Walkin’ on water

One of the primary advantages of using an Alaskan weir (aka fish weir, portable resistance board weir) to sample salmon and other fish populations is its ability to operate effectively at a wide range of flows, such as the 1,500 cfs shown here. For high flows we fasten plastic drums under the weir panels to increase the panel’s buoyancy and keep the weir above water. However, high flows create high turbidity levels, which makes fish counting under these conditions difficult without a little technological help. We use a Vaki Riverwater that provides infrared images of fish when the turbidity is too high for the camera and video systems to work effectively.

Photo source: FISHBIO