[Show abstract][Hide abstract] ABSTRACT: Mesocosm-testing of aerially applied herbicides propanil and Basis Gold (86.8% atrazine) and indicated high drift rates (10–20% of field rates) resulted in adverse impacts on aquaculture production-pond phytoplankton, zooplankton, and critical water-quality variables. Effects on fry pond phytoplankton, zooplankton, and water quality from these herbicides were evaluated at 30% of field application rates, equal to the worst-case scenario from drift to these smaller ponds with consequent higher concentrations. The study was conducted in 12 outdoor pool mesocosms of 500 L volume, filled with pond water from an adjacent 0.1 ha pond fertilized and prepared as recommended for sunshine bass, Morone chrysops × M. saxatilis, fry stocking. Plankton and water quality samples were taken just prior to herbicide application (day 0) and on days 1,2,3,4-zooplankton only, and on day 7 after application. Field application rates for Basis Gold and propanil were 0.8 kg active ingredient and 1.80 kg/ha, respectively. Significant changes from control treatment values were found for several parameters in both herbicide treatments. Following application on June 20, net primary productivity was significantly depressed on day 1 in the propanil treatments, but increased on days 2 and 3. Morning dissolved oxygen (DO) was lower on days 1–3, but not to critical levels. Also, in the presence of propanil, pH and consequently UIA were lower from day 1 to 3. Basis Gold reduced morning DO on days 2 and 3, but not net primary productivity. Nitrite-N, however, was significantly higher on day 1. Phytoplankton total numbers, and the cyanobacterium Chroococcus sp. which dominated, were reduced by propanil on days 1 -3; and similarly affected by Basis Gold on days 2 and 3. Numbers of green algae, Scenedesmus sp. and Coelastrum sp., and diatoms were, however, stimulated by propanil and diatoms by Basis Gold. Zooplankton were little affected by either herbicide. Thus, high levels of drift from propanil and Basis Gold should not result in negative impacts on fry production.
Journal of Applied Aquaculture 01/2007; 19(2):101-112.
[Show abstract][Hide abstract] ABSTRACT: An experiment was conducted to evaluate the effect of temperature on the acute toxicity of copper sulfate to juvenile channel catfish (Ictalurus punctatus). Alkalinity and hardness were 30 and 26 mg l−1, respectively. The 7–10-g fingerlings were acclimated in four climate chambers at test temperatures of 21, 23, 25, and 27 °C for 2 weeks. After determining an acutely lethal copper dose, aerated tanks of 7.6 l were placed in each climate chamber in quadruplicate. To each, seven acclimated channel catfish fingerlings were added. The 72-h cumulative mortality from 20 mg l−1 copper sulfate was significantly lower in the 27 °C treatment (25%) compared to the 21, 23, and 25 °C treatments, where cumulative mortality was 79–96%. Total mortality at 72 h was significantly correlated (P
[Show abstract][Hide abstract] ABSTRACT: Seven aerially applied cotton herbicides and defoliants were tested for possible adverse impacts on pond phytoplankton and zooplankton and critical water quality variables. Treatments simulated direct spraying of ponds and high and low amounts of drift judged able to reach the pond, 1/10 and 1/100 direct rates, respectively. The study was conducted in twelve 500-l outdoor pool mesocosms filled with pond water from an adjacent goldfish Carassius auratus culture pond. Plankton and water quality samples were taken just prior to application and at 24 and 48 h after application. Sampling for chemicals showing effects were continued approximately weekly until oxygen levels in drift treatments returned to no significant difference from control. Chemicals tested and direct rates (kg active ingredient ha−1) were diuron as herbicide (1.4), paraquat (0.83), quizalofop (0.05), dimethipin (0.15), diuron as defoliant (0.1675), ethephon (0.176), tribufos (0.99) and sodium chlorate (5.28). Except for the diuron compounds, the cotton herbicides and defoliants produced no measurable impacts on pond plankton or associated water quality. Following application on March 5 of diuron, used as an herbicide, chlorophyll a levels and photosynthesis were significantly depressed in relation to diuron concentration. Recovery occurred slowly, and at the high drift dosage by week 3 morning oxygen levels returned to near control levels, although chlorophyll a levels were 1/3 the control. However, the off-flavor cyanobacterium, Anabaena laevendri, was essentially eliminated by week 3; and pH and thus un-ionized ammonia were much lower in high drift treatments. Copepod adult and nauplii zooplankton levels were depressed at week 2. However, rotifer numbers increased in the low drift treatment in weeks 3 and 4 and those of copepod nauplii in week 3. Fall application of diuron, as a defoliant at 1/10 the spring rate, produced similar effects when compared by concentration. The main adverse impact of diuron drift is on dissolved oxygen levels and can be anticipated by provision of adequate aeration capacity.
[Show abstract][Hide abstract] ABSTRACT: Ten common aerially applied herbicides for rice were tested for possible adverse impacts on pond phytoplankton and zooplankton and critical water quality variables. Treatments simulated direct spraying of ponds and amounts of drift judged able to reach the pond at 1/10 and 1/100 direct rates. The study was conducted in 12, 500-l outdoor pool mesocosms. Pond water from an adjacent baitfish rearing pond was used. Water quality measurements were made prior to application and at 24 and 48 h after application. Commercial compounds tested and direct rates in kg active ingredient ha−1 were clomazone (0.6), thiobencarb (3.4), pendamethalin (1.1), propanil-dry, flowable (4.5), quinclorac (0.6), halosulfuron (0.07), bensulfuron methyl (0.07), triclopyr (0.4), 2,4-d-amine (1.7), and molinate (5.6). In addition, propanil was evaluated in a second application scenario at the same rates and to the same pond water sample as the initial application. Except for propanil, the rice herbicides produced no measurable effect on pond plankton or associated water quality. Following the first application at full rate for propanil, morning oxygen levels were reduced to critical levels (below 3 mg/l) for 2 days. After a second application of propanil at the full and 1/10 rates, oxygen levels were not decreased, although there were significant increases in chlorophyll a and zooplankton concentrations.
[Show abstract][Hide abstract] ABSTRACT: Harvestable, fed channel catfish, Ictaluruspunctatus were given access to two potential prey-fingerling Nile tilapia, Oreochromis niloticus and channel catfish in replicated 0.045-ha experimental, channel catfish production ponds. Three ponds were stocked in the spring with the fingerling Nile tilapia, which subsequently reproduced. Stomach contents were examined from subsamples of 50 channel catfish from each pond in October and results tabulated by catfish size group. An average of 19% of channel catfish in subsamples had consumed one or more 40-85 mm total length (TL) tilapia. Although mean frequencies of foraging did not significantly differ among catfish size groups, competition for feed pellets among size groups is hypothesized to have stimulated foraging and produced the greater foraging by smaller size groups when larger size groups were more abundant. The following spring, 90-200 mm TL fingerling channel catfish were stocked in six of the experimental channel catfish production ponds. No catfish fingerlings were found in stomachs from subsamples of 25 fish from each pond one month after stocking of fingerlings. However, a total of six fingerings (125-135 mm TL) from three ponds, seined with the larger catfish, sustained a large bite wound consistent with foraging behavior by catfish.
Journal of Applied Aquaculture 01/2001; 11(4):75-82.
[Show abstract][Hide abstract] ABSTRACT: Presented is a rapid distillation device for use with solid-phase microextraction (SPME). We apply this device specifically for determining two semivolatile off-flavor compounds, methylisoborneol and geosmin, in channel catfish. The presence of these two compounds in channel catfish filets results in unwelcome tastes. In the presented procedure, a catfish tissue sample is placed within a sample container located inside the microwave device. Microwave radiation is applied and distillates formed migrate through a condenser via a purge gas and are collected in a sample vial. A SPME fiber is placed within the stirred collected distillate and methylisoborneol and geosmin are extracted. Qualitative and quantitative results of these extractions are obtained using a gas chromatograph-ion trap mass spectrometer. This solventless technique results in detection limits far below the human threshold for these off-flavor compounds in channel catfish.
Journal of Chromatography A 01/1999; · 4.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two experiments were conducted to evaluate the effects of calcium or magnesium hardness on the acute toxicity of copper sulfate to juvenile channel catfish (Ictalurus punctatus) in low alkalinity environments. A preliminary bioassay determined the 48-h LC50 of copper sulfate to be 1.25 mg l−1 for juvenile catfish placed in water with calcium hardness and total alkalinity set at 20 mg l−1 CaCO3. In the first experiment, catfish were exposed to 1.25 mg l−1 copper sulfate in environments where calcium hardness was varied from 10–400 mg l−1 CaCO3. Total alkalinity was 20 mg l−1 CaCO3. As calcium hardness increased, copper-induced catfish mortalities decreased significantly from 90% at 10 mg l−1 CaCO3 to 5% at 400 mg l−1 CaCO3. In the second experiment, catfish were exposed to 1.25 mg l−1 copper sulfate in environments containing either calcium or magnesium hardness, 20 and 400 mg l−1 CaCO3, with total alkalinity set at 20 mg l−1 CaCO3. Survival rates in calcium hardness treatments were consistent with those in the first experiment. However, 100% mortality was observed in both treatments containing magnesium-based hardness. These data suggest a calcium-specific mechanism with respect to acute copper toxicity in channel catfish.
[Show abstract][Hide abstract] ABSTRACT: Eight, common, aerially-applied herbicides for soybeans and the rice herbicide propanil were tested for possible adverse impacts on pond phytoplankton productivity, Zooplankton populations and critical water quality variables. Treatments simulated direct spraying of ponds and bracketed amounts of drift judged able to reach the pond at and direct rates. The study was conducted in 12, 500-1 outdoor pool mesocosms. Pond water was pumped from an adjacent fingerling rearing pond. Water quality measurements were made prior to application and at 24 and 48 h after application. Commercial compounds tested and full rates (kg active ha−1) were fomasefen, aciflourfen and glyphosate (0.43); bentazon (0.57); imazaquin (0.14); fluazifop (0.10); clethodim (0.07); chlorimuron (0.0045); and propanil (0.45 kg). Ten of 1152 soybean herbicide means significantly differed and without pattern. Thus, these herbicides were judged not to affect pond plankton or associated water quality. Propanil at the full rate reduced primary productivity and morning oxygen to critical levels for 3 days.
[Show abstract][Hide abstract] ABSTRACT: Described is a rapid microwave-mediated steam distillation device for determining two predominant off-flavor compounds, geosmin and methylisoborneol, in catfish tissue. A microwave on-time of 10 min is needed to efficiently remove these off-flavor compounds from the sample matrix and trap them on a solid phase adsorbent. A minimal amount of organic solvent is used to elute the trapped compounds. The extract is then analyzed by gas chromatography with ion trap detection in the selective ion storage mode. Detection limits in the sub-parts-per-billion range are obtained with this method.
[Show abstract][Hide abstract] ABSTRACT: Methylisoborneol (MIB) and geosmin (GEO) are algal off-flavor compounds, which when present in catfish tissue create undesirable taste and odors in the prepared products. These undesirable taste and odor problems are not limited to catfish aquaculture. A procedure was developed for the determination of off-flavor compounds in channel catfish tissue that involves microwave radiation distillation with solid phase trapping. This is a modification of a microwave distillation−cold trapping procedure but without the need of a cryogen or a liquid−liquid extraction step. A channel catfish fillet sample is placed in a container located within a microwave oven. This container, which is directly connected to a thermostated condenser containing a solid phase adsorbent, is continually purged with argon gas. The trapped distillate components are eluted with ethyl acetate and then injected into a gas chromatograph−ion trap mass spectrometer for analysis. This technique offers a rapid and sensitive means of off-flavor analysis in fish tissue and improved recovery for MIB from 73 ± 3% (50 ppb) to 85 ± 5% (10 ppm) compared to 62 ± 6% for microwave−cold trap collection. The method detection limits are 1.7 and 1.1 ppb for MIB and GEO, respectively. Keywords: Off-flavors; methylisoborneol; geosmin; catfish; microwave-assisted distillation
Journal of Agricultural and Food Chemistry - J AGR FOOD CHEM. 03/1996; 44(3).
[Show abstract][Hide abstract] ABSTRACT: Several compounds exist which are responsible for unwanted taste and odor characteristics that have been found in the edible tissue of the channel catfish (Ictalurus punctatus). Methylisoborneol (MIB), one compound responsible for these off-flavors, is produced through the metabolism of cyanobacteria in aqueous systems such as reservoirs and ponds. The channel catfish accumulates MIB in its tissues from the intake of its culture-pond water. Current methods of analysis for MIB, such as closed- and open-loop stripping, and liquid-liquid extraction, are time-consuming and labor-intensive. A method for the analysis of MIB in catfish culture-pond water is described which, unlike other methods, is rapid, inexpensive, and does not require specialized sample preparation equipment. This method utilizes C18 solid-phase extraction followed by capillary gas chromatography with detection by mass spectrometry. Standard MIB and the internal standard, butylisoborneol (BIB), were prepared from the reaction of d-camphor with methylmagnesium chloride and n-butyllithium, respectively. Extraction efficiencies for MIB in channel catfish pond water averaged 89% at 101 parts per trillion (ppt) and 84% at 202 parts per billion (ppb). The detection limit of the method was calculated to be 11.5 ppt.
[Show abstract][Hide abstract] ABSTRACT: Three experiments were conducted to evaluate the relative importance of calcium hardness and bicarbonate alkalinity to the acute response of juvenile channel catfish (Ictalurus punctatus) exposed to a toxic concentration of copper sulfate. A preliminary bioassay revealed 28 mg·l−1 copper sulfate caused 50% mortality within 48 h (48-hLC50) in juvenile channel catfish placed in water with calcium hardness and bicarbonate alkalinity, set at 75 mg·l−1 CaCO3. Catfish were then exposed to 28 mg·l−1 copper sulfate concentrations in environments where hardness or alkalinity concentrations were varied. Bicarbonate alkalinities above 75 mg·l−1 CaCO3, with calcium hardness held at 20 mg·l−1 CaCO3, significantly reduced catfish mortalities from 97–100% to 63–70%. Copper-induced mortalities were 100% for all fish placed in calcium hardness treatments (20–250 mg·l−1 CaCO3) in which bicarbonate alkalinity was held at 20 mg·l−1 CaCO3. When bicarbonate alkalinity was held constant at 75 mg·l−1 CaCO3 and calcium hardness was varied from 20 to 250 mg·l−1 CaCO3, copper related catfish mortalities displayed high variability and means ranged from 6.7 to 60%. Mortalities decreased as calcium concentrations increased. Although differences in mortalities were not statistically significant, the latter hardness findings appear to suggest a biologically significant calcium effect on copper toxicity in the presence of sufficient alkalinity concentrations.