Evaluation of a Prefabricated Fish Passage Design for Great Plains Fishes

Connectivity is critical for stream fish persistence, and fish passage structures are a useful conservation tool to reconnect fragmented systems. The design of fish passage structures is a tradeoff between the area available for construction, slope, and costs associated with the structure. The Longrie-Fecteau fish passage structure was designed to be modular, adjustable to barrier-specific needs, and to have a low slope (2%) to pass small-bodied fishes. We evaluated fish passage through this structure in Fountain Creek, Colorado, USA, via a PIT tag mark-recapture study. We documented four native Great Plains fish species successfully ascending the passage structure, with most passage occurring at night. We estimated a 3% probability of a released fish entering the structure, then 89% and 99% passage to the midpoint and exit of the 123 m structure, respectively. Low entrance efficiency was due to low recapture probability of small-bodied study organisms in a relatively large system, and the low percentage of space of the entryway on this barrier (<3% of the length of the barrier). Fish that entered the structure ascended quickly, with median time for successful ascent of 19 min, and minimum time of 6 min. The Longrie-Fecteau fish passage structure is a conservation tool that may broaden the adoption of fish passage structures for small-bodied fishes due to its modularity and low slope.

Automated summary

The design of fish passage structures is a tradeoff between construction area, slope, and costs. The Longrie-Fecteau fish passage structure, with its modularity and low slope, allows small-bodied fishes to successfully ascend. Evaluation of its effectiveness in Fountain Creek, Colorado documented successful passage of four native fish species, primarily at night. The structure has a 3% entrance efficiency, but once fish enter, they ascend quickly with a median time of 19 minutes.