|Steeby, Jim - MSU-ES|
Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: May 5, 2006
Publication Date: June 1, 2006
Citation: Torrans, E.L., Steeby, J. 2006. OXYGEN MANAGEMENT OF CHANNEL CATFISH HATCHERIES. Global Aquaculture Advocate 9(3):56,57. Interpretive Summary: The effect of dissolved oxygen concentration on hatching and survival of channel catfish eggs and fry was studied. It was determined that dissolved oxygen should be near or above saturation during the last day of egg incubation to prevent premature hatching and increased mortality of the fry. A survey of dissolved oxygen in commercial hatcheries indicates that survival could be increased by 10-20% across the industry with proper oxygen management.
Technical Abstract: Eight channel catfish Ictalurus punctatus spawns were split into two approximately equal portions and incubated in separate 185-L square fiberglass tanks. Eight of the tanks were aerated with air supplied by a blower; the other eight tanks were aerated with liquid oxygen (LOX). Dissolved oxygen (DO) averaged 7.4±0.02 (94.3% saturation) and 18.4±0.28 mg/L (232.8%) through hatching in the low and high oxygen treatments, respectively. Eggs hatched six hours earlier in the low oxygen incubation but reached swim-up stage 31 h later (P<0.001). Survival to swim-up stage in the low oxygen treatment was reduced by 18.5% (P<0.10) and fry dry weight was reduced by 5.7% (P<0.05). Oxygen consumption was determined throughout the study using respirometry. Oxygen consumption increased through swim-up stage as expected. However, the incipient limiting level (the oxygen concentration at which metabolism became oxygen-limited) peaked during the last day of incubation at 96% saturation, and decreased to less than 50% saturation after hatching. It is postulated that premature hatching observed in this study was precipitated in the last day of incubation when the incipient limiting level (96% saturation) exceeded the environmental oxygen saturation (94.3%) to which the eggs were exposed. A field survey of 26 commercial catfish hatcheries in the Mississippi delta was conducted during the 2005 spawning season. The hatcheries sampled represent approximately 40% of the annual hatching capacity of the 1.8-billion-fry industry. Oxygen saturation in the hatching troughs sampled ranged from 45.2% to 100.2%. Nearly half of the hatcheries (12 of 26) maintained DO at less than 90% saturation (7.2 mg/L at 26.7 C/80 F), while only 7 of 26 maintained DO at over 96% saturation (7.8 mg/L at 26.7 C). It is possible that production of swim-up fry could be increased by as much as 200-400 million/year by maintaining water at >96% oxygen saturation during the last day of incubation.