|Steeby, J - MISS. STATE UNIV.|
Submitted to: Aquaculture
Publication Type: Abstract Only
Publication Acceptance Date: August 2, 2005
Publication Date: February 13, 2006
Citation: Torrans, E.L., Steeby, J. 2006. Oxygen Consumption of Channel Catfish Ictalurus punctatus Eggs and Fry: Implications for Hatchery Management [Abstract]. In: Book of Abstracts. Aquaculture America, February 13-16, 2006, Las Vegas, Nevada. p. 328. 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 (P<0.0001). Hatching time was noted for each egg mass. When the fry reached swim-up stage the tanks were harvested. Metabolic rates were determined using an optical DO sensor in a closed micro-respirometer (see poster session for details). Metabolic rate increased through swim-up stage as expected. However the incipient limiting level (the 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. Eggs hatched six hours earlier in the low oxygen incubation but reached swim-up stage 31 h later (P<0.001). It is postulated that premature hatching may be precipitated in the latter stages of incubation when the environmental oxygen saturation is below the incipient limiting level, which occurred during the last day of incubation in this study. 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). 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 hatching capacity of the industry. Oxygen saturation in hatching troughs ranged from 45.2% to 100.2%. Nearly half of the hatcheries (12/26) maintained DO at less than 90% saturation (7.2 mg/L at 26.7 C/80 F), while only 7/26 maintained DO at over 96% saturation (7.8 mg/L at 26.7 C). Our data indicates that time to swim-up stage could be reduced by over a day and survival to swim-up in the 1.8-billion-fry industry could be significantly increased by maintaining hatchery water >96% saturation.