Technical Abstract: A 2004 field study conducted during actual channel catfish Ictalurus punctatus harvests, and a small-scale research study conducted in 2005, required continuous collection of dissolved oxygen concentration and temperature at two depths in the water column. The on-farm study required data collection in grading nets loaded with high densities of channel catfish, whereas the small-scale study was conducted in one-tenth-acre channel catfish research ponds. Commercially available monitoring units did not meet study requirements, so a free-floating data collection unit comprised of a combination of state-of-the-art sensor and datalogger technology and readily available materials was developed. The data collection units proved durable under conditions existing in both loaded grading nets and in small research ponds.