Assessment of an infrared fish counter (VAKI Riverwatcher) to quantify fish migrations in the Murray-Darling Basin
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Authors: B Zampatti, J McPherson, K Beyer, L Baumgartner, M Jones
February 8, 2012
NSW Fisheries Final Report Series No 116
Baumgartner, L., Bettanin, M., McPherson, J., Jones, M., Zampatti, B. and Beyer, K., 2010. Assessment of an infrared fish counter (VAKI Riverwatcher) to quantify fish migrations in the Murray-Darling Basin. Industry & Investment NSW – Fisheries Final Report Series No. 116. Cronulla, NSW, Australia. 47pp.
For many years, scientists have used manual trapping methods to capture migrating fish. In terms of costs and logistics, it is impossible to continuously trap migrating fish, but the long-term deployment of a remote electronic monitoring unit can offer a cost-effective alternative to manual trapping. Few such systems are available and virtually none have been assessed for Australian waterways. If a system can be found which accurately counts and measures fish, it could be used to determine long-term trends in fish migration over time. In this project, a field study was done on the effectiveness of an infrared fish counter, the VAKI Riverwatcher, in anticipation of wider application throughout the Murray-Darling Basin.
The VAKI Riverwatcher technology is based on an electronic fish counter which also records the date and the sizes and shapes of fish which pass through an infrared scanner. The system comprises a scanner unit, display unit, storage cabinet and optional photo tunnel. The scanner unit generates an infrared net of light beams inside a frame. When set in a river or creek, fish which move through the scanner ultimately break the infrared beams. This action triggers the unit to record the outline of the fish, then take a length measurement before recording a 5 second video to aid subsequent identification of the fish species.
Researchers assessed a Riverwatcher unit at Lock 10 (Wentworth) on the Murray Riverin November and December 2008. The unit was used in conjunction with other electronic monitoring gear, and also fish traps, to assess the ability of the Riverwatcher to distinguish different species, count migrating fish, estimate the size of migratory fish and to assess fish behaviour in and around the unit. The Riverwatcher performed well and counted hundreds of migrating fish. Fish counts from the unit roughly corresponded with those caught within a fish trap upstream of the unit. However, the unit tended to underestimate fish size and some fish avoided contact with the unit.
Overall, the assessment was successful and it is recommended that the system be refined for further use in the Murray-Darling Basin. Additional trials would help to determine if the gear is suitable for determining trends in fish movement over a longer time period. Even though the unit may underestimate counts and sizes of fish, it could provide a useful tool to determine cues for migration and to investigate seasonal changes in fish movement rates. If the initial promise is borne out during these subsequent evaluations, the technology could be implemented at several key fish migration sites as a way of assessing the effectiveness of river rehabilitation efforts.