Coliform Organisms in Waters of Channel Catfish Ponds

Water from 48 channel catfish Ictalurus punctatus ponds at Auburn and Greensboro, Alabama, USA, usually contained less than 1,000 total coliform and 200 fecal coliform bacteria per 100 mL. There were no sources of human fecal matter to ponds. Also, the fecal coliform: fecal streptococci ratio was less than 1.0 and typical of fecal contamination by warm-blooded animals other than humans. The abundance of coliforms was greater in spring and summer than in fall and winter in catfish ponds and sportfish ponds at Auburn, Alabama. In spite of high organic matter inputs in feed, catfish ponds had no greater abundance of coliforms than sportfish ponds.     

Delayed Feeding of Channel Catfish Fry Stocked in Ponds

We compared production variables between channel catfish, Ictalurus punctatus, nursery ponds fed according to industry standards, that is feeding immediately at stocking, to an alternative practice of delaying feeding for 6 wk after stocking in an effort to utilize natural pond productivity and reduce feed use. Twelve 0.04 ha ponds were fertilized and stocked with swim‐up fry (4–5 d posthatch) at a rate of 10,000/pond (250,000/ha). Ponds were then randomly assigned to either the standard feeding protocol (feeding daily starting immediately at stocking) or an alternative feeding protocol (no feeding until 6 wk post‐stocking). After 18 wk of production, there were no differences in water quality or zooplankton abundance between the two treatments. Fish length was not affected by treatment throughout the study, and survival and total weight harvested were similar. Total kg of feed fed was significantly reduced in the delayed feed treatment, averaging 26 kg/pond less feed fed. If proper fertilization practices are implemented, large numbers of desirable zooplankton for catfish fry culture are attained, and these zooplankton are able to sustain catfish fry stocked up to 250,000/ha. Therefore, no commercial diets are required during the first 6 wk of culture, saving over $95.55/ha in initial feed costs.     

Effects of a Bacterial Inoculum in Channel Catfish Ponds

A commercial bacterial Inoculum cultured on site called Biostart was applied to three channel catfish Ictalurus punctatus ponds at Auburn, Alabama, USA, three times per week from May until October 1996. There were few significant differences (P × 0.1) in concentrations of water quality variables between ponds treated with bacteria and control ponds. In addition, bottom soil carbon and nitrogen did not differ between treated and control ponds. However, survival and net production of fish was significantly (P × 0.1) greater in ponds that received the bacterial inoculum than in controls. The mechanism by which the bacterial treatment influenced fish survival cannot be explained from data collected in this study. Further studies of probiotics are needed to define the potential benefits of these treatments to aquacultural production and to determine their mechanisms of action in pond ecosystems.     

Factors Affecting Sediment Oxygen Demand in Commercial Channel Catfish Ponds

Sediment oxygen demand (SOD) measured in 45 commercial channel catfish ponds in northwest Mississippi using in situ respirometry ( N = 167) ranged from 63 to 1,038 mg/m² per h. Mean SOD in this study (359 mg/m² per h) was greater than that reported previously for catfish ponds but was similar to SOD in semi-intensive marine shrimp ponds. Nine variables were selected and measured to assess their relative importance in accounting for variation in SOD. Six variables were included in multiple regression models that explained slightly more than half of the variation in SOD. These variables were: dissolved oxygen concentration at the beginning of respirometry incubation:, particulate organic matter concentration in water above the sediment surface: organic carbon concentration at the immediate sediment-water interface (flocculent or F-layer) combined with the upper 2 cm of sediment (S-layer); organic carbon concentration in the mature (M) underlying sediment layer: water temperature: and total depth of accumulated sediment. Sediment oxygen demand was most sensitive to changes in dissolved oxygen concentration in the overlying water, particulate organic matter concentration in the water, and the concentration of organic carbon in the combined flocculent and upper sediment (F+S) layer. Models for SOD in this research predict that the mass of sediment below the upper 2-cm surface layer on average contributes only ∼20% of total SOD. Stratification and normal daily fluctuation of dissolved oxygen concentration in eutrophic culture ponds likely limit expression of sediment oxygen demand. Maintaining aerobic conditions at the sediment-water interface will minimize accumulation of organic matter in pond sediment.     

Impact of Copper Sulfate on Plankton in Channel Catfish Nursery Ponds

Many fish culturists are interested in applying copper sulfate pentahydrate (CSP) to channel catfish, Ictalurus punctatus, nursery ponds as a prophylactic treatment for trematode infection and proliferative gill disease by killing snails and Dero sp., respectively, before stocking fry. However, copper is an algaecide and may adversely affect phytoplankton and zooplankton populations. We evaluated the effects of prophylactic use of copper sulfate in catfish nursery ponds on water quality and phytoplankton and zooplankton populations. In 2006, treatments of 0 mg/L CSP, 3 mg/L CSP (0.77 mg/L Cu), and 6 mg/L CSP (1.54 mg/L Cu) were randomly assigned to 0.04‐ha ponds. In 2007, only treatments of 0 and 3 mg/L CSP were randomly assigned to the 16 ponds. Ponds treated with CSP had significantly higher pH and significantly lower total ammonia concentrations. Treatment of both CSP rates increased total algal concentrations but reduced desirable zooplankton groups for catfish culture. CSP has been shown to be effective in reducing snail populations at the rate used in this study. CSP treatment also appears to be beneficial to the algal bloom, shifting the algal population to green algae and increasing total algal biomass within 1 wk after CSP treatment. Although zooplankton populations were adversely affected, populations of important zooplankton to catfish fry began rebounding 6–12 d after CSP treatment. Therefore, if CSP is used to treat catfish fry ponds of similar water composition used in this study, fry should not be stocked for about 2 wk after CSP application to allow time for the desirable zooplankton densities to begin increasing.     

Production Characteristics of PanSize Channel Catfish in Cages and Open Ponds1

Production characteristics of pan-size (approximately 227 g) channel catfish (Ictalurus puncturus) were determined in cages and open ponds stocked with fingerlings to densities of 20,000 and 12,500 fish/ha. After 145 days, mean fish weight in all treatments exceeded 227 g. Mean survival was similar in all treatments. Food conversion ratios were significantly better in ponds than in cages but density did not affect the ratios. Neither density nor production system affected production (as measured by total weight produced) when initial density differences were considered (analysis of covariance). Variability in total length at harvest was similar between production systems; however, low density treatments were less variable than high density treatments. Results of this study indicate that pan-size channel catfish can be cultured efficiently at stocking densities well above the 12,500 fish/ha (5,000 fishlacre) generally used when culturing fish to larger sizes.     

Phosphorus Budgets for Channel Catfish Ponds Receiving Diets with Different Phosphorus Concentrations

Phosphorus budgets were prepared for channel catfish Ictalurus punctatus ponds at Auburn, Alabama, that received one of five diets ranging from 0.60 to 1.03% phosphorus. Fish production did not differ ( P > 0.05) among diets. There were few differences among treatments with respect to soluble reactive phosphorus, total phosphorus, and chlorophyll a concentrations or gross primary productivity. Phosphorus loss in effluents when ponds were drained for harvest did not differ among treatments ( P > 0.05). Phosphorus removed from ponds in fish at harvest and the amounts of phosphorus adsorbed by bottom soils increased as dietary phosphorus concentration increased (P < 0.05). Low-phosphorus diets did not decrease phytoplankton productivity or improve effluent quality. Uptake of phosphorus by bottom soils is a major factor controlling phosphorus concentrations in pond water. Low-phosphorus diets can be beneficial in catfish pond management by reducing the phosphorus load to bottom soils and conserving their ability to adsorb phosphorus.     

Copper Concentrations in Channel Catfish Ictalurus punctatus Ponds Treated with Copper Sulfate

Copper sulfate (CuSO₄5H₂O) is used to reduce the abundance of blue-green algae and combat off-flavor in channel catfish culture. Copper sulfate usually is applied at a concentration of one-one hundredth of the total alkalinity. A study was performed at the Auburn University Fisheries Research Unit to determine the duration of elevated copper (Cu) concentration following copper sulfate applications. Two alkalinity treatments, 20-40 mg/L and 110-130 mg/L (as CaCO₃), were examined. Copper sulfate was applied biweekly for 14 wk at 03 mg/L for the low alkalinity treatment and 1.2 mg/L for the high alkalinity treatment. Total copper concentrations in pond waters declined to the background level by 48-h post treatment. In addition, total copper concentrations were determined in waters of 38 catfish production ponds located in west central Alabama. The mean and standard deviation were 0.0092 ± 0.0087 mg Cu/L. Copper quickly precipitates from the water or is absorbed by sediments following copper sulfate treatment. Although concentrations of copper in pond waters increase immediately following copper sulfate treatment, they rapidly decrease and seldom exceed the United States Environmental Protection Agency's National Recommended Water Quality Criteria for Priority Toxic Pollutants of 0.013-mg Cu/L. Findings of this study suggest that copper sulfate treatment will not contaminate effluent from catfish ponds because of the short time that applied copper remains in the water column. Furthermore, the most frequent applications of copper sulfate occur in late summer months when rainfall is minimal and pond overflow is rare.     

Seasonal Changes in Water Quality in Commercial Channel Catfish Ponds in Mississippi

Selected water quality variables were measured at monthly intervals for 1 yr in 10 commercial channel catfish ponds in northwest Mississippi. Temporal changes in most variables appeared to be related to seasonal periodicity of phytoplankton abundance. Phytoplankton standing crops and total organic matter were highest in summer months when primary production was favored by warm water temperatures, high solar irradiance, and large inputs of nutrients resulting from high summer fish feed allowances. As day length, water temperature, and feed inputs decreased in autumn and winter, phytoplankton abundance and organic matter concentrations decreased. Seasonal changes in total nitrogen and total phosphorus concentrations were similar to phytoplankton abundance because much of the total nitrogen and phosphorus was contained within phytoplankton cells. Contrasting to the seasonal trend for total nitrogen, concentrations of dissolved inorganic nitrogen were lowest in the summer and highest in the cooler months. Rapid assimilation by phytoplankton served to maintain relatively low concentrations of dissolved inorganic nitrogen during the summer despite highest nitrogen loading rates during that period. Low water temperatures and generally less favorable conditions for phytoplankton growth decreased rates of nitrogen assimilation in the winter and ammonia, nitrite, and nitrate accumulated. Soluble reactive phosphorus concentrations were low throughout the year because physico-chemical processes, such as precipitation and adsorption to bottom muds acted to continually remove inorganic phosphorus from the water column.     

Effects of Stocking Density on Growth of Juvenile Channel Catfish Overwintered in Ponds

Channel catfish, Ictalurus punctatus, juveniles (mean weight 78.0 ± 3.5 g) were stocked into nine 0.04-ha earthen ponds at three rates (4,940 fish/ha, 12,350 fish/ha, and 24,700 fish/ha) and fed a prepared diet (32% protein) according to a fish size/water temperature-dependant feeding chart for 160 days during the winter. Morning water temperatures averaged 5.8°c during the study. No significant differences (P > 0.05) were found in individual fish length, survival, and percentage weight gain among treatments and averaged 19.4 cm, 96.2%, and -13.0%, respectively. No significant differences (P > 0.05) in whole-body composition were found among treatments. Percentage moisture, protein, and fat averaged 12.4, 50.8, and 28.4%, repectively. Stocking juvenile channel catfish at the lower rate, 4,940 fish/ha, did not significantly increase winter growth compared to growth of fish stocked at higher rates (12,350) and 24,700 fish/ha).     

Production and Processing Trait Comparisons of Channel Catfish,Blue Catfish,and Their Hybrids Grown in Earthen Ponds

Fingerling HS‐5 channel catfish, Ictalurus punctatus, NWAC 103 channel catfish, D&B blue catfish, Ictalurus furcatus, HS‐5 female channel × D&B male blue catfish F₁ hybrids, and NWAC 103 female channel × D&B male blue catfish F₁ hybrids were stocked into twenty‐five 0.04‐ha earthen ponds at 12,500 fish/ha and grown for 277 d. Fish were fed daily at rates from 1.0 to 3.0% biomass based on feeding activity and temperature and adjusted weekly assuming a feed conversion ratio (FCR) of 1.8 and 100% survival. At harvest, 40 fish from each pond were sampled, and all other counted and weighed. Mean survival, growth rate indexes (a), FCR, and skin‐on fillet percentages were not significantly different. Mean harvest weights and net production were higher for HS‐5 channel and its hybrid than for the NWAC 103 channel, NWAC 103 hybrid, and D&B blue catfish, partially because of their larger mean stocking weights. D&B blue catfish was more uniform in size than NWAC 103 channel and NWAC 103 hybrid. D&B blue catfish was the easiest to seine. HS‐5 hybrids and NWAC 103 hybrids had lower mean head percentage and a better processing yield than their parent channel catfish.     

Economics of Intensively Aerated Catfish Ponds

The US catfish industry is evolving by adopting production‐intensifying practices that enhance productivity. Catfish producers have increased aeration rates over time, and some now use intensive rates of aeration (>9.33 kW/ha). Costs and production performance were monitored at commercial catfish farms using high levels of aeration (11.2–18.7 kW/ha) in Alabama, Arkansas, and Mississippi. A multivariate‐cluster analysis was used to identify four different management clusters of intensively aerated commercial catfish farms based on stocking density, size of fingerlings at stocking, and feed conversion ratios (FCR). Breakeven prices of hybrid catfish raised in intensively aerated pond systems were estimated to range from $1.86/kg to $2.17/kg, with the lowest costs associated with the second greatest level of production intensity. The two medium‐intensity clusters generated sufficiently high revenues for long‐term profitability. However, the least‐intensive and the most‐intensive clusters were economically feasible only when catfish and feed prices were closer to less probable market prices. Feed price, FCR, and yield contributed the most to downside risk. Intensive aeration in catfish ponds, up to the levels analyzed in this study, appears to be economically feasible under the medium‐intensity management strategies identified in this analysis.     

Possible Effects of Sodium Chloride Treatment on Quality of Effluents from Alabama Channel Catfish Ponds

Channel catfish ponds are treated with salt (sodium chloride) to increase chloride concentration and prevent nitrite toxicity in fish. A survey indicated that most farmers try to maintain chloride concentration of 50 to 100 mg/L in ponds by annual salt applications. Averages and standard deviations for selected water quality variables in salt-treated ponds were as follows: chloride. 87.2 ± 37.5 mg/L; total dissolved solids (TDS), 336 ± 96 mg/L; specific conductance, 512 ± 164 μmhos/cm. Maximum values were 189 mg/L for chloride, 481 mg/L for TDS, and 825 μmhos/cm for specific conductance. Good correlations between specific conductance values and both chloride and TDS concentrations suggest that specific conductance can be a rapid method for estimating concentrations of these two variables in surface water. The maximum limit for chloride concentration in Alabama streams allowed by the Alabama Department of Environmental Management is 230 mg/L. The usual recommended upper limit of TDS for protection of aquatic life in freshwater streams is 1,000 mg/L. Based on the observed relationship between TDS concentration and specific conductance in Alabama catfish ponds, 1,000 mg/L TDS corresponds to 1,733 μmhos/cm specific conductance. It is unlikely that effluents from salttreated catfish ponds would violate the in-stream chloride standard of 230 mg/L or harm aquatic life in streanis. Nevertheless, chloride concentrations in ponds should be measured before salt application as a safe guard against excessive salt application and chloride concentrations above the in-stream chloride standard.     

Production Characteristics and Size Variability of Channel Catfish Reared in Cages and Open Ponds1

Production characteristics of channel catfish (Ictalurus punctatus) reared in cages and open ponds were compared. Fish reared in open ponds had significantly better growth and food conversion ratios than fish reared in cages. Cages and open ponds stocked with fish which were closely graded in size produced fish with less size variability at harvest compared to ponds and cages stocked with nongraded and coarsely graded fish. The decrease in size variability at harvest was reflected in a greater proportion of marketable fish.     

Factors Affecting Metabolism of Commercial Channel Catfish Ponds as Indicated by Continuous Dissolved Oxygen Measurement1

Continuous dissolved oxygen (DO) measurements were analyzed to evaluate the rates of pond metabolic processes related to productivity and respiration in three commercial catfish ponds in northwest Mississippi. Multiple regression models were constructed to assess the relative importance of various forcing functions on indices of net primary productivity (NPP) and whole pond respiration (WPR), duration of automated aeration, and DO concentration below various threshold values. Water temperature, solar radiation, wind run, cumulative feed, and lagged values of these parameters were considered as forcing functions. Generally, NPP and WPR were most strongly affected by water temperature and only weakly related to solar radiation. The duration of nightly aeration was also strongly related to water temperature, although 10-d cumulative feed was an important predictor in one pond. The best predictors of duration of DO below certain threshold values were NPP, WPR and wind run, the importance of which varied depending upon the pond and the threshold value considered. Change in feeding rate from one day to the next was inversely related to feeding rate on the previous day. The results of this analysis suggest that NPP and WPR rates, and the duration of required nightly aeration in commercial catfish ponds are controlled by factors not amenable to practical management control.     

Effects of Short-Term Feed Withdrawal on Water Quality in Channel Catfish,Ictalurus punctatus,Ponds

The efficacy of short-term feed withdrawal as a method of reducing ammonia concentrations in catfish production ponds was investigated. Channel catfish, Ictalurus punctatus, fingerlings averaging 35 g were stocked at 9,880 fish/ha into six 0.04-ha ponds and fed twice daily to satiation for 131 days. For a 9-day period immediately prior to harvest (days 132-140), feeding of fish in three ponds was terminated, while feeding of fish in three other ponds was continued. Total ammonia-nitrogen concentrations were not significantly reduced (P > 0.05) in unfed ponds until 9 days after feeding was terminated. However, after 7 days without feed, un-ionized ammonia concentrations were significantly higher (P < 0.05) in ponds where fish were not fed, due to significantly higher (P < 0.05) pH levels. Short-term (9 days) feed withdrawal had little effect on lowering total ammonia and actually increased concentrations of toxic un-ionized ammonia in ponds.     

Effects of Mosquitofish,Gambusia affinis,on Channel Catfish,Ictalurus puncatatus,Production Ponds

Mosquitofish, Gambusia sp., have been spread throughout the world to biologically control mosquitoes. However, the fish has gained a reputation as an invasive species and has been implicated in displacing native aquatic species. Gambusia affinis are native to the southeastern United States and commonly occur in commercial channel catfish, Ictalurus punctatus, production ponds. We investigated effects of mosquitofish presence on zooplankton populations, water quality, disease occurrence, and fish production in experimental ponds. There were no differences between ponds with or without mosquitofish in numbers of calanoid copepods, cyclopoid copepods, total copepods, Bosmina sp., Ceriodaphnia sp., Moina sp., Daphnia sp., or total cladocerans. There were also no differences in copepod and cladoceran sizes. Copepod nauplii were more numerous during the summer months in ponds with mosquitofish. There were no differences in water quality variables (soluble reactive phosphorus, nitrate, nitrite, ammonia, total nitrogen, total phosphorus, pH) or phytoplankton density between ponds stocked with and without mosquitofish. Catfish production and disease occurrence were also similar between ponds with and without mosquitofish. Although mosquitofish may cause problems when stocked outside their native range, there does not appear to be any adverse effects of mosquitofish presence in catfish production ponds.     

Water and Sediment Quality,Phytoplankton Communities,and Channel Catfish Production in Sodium Nitrate-Treated Ponds

Three channel catfish (Ictalurus punctatus) ponds were treated at two-week intervals with sodium nitrate at 2 mg NO₃ ^?-N/L per application and three ponds served as controls. Average concentration of nitrite-nitrogen measured midway between application dates never exceeded 1.2 mg/L in treated ponds, but on most sampling dates, nitrate concentrations were greater than those in control ponds (P < 0.1). Disappearance of nitrate-nitrogen from waters of treated ponds resulted primarily from nitrate reduction to free nitrogen gas. Soluble reactive and total phosphorus concentrations tended to be higher (P < 0.1) in treated ponds than in control ponds. There were no differences (P > 0.1) in pH and concentrations of total alkalinity, total ammonia nitrogen, and dissolved oxygen between treated and control ponds. The higher chlorophyll a concentration (P < 0.1) suggested that greater availability of nutrients in treated ponds resulted in more phytoplankton growth than in control ponds. Because of greater phytoplankton biomass, turbidity was higher and Secchi disk visibility less in treated ponds as compared to control ponds (P < 0.1). There were no obvious differences in phytoplankton community composition with respect to treatment—blue-green algae dominated the phytoplankton community in both treated and control ponds. Redox potential in sediment during crops was higher in ponds treated with sodium nitrate than in control ponds, indicating less anaerobic conditions. However, catfish survival, production, and feed conversion ratio did not differ (P > 0.1) between treatment and control.