Weir Fish Counters

Three parallel electrodes embedded in the base of a weir are connected to a resistivity counter which can be used to count fish passage across the electrodes. The maximum length of a single weir section is strongly dependant on the conductivity of the water.

How does a counter work?

Blackwater, Co. Kerry
This is a three stage crump weir. The weirs crest heights are staggered to different levels to facilitate counting across the entire river under a range of different flow conditions.

Currane, Co. Kerry
The weir sections are of pre-fabricated fiberglass with electrodes embedded into the base of the weir. A transparent panel incorporating under-water lights, upstream of the electrodes, illuminates the area for CCTV verification at night.

River Boyne, Co. Meath
To prevent cross-talk across the electrodes through the underlying concrete weir the electrodes are mounted on high-density polyethylene. Using polyethylene has the added advantage of providing a good contrast for any salmon swimming over the weir.

River Eaney, Co. Donegal
A two stage crump weir completed in 2000. The equipment hut is raised clear of potential flood levels.

Casla, Co. Galway
This is a single channel weir with a wide-angle camera mounted mid-stream on a scaffolding frame. Overhead lights allow video verification of the counters performance 24 hours a day.