The Fish Ladder
For permission to build a new dam, the Wisconsin Department of Natural Resources required that it be accompanied by a fish ladder. (Also referred to as fishway or fish passage.) The concern was that once the dam was in place certain protected species of fish could become isolated either in the pond or in the stream below the dam. To comply, a special circular slowly flowing route was designed by Friends of Beckman Mill Coordinator Bob Fosler and was approved by the Department of Natural Resources,U. S. Corps of Engineers and Rock County.
Building of the Fish Ladder Begins in 2001
Actual construction began in June, 2001 and was completed five months later in November. All work was performed by the Friends of Beckman Mill volunteer work crew and required 1,940 man hours of labor, 108 yards of concrete, 347 tons of rocks and boulders, plus reinforcing rod, concrete forms, and other materials.
The unique fish ladder incorporates a curved 140-foot long series of “pools” and “riffles”. The pools, of which there are seven, act as miniature holding ponds while the eight riffles slow the flow of water to allow small species of fish to navigate the route from the stream below the dam to the pond. Limestone paths border the passage on both sides. Water flow is controlled by a gate at the inlet.
The two protected species of fish are the Redfin Shiner (Lythrurus umbratilis) and the Starhead Top Minnow(Fundulus dispar). When mature the Redfin Shiner is less than 4 inches in length and the Starhead, less than 2.5 inches.