We would like to inform you about a research carried out by Scottish Natural Heritage that addresses how different types of counters compare.
There they claim that the optical counters such as the VAKI Riverwatcher suffer less than current resistivity counters from false counts since an outline of the object responsible is recorded for the operator to verify. Also that a camera add-on can reduce the possibility of false counts.
The report also states that since optical counters can estimate the size of each fish with a reasonable degree of accuracy, they are more reliable than resistivity counters for distinguishing between Atlantic salmon and Sea trout.
Excellent performance of optical counters
Finally the tests conducted by the Icelandic Institute of Freshwater Fisheries on the River Blanda found the VAKI Riverwatcher Counter to be 98,9% accurate, whilst a more recent time-lapse video validation study on the Itchen in England found the counter to be 93% accurate in counting fish. Furthermore, when debris, turbidity and air bubble entrainment were kept to a minimum the accuracy increased to 100%.