length frequency plot for fish sampled a) by electrofishing and seine netting at pumping sites, and b) those collected after being entrained by the pump (all treatments pooled).
Table 1.
Number of fish entrained within the experimental pump system.
Figure 2.
Mean (± S.E.) Cath per unit effort (number of fish/Megalitre) across different mesh and velocity treatments.
Table 2.
Odds ratios for probability of screen contact for different mesh sizes when compared to the no mesh treatment at 0.1 m.sec−1.
Figure 3.
Length frequency plot showing the size range of fish observed by sonar to make a) contact or b) avoid contact with the experimental screen.
Figure 4.
Predicted relationship of probability of screen contact with length and rheotaxis of fish (see methods for description of rheotactic behaviour).
Solid lines are at 0.1 m.sec−1 and broken lines are at 0.5 m.sec−1.
Table 3.
Odds Ratios of rheotactic categories compared to random orientation.
Figure 5.
Location of the four study sites on the Namoi River showing the Murray-Darling Basin (grey thatched).
Figure 6.
Schematic representation of the experimental pumping station showing major components.
The experimental screen was cylindrical and comprised a series of removable panels to adjust approach velocity and mesh size. Fish that were entrained into the system travelled through the intake pipe, through the pump, along the lay-flat discharge pipe and were collected in fyke nets fitted to a settling tank. Fish behaviour in front of the screen face was quantified using DIDSON.
Figure 7.
Diagram of the experimental fish screen showing position of mesh screen panels (M) and position of sonar for the a) 0.1 m.sec−1 approach velocity, b) 0.5 m.sec−1 approach velocity.
Degrees are relative to 0° facing directly into downstream flow (indicated by the arrow). Mesh panels (M) of different aperture size could be interchanged or replaced with solid panels to manipulate approach velocity. To achieve the maximum velocity of 0.5 m.sec−1 all sides except two needed to be fitted with solid panels.
Table 4.
Tabular representation of the two Latin square experimental designs showing the order of allocation of mesh treatments within replicate runs for each of two approach velocities.
Figure 8.
Screenshot showing acoustic echogram obtained from sonar (a) alongside post-processing modules created in Echoview, including a background reduction and target identification module (b) and fish tracking module (c).
Screen panels can be seen as light coloured bands at the image bottom.