Biochemical Oxygen Demand in Channel Catfish Ictalurus punctatus Pond Waters

A study of the biochemical oxygen demand (BOD) of waters from ten channel catfish ponds at Auburn, Alabama, revealed that the 5-d BOD (BOD₅) seldom exceeded 8 mg/L and that the ultimate BOD (BOD_u) was usually less than 30 mg/L. Water samples from catfish ponds usually needed to be diluted only 2 or 3 times to permit BOD₅ measurements, and nitrification occurred even during a 5-d incubation period. Catfish pond waters were not extremely high in ammonia nitrogen concentration, and ammonia nitrogen introduced in the ammonium chloride-enriched dilution water caused an appreciable increase in BOD of some samples. Plankton respiration is a major component of carbonaceous BOD (CBOD) in catfish pond waters. Thus, the BOD is not expressed as rapidly during 5-d incubations as in typical waste-water. The ultimate BOD (BOD_u) would be a good measurement of oxygen demand for catfish pond effluents, but it is difficult to measure. Data from this study suggest that BOD_u can be estimated from BOD₅, but the correlation is not strong ( R ²= 0.62). An alternative is to develop a short-term BOD measurement specifically for effluents from channel catfish and other aquaculture ponds. This study suggests that a 10-d BOD conducted without nitrification inhibition or addition of ammonia nitrogen in dilution water might be a better alternative to standard BOD₅ or BOD_u measurements normally used in wastewater evaluation.     

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.     

Threadfin Shad Dorosoma petenense Effects on Water Quality, Phytoplankton, and Channel Catfish Production in Ponds

Threadfin shad Dorosoma petenense are often stocked into commercial catfish ponds for biological control of algae. It is thought that the fish will alter the phytoplankton community, improve water quality, and enhance channel catfish production. Co-stocking of shad and catfish is a common practice, although there is limited information regarding the effects of threadfin shad on pond dynamics and catfish production. To evaluate the influence of shad in catfish ponds, this study was conducted in ten 0.04-ha experimental earthen ponds near Auburn, Alabama. All ponds were stocked in April with 600 fingerling channel catfish Ictal-urus punctatus (13,200/ha) with a mean length of 10.4 cm (4.1 in). Additionally, five of these ponds were randomly chosen and stocked with 70 adult threadfin shad (1,750/ha) weighing a total of 3.3 kg (16.5 kg/ha). At harvest in November, an average of 1,284 threadfin shad (32,100/ha), weighing a total of 55 kg (1,375 kg/ha) were collected from each shad pond. Water quality was improved with the addition of threadfin shad to channel catfish ponds. Mean total ammonia-nitrogen was significantly lower and less variable in the shad treatment. Observed mean nitrite concentrations, though not significant, were lower in the shad treatment. The phytoplankton community of the shad treatment had significantly higher density, more taxa, and smaller organisms. Pond water in the shad treatment had higher projected early morning dissolved oxygen levels requiring less aeration. Channel catfish had significantly higher survival in the shad treatment, furthermore, though not statistically significant, observed mean fish production was higher and feed conversion ratio was lower than in the no-shad treatment.     

Environmental Assessment of Channel Catfish Ictalurus punctatus Farming in Alabama

An environmental assessment was made of Alabama channel catfish Ictalurus punctatus farming which is concentrated in the west‐central region of the state. There are about 10,000 ha of production ponds with 10.7% of the area for fry and fingerlings and 89.3% for food fish. Food fish production was about 40,800 tons in 1997. Watershed ponds filled by rainfall and runoff make up 76% of total pond area. Water levels in many of these ponds are maintained in dry weather with well water. The other ponds are embankment ponds supplied by well water. Harvest is primarily by seine‐through procedures and ponds are not drained frequently. The main points related to Alabama catfish farming and environment issues are as follows: 1) catfish farming in Alabama is conservative of water, and excluding storm overflow, about two pond volumes are intentionally discharged from each pond in 15 yr; 2) overflow from ponds following rains occurs mostly in winter and early spring when pond water quality is good and stream discharge volume is high; 3) total suspended solids concentrations in pond effluents were high, and the main sources of total suspended solids were erosion of embankments, pond bottoms, and discharge ditches; 4) concentrations of nitrogen and phosphorus in effluents were not high, but annual effluent loads of these two nutrients were greater than for typical row crops in Alabama; 5) ground water use by the industry is about 86,000 m³/d, but seepage from ponds returns water to aquifers; 6) there is little use of medicated feeds; 7) copper sulfate is used to control blue‐green algae and off‐flavor in ponds, but copper is rapidly lost from pond water; 8) although sodium chloride is applied to ponds to control nitrite toxicity, stream or ground water salinization has not resulted from this practice; 9) fertilizers are applied two or three times annually to fry and fingerling ponds and occasionally to grow‐out ponds; 10) hydrated lime is applied occasionally at 50 to 100 kg/ha but this does not cause high pH in pond waters or effluents; 11) accumulated sediment removed from pond bottoms is used to repair embankments and not discarded outside ponds; 12) sampling above and below catfish pond outfalls on eight streams revealed few differences in stream water quality; 13) electricity used for pumping water and mechanical aeration is only 0.90 kW h/kg of production; 14) each metric ton of fish meal used in feeds yields about 10 tons of dressed catfish. Reduction in effluent volume through water reuse and effluent treatment in settling basins or wetlands does not appear feasible on most farms. However, some management practices are recommended for reducing the volume and improving the quality of channel catfish pond effluents.     

Measurement of 5-day biochemical oxygen demand without sample dilution or bacterial and nutrient enhancement

A direct method for measuring the 5-day biochemical oxygen demand (BOD₅) of aquaculture samples that does not require sample dilution or bacterial and nutrient enrichment was evaluated. The regression coefficient (R²) between the direct method and the standard method for the analyses of 32 samples from catfish ponds was 0.996. The slope of the regression line did not differ from 1.0 or the Y-intercept from 0.0 at P = 0.05. Thus, there was almost perfect agreement between the two methods. The control limits (three standard deviations of the mean) for a standard solution containing 15 mg/L each of glutamic acid and glucose were 17.4 and 20.4 mg/L. The precision of the two methods, based on eight replicate analyses of four pond water samples did not differ at P = 0.05.     

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.     

Disinfection, Microbial Community Establishment and Shrimp Production in a Prototype Biosecure Pond

Plankton community establishment and shrimp production in a prototype biosecure pond were compared to three control ponds. The biosecure pond was enclosed and intake water was disinfected, while control ponds were neither enclosed nor disinfected. All ponds were managed with no water exchange and stocked with 100 postlarvae/m², Litopenaeus vannamei . Residual oxidant concentrations in the biosecure pond dropped rapidly after cessation of chlorinated water addition. This was followed by a sharp increase in water column bacterial abundance, after which the pond was fertilized and inoculated with cultured Chaetocerous gracilis . After crash of the initial C. gracilis bloom in the biosecure pond, this species was not observed again. Following initial large fluctuations in biosecure pond bacterial abundance, phytoplankton biomass, oxygen consumption and nitrification rates, these parameters appeared to stabilize at levels similar to the control ponds. Early season compositional differences in phytoplankton, zooplankton, and bacterial communities were observed. No differences were seen in late-season phytoplankton and bacteria; however, zooplankton biomass tended to be lower in the biosecure pond than in the control ponds throughout the season. Shrimp production in all ponds was greater than 9,000 kg/ha. Production in the single biosecure pond was not a significant outlier compared to production in the triplicate control ponds.     

Modeling industry-wide sediment oxygen demand and estimation of the contribution of sediment to total respiration in commercial channel catfish ponds

Data collected from 45 commercial channel catfish, Ictalurus punctatus, ponds were used to develop empirical models predicting sediment oxygen demand (SOD). Seven acceptable models were combined with a Monte-Carlo sampling distribution to predict industry-wide sediment oxygen demand (SOD_i). The SOD_i values obtained from the best equation were used in simulations to assess the effect of diurnally varying water column dissolved oxygen (DO) concentrations on SOD and the effect of pond water depth on the contribution of SOD to overall pond respiration. Estimated SOD_i ranged from 62 to 962 mg m⁻² h⁻¹, with a mean of 478 mg m⁻² h⁻¹. There was a 95% probability of mean SOD_i being ≥700 mg m⁻² h⁻¹. The effects of diurnal variation in DO concentration in the water column on expression of SOD was modeled by combining maximum SOD_i, an empirical relationship between DO and SOD, and simulated pond DO concentrations. At DO concentrations >15 mg l⁻¹, diel SOD in catfish ponds exceeded 20 g O₂ m⁻² day⁻¹. But when average diel DO was <4 mg l⁻¹ and the range of DO concentration was 6–8 mg l⁻¹, SOD decreased to 13 g O₂ m⁻² day⁻¹ because DO availability limited the full expression of potential SOD. Respiration totals for sediment (average SOD_i), plankton, and fish respiration were calculated for pond water depths ranging from 0.25 to 4 m. Although whole-pond respiration increases as pond depth increases, the proportion of total respiration represented by sediment decreased from 48 to 10% by increasing water depth over this range. The results of these studies show that SOD is a major component of total pond respiration and that certain management practices can affect the impact of SOD on pond oxygen budgets. Mixing ponds during daylight hours, either mechanically or by orienting ponds for maximum wind fetch, will increase oxygen supply to sediments, thereby allowing maximum expression of SOD and maximum mineralization of sediment organic matter. Given a mixed condition caused by wind or other artificial means, the construction of deeper ponds increases the total mass of DO available for all respiration, causing nighttime DO concentrations to decline at a slower rate, reducing the need for supplemental aeration. Because a pond’s water volume decreases over time from sediment accumulation, annual aeration costs will increase with pond age. Constructing ponds with greater initial depth will therefore reduce long-term cost of aeration, allow more flexible management of pond water budget, and reduce the long-term expense associated with pond reconstruction.     

Comparison of bacterial communities in channel catfish Ictalurus punctatus culture ponds of an industrial ecological purification recirculating aquaculture system

The industrial aquaculture pond system has gradually replaced the use of traditional earthen pond, as it causes less pollution and is more economical. In this study, an industrial ecological purification recirculating aquaculture system consisting of the water source pond, high‐density culture ponds, a deposit pond, and ecological purification ponds for channel catfish cultivation was established. Twelve water samples from different ponds were sequenced, and the bacterial communities were analysed. The abundances of Cyanobacteria and Merismopedia varied in different functional ponds of the system. The water quality was stable after two months of cultivation at 1.89 ± 0.22 mg/L total nitrogen, 1.1 ± 0.08 mg/L NH₄‐N and 0.43 ± 0.1 mg/L total phosphorus. The fish weight increased in a nearly linear manner, reaching 237.63 ± 23.8 per fish at day 120. An analysis of the environmental parameters, water quality and fish weight suggested that the system had an effective water purification process. Canonical correspondence analysis showed that the community was affected at the genus and phylum levels by different environmental parameters. We identified several dominant beneficial bacteria with nutrient removal abilities. Overall, our results demonstrated that the ecological purification recirculating aquaculture system had notable effects on water quality improvement and promoted changes in bacterial populations. These results provide important information on the microbial ecology of pond industrial eco‐aquaculture systems.     

Effects of simazine treatment on channel catfish and bluegill production in ponds

Application of 13.4 kg/ha of simazine to the bottom of channel catfish (Ictalurus punctatus) ponds before flooding resulted in an extended period of low dissolved oxygen, a 19% reduction (P < 0.01) in channel catfish yield, and poorer feed conversion by fish when compared to control ponds. A single application of 1.5 mg/l of simazine to the water of fertilized bluegill (Lepomis macrochirus) ponds also decreased dissolved oxygen. The 11% reduction in bluegill yield was not statistically significant (P > 0.05). Simazine treatment caused an initial reduction in macrophyte coverage in bluegill ponds, but macrophyte coverage increased as simazine concentrations in the pond water declined.     

Effect of Dietary Protein Concentration and Stocking Density on Production Characteristics of Pond-Raised Channel Catfish Ictalurus punctatus

Diets containing 28% and 32% crude protein were compared for pond‐raised channel catfish Ictalurus punctatus stocked at densities of 14,820, 29,640, or 44,460 fish/ha. Fingerling channel catfish with average initial weight of 48.5 g/fish were stocked into 30 0.04‐ha ponds. Five ponds were randomly allotted for each dietary protein ± stocking density combination. Fish were fed once daily to satiation for two growing seasons. There were no interactions between dietary protein concentration and stocking density for any variables. Dietary protein concentrations (28% or 32%) did not affect net production, feed consumption and weight gain per fish, feed conversion ratio, survival, processing yields, fillet moisture, protein and ash concentrations, or pond water ammonia and nitrite concentrations. Fish fed the 32% protein diet had slightly but significantly lower levels of visceral and fillet fat than fish fed the 28% protein diet. As stocking density increased, net production increased, while weight gain of individual fish, feed efficiency, and survival decreased. Stocking densities did not affect processing yield and fillet composition of the fish. Although highly variable among different ponds and weekly measurements, ponds stocked at the highest density exhibited higher average levels of total ammonia‐nitrogen (TAN) and nitrite‐nitrogen (NO₂‐N) than ponds stocked at lower densities. However, stocking density had no significant effect on un‐ionized ammonia‐nitrogen (NH₃‐N) concentrations, calculated based on water temperature, pH, and TAN. By comparing to the reported critical concentration, a threshold below which is considered not harmful to the fish, these potentially toxic nitrogenous compounds in the pond water were generally in the range acceptable for channel catfish. It appears that a 28% protein diet can provide equivalent net production, feed efficiency, and processing yields as a 32% protein diet for channel catfish raised in ponds from advanced fingerlings to marketable size at densities varying from 14,820 to 44,460 fish/ha under single‐batch cropping systems. Optimum dietary protein concentration for pond‐raised channel catfish does not appear to be affected by stocking density.     

Ionic Supplementation of Pond Waters for Inland Culture of Marine Shrimp

Saline well water used to fill ponds for inland culture of marine shrimp in Alabama often have low concentrations of potassium and magnesium. In 2002, pond waters on a shrimp farm were treated with enough muriate of potash and potassium-magnesium sulfate (K-Mag) to increase potassium concentration from 6.2 mg/L to about 40 mg/L and magnesium concentrations from 4.6 mg/L to about 20 mg/L. Salinity in ponds averaged 2.6 ppt at the time of mineral salt additions. The concentrations of potassium and magnesium remained fairly constant throughout the growing season without further applications of salts, and salinity increased to about 4 ppt mainly as a result of concentration through evaporation. Survival and production on the farm averaged 19% and 595 kg/ha, respectively, in 2001. In 2002, average survival improved to 67% and average production was 4,068 kg/ha. Ponds were stocked at similar rates and managed by similar procedures both years. Magnesium concentration was very low related to the concentration expected in normal seawater diluted to the same salinity as the pond water, while potassium was near the expected concentration. Thus, increased potassium concentration is thought to have influenced production much more than did the increase in magnesium concentration. K-Mag does not dissolve as readily as muriate of potash. Thus, K-Mag should not be dumped in shallow water areas of ponds to dissolve as can be done with muriate of potash. It should be broadcast over the pond surface, predissolved and splashed over the pond surface, or placed in porous bags suspended in front of aerators. Although a single application of mineral salts was effective, 2002 was a dry year. On a wet year, ions may be diluted or flushed out in overflow and more than one treatment with mineral salts might be necessary during the growing season.     

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 Dietary Protein and Feeding Rate on Channel Catfish Ictalurus punctatus Production, Composition of Gain, Processing Yield, and Water Quality

A 2 ± 4 factorial experiment was conducted to examine effects of dietary protein level (28, 32, 36, and 40%) and feeding rate (satiation or ± 90 kg/ha per d) on production characteristics, processing yield, body composition, and water quality for pond-raised channel catfish Ictalurus punctatus. Fingerling channel catfish with a mean weight of 64 g/fish were stocked into 40 0.04-ha ponds at a rate of 17,290 fish/ha. Fish were fed once daily to apparent satiation or at a rate of ± 90 kg/ha per d for 134 d during the growing season. Dietary protein concentration had no effect on feed consumption, weight gain, feed conversion, survival, aeration time, or on fillet moisture, protein, and fat levels. Fish fed to satiation consumed more feed, gained more weight, had a higher feed conversion, and required more aeration time than fish fed a restricted ration. Visceral fat decreased, and fillet yield increased as dietary protein concentration increased to 36%. Carcass yield was lower for fish fed a diet containing 28% protein. Increasing feeding rate increased visceral fat but had no major effect on carcass, fillet, and nugget yields. Fish fed to satiation contained less moisture and more fat in the fillets that those fed a restricted ration. Nitrogenous waste compounds were generally higher where the fish were fed the higher protein diets. Although there was a significant interaction in pond water chemical oxygen demand between dietary protein and feeding rate, generally ponds in the satiation feeding group had higher chemical oxygen demand than ponds in the restricted feeding group. There was a trend that pond water total phosphorus levels were slightly elevated in the satiation feeding group compared to the restricted feeding group. However, pond water soluble reactive phosphorus and chlorophyll-a were not affected by either diet or feeding rate. Results from the present study indicate that a 28% protein diet provides the same level of channel catfish production as a 40% protein diet even when diet is restricted to 90 kg/ha per d. Although there was an increase in nitrogenous wastes in ponds where fish were fed high protein diets, there was little effect on fish production. The long term effects of using high protein diets on water quality are still unclear. Feeding to less than satiety may be beneficial in improving feed efficiency and water quality.     

Culture environment and the odorous volatile compounds present in pond-raised channel catfish (<Emphasis Type="Italic">Ictalurus punctatus</Emphasis>)

A headspace solid-phase micro-extraction (SPME) coupled with GS-MS method was used to measure volatile compounds in fillets from musty off-flavor, muddy off-flavor, and on-flavor channel catfish (Ictalurus punctatus), along with water and soil samples from the farm ponds in which the fish had been raised. Two ponds of each type of flavor were selected, and five fish, water, and soil samples were collected from each pond. Linear and multiple linear regression analyses were carried out between/among off-flavor strength and volatile compound contents to investigate their possible correlations. The combination of two strong off-flavor compounds, 2-methylisoborneol (MIB) and geosmin (GSM), was probably mainly responsible for the musty off-flavor in the catfish fillets, and an odorous alcohol, 1-hexanol, was correlated with muddy off-flavor (p =?0.015). There was a strong correlation between beta-cyclocitral and MIB in a pond that gave musty off-flavor catfish contents (p =?0.006), suggesting that these compounds might be generated by similar cyanobacteria. The contents of GSM, MIB, and beta-cyclocitral were high in the water of ponds that yielded off-flavor fish, indicating that catfish might acquire these compounds from pond water.     

Dry-Tilling of Pond Bottoms and Calcium Sulfate Treatment for Water Quality Improvement

Three different pond bottom treatments were evaluated in 12 earthen ponds. Bottoms of four ponds on the Auburn University Fisheries Research Unit, Auburn, Alabama, were dried for 1 mo and tilled with a roto-tiller (dry-till treatment). Four other ponds were dried and tilled, and after filling with water, enough gypsum (calcium sulfate) was applied to give a total hardness of about 200 mg/L. Gypsum was reapplied as needed to maintain the hardness (dry-till with gypsum treatment). Four ponds were not subjected to bottom drying, tilling or gypsum treatment (controls). Channel catfish Ictalurus punctatus fingerings were stocked at 15,000/ha. Selected water quality variables were measured at 1- to 2-wk intervals during the growing season. Concentrations of most variables increased over time because feeding rate was increased progressively as fish grew. Compared to the controls, both treatments had lower concentrations of total phosphorus and soluble reactive phosphorus, and higher concentrations of dissolved oxygen ( P < 0.05). In addition, ponds of the dry-till with gypsum treatment had in addition lower concentrations ( P < 0.05) of chlorophyll a , chemical oxygen demand, gross primary productivity, and total alkalinity than control ponds. The reduction in chlorophyll a concentration suggested less phytoplankton in gypsum-treated ponds, and this effect was probably related to lower phosphorus availability because of calcium phosphate formation. Secchi disk visibility, total suspended solids concentrations, and turbidity did not differ significantly among the treatments ( P < 0.05). Total fish production and survival rate did not differ significantly ( P < 0.05) among the treatments. These findings suggest that water quality improvement can be achieved by drying and tilling pond bottoms between crops, and benefits possibly may be increased by treating low hardness waters with gypsum.     

Costs and Risk of Catfish Split‐pond Systems

Split ponds are recently developed pond‐based aquaculture systems that allow intensification of catfish aquaculture. Successful industry‐wide adoption of newly developing technologies like split‐pond systems will depend upon their productivity and cost efficiencies. Costs and production performance of the following three split‐pond design scenarios were monitored in Arkansas and Mississippi: (1) research design developed at the Thad Cochran National Warmwater Aquaculture Center, Stoneville, Mississippi; (2) waterwheel design tested on commercial catfish ponds; and (3) screw‐pump design tested on commercial catfish ponds. An economic engineering approach using standard enterprise budget analysis was used to develop estimates of breakeven prices (BEPs) ($/kg) for producing foodsize hybrid catfish (♂Ictalurus furcatus × ♀Ictalurus punctatus) for each scenario. Estimates of BEPs of hybrid catfish raised in split ponds ranged from $1.72 to $2.05/kg. The cost of catfish production in split ponds was sensitive to yield, fish prices, and feed prices. Annual net cash flows from both commercial split‐pond systems were high and sufficient to make the investment profitable in the long run. Feed price, feed conversion ratio, and yield contributed the most to downside risk of split ponds.     

Characteristics of Effluents from Central Arkansas Baitfish Ponds

Scientific information on baitfish effluents is important to provide a basis for the development of appropriate and cost-effective management practices that minimize environmental impacts. Effluents from 10 commercial golden shiner Notemigonus crysoleucas ponds in central Arkansas were sampled December 2000 through June 2001. Grab samples of the first and last 10% of pond volume were collected during intentional draining events. Effluents were sampled as they exited pond drainpipes and at the ends of drainage ditches just prior to stream discharge. Concurrent receiving stream samples were collected upstream and downstream of the discharge point. Total nitrogen (TN), total phosphorus (TP), 5-d biochemical oxygen demand (BOD_S), and total suspended solids (TSS) of each sample were measured. Mean whole effluent concentrations for the first 10% were 36 mg TSS/L, 9 mg/L BOD₅, 2 mg TN/L, and 0.5 mg TP/L. The water quality of the first and last 10% of pond effluent were not significantly different ( P < 0.05). Filtering effluents through a 5-pm mesh screen did not significantly reduce nutrient concentrations. Serial fractionation of effluents resulted in small but significant decreases in TSS concentrations in samples filtered through the 10, 8, and 5-μm meshes ( P < 0.05). Effluent discharge through farm ditches generally did not improve effluent water quality. Effluents collected at ditch ends were significantly less than drainpipe samples in BOD, concentrations only ( P < 0.05). Limited data on receiving stream water quality indicated that only TP concentrations were greater in pond effluents than in receiving streams. Overall, baitfish pond effluents are similar in composition to effluents of other phytoplankton-based pond production systems.     

Farm-level costs of settling basins for treatment of effluents from levee-style catfish ponds

Compelled by pending regulatory rule changes, settling basins have been proposed as a treatment alternative for catfish pond effluents, but the associated costs to catfish farmers have not been estimated. Economic engineering techniques were used to design 160 scenarios as a basis for estimating total investment and total annual costs. For static-water, levee-style catfish pond facilities, sizing of settling basins is controlled by factors such as type of effluent to be treated, pond layout, size of the largest foodfish pond, number of drainage directions, scope of regulations governing effluents, and the availability of land. Regulations that require settling basins on catfish farms would increase total investment cost on catfish farms by $126–2990 ha⁻¹ and total annual per-ha costs by $19–367 ha⁻¹. More numerous drainage directions on farms resulted in the greatest increase in costs. While both investment and operating costs increased with larger sizes of foodfish ponds, costs per ha were relatively greater on smaller than on larger farms. For farms on which existing fish ponds would have to be converted to settling basins, over half of the cost was due to the production foregone and annual fixed costs of the pond. Requiring catfish farmers to construct settling basins would impose a disproportionately greater financial burden on smaller farms. The magnitude of the increased costs associated with settling basins was too high relative to market prices of catfish for this technology to be economically feasible.     

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.