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The present study was designed to determine the optimal level of calcium hardness in hatching waters to incubate channel catfish Ictalurus punctatus × blue catfish I. furcatus hybrid catfish eggs. Hatching success of hybrid catfish eggs was higher (P < 0.05) at a calcium hardness (CaCO3) of 75 mg/L in hatching waters than at a calcium hardness of 25 or 50 mg/L; however, further increases in calcium concentration did not improve hatching success. A minimum water hardness of CaCO3 at 75 mg/L is recommended for incubating hybrid catfish eggs. Received September 13, 2011; accepted November 22, 2011 [ABSTRACT FROM AUTHOR]

A 2 x 2 factorial experiment was conducted to evaluate the effects of commercial diets (32% protein, 3% fat [32/3 diet] or 36% protein, 8% fat [36/8 diet]; Malick Aquafeed, Inc.) and the influence of strain (U.S. Department of Agriculture [USDA] 103 or Norris) on performance variables and mitochondrial respiratory chain enzyme activities in the liver, muscle, and intestine of channel catfish Ictalurus punctatus. Juvenile channel catfish (average weight = 29.71 and 38.79 g for USDA 103 and Norris strains, respectively) were stocked into sixteen 152-L aquaria at a density of l0 fish/aquarium. Four aquaria were used for each dietary treatment. Fish were fed twice daily to apparent satiation for 16 weeks. Results indicated that diet and strain had significant (P < 0.05) main effects on weight gain, feed consumption, feed efficiency, and specific growth rate. Diet composition had a significant main effect on condition factor, regardless of strain. There was a significant (P < 0.0007) fish strain x diet composition interaction effect on feed efficiency. Regardless of strain, fish fed the 36/8 diet formula had higher activities for respiratory enzyme complexes I, II, III, and IV in the liver, intestine, and muscle than fish fed the 32/3 diet. The main effect was significant but not consistent for complex I and IV activities in the liver and muscle and complex II activities in the liver and intestine. The fish strain x diet composition interaction effect was significant for complex I activity in the liver and for complex II and IV activities in the muscle. These data demonstrate that the USDA 103 strain of channel catfish appears to possess superior traits in growth performance compared with the Norris strain. Our data indicate that diet has an important effect on channel catfish production and that a commercial 36/8 diet produces enhanced growth performance and mitochondrial enzyme activities relative to a 32/3 diet. [ABSTRACT FROM AUTHOR]

This study was conducted to gain a better understanding of the effect of exposure to the myxozoan Henneguya ictaluri (the agent of proliferative gill disease [PGD]) on host physiology by measuring the variation in selected blood characteristics in three differently affected host taxa (channel catfish Ictalurus punctatus, blue catfish I. furcatas, and blue catfish x channel catfish hybrid fingerlings). Forty-five fish of each host taxon were exposed to PGD, mad 10 fish of each host taxon were sampled at 24, 96, and 168 h. Fish were weighed, blood was collected and analyzed for a suite of physiological variables, and wet mount preparations of gill clips were examined grossly for the presence of cartilage breaks. The results of this study are consistent with the current knowledge regarding H. ictaluri infections in blue catfish, channel catfish, and blue catfish x channel catfish hybrids. Chondrocytic lysis was observed in channel catfish and hybrid catfish at 96 and 168 h but was not observed in blue catfish. There was an observed reduction in oxygen partial pressure (pO2) and an increase in carbon dioxide partial pressure (pCO2) at 96 h in the blood of channel catfish and hybrid catfish, but these changes were not exhibited by blue catfish. For all species, pH decreased as lactate concentrations increased. The lack of physiological changes and the absence of H. ictaluri sporozoites and DNA in gill tissue lead us to speculate that H. ictaluri is unable to estabfish infection in blue catfish. Current research investigating the mechanisms of infection and portals of parasite entry into blue catfish, channel catfish, and blue catfish x channel catfish hybrids is underway to better elucidate the defenses employed by blue catfish against H. ictaluri. [ABSTRACT FROM AUTHOR]

Over-fertilization with phosphorus and carryover copper residual in the sediment from copper sulfate treatment in double-cropped ponds were suspected as the primary causes of low larval percid survival in coolwater aquaculture ponds. Consequently, in this study, we compared saugeye (male sauger Sander canadensis X female walleye S. vitreus) survival, growth, and yield among ponds that were single-cropped with only saugeyes in the spring during the previous two consecutive years (SS ponds) and ponds that were double-cropped (with saugeye culture in the spring and channel catfish Ictalurus punctatus culture in the summer) during the previous two consecutive years (DD ponds). We also compared sediment phosphorus (soluble reactive phosphorus [SRP] and total phosphorus [TP]), sediment copper concentrations, phytoplankton biomass, and zooplankton biomass. Fish survival (number harvested) and fish yield (mass harvested) were significantly lower in DD ponds than in SS ponds in 2001 but were similar in 2002 (a year of wide temperature fluctuation early in the production season). Sediment analyses revealed that DD ponds had significantly lower SRP and TP but higher copper concentrations than did SS ponds. A detailed study done in 2002 revealed that individual length and wet weight of percids were significantly higher in the SS ponds than in DD ponds; phytoplankton biomass was similar in both sets of ponds, while zooplankton biomass was significantly lower in DD ponds. These results suggest that residual materials used in double-cropped channel catfish ponds may negatively affect subsequent years' percid culture. [ABSTRACT FROM AUTHOR]

Fungal infestations of channel catfish Ictalurus punctatus eggs can lower hatch rate, which requires the producer to spawn more channel catfish or risk fingerling shortages. Hydrogen peroxide (H2O2) treatments (0.0, 15.6, 31.3, 62.5, 125,250, 500, 1,000, 2,000, and 4,000 mg/L) were evaluated to determine their effect on channel catfish hatch rate (number of fry/number of eggs X 100) and control of naturally occurring infestations of fungi Saprolegnia spp. in an experimental compartmentalized trough hatching system. Experiments were run at water temperatures of 23.2-24.0°C, dissolved oxygen concentrations of 4.5- 6.8 mg/L (53-79% saturation), total alkalinity of 209-217 mg/L, and total hardness of 91-110 mg/L. Treatments were applied to hatching compartments while well water was flowing at a rate of one water exchange every 30 rain and egg density was 2.5 g eggs/L of water. Observations for fungal development were made daily, and the maximum measure of fungal growth was recorded. An initial range-finding study demonstrated that H2O2 concentrations greater than 500 mg/L lowered the hatch rate. In later experiments, concentrations of 125, 250, and 500 mg/L applied for 6 d significantly increased the hatch rate and reduced fungal growth when compared with the controls. The 250-mg/L H2O2 treatment had the highest mean hatch rate (64.4% compared with 24.7% for the controls), lowest incidence of fungal infestation (27.3% compared with 100% for the control), and the lowest average fungal growth (an average measure of 0.95 cm compared with 7.23 cm for the controls). [ABSTRACT FROM AUTHOR]

A 4-year pond study was conducted to compare net production, feed conversion, processing yield, and body composition of channel catfish Ictalurus punctatus that were fed once daily, fed every other day (EOD) to satiation, or fed an amount not exceeding 110 kg.ha⋅ha-1⋅d-1 in a multiple-batch cropping system. The greatest amount of feed administered was observed for the daily satiation group, followed by the 110-kg⋅ha-1d-1 group and the EOD group (P ≤ 0.05). Net production of fish fed daily to satiation did not significantly differ from that of fish fed up to 110 kg⋅ha-1⋅-1, but that of fish fed daily (satiation or ≤ 110 kg/ha) was significantly higher than that of fish fed EOD to satiation. Feed conversion ratio was significantly lower in fish fed up to 110 kg⋅ha-1⋅d-1 or EOD to satiation than that of fish fed daily to satiation. Carcass, fillet, and total meat yields did not differ among feeding regimens. Fish fed EOD to satiation had lower fillet fat and higher fillet moisture than fish fed daily to satiation. Feed restriction to no more than 110 kg⋅ha-1⋅d-1 did not significantly affect fillet composition of channel catfish compared with fish fed daily to satiation. It appears that limiting the feeding rate to 110 kg⋅ha-1⋅-1 at a stocking density of 14,830 fish/ha would improve feed efficiency without causing significant reduction in weight gain, net production, or processing yield and would thus increase farm profits. Feeding channel catfish EOD to satiation may be acceptable as a short-term strategy when economic conditions justify it. However, it may not be economical for the long term because of lower production, increased length of the production cycle, and reduced processing yield. [ABSTRACT FROM AUTHOR]

Channel catfish Ictalurus punctatus do not feed well at low temperatures. It is generally thought that a diet containing fish meal enhances feed palatability at low temperatures since fish meal is highly palatable to fish. There is a lack of information on the effects of fish meal levels on the growth performance of channel catfish reared at low temperatures. Therefore, a study was conducted in a recirculating system to examine the effects of fish meal levels on the feed consumption, weight gain, and feed efficiency of juvenile channel catfish reared at various temperatures. Fish with an initial weight of 9.6 ± 0.1 g were stocked in 23-L clear polycarbonate tanks maintained at approximately 17, 21, or 27 °C. The fish were fed with diets containing 0, 4, or 8% menhaden Brevoortia spp. fish meal for 9 weeks. There was a significant interaction between water temperature and fish meal level with respect to weight gain. At 27°C, fish fed diets containing 4% and 8% fish meal gained significantly more weight than fish fed the all-plant-protein diet. However, the level of fish meal had no significant effect on the weight gain of fish at 17°C or 21°C. This suggests that the olfactory and gustatory responses of channel catfish to fish meal (up to 8% in the diet) may not be as sensitive at low temperatures as at optimum temperatures. The results also indicate that more than 4% fish meal in the diet is not beneficial for the optimum growth and feed efficiency of channel catfish fingerlings raised at 27°C. [ABSTRACT FROM AUTHOR]

Sixty-eight families of USDA303 channel catfish Ictalurus punctatus were evaluated for growth performance for 30 d. The fastest- and slowest-growing channel catfishfamilies were further evaluated to examine the hypothesis that genes or gene products associated with the growth regulatory and stress axes can be used to describe differences in growth performance. Research examined mRNA levels of genes involved in the growth hormone-insulin-like growth factor (GH-IGF) network in fast- (family A) and slow-growing (family H) USDA303 catfish. Fish (59.0 ± 2.4 g) were fed for 7 weeks, weighed, and had tissues for RNA extraction. The remaining fish were subjected to an acute 10-min dewatering stress. Insulin-like growth factor-II mRNA was higher in the muscle of fast-growing fish, while the levels of IGF-I receptor (IGF-IR) and IGF-I1 receptor (IGF-II) were similar. Muscle IGF-IIR mRNA was two-fold higher than muscle IGF-IR mRNA. There were no differences in liver and muscle IGF-I and GH receptor mRNA or pituitary GH mRNA between the fast- and slow-growing fish. Fast-growing fish consumed 135% more feed than slow-growing fish, though the abundances of ghrelin mRNA in the gut and neuropeptide Y mRNA in the hypothalamus were similar. Cortisol levels were negatively correlated to weight gain. These results suggest that the variation in growth between fast- and slow-growing USDA303 catfish is explained, in part, by the variation in the GH-IGF and stress axes. The relationship between cortisol and weight gain warrants further investigation for possible exploitation in our selective breeding program. [ABSTRACT FROM AUTHOR]

The channel catfish Ictalurus punctatus is an important aquaculture species in the United States and has received considerable research attention in efforts to improve production. Three traits of importance to the U.S. farm-raised channel catfish industry are disease resistance, growth, and reproduction. While many factors affect these three traits, a fish's response to stress can have a substantial impact on production attributes. Understanding the relationships between the stress response and components of that response, such as plasma cortisol concentration, is important to the development of better management and breeding practices to maximize production. Although much of the data regarding the fish physiological consequences of stress and elevated plasma cortisol has been collected from studies of salmonids, recent advances have been made toward understanding these relationships in channel catfish. The present review synthesizes the research conducted over the past several years regarding the effects of stress and cortisol on disease susceptibility, growth, metabolism, and reproduction of channel catfish in the context of how stress and cortisol affect economically important production traits for aquaculture. [ABSTRACT FROM AUTHOR]

Two practical diets that differed in cost based upon protein sources were evaluated as treatments relative to production and associated economics of the fingerling-stocker phase of culture for channel catfish Ictalurus punctatus. The commercially manufactured fingerling feeds contained approximately 35% crude protein and were fed to fingerling channel catfish (mean weight = 13.8 g; mean length = 12.2 cm, respectively) stocked into experimental earthen ponds (0.05 ha) at a density of 123,550 fish/ha. There were five replicates (ponds) per treatment. The fish were fed daily to satiation, unless some physical or biological factor warranted an abstention of one or more days. After 180 d, all ponds were harvested by seine and then completely drained. Mean individual harvest weight and length of fish fed the high-cost practical diet were significantly greater than those of fish fed the low-cost diet. Survival and feed conversion ratios were not significantly different between dietary treatment groups. The percentage of harvested fish exceeding 114 g, a size that escapes predation by cormorants Phalacrocorax spp., ranged from 47% to 56% for the low-cost treatment and from 72% to 77% for the high-cost treatment. Individual stocker production cost was US$0.217 for the low-cost dietary treatment and $0.258 for the high-cost treatment. Economic analyses were used to compare the three-phase (modular) production scheme (which incorporated the two diet-dependent fingerling-stocker management scenarios) with the traditional multiple-batch system (partial harvest and topping off). Total production costs for the three-phase system were $0.04-0.24 per kilogram less than those of the multiple-batch production system. Total cost of food fish production in the three-phase system ranged from $1.406 (low-cost diet) to $1.417 (high-cost diet) per kilogram. The fingerling-stocker phase offers a variety of management options to meet different production goals, and the three-phase system appears to be a cost-effective alternative management strategy for the farming of channel catfish. [ABSTRACT FROM AUTHOR]

Commercially produced, food-size channel catfish Ictalurus punctatus that were harvested using routine procedures had significant elevations in plasma cortisol, glucose, and lactate compared with preharvest fish captured from open ponds. Blood samples were taken from 10 fish in each of two treatments (liquid oxygen diffuser- and paddlewheel-aerated holding socks) and four sampling periods (before harvest, after socking, before loading, and before unloading) during each of 10 harvest events. Water column temperatures averaged approximately 27°C during the study. Ten fillet samples were taken from fish held overnight in paddlewheel- and liquid oxygen-aerated holding socks during some harvest events. Mean plasma cortisol levels averaged 3.02 ng/mL before harvest, 84.38 ng/mL immediately after socking, 135.22 ng/mL after 18 h in the sock (i.e., before loading onto the truck), and 128.54 ng/mL after 2-3 h on the truck (i.e., before unloading). Mean plasma glucose levels averaged 34.7 mg/dL before harvest, 95.41 mg/dL after socking, 134.53 mg/dL before loading, and 134.86 mg/dL before unloading. Mean plasma lactate levels averaged 2.43 mmol/L before harvest, 13.24 mmol/L after socking, 11.53 mmol/L before loading, and 7.88 mmol/L before unloading. These results should not be considered maximal until additional studies are conducted with average water temperatures at their highest. There were significant changes within treatment over 7 d of refrigerated storage for fillet pH, color, and drip loss; however, there were no consistent trends between treatments. Results indicate that routine capture and hauling procedures are stressful to commercially produced, food-size channel catfish under the examined conditions and that using liquid oxygen for aerating fish in holding socks does not significantly improve fillet quality or reduce stress levels. [ABSTRACT FROM AUTHOR]

Environmentally derived "off-flavors" such as earthy" and "musty" in cultured channel catfish Ictalurus punctatus are attributed to the presence of certain species of cyanobacteria (blue-green algae) in ponds. The musty off flavor is caused by absorption of the metabolite 2-methyl-isobomeol (MIB) into channel catfish flesh. Most channel catfish producers manage off-flavor episodes by the application of algicides; however, these algicides have high environmental persistence and broad-spectrum toxicity. Recent research has discovered several natural and natural-based quinones that are effective and selective in reducing the abundance of the MIB-producing cyanobacterium Planktothrix perornata. In this study, efficacy testing of one of these quinones, anthraquinone-59, in a channel catfish pond found that it is effective in reducing the abundance of P. perornata and subsequently lowering the MIB levels in channel catfish. [ABSTRACT FROM AUTHOR]

A closed, stirring respirometer was designed to agitate small egg mass samples of channel catfish Ictalurus punctatus while measuring oxygen consumption by the eggs. Egg mass samples ranging in size from 15 to 46 g were placed on a screen platform above a magnetic stir bar in the respirometer; the degree of agitation was controlled with a magnetic stir plate. Dissolved oxygen (DO) concentration and temperature were measured with a luminescent DO sensor and meter. The respirometer was used to determine routine metabolic rate and limiting oxygen concentration (the presumed hypometabolic transition zone) on egg mass samples front 10 different spawns at 0 to 5 d postfertilization. Routine metabolic rate increased from 4.8 ± 1.3 (0 d postfertilization) to 174.0 ± 7.8 mg O2·kg-1·h-1 (5 d postfertilization). The limiting oxygen concentration increased similarly up to 87.0% ± 2.7% (maximum individual value = 95.9%) air saturation by 5 d postfertilization. The respirometer described could not be used for sac fry, but it proved effective with clumped channel catfish eggs. Preliminary channel catfish hatchery management recommendations are to maintain DO concentrations in hatchery troughs at air saturation at least during the last day of egg development. [ABSTRACT FROM AUTHOR]

Soybean meal, the major protein source used in commercial feeds for channel catfish Ictalurus punctatus, contains natural phytoestrogens known as isoflavones, many of which have been found to be endocrine disruptors. This study investigated whether genistein (an isoflavone) in a soybean-based diet would increase plasma vitellogenin (Vtg) concentrations and whether it would compete with estradiol E2; for binding sites on adult channel catfish hepatic estrogen receptors (ERs). Three-year-old channel catfish males and females were fed a casein-based diet (control) or a soybean-based diet. The genistein concentrations were 93.2 ng/g and 415,800 ng/g in the control and soybean diets, respectively. The binding specificity of the ERs was assessed by binding-affinity studies. In order of decreasing binding affinity, ethinylestradiol > E2; > genistein > testosterone, demonstrating that the hepatic ERs in channel catfish bind estrogens and genistein more than androgens. No significant differences in affinity (Kd) were observed for hepatic ERs in male or female catfish fed the soybean diet compared with those fed the control diet. Significant increases in binding capacity (Bmax;) for males fed the soybean diet (158 ± 15 fmol/mg protein) were evident compared with males fed the control diet (73 ± 4 fmol/mg protein). Genistein competed with [³H]E2; for hepatic ERs in both the male and female channel catfish. The relative binding affinities in male ERs were higher (2.72) than those in female ERs (1.17) for genistein. Because diets of farm-raised channel catfish are routinely composed of high quantities of soybean meal, the findings that genistein stimulates Vtg production in male channel catfish and binds to the ERs in both male and female channel catfish suggest that dietary genistein could alter production traits. However, further research to elucidate the effects of genistein on catfish reproduction is necessary to determine the impact of this phytoestrogen on catfish physiology. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of 24-h slush-ice storage of carcasses of channel catfish Ictalurus punctatus on subsequent fillet yield, shape, and color. Channel catfish were sorted into three size-classes based on carcass (unskinned, with head and viscera removed) weight: small (250-425 g), medium (426-550 g), and large (551-1,000 g). In each of three replicate trials, 40 carcasses from each size-class were processed immediately after being killed (immediately processed treatment) and 40 carcasses from each size-class were held in ice water slush for 24 h and then processed (slush-ice treatment). Slush-ice-treated fish had higher unskinned fillet yield (+1.7%), skinned fillet yield (+1.2%), shank fillet yield (+0.6%), and nugget yield (+0.7%) than immediately processed fish. Measures of fillet yield increased in both treatments as carcass size increased. Immediately processed fillets were shorter (maximum distance anterior to posterior margin) and deeper (maximum distance from dorsal to ventral margin), and had less surface area than slush-ice fillets 24 h after slaughter. Sensory panelists perceived fillets from the slush-ice treatment to be larger than immediately processed fillets in 74% of comparisons of fillet pairs of equal weight. No fillet color differences were detected between treatments. Commercial catfish processors could increase fillet yield by storing carcasses in slush ice before filleting. However, costs associated with chilling and holding carcasses and quality issues, such as fillet drip-loss, texture, and shelf life, need to be addressed to determine whether slush-ice storage of carcasses will be beneficial to commercial catfish processors. [ABSTRACT FROM AUTHOR]

Short-term exposures to elevated temperatures reduce germ cell numbers in the gonads of some fishes, suggesting that heat treatment may be a viable method for delaying or suppressing reproductive development in cultured fishes. The objective of this study was to determine the effects of high temperatures on early gonadal development in channel catfish Ictalurus punctatus. Twenty-three-day-old (after hatching) channel catfish were exposed to temperatures of 27°C (control), 34°C, and 36°C for 4 weeks. Groups of 250 fry were placed in individual 152-L glass aquaria with external biofilters, and four replicated aquaria were used per temperature treatment. Water temperature was regulated with submersible heaters. At the end of treatment, body weight and standard length were measured in 30 individuals per aquarium and gonads were examined histologically in 10 individuals of each sex per aquarium. For statistical analysis, the unit of replication was the aquarium, and differences between treatments were considered significant at α < 0.05 by one-way analysis of variance (ANOVA) and Duncan's multiple-range test. Exposure to 34°C reduced oocyte size in ovaries and testicular size (cross-sectional area) and slightly decreased body weight but not standard length. Exposure to 36°C significantly reduced ovarian and testicular size. and 52% of females seemed to lack germ cells and may have been sterilized. However, exposure to 36°C also greatly reduced body growth and caused spinal curvatures and kidney abnormalities, suggesting that 36°C impairs the general health and growth of catfish fry. The results of this study are consistent with the concept that heat treatment can be used to manipulate reproductive development in channel catfish. Further research is needed to establish the appropriate combination of temperature level and treatment duration so as to reduce or eliminate germ cells without adversely affecting somatic growth during the period of treatment. [ABSTRACT FROM AUTHOR]

Samples of water supply and effluent were collected from five commercial hatcheries for channel catfish Ictalurus punctatus in northwestern Mississippi. Hatcheries were visited three times at 2-week intervals during the peak of the catfish spawning season. Samples were analyzed for total suspended solids, soluble and total phosphorus, total ammonia, total nitrogen, and 5-d biochemical oxygen demand (BOD5). Net pollutant loads (effluent concentration minus inflow concentration) were low for all variables. Maximum average net loadings were 10.7 mg/L for total suspended solids, 0.13 mg/L for total phosphorus, 0.28 mg/L for total nitrogen, and 2.07 mg/L for BOD5. Because net pollutant loadings were low and groundwater supplies initially had low concentrations of solids and organic matter, effluents were of excellent quality with respect to those variables. Four of the groundwater supplies contained substantial background levels of phosphorus or nitrogen; accordingly, effluents from those hatcheries had moderate levels of those substances. The highest average effluent concentrations (ranges for all samples in parentheses) were as follows: total suspended solids, 12.3 mg/L (7-19 mg/L); soluble reactive phosphorus, 0.36 mg/L (0.007-0.390 mg/L); total phosphorus, 0.45 mg/L (0.15-0.53 mg/L); total ammonia nitrogen, 0.49 mg/L (0.13-0.57 mg/L); total nitrogen. 0.60 mg/L (0.19-0.72 mg/ L); and BOD5, 3.03 mg/L (0.85-4.03 mg/L). These concentrations are lower than the corresponding concentrations in most potential effluent-receiving streams in northwestern Mississippi, and total effluent volume from catfish hatcheries constitutes less than 0.02% of total annual streamflow in the region. It is therefore unlikely that catfish hatchery effluents will have a negative effect on receiving stream water quality. [ABSTRACT FROM AUTHOR]

The efficacy of formalin and hydrogen peroxide to increase survival associated with external saprolegniasis on fingerlings of channel catfish Ictalurus punctatus was evaluated in four laboratory trials. Fungal epizootics were initiated according to procedures developed in a fungal-disease model. Fish were abraded with a dremel tool and then placed in an aerated static infection tank containing fungal-infected hemp seeds held in teaballs that were suspended in 100 L of water for 24 h (trials 1-3) or 6 h (trial 4). In the formalin trials, treatment regimens of 0, 82, and 166 mg/L (trial 1) or 0 and 83 mg/L (trial 2) were administered to channel catfish for 60 min once every other day for a total of three treatments (trial 1) or once daily for a total of seven treatments (trial 2). In the hydrogen peroxide trials, treatment regimens of 0, 75, and 102 mg/L (trial 3) or 0 and 75 mg/L (trial 4) were administered to channel catfish for 60 min once every other day for a total of three treatments. Each treatment regimen was tested in triplicate, with 10 fish per replicate. Formalin exposures of 83 (seven treatments; 33% survival) and 166 mg/L (three treatments; 63% survival) for 60 min significantly (P ≤ 0.01) increased channel catfish survival in comparison with controls (of which 3% and 13%, respectively, survived). In trial 4, hydrogen peroxide exposure of 75 mg/L (63% survival) for 60 min significantly (P ≤ 0.01) increased channel catfish survival in comparison with the untreated controls (13% survival). Formalin and hydrogen peroxide treatments were effective in increasing survival in channel catfish infected with fungus. [ABSTRACT FROM AUTHOR]

Three protein sources were evaluated as supplements to grow-out feeds for mixed-sized channel catfish Ictalurus punctatus stocked at 16,750 fish/ha in 0.04-ha earthen ponds. Three practical diets were tested: (1) meat, bone, and blood meal (MBM), (2) fish meal containing menhaden Brevoortia spp., and (3) soybean meal and wheat (lysine added). The fish were fed to satiation once daily for 133 d. For total fish harvested, dietary protein did not affect the weight gain, hepatosomatic index, percent survival, harvest yield, protein efficiency ratio, percentage of intraperitoneal fat, or dress-out percentage. Feed consumption and the feed conversion ratio were significantly higher in fish fed the MBM diet. This diet also produced a significantly lower percentage of lipids in the fillets. Significant differences were shown for fatty acids found in the fillets of large fish and small fish fed all diets. A size-related significant difference was found for the total saturated fatty acids, where values for the fillets of small fish were lower than those of large fish. Conversely, a size-related significant difference was found for the total monounsaturated fatty acids in the fillets, where the large fish had lower levels than those of the small fish. When the fatty acids found in the fillets were classified as total polyunsaturated fatty acids (total omega-3 fatty acids or total omega-6 fatty acids), no significant differences in concentrations as a result of diet were found. This suggests that all three protein sources performed similarly and that the all-vegetable diet supplemented with lysine is a suitable alternative to diets containing animal and fish protein sources for channel catfish grown under pond production conditions. [ABSTRACT FROM AUTHOR]

Aeration allows for higher feeding rates and increased production of channel catfish Ictalurus punctatus in intensive and semi-intensive aquaculture systems. However, the effect of specific dissolved oxygen (DO) concentrations on various production parameters remains unknown. The purpose of this 2-year study was to determine the effect of daily minimum DO concentration on channel catfish production. Six 0.1-ha ponds were each equipped with three 0.37-kW (0.5-hp) aerators and one 0.37-kW circulator. Dissolved oxygen concentrations were monitored and recorded with a commercial oxygen monitor that also controlled aeration. During both years, aeration in the high-oxygen treatment was initiated when the DO concentration dropped below 5.0 mg/L (mean, 64% saturation from May to September); aeration in the low-oxygen treatment was initiated when the DO concentration dropped below 2.5 mg/L (32% saturation; 2001) or 1.5 mg/L (19% saturation; 2002). The minimum DO concentrations resulting from this aeration protocol differed somewhat from aerator set points. In the low-oxygen treatment, delaying aeration until the DO concentration dropped below 2.5 mg/L reduced feed consumption by 6% relative to the high-oxygen treatment. Other production parameters were not significantly different. In 2002, when aeration was delayed until the DO concentration dropped below 1.5 mg/L, the low-oxygen treatment group exhibited reductions in food consumption (45% less than consumption by the high-oxygen treatment), average fish weight (31% less), and net production (54% less). Even at the high feeding rates of 2002 (maximum of 680 kg ⋅ ha-1 ⋅ d-1; 44,066 kg/ha total in one pond), other water quality variables were acceptable. Net production in the high-oxygen treatment in 2002 averaged 23,547 kg/ha, a potential record for channel catfish in earthen ponds. Neither the feed conversion ratio nor survival was significantly different between treatments in either year. While these results cannot be directly extrapolated to large commercial ponds, it appears that increased aeration may increase production well above current commercial levels. [ABSTRACT FROM AUTHOR]

We evaluated the effectiveness of weekly low-dose applications of copper sulfate (0.12 mg of Cu/L of water) for reducing the prevalence of off-flavor in channel catfish Ictalurus punctatus on commercial farms. The study was conducted over 3 years in ponds (3.2-8.4 ha) on two catfish farms in western Mississippi. Farm managers applied copper sulfate (0.5 mg of copper sulfate pentahydrate/L of water) weekly beginning in the late spring or early summer and continued until the water temperature dropped below 20°C. Water samples were collected from treated and untreated ponds approximately every 3 weeks during the application period and were monitored for levels of the musty compound 2-methylisoborneol (MIB), chlorophyll a, and phytoplankton community structure and abundance. In addition, channel catfish were caught from each study pond during the third year of the study and were checked for flavor. Levels of MIB and the abundance of the MIB-producing cyanobacterium Oscillatoria perornata were significantly lower in treated ponds than in control ponds at one farm, while numbers of green algae and diatoms at both farms were significantly higher in treated ponds than in control ponds. Also, fish flavor analysis indicated that the overall prevalence of all types of off-flavor was 50% lower in treated ponds than in control ponds. Based upon our results, weekly low-dose applications of copper sulfate appear to be beneficial in mitigating musty off-flavor problems in commercially produced channel catfish. Copper sulfate treatment reduced potential harvest delays by nearly half and reduced costs associated with off-flavor by 35%. However, the economic benefit of treatment was not statistically significant, although this result is probably attributable to the small data set used for economic analyses rather than ineffectiveness of treatment. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of initial fish size and weekly feeding frequency during the growing season on production characteristics and body condition of pond-raised channel catfish Ictalurus punctatus. Two sizes of channel catfish (averaging 39 or 249 g/fish) were stocked into eighteen 0.04-ha ponds at a density of 14,820 fish/ha. On days fed fish were fed to apparent satiation with a commercial 28% protein diet for 15 weeks. Fish fed once weekly to satiation gained 92% or 39% of initial weight for small and large fish, respectively. Maintenance feeding frequency (satiation) for these sizes of fish stocked at 14,820 fish/ha would be less frequent than once weekly. The condition factor improved as weekly feeding frequency increased. Larger fish had a better survival than smaller fish. However, fish survival was not affected by weekly feeding frequency. Based on results from the present study, it appears that feeding once weekly to satiation can maintain the body weight of advanced fingerling and larger sized channel catfish stocked at the density used in the present study. However, if economic conditions permit, fish should be fed more frequently to maintain a better body condition. This is especially true for smaller fish raised using a multiple-batch cropping system. [ABSTRACT FROM AUTHOR]

A histological study was done to evaluate the effect of waterborne exposures of copper sulfate (CuSO4) on channel catfish Ictalurus punctatus. Channel catfish were exposed daily for 11 consecutive days to three concentrations of CuSO4 representing one, three, and five times the recommended therapeutic level based on the total alkalinity. Fish were treated with CuSO4 in water flow-through tanks at a flow rate of 0.633 L/min. More than half the Cu was flushed in 1 h, which is similar to the elimination rates in ponds (due to the rapid uptake of Cu by aquatic plants or algae and the binding to organic and inorganic material). All fish were clinically normal and no fish died during the experiment. All examined tissues were grossly and histologically normal as well. The absence of histological lesions was attributed to the brief daily exposure to copper and to moderate total alkalinity and total hardness of the well water used. The results of this study suggest that CuSO4 is safe for channel catfish provided that the treatment applied is considered in relation to the total alkalinity of the water. Our study followed a protocol developed in cooperation with the U.S. Food and Drug Administration, Center for Veterinary Medicine, and was designed to support the data package required for the approval of CuSO4 as an aquaculture therapeutant. [ABSTRACT FROM AUTHOR]

The stocking of size-graded catfish into production ponds should increase production efficiency, but grading large numbers of fish with existing technology is laborious. We evaluated the effectiveness of a mechanical grader recently developed at the University of Arkansas at Pine Bluff (UAPB) relative to that of box and sock graders and assessed injuries sustained by stocker channel catfish Ictalurus punctatus during grading. Three 0.25-acre ponds were stocked at 11,777 lb/acre. Initial total length (TL) ranged from 6.3 to 15.7 in, and initial weight of individuals ranged from 0.04 to 1.10 lb. The fish population in each pond was divided into three groups graded with the box grader, UAPB grader, or sock grader. Fish were graded twice with the box and UAPB graders; a bar spacing of 1 3/32 in was used to grade off small fish and a spacing of 1 3/8 in to grade off large fish. Sock grader mesh size was 1 3/8 in. Mean weights and lengths of the size-classes produced by grading (small, medium, and large) were compared to those of the initial population in each pond. Blood samples were collected from sampled fish, and serum was analyzed for creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) activities to assess fish injury levels. Each grader separated the initial population into distinct populations. Mean weight and TL of the medium size-class was significantly lower for the UAPB grader than for the box grader. The frequency distributions of the fish populations obtained from each grader differed significantly. Undergrade and overgrade error for the medium size-class did not differ significantly between the box and UAPB graders. Undergrade error averaged 5.4% for TL and 1.6% for individual weight; overgrade error averaged 7.8% for TL and 10.3% for weight. Serum CPK and LDH activities were highly variable, which prevented detection of significant treatment differences. [ABSTRACT FROM AUTHOR]

Fry survival in the catfish industry is variable, and failure to survive cannot be completely attributable to diseases, fertilization practices, or lack of zooplankton abundance. The variability in fry survival may be related to current handling and stocking methods. When stocked, fry are transferred relatively quickly from hatchery water to pond water. Generally, temperature differences are monitored between hatchery water and pond water, but little attention is paid to pH differences. We conducted studies to determine the tolerance of channel catfish Ictalurus punctatus fry to pH changes. Catfish fry showed a high tolerance for decreasing pH values but a relatively low tolerance for increasing pH values. We estimate that an increase in pH of 0.7 units will cause 10% mortality in 8-d-posthatch catfish fry, and an increase of 1.4 pH units will cause 50% mortality. We recommend that farmers monitor pH before stocking fry and stock ponds that tend to increase in pH throughout the day early in the morning. [ABSTRACT FROM AUTHOR]