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.     

Evidence for Control of Water Quality in Channel Catfish Ictalurus punctatus Ponds by Phytoplankton Biomass and Sediment Oxygenation

A data set describing annual variation of water quality in ten commercial channel catfish Ictalurus punctatus ponds was subjected to exploratory statistical analysis to infer ecological processes affecting pond water quality. Two factors explained 67% of the variation in concentrations of water quality variables. The first factor (Factor 1) explained 49% of the variance and was associated with a large negative loading by total ammonia-nitrogen and large positive loadings by total nitrogen, total phosphorus, chemical oxygen demand, and chlorophyll a . Factor 1 was interpreted with respect to factor loadings to represent the effect of phytoplankton biomass. The second factor (Factor 2) explained an additional 18% of the variance and was associated with a large negative loading by soluble reactive phosphorus and large positive loadings by nitrite-nitrogen and, to a lesser extent, nitrate-nitrogen. Factor 2 was interpreted to be related to variation in pond sediment oxygenation. Although factor analysis indicated the overwhelming effect of phytoplankton biomass on water quality, opportunities for management of phytoplankton communities in large commercial aqua-culture ponds are limited. However, maintenance of an oxidized sediment-water interface may improve water quality by limiting the diffusion of reductant-soluble phosphorus from sediment to water and increasing sediment nitrification rates.     

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.     

Influence of a Bacterial Amendment on Water Quality in Small Research Ponds for Channel Catfish,Ictalurus punctatus,Production

There has been considerable interest worldwide in applying bacterial inocula to channel catfish ponds for improving water quality, especially for acceleration of ammonia nitrogen oxidation through bacterial nitrification. The effects of a selected bacterial amendment on water quality in small research ponds for channel catfish production were evaluated at the E. W. Shell Fisheries Center, Auburn University, Auburn, Alabama. Three ponds were treated with the bacterial amendment Waste & Sludge Reducer? (Keeton Industries, Wellington, CO, USA) at three times the dose recommended by the manufacturer every 2 wk, and three ponds served as controls. There were nonconsistent minor differences in water quality between ponds treated with a commercial bacterial amendment and control ponds on several sampling dates. However, the average concentrations of water quality variables did not differ (P > 0.05) between the treatments and control. Channel catfish yield was not improved by applying the bacterial amendment. This study demonstrates that the bacterial amendment was of no benefit in improving water quality in well‐managed catfish ponds where stocking rates, feeding rates, and amount of aeration are balanced.     

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.     

Water Quality and Phytoplankton Communities in Intensive Shrimp Culture Ponds in Kung Krabaen Bay, Eastern Thailand

Water quality and phytoplankton communities were studied in 20 intensive shrimp culture ponds and in the inlet and drainage canals at Kung Krabaen Bay, Eastern Thailand during the first shrimp crop of 1992. The grow-out ponds were categorized into two groups: low stocking density (<60 PL/m²) and high stocking density (>60 PL/m²). The results showed that there were no significant differences in water quality between the two stocking density groups. Phytoplankton collected using a 60-μm mesh net consisted of 79 genera with concentrations ranging from 1,822 to 72,527 cells/L from the first month up to the time of shrimp harvesting. Water quality deteriorated in high and low stocking density shrimp ponds, which had an influence on abundance and diversity of net phytoplankton communities. Biochemical oxygen demand and ammonia-nitrogen were most closely related to abundance of net phytoplankton communities during the shrimp grow-out period. Salinity, temperature, and dissolved oxygen appeared to play an important role in phytoplankton community variation in inlet and drainage canals. Phytoplankton community structure in drainage canals showed more variation than in ponds. The management implications of the results and recommendations for further studies are also considered.     

湛江港沙湾对虾养殖场虾池水质状况分析

2002年4～7月,对湛江港沙湾对虾养殖场虾池的水质及对虾的生长情况进行连续监测,应用单项指标评价、富营养化评价等方法,对该养殖场的水质状况进行了评价和营养分级。结果表明,该养殖场的水质呈高N低P状态,水温、DO和大部分池的pH、DRP符合第二类海水水质标准,DIN超标,超标率达70%,该养殖场目前处于P中等限制潜在性富营养水平阶段。     

Water Quality and Plankton Communities in Hybrid Catfish (♀ Channel Catfish,Ictalurus punctatus × ♂ Blue Catfish,Ictalurus furcatus) Ponds After Partial Fish Harvest

Twelve 0.4‐ha ponds were stocked with 10,000 hybrid catfish fingerlings in March 2015. Six ponds were partially harvested in August to remove fish larger than ～0.57 kg. All remaining fish were removed in October and November. Partial harvest of faster‐growing fish removed ～26% of the fish initially stocked; feeding rate (and therefore external nutrient loading) was reduced by about the same amount. However, reduced nutrient loading after partial fish harvest had no meaningful effects on water quality, phytoplankton biomass, phytoplankton and zooplankton community structure, or supplemental aeration. Lack of ecosystem change was caused by persistent internal recycling of nutrients added to the system before partial harvest and continued high (albeit reduced) external nutrient loading after partial harvest. Decisions to employ partial fish harvest to manage single‐cropped hybrid catfish ponds should be based on economic considerations and risk reduction rather than the expectation that fish biomass reduction will improve water quality.     

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.     

珠江三角洲密养池塘的水质特点分析

对珠江三角洲的几个典型基塘进行了一个养殖周期的跟踪调查,发现密养池塘中的NH4-、TN、COD、Chla等指标均有明显的升高,而NO3-、TP、SRP、BOD等指标无明显升高,DO没NO2-也占约 比例上升,占50%以上,NO2有明显下降。密养池塘无机氮的组成发生了明显的变化:NH4-比例,降到40%以下。池塘是以P为浮游植物生长的限制性因子。P的限制因素解除,浮10%,NO3游植物将迅速增长。池塘底泥中TP、TN、有机质明显高出基面堆叠土,以P的富集最为强烈。富营养化评价结果表明,珠江三角洲密养池塘达到了重度富营养化水平,而且养殖年限越高,富营养化程度越高。     

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.     

水产养殖池塘沉积物有机质富集的环境效应与修复策略

沉积物有机质富集十养殖池塘的重要特征,有机质的分解将驱动营养物质的释放,其主要机制在于自身的矿化与底层厌氧状态的形成,后者将进一步促进有毒有害物质的产生和累积,进而影响水产品的产量与质量。因此,必须针对沉积物有机质富集的特征开展技师而准确的检测,同时采用选择性去除、原位氧化和生态修复相结合的方法对其实施有效地处置,以调节养殖池塘生态系统的结构与功能,最大限度地利用可再生资源和天然饵料,进而实现渔业生产与水环境的可持续发展.     

高位虾池养殖过程主要理化因子的变化及水质评价

研究了湛江东海岛2口凡纳滨对虾高位养殖虾池水体主要理化因子在养殖过程中的动态变化及其相互关系,并用营养状态质量法对该养殖场的水质状况进行评价.试验结果表明,养殖过程水体中DO、pH、温度和盐度波动较小、变化平缓,而COD、DOC、营养盐和叶绿素a的含量随养殖过程而上升.主要理化因子之间的相关关系复杂,但叶绿素a与营养盐之间存在显著的正相关关系.在养殖中后期,表征富营养化的NQI值大幅度升高,水体富营养化程度严重.     

Comparison of Satiate and Restricted Feeding of Channel Catfish with Diets of Varying Protein Quality in Production Ponds

A 2 × 3 factorial experiment was conducted using satiate and restricted feeding with 32% crude protein diets containing low, medium, and high quality protein. Protein quality in the experimental diets was varied primarily by substituting peanut meal and cottonseed meal for soybean meal. Percentages of lysine, the first-limiting amino acid, were 1.14, 1.33, and 1.61 in the low, medium, and high quality protein diets respectively. Digestible energy concentration of the diets was 2.9 kcal/g. Channel catfish were grown from an average weight of 47 g to marketable size over a 15 wk period at a stocking density of 13,750 fish/ha in 400 m² earthen ponds. Each treatment was replicated in three ponds. Fish in the satiation group were fed as much as they would consume each day for the 15 wk experimental period. Fish in the restricted group were fed as much as they would consume until the daily feed allowance reached 65 kg/ha, which was reached at approximately week 5 of the experiment, and thereafter, there was no further increase in feed allowance. There was no significant interaction between feeding regimen and dietary protein quality for weight gain or feed conversion. Weight gain and feed efficiency under both satiation and restricted feeding increased linearly as protein quality increased. Protein quality had no influence on protein efficiency ratio (PER) under satiate feeding but had a positive effect on PER under restricted feeding. Protein quality had a positive linear effect on dressing percentage under restricted feeding, but in those fish fed to satiation, dressing percentage only increased between the low and high quality protein treatments. Protein quality had a negative linear effect on muscle fat but had no effect on visceral fat under satiate or restricted feeding. These results indicate that channel catfish are sensitive to protein quality differences in practical feeds at both satiate and restricted feeding rates, and that reduction in protein quality reduces dressing yield and increases muscle fat in food size fish.     

Studies on Vaccination of Channel Catfish,Ictalurus punctatus,Against Edwardsiella ictaluri

Enteric septicemia of cattish (ESC), caused by the bacterium Edwardsiella ictaluri, has become the most significant disease problem affecting the commercial channel catfish, Ictalurus punctatus, industry in the United States. Although antibiotics are used extensively for the control of ESC, there are inherent problems associated with their use. Consequently, experiments were initiated to evaluate the effectiveness of vaccination program that used immersion and oral delivery methods to administer a killed E. ictaluri vaccine to fry and fingerling channel cafish. In a preliminary pond study with laboratory challenge, mortality in a group vaccinated with a combination of immersion and oral procedures was only 5.0% in both high- and low-dose challenges. This was significantly different (P c 0.01) from non-vaccinated controls, which had 46.7%mortality in the lowdose challenge and the 6 1.7% mortality in the highdose challenge. This corresponds to relative percent survival (RPS) values of 89.3 and 91.9 respectively. Subsequent field trials further indicated the efficacy of a vaccination program for the prevention of ESC in channel catfish. In 1987-1988, a field study was conducted using 12 commercial ponds, with three replicates of four treatments. The four treatments included vaccination by immersion only, oral only, a combination of both immersion and oral procedures, and non-vaccinated conwols. Relative percent survival was 57.4 for the immersion only treatment, 50.3 for the oral only treatment, and 53.5 for the combination immersion and oral treatment. In 1989-1990, no significant difference was found between vaccinated and non-vaccinated fish. However, in 1989-1990, a vaccine-oil emulsion was topcoated on a floating feed, rather than incorporating vaccine in a sinking pellet. In 1990-1991, overall mortality in vaccinated fish was significantly less (P < 0.05) than non-vaccinated fish, with 41.2% mortality in vaccinates compared to 63.5% in non-vaccinated fish, for an RPS of 35.1. In examining RPS values for individual farms, two farms had excellent results, with RPS values of 81.3 and 76.9; two farms had only moderate success, with RPS values of 26.6 and 15.4; and one location had greater mortality in the vaccinated fish than in the non-vaccinated fish. However, that farm had only two ponds in the study and experienced significant losses to proliferative gill disease in the pond with vaccinated fish.     

Seasonal Trends in Flavor Quality of Channel Catfish,Ictalurus punctatus,from Commercial Ponds in Mississippi

Seasonal trends in types and intensities of fish flavors were determined for channel catfish, Ictalurus punctatus, from 10 ponds located on a commercial farm in west-central Mississippi. Fish were sampled bimonthly from July-September, 1990 and monthly from October, 1990-July, 1991. Sensory evaluation indicated that, on a yearly basis, 19% of ponds could be considered on- flavor. Off-flavors were strongest from July through September when 76% of ponds had fish tainted by 2-methylisoborneol (MIB). In nine ponds, the onset of MIB off-flavor episodes could be correlated with the presence of an MIB-producing cyanobacterium Oscillatoria chalybea. In seven ponds, fish lost the MIB off-flavor within 3 to 8 weeks after the fist date in September that 0. chalybea was noticed to be absent from the water. In June, 0. chalybea reappeared and caused MIB off-flavors in eight ponds. During the winter and spring, ponds were affected by woody (22%) and decay (25%) offflavors. The most prevalent algal species-Raphidiopsis brookii, 0. aaardhii. and Microcystis aeruginosa-were not associated with off flavor problems. On average, MIB off-flavor episodes lasted for 115 days (range: 27-344), and seven ponds were considered free of off-flavors for an average of 74 days (range: 14-140) in October, November, and December.     

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.     

Physical and chemical characteristics of sediments in catfish, freshwater prawn and carp ponds in Thailand

Sediment samples were collected from 42 catfish (Clarias hybrid) ponds, 40 freshwater prawn (Macrobrachium rosenbergii) ponds and 18 carp (Puntius spp.) ponds in Thailand. Regression analysis revealed that pond age (1–30 years) was not a major factor influencing the physical and chemical composition of pond sediments. Sediment depth, F+S horizon thickness and bulk density of S horizon were greater (P<0.05) in carp ponds than in catfish and prawn ponds. This occurred because sediment was removed from catfish and prawn ponds more frequently than from carp ponds. Total carbon, organic carbon and total nitrogen concentrations were greater (P<0.05) in carp ponds than prawn and catfish ponds. Few ponds had sediment organic carbon concentrations above 3%, and carbon:nitrogen ratio values did not differ (P>0.05) among ponds for the three species. Total phosphorus and other sediment phosphorus fractions increased in the order prawn ponds, carp ponds and catfish ponds. Sediment sulphur concentrations also increased in the same order. There were no differences in major or minor nutrient concentrations in sediment that would influence aquacultural production. Although there were significant correlations (P<0.05) between various sediment quality variables, no single variable or group of variables would be useful in estimating sediment quality. Pond bottom management practices used by producers in Thailand included drying of pond bottoms between crops, liming, tilling and periodic sediment removal. These practices have maintained relatively good bottom quality. They should be continued in Thailand and adopted in other places.     

Production Characteristics, Water Quality, and Costs of Producing Channel Catfish Ictalurus punctatus at Different Stocking Densities in Single-batch Production

Channel catfish Ictalurus punctatus farming is the largest component of aquaculture in the USA. Culture technologies have evolved over time, and little recent work has been conducted on the effects of stocking density on production characteristics and water quality. Twelve 0.1‐ha ponds were stocked with 13‐ to 15‐cm fingerlings (16 g) at either 8600, 17,300, 26,000, or 34,600 fish/ha in single‐batch culture with three replicates per treatment. Fish were fed daily to apparent satiation with a 32% floating commercial catfish feed. Nitrite‐N, nitrate‐N, total ammonia nitrogen (TAN), total nitrogen, total phosphorus, chemical oxygen demand (COD), Secchi disk visibility, chlorophyll a, chloride, total alkalinity, total hardness, pH, temperature, and dissolved oxygen (DO) were monitored. Ponds were harvested after a 201‐d culture period (March 26, 2003 to October 13, 2003). Net yield increased significantly (P < 0.05) as stocking density increased, reaching an average of 9026 kg/ha at the highest density. Growth and marketable yield (>0.57 kg) decreased with increasing stocking density. Survival was not significantly different among densities. Mean and maximum daily feeding rates increased with density, but feed conversion ratios did not differ significantly among treatments (overall average of 1.42), despite the fact that at the higher stocking densities, the feeding rates sometimes exceeded 112 kg/ha per d (100 lb/ac per d). Morning DO concentrations fell below 3 mg/L only once in a 34,600 fish/ha pond. Concentrations of chlorophyll a, COD, nitrite‐N, and TAN increased nominally with increasing feed quantities but did not reach levels considered problematic even at the highest stocking densities. Breakeven prices were lowest for the highest stocking density even after accounting for the additional time and growth required for submarketable fish to reach market size. While total costs were higher for the higher density treatments, the relatively higher yields more than compensated for higher costs.     

Comparison of Channel Catfish,Ictalurus punctatus,and Blue Catfish,Ictalurus furcatus,Fed Diets Containing Various Levels of Protein in Production Ponds

A comparative study was conducted on growth and protein requirements of channel catfish, Ictalurus punctatus, and blue catfish, Ictalurus furcatus. Four diets containing 24, 28, 32, or 36% protein were fed to both channel (initial weight 6.9 g/fish) and blue (6.6 g/fish) catfish for two growing seasons. There were significant interactions between dietary protein and fish species for weight gain and feed conversion ratio (FCR). No significant differences were observed in weight gain of channel catfish fed various protein diets, whereas higher protein diets (32 and 36%) resulted in better weight gain in blue catfish than lower protein diets (24 and 28%). No consistent differences were observed in the FCR of channel catfish fed various levels of dietary protein, whereas significantly higher FCRs were noted in blue catfish fed the 24 and 28% protein diets compared with fish fed 32 and 36% protein diets. Regardless of dietary protein levels, blue catfish had higher carcass, nugget, and total meat yield, and higher fillet moisture and protein, but lower fillet yield and fillet fat. Regardless of fish species, fish fed the 36% protein diet had higher carcass, fillet, and total meat yield than fish fed the 28 and 32% protein diets, which in turn had higher yields than fish fed the 24% protein diet. It appears that blue catfish can be successfully cultured by feeding a 32% protein diet.