John Colt

Evaluation of the short-term toxicity of nitrogenous compounds to channel catfish, Ictalurus punctatus

Abstract The acute toxicity of un-ionized ammonia, nitrite, and nitrate to 50–76-mm fingerling channel catfish ( Ictalurus punctatus ) was investigated using a static bioassay system at 22, 26 and 30°C. The 96-h LC50 values at 30°C for un-ionized ammonia, nitrite, and nitrate were 3.8, 44, and 6 200 mg/l.

The effects of nitrite on the short-term growth and survival of channel catfish, Ictalurus punctatus

Abstract The effect of nitrite on the growth and survival of juvenile channel catfish ( Ictalurus punctatus ) was evaluated in a 31 day growth trial. The growth of the juvenile fish was reduced at NO 2 − N levels of 1.60 mg/l and above. Mortality was increased significantly at 3.71 mg/l NO 2 − N and above. The reduction in growth at the highest nitrite concentration without mortality was only 20%. The growth response of the fish at nitrite concentration levels with significant mortality was extremely variable.

The performance and design of packed column aeration systems for aquaculture

Abstract The packed column aerator (PCA) is a highly efficient aerator that can be used for oxygen and nitrogen + argon removal. Standard transfer efficiencies (N 0 ) for oxygen range from 1·5 to 2·0 kg O 2 /kWh. If 1–2 m of hydraulic head is available, N 0 can be as high as 80 kg O 2 /kWh. A mass transfer model was developed for design purposes. Recommended design parameters and procedures are presented for full-scale PCA.

The computation and reporting of dissolved gas levels

Abstract Provisional standards are proposed for the computation and reporting of dissolved gas levels in freshwater and seawater. Total gas pressure should be reported in terms of excess pressure ( Δ P ). while component gases such as nitrogen, argon, oxygen and water vapor should be reported in terms of partial or excess pressure. Barometric pressure, dissolved oxygen, water temperature and salinity must also be reported.

Production of Gas Supersaturation by Aeration

Abstract The use of submerged aerators in hatcheries can produce lethal concentrations of dissolved gases. Because the mass-transfer relationships for oxygen, nitrogen, and argon are similar, the aerators with the highest oxygen transfer efficiencies also produce the highest concentration of total dissolved gas. The dissolved-gas concentrations produced by aeration depend on ΔS∞, the percent gas supersaturation in the aeration basin after a long period of aeration divided by the depth of the aeration basin; N0, the standard transfer efficiency; the depth of the aeration basin; and the number of aerators used in series. The effect of these parameters on dissolved-gas concentrations are presented for conditions typical of trout and salmon hatcheries. The prevention of lethal and sublethal gas concentrations will result in a significant decrease in the efficiency of submerged aeration systems for oxygen transfer in aquaculture.

The effect of gas supersaturation on the growth of juvenile channel catfish, Ictalurus punctatus

Abstract Juvenile channel catfish, Ictalurus punctatus , were exposed to ΔPs ranging from −3 to 117 mm Hg for 35 days. Gas bubble trauma was observed at 76 and 117 mm Hg, but not at 36 or −3 mm Hg. The mortality in the 76 and 117 mm Hg treatments was 1% and 54%, respectively. Gas supersaturation had no effect on the growth of surviving fish at any level.

Seasonal changes in dissolved-gas supersaturation in the Sacramento River and possible effects on striped bass

Abstract During 1981–1982, dissolved-gas supersaturation levels were monitored in the Sacramento River system in central California. Gas supersaturation was highest in the spring when temperature and flow were increasing rapidly, and was caused primarily by inflows of highly supersaturated water from the American and Feather rivers. Entrainment of air at dams does not appear to be responsible for gas supersaturation in these two rivers. Gas supersaturation in the Sacramento-San Joaquin River system may adversely affect the eggs and larvae of wild striped bass Morone saxatilis and salmonids in hatcheries. Received April 9, 1983 Accepted May 11, 1984

Effects of gas-supersaturated water on Rana catesbeiana tadpoles

Abstract Rana catesbeiana tadpoles were exposed to gas supersaturated water which resulted in inflation of the gastrointestinal tract with gas. Affected tadpoles floated on the surface, either with their left sides elevated or on their backs. These clinical signs, similar to those of gas bubble disease, could be reversed by reducing the dissolved gas levels. Based on post-exposure observation for 30 days, a 4-day exposure to a ΔP of 160 to 170 mm Hg had no effect on survival. A 10-day exposure increased mortality and the levels of systemic Aeromonas hydrophila bacteria, the etiology of a serious amphibian disease, “Redleg”. Bacterial levels returned to control levels after a 6-day recovery period.