Verdel K. Dawson

The Half-Life of Biological Activity of Antimycin Determined by Fish Bioassay

Abstract The half-life of biological activity of antimycin, a powerful fish toxicant, was determined using fish bioassays at different test temperatures and pHs. The species exposed in decreasing order of sensitivity to the toxicant include rainbow trout, bluegill, green sunfish, goldfish, channel catfish, and black bullhead. Antimycin is deactivated more rapidly at higher temperatures, but the high temperatures did not influence the deactivation as greatly as high pH levels. The half-lifes at the different pHs are as follows: pH 6 and 6.5 = 310 hours, pH 7.5 = 120 hours, pH 8 = 100 hours, pH 8.5 = 46 hours, pH 9.0 = 9.7 hours, pH 9.5 = 4.6 hours, and pH 10 = 1.5 hours.

Computer Program Calculation of Gas Supersaturation in Water

Abstract A short computer program, written in BASIC for the Apple IIe or IBM PC computer, efficiently performs all the calculations required to determine gas pressure and percent saturation values for water. Input for the program is limited to empirical determinations of barometric pressure, water temperature, differential dissolved gas pressures, dissolved oxygen, and salinity. An optional routine is included for obtaining a printed report of input data and results. The program can be easily modified to run on most other microcomputers that use BASIC programming language.

Rapid method for measuring rotenone in water at piscicidal concentrations

Abstract A high-performance liquid chromatography (HPLC) procedure that is rapid, specific, and sensitive (limit of detection <0.005 mg/liter) was developed for monitoring application and degradation rates of rotenone. For analysis, a water sample is buffered to pH 5 and injected through a Sep Pak(R) C18 disposable cartridge. The cartridge adsorbs and retains the rotenone which then can be eluted quantitatively from the cartridge with a small volume of methanol. This step effectively concentrates the sample and provides sample cleanup. The methanol extract is analyzed directly by HPLC on an MCH 10 reverse-phase column; methanol: Water (75:25, volume : Volume) is the mobile phase and flow rate is 1.5 ml/minute. The rotenone is detected by ultraviolet spectrophotometry at a wavelength of 295 nm. Received November 29, 1982 Accepted May 24, 1983

Comparison of column aerators and a vacuum degasser for treating supersaturated culture water

Abstract Supersaturation of nitrogen gas in water is a common problem in fish culture; mild cases cause stress and severe incidences cause gas bubble disease. Numerous techniques have been proposed for the elimination of excess gas. A vacuum degasser, a column aerator, and a combination of the two aeration systems were evaluated for treating supersaturated well water at the La Crosse (Wisconsin) National Fishery Research Laboratory. The degasser, the column aerator, and the combined systems effectively reduced nitrogen gas from about 133% to near 100% of saturation. However, the vacuum degasser also decreased the dissolved oxygen from 27 to 22% of saturation, whereas the column aerators increased the oxygen level to over 91 % of saturation. The column aerator system is recommended because it is easy to construct, reasonable in cost, requires little maintenance, consumes no energy other than head pressure, and is highly efficient for altering concentrations of nitrogen and oxygen to levels suitable for fis...

Removal of Toxic Chemicals from Water with Activated Carbon

Abstract Activated carbon was effective in removing fish toxicants and anesthetics from water solutions. Its capacity to adsorb 3-trifluoromethyl-4-nitrophenol (TFM), antimycin, Noxfish(R) (5% rotenone), Dibrom(R), juglone, MS-222, and benzocaine ranged from 0.1 to 64 mg per gram of carbon. The adsorptive capacity (end point considered as a significant discharge) of activated carbon for removal of TFM was determined at column depths of 15, 30, and 60 cm; temperatures of 7, 12, 17, and 22 C; pHs of 6.5, 7.5, 8.5, and 9.5; and flow rates of 50, 78, 100, 200, and 940 ml/min. Adsorptive capacity increased when the contact time was increased by reducing the flow rate or increasing the column depth. The adsorptive capacity was not significantly influenced by temperature but was substantially higher at pH 6.5 than at the other pHs tested. A practical and efficient filter for purifying chemically treated water was developed.

An Integrated System for Treating Nitrogen Supersaturated Water

Abstract Groundwater is commonly supersaturated with nitrogen and must be treated before it is used for culturing fish–especially sensitive species such as lake trout (Salvelinus namaycush) and Atlantic salmon (Salmo salar). We treated water with an integrated system that passed water through a packed column aerator, then through a vacuum degasser, and finally through another packed column aerator (installed as a backup system). Packed-column aeration prior to vacuum degassing provided increased efficiency because only a small amount of vacuum was required to remove the remaining excess nitrogen, and oxygen levels were not affected by the vacuum degasser. In well water passed through packed columns, nitrogen gas was reduced from 131 to 105% of saturation and oxygen was increased from 23 to 86% of saturation. With a vacuum pressure of 3 in Hg, the degasser further reduced the nitrogen gas from 105 to 99% of saturation, and oxygen saturation remained near 86%. The integrated system provided water in which a...

Potential for nitrosamine formation in seven fishery chemicals

Abstract In recent years, nitrosamines have been reported as possible causes of cancer, mutations, or birth defects. Inasmuch as these compounds may be formed by the interaction of certain amines with nitrite in the aquatic environment, we evaluated seven fishery chemicals for their potential to form nitrosamines: the experimental fish toxicant digeranylethanolamine (GD-174); the four therapeutants Terramycin, erythromycin, Hyamine 1622, and Hyamine 3500; and the two tracer dyes rhodamine B and rhodamine WT. The results indicate that the controlled use of the seven fishery chemicals in natural environments will not lead to the formation of nitrosamines.

Aspects of the Life History of the Calico Crayfish with Special Reference to Egg Hatching Success

Abstract Life history data were collected on adult (≥25 mm carapace length) female calico crayfish (Orconectes immunis) in conjunction with an egg-hatching study during 1986–1988. Eggs stripped from 10 females in October 1986 and 10 females in September 1987 were pooled each year and hatching success was monitored for samples of 100 eggs placed in each of eight diluter aquaria at 12°C. In fall 1987, berried calico crayfish were cultured at 12, 25, and 30°C and hatching was monitored. Data on length, weight, and number of eggs produced were collected for 28 females in September 1987 and 36 females in April 1988. An additional 456 female crayfish were checked for the presence of eggs. Hatching success was 86% in 1986 and 89% in 1987. The eggs on berried females held at 12°C started to hatch within 33 d. At 25°C, hatching started within 10 d. At 30°C, no hatching occurred, the eggs became orange (indicating death), and most of the eggs later developed fungal infections. The average number of eggs carried was...