Design and Testing of a Closed, Stirring Respirometer for Measuring Oxygen Consumption of Channel Catfish Eggs

—A closed, stirring respirometer was designed to agitate small egg mass samples of channel catfish Ictalurus punctatus while measuring oxygen consumption by the eggs. Egg mass samples ranging in size from 15 to 46 g were placed on a screen platform above a magnetic stir bar in the respirometer; the degree of agitation was controlled with a magnetic stir plate. Dissolved oxygen (DO) concentration and temperature were measured with a luminescent DO sensor and meter. The respirometer was used to determine routine metabolic rate and limiting oxygen concentration (the presumed hypometabolic transition zone) on egg mass samples from 10 different spawns at 0 to 5 d postfertilization. Routine metabolic rate increased from 4.8 6 1.3 (0 d postfertilization) to 174.0 6 7.8 mg O 2 kg 1 h 1 (5 d postfertilization). The limiting oxygen concentration increased similarly up to 87.0% 6 2.7% (maximum individual value 1⁄4 95.9%) air saturation by 5 d postfertilization. The respirometer described could not be used for sac fry, but it proved effective with clumped channel catfish eggs. Preliminary channel catfish hatchery management recommendations are to maintain DO concentrations in hatchery troughs at air saturation at least during the last day of egg development. Approximately 2.3 3 10 eggs are produced annually by the U.S. channel catfish Ictalurus punctatus industry (Steeby and Wagner 2005). The industrywide hatch rate averages close to 80% but is highly variable (Broussard and Stickney 1981). Although the basic mechanics of channel catfish hatchery operations have remained relatively unchanged since the early efforts (Clapp 1929), research has addressed several factors affecting hatch and fry