While much information on the size of salmon stocks at a district or regional level is obtained from analysis of the national catch and the coded wire tagging information, the fish counter programme was established by the Marine Institute in co-operation with Inland Fisheries Ireland from 1994 to 2000, to provide more direct estimates of stock size in individual rivers. This information in turn is used in the development of population models to estimate stock specific “Conservation Limits” and to subsequently assess whether these conservation limits are being met in these index rivers and therefore in other rivers without automatic counters.
Inland Fisheries Ireland are now trained in the operation, downloading and maintenance of two specific counter types i.e. the resistivity counter and the infra red counter. Many counters were fully transferred to Inland Fisheries Ireland by the end of 2006. The Marine Institute will continue to investigate, test and develop fish counting technologies on experimental rivers sites around the country in co-operation with Inland Fisheries Ireland.
The video clip shows a salmon swimming through a counting zone.
Many systems also incorporate CCTV or image-capture technology to further interpret data collected by the fish counter.