User manual

Science Manual – Using Video Images for Fisheries Monitoring 15
For smaller sites, a less powerful LED lamp (Table 3.1) supplied by RF Concepts
(Table 3.4) would provide sufficient light to enable fish counting. This lamp is
waterproof but cannot be immersed. When positioning lighting, remember that a lot
of light will be absorbed at the water surface and that infrared light is rapidly
attenuated in water.
3.3.3 Floodlights
Security floodlights can be deployed in air to illuminate the area. Red filters can be
attached to reduce any potential impact on fish movements. Floodlights will not be
suitable for a stand-alone battery-powered site, due to the high power requirements.
3.3.4 Fluorescent tube lighting
Fluorescent tubes are used for overhead lighting above some resistivity weirs where
suitable covering or housing exists. This is generally restricted to the non-spate rivers
like the Test and Itchen, but is effective in providing good quality images for analysis
and motion detection.
An underwater light box using fluorescent tubes as its light source was fitted to the
bottom of a fish pass on the Cardiff Bay Barrage. The subsequent poor reliability,
high maintenance and overall cost of this deployment, together with the recent
technological advances of LED lighting, means that this method is not a viable
option.
Figure 3.5: A covered resistively weir lit by fluorescent tubes, River Test