Web-Based Calculator for Estimating Oxygen Consumption By Channel Catfish
Philip R. Pearson, Rachel V. Beecham, Susan Bailey, C. Doug Minchew, Mary Flanagan

Liquid oxygen is used to oxygenate water in grading nets that hold channel catfish overnight before being transported to the processing plant and in the hauling trucks used for channel catfish transport. It is important for planning purposes to estimate the volume of oxygen required to transport a given biomass of catfish. Using an empirically derived equation for hourly channel catfish respiration, a web-based program was developed that allows channel catfish farmers and live haulers that use diffused oxygen aeration systems to compute estimates of oxygen consumption as a guide for setting flow rates for diffusers placed in grading nets and haul tanks, respectfully. The user enters data on the water temperature, individual fish size, total fish biomass, duration of holding period, and cost information. The program estimates the oxygen gas consumption with respect to time and biomass, the liquid oxygen equivalent of that volume of oxygen, liquid oxygen expense, and the ratio of liquid oxygen expense to gross revenue. The program can be downloaded from www.ars.usda.gov/services/software/download.htm?softwareid=149.

The Effect of Pond Circulation and Paddlefish on Water Quality, Plankton, and Catfish Production
Bartholomew Green, Peter Perschbacher, Jerry Ludwig, Kevin Schrader

The objective of this study was to determine the effect on water quality, plankton and channel catfish production of stocking paddlefish in ponds without circulation or equipped with a horizontal discharge or vertical discharge upwelling circulator. Four ponds each were equipped with an approximately 6 RPM horizontal discharge circulator, an up-welling vertical discharge circulator or no circulator. All ponds were equipped with a ½-hp electric paddlewheel aerator. Ponds were stocked with stocker catfish at 3,200 lb/acre and understocked with fingerlings at 6,000/acre. Chlorophyll a concentrations were similar among treatments, and averaged 271.2, 226.2, and 262.6 mg/m³ for the control, horizontal and vertical circulation treatments, respectively. Diatoms predominated algal populations in all treatments ponds through mid-July, after which blue-green algae predominated until harvest. Off-flavor algae were present in control ponds as early as May, but were absent from circulated ponds until early-July. No treatment differences were detected among water quality variable means. Net catfish yield was similar among treatments and averaged 7,934 lb/acre, of which 90% exceeded 1.25 lb average weight. Paddlefish survival was poor, confounding results. Observed minimum daily pond dissolved oxygen concentrations were higher and daily hours of aeration were lower in the horizontal circulation treatment during July-September.