Evaluation of an electric fish barrier on the South Canal, an irrigation ditch on the lower Gunnison River, Colorado

Evaluation of an electric fish barrier on the South Canal, an irrigation ditch on the lower Gunnison River, Colorado

An electric fish barrier was installed on the east portal of South Canal to reduce fish entrainment associated with the construction of two hydropower plants in 2012. The objective of this study was to monitor fish entrainment and evaluate the effectiveness of the barrier. Three groups of fish were tagged and released upstream of the barrier; fish from the canal, wild Gunnison River fish, and hatchery reared fingerlings. Mark recapture boat electrofishing was completed and population estimates were made with the Huggins Closed Capture model using fish length to model capture probabilities. The study reach contained 2,994 ± 1,043 fish (>150 mm) in October 2011, 1,764 ± 279 in October 2013, 1,224 ± 239 in July 2014 and 1,900 ± 379 in October 2014. Fish population estimates have declined after the electric barrier, significantly at the 95% level for brown trout but not for rainbows. A total of 288 tagged fish less than 300 mm and four fish greater than 300 mm were recovered below the barrier, representing 1.3% of all tagged fish. The electric barrier appears to meet its objective and successfully exclude larger fish from the study reach, but not smaller age 0, age 1, or age 2 trout. The entrainment, growth and survival of smaller fish maintains a stable population of fish in the canal, but fewer entrained mature fish is likely a benefit to the fish population of the Gunnison River. Further study is needed to evaluate if smaller adult trout can be successfully excluded by the electric barrier with operational modifications.

Kowalski, Dan

Sport fish

Fishing

South canal

Research

18 pages

2012

Text

application/pdf

English