Effects of Dissolved Oxygen Concentration on Oxygen Consumption and Development of Channel Catfish Eggs and Fry: Implications for Hatchery Management

Abstract

Eight channel catfish Ictalurus punctatus spawns were split into two similar portions and incubated under controlled conditions to determine the effect of dissolved oxygen (DO) concentration on the development and survival of eggs and fry. The DO concentration was 7.42 ± 0.03 mg/L (mean ± SD; 92.5% saturation) and 18.40 ± 0.28 mg/L (230% saturation) through hatching in the low‐ and high‐oxygen treatments, respectively. Eggs hatched 6 h earlier in the low‐oxygen treatment, but fry reached swim‐up stage 31 h later. Survival to the swim‐up stage in the low‐oxygen treatment was 16.4 percentage points lower than in the high‐oxygen treatment (72.5% versus 88.9%, respectively). The routine metabolic rate and limiting oxygen concentration were also determined for eggs, sac fry, and swim‐up fry. Oxygen consumption increased through swim‐up stage, as expected. However, the limiting oxygen concentration peaked during the last day of incubation at 88.1 ± 2.9% saturation and decreased to 40.1 ± 2.0% saturation upon hatching. Premature hatching observed in the low‐oxygen treatment was apparently initiated when the limiting oxygen concentration approached the ambient oxygen saturation on the last day of incubation. A survey of DO management in 26 commercial catfish hatcheries in the Mississippi Delta revealed that DO saturation in the hatching troughs ranged from 45.2% to 100.2%, with only nine hatcheries (35% of the hatcheries sampled) having a DO saturation greater than 95%. Seventeen hatcheries (65%) had a DO saturation less than that maintained in the low‐oxygen treatment in our hatching experiment and could experience greater mortality through swim‐up than we observed. We recommend that hatcheries initially run well water through a packed column and use blowers or liquid oxygen to maintain the DO concentration in hatching troughs at or above air saturation as eggs near the time of hatching.

Safety of Copper Sulfate to Channel Catfish Eggs

“…Prematurely hatched fry were present in each treatment and comprised less than 1% of the total hatch; data indicated that PMH fry were arbitrarily distributed among all treatments. Torrens and Steeby (2008) suggested that low DO on the last day of incubation may account for PMH fry, and those authors found that it takes longer for these fry to reach the swim-up stage in comparison with normal fry; fry in the present study were euthanized when hatching was complete and before the swim-up stage. Straus et al (2009b) described the elimination rates of CuSO 4 from this system and the reasons for choosing the 0.22-µm nylon filter pore size and for obtaining the water sample 30 s after the treatment was applied.…”

A Vertical‐Lift Incubator (the “Seesaw”) Designed for Channel Catfish Egg Masses

“…We found survival to swim-up stage from the trough with the lowest DO concentration to be 80.9%, only 4% below the study average of 84.9% and slightly higher than the industry average of 79.3%. Our results suggest the vertical-lift incubator provides superior water (and oxygen) movement through the egg masses, and thus achieved a higher internal DO concentration in the egg masses than did Torrans and Steeby (2008) with a lower external DO concentration. However, the effect of the new incubator design on the water circulation and oxygen delivery to the center of the egg masses, which is the presumptive factor limiting egg-mass loading densities in traditional paddle-type incubators, was not directly determined.…”

“…Nitrite-N in all troughs tested was below detectable levels. Torrans and Steeby (2008) split channel catfish egg masses in half and incubated each in a separate tank using forced-air agitation. They observed premature hatching and a 16.4% poorer survival to swim-up stage with eggs incubated in water with a DO concentration of 92.5% air saturation.…”

“…Although most hatcheries (including this one) provide additional forced-air aeration to hatching troughs, none was used in the experimental troughs. Using the oxygen consumption data of developing embryos determined by Torrans and Steeby (2008) and the actual egg weights, water flows, and inlet DO concentrations in the troughs, the DO concentrations in the hatchery troughs should have dropped on days 3, 4, and 5 by 2.11, 3.04 and 3.98 ppm, respectively. In actuality, DO concentrations in the troughs decreased by an average of only 1.19, 1.24, and 1.40 ppm, respectively (Figure 3).…”

Evaluation of Sodium Carbonate Peroxyhydrate as a Potential Catfish Egg Disinfectant

“…Both SCP and hydrogen peroxide increased dissolved oxygen in the hatching troughs. This is a beneficial effect because DO concentrations above 7.4 mg/L at 268C have been shown to improve channel catfish hatching success (Torrans and Steeby 2008). The greatest effect of SCP on water quality appeared to be pH.…”