Evaluation of a Low Head Oxygenator at Giant Springs State Fish Hatchery, Great Falls, Montana

Oxygen content of water is often the primary limiting factor for fish production, as it was at the Giant Springs State Fish Hatchery, Great Falls, Montana. Spring water supplying the 24 outdoor rearing raceways has a dissolved oxygen concentration of only 6.2 ppm and is also supersaturated with gas, primarily nitrogen. The low head oxygenator (LHO) manufactured by Zeigler Brothers, Inc., was tested. The units were evaluated to determine absorption efficiency, degassing ability, and effect on fish performance. The LHO units efficiently increased the DO, reduced nitrogen from 120 to 110% saturation, and reduced total gas from 112 to 108%. Carrying capacity of raceways with the LHO units was at least 2.2 times greater than that of the controls at the time the tests were ended.