|Steeby, J - MISS. STATE UNIV.|
Submitted to: Catfish Farmers of Arkansas
Publication Type: Abstract Only
Publication Acceptance Date: November 15, 2005
Publication Date: January 26, 2006
Citation: Torrans, E.L., Steeby, J. 2006. Managing Oxygen in Catfish Hatcheries to Increase Fry Survival [Abstract]. In: Book of Abstracts. Catfish Farmers of Arkansas Annual Meeting, January 22-28, 2006, Hot Springs, Arkansas. 2006 CDROM. 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% saturation) through hatching in the low and high oxygen treatments, respectively. Hatching time was noted for each egg mass. When the fry reached swim-up stage the tanks were harvested. Eggs hatched six hours earlier in the low oxygen treatment but reached swim-up stage 31 h later. Survival to swim-up stage in the low oxygen treatment was reduced by 18.5% (72.5% vs. 88.9% in the high oxygen treatment) and fry dry weight was reduced by 5.7%. Oxygen consumption (a measure of metabolic rate) was determined throughout the study using respirometry. Oxygen consumption increased through swim-up stage as expected. However, the incipient limiting level (the oxygen concentration required for maximum metabolism) 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 actual 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 catfish 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 estimated 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.