At some sites, the pre-fabrication of almost the entirety of a fish pass can reduce the total cost of installing a fish pass on a weir or barrier.

This is particularly true if the access to a site is very difficult, or restricted. One site of this type is Narborough weir on the River Nar. Following the design of the fish pass, Fishtek fabricated the entire fish and eel pass unit for the site.

This was a pair of Larinier and eel pass units, which were dropped into notches cut in the existing structures at the upstream end and supported further down each fish pass unit by an intermediate ‘pier’. The resulting fish pass allows fish passage past what was previously a largely impassable barrier.