Mesotórax (mesothorax = th2) sensu Chabrier apud Shuckard, 1836 Segmento

3.2.5.1 Release

Release times varied from 11:35 to 22:45 but were more frequently in the late afternoon to evening (Table 3.2), with recaptures extending into the night and resuming the following day. This was to replicate the natural tendency for smolts to migrate at night. Diel timing of turbine passage may be an important risk factor due to visual cues for avoidance and evasion behaviour. TREATMENT fish were released from a bucket of water through a 15 cm diameter plastic pipe with its exit directly into the turbine intake basin, 2 m downstream of the trash rack and 4.5 m upstream from the turbine mouth. The intent was to allow the fish sufficient time to orient with the prevailing flow before entering the turbine. In order to prevent fish from escaping upstream, a fence of 10 mm smooth plastic mesh was fitted across the trash rack (Figure 3.2) and remained in place for the duration of the experimental period (7 April to 21 April). This fence may have altered local intake basin velocities slightly. However it is expected that overall mean intake basin velocity would be unaltered, as it is fixed primarily by turbine speed. Hence it is felt that strike probabilities and fish behaviour would have been minimally affected, but no empirical comparison was made between the screen-installed and screen-not-installed condition. CONTROL fish were released simultaneously with, and in the same way as the treatment fish, but 2 m downstream of the turbine. The release equipment was carefully checked to ensure that it would cause no damage to fish as a result of the release process.

Table 3.2. Experimental releases (or sampling, in the case of the UNHANDLED control fish) by date.

Date

Turbine

speed CONTROL TREATMENT UNHANDLED

Release time 2014-04-07 - - - 10 - 2014-04-10 SLOW 14 16 - 19:20 2014-04-11 FAST 14 16 - 17:45 2014-04-15 FAST 18 27 - 19:20 2014-04-16 - - - 19 - 2014-04-17 FAST 18 24 - 15:51, 17:35, 19:06 2014-04-18 FAST 19 28 - 11:35, 12:51, 14:22, 22:10, 22:45 2014-04-20 - - - 30 - 2014-04-21 SLOW 19 25 - 20:15

Figure 3.2. View of the upstream fence laid over the trash rack at the turbine intake in order to prevent fish escapement upstream and the entrance of wild fish during the trials.

3.2.5.2 Underwater CCTV monitoring

Two underwater cameras (Sony model IR 37CSHR-IR) were installed in the intake basin, connected to a digital video recorder (Avtech model KPD674 4-channel CCTV DVR H.264). The first was 2.5 m directly upstream of the turbine ca. 0.5 m

below the surface and 1 m from the floor of the basin with the entire submerged part of the turbine mouth in the field of view. The second was on the true right wall of the basin, in line with the mouth of the turbine and pointing across it, ca. 0.2 m from the floor of the basin. The intention was to quantify rate of contact between the leading edges of the turbine and introduced fish, and characterise approach behaviour. The cameras were sensitive to infrared (IR) light and equipped with IR light emitting diodes, which were also supplemented with additional small external IR lights. However the video record during darkness was completely obscured by entrained bubbles and particles lit by these lights, and so no observation was possible at night. During the day, although useful for identifying and qualitatively describing fish behaviour, the clarity and contrast of video in the shaded conditions in the basin prevented any potential observation of leading edge contact.

3.2.5.3 Recapture

A diagonal fence was installed below the turbine to guide fish into a funnel net with a mesh box at its end (Figure 3.3). The fence was constructed in several panels using metal frames and welded mesh, covered with 10 mm smooth plastic mesh and each panel shaped to fit the natural shape of the outflow basin bed. After installation the surface of the fence was checked to ensure that any potential damage to fish from contact with it was at a minimum and that there were no gaps through which fish could escape. The fence was set at an angle of 45 degrees to the flow (plan view), and inclined at a 40 degree angle to the bed. This provided a large surface area of mesh for the bulk of water to shed through, whilst guiding fish towards the recapture box. A flap of additional plastic mesh was included at the base of the fence and was covered with substrate material to ensure no gaps between the fence and the substrate. This recapture system remained in place for the duration of the experimental period.

Figure 3.3. View of the downstream fence and recapture net and box, during installation (left panel). Crowding fish towards the recapture net and box during the trials (right panel).

Not all fish arrived in the recapture system naturally and instead held station in the turbine outflow basin. These fish were encouraged into the recapture box using mesh crowding panels (Figure 3.3), and any fish remaining uncaught were carefully corralled using a seine net. In all cases the method of capture was recorded. A number of wild salmon smolts and brown trout were also captured during the trials. These must have been present within the screened off area (either above or below the turbine), and were captured and photographed. On 24 April 2014, the screen above the turbine was removed, allowing a large number of wild smolts to pass through the turbine into the recapture area. A sample of these fish were captured and processed. Results pertaining to wild fish captured below the turbine are included in Appendix A3.2.