Over the last few weeks there has been a lot of discussion about invasive carp, including the release of the preliminary results at Barkley Lock, the recommendation from the Tennessee Valley Authority for BAFF systems to be installed at up to seven locations, and media outlets picking up on the news that invasive carp have undergone a name change.
For Fish Guidance Systems the key discussion is over the preliminary, real world, results from Barkley Lock in Kentucky, where a trial BioAcoustic Fish Fence (BAFF) system has been operating since December 2019.
Results, released by Judge White at the end of June, are preliminary but ‘254 fish were tagged and tracked from November 1, 2020, to February 13, 2021. Out of those fish, 57 crossed the barrier when it was turned off (a total of 129 crossings); only four fish crossed the barrier when it was turned on (a total of 7 crossings). Additionally, the fish approached the barrier 3,181 times when it was turned off; the fish approached the barrier 612 times when it was turned on.’
This means that in preliminary results the BAFF system is 95% effective in deterring invasive carp from passing the barrier, but how is this number achieved?
How is the 95% effective number achieved
To determine the effectiveness of the deterrent, a simple formula, that includes data from when the system is off and on, is used
100x(BAFF OFF CROSSINGS)/(BAFF ON CROSSINGS + BAFF OFF CROSSINGS) %,
An event is when there is a confirmation of at least three detections upstream of the 15 metre buffer zone around the BAFF. The system itself is currently being trialled by having the system switched on for one week and then switched off the following week. The buffer zone allows for some uncertainty over the exact line of the BAFF at any given time owing to water movements and streaming characteristics of the bubbles.
This methodology allows researchers to have two sets of data, one from when the water around the lock is not affected by the BAFF system, and another set with the system is active. This allows researchers to reduce variables such as water temperature, height and turbidity as the data sets are only a week apart.
With the data collected between November 2020 and February 2021 fed into the above formula, the system during this period can be said to be 95% effective as a deterrent.
Judge White stated that ‘the news was promising and a critical first step in understanding the technology, but that more time is needed to complete the study. The U.S. Fish and Wildlife Service wants to observe fish behavior over different seasons (spring, summer, fall, and winter), and there’s ongoing efforts to tag more carp for a larger sample size of data.’
For further information on the BAFF system, and the results at Barkley Lock, please contact [email protected].
