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.     

Food inputs, water quality and nutrient accumulation in integrated pond systems: A multivariate approach

A participatory on-farm study was conducted to explore the effects of food input patterns on water quality and sediment nutrient accumulation in ponds, and to identify different types of integrated pond systems. Ten integrated agriculture-aquaculture (IAA) farms, in which ponds associate with fruit orchards, livestock and rice fields were monitored in the Mekong delta of Vietnam. Pond mass balances for nitrogen (N), organic carbon (OC) and phosphorus (P) were determined, and pond water quality and sediment nutrient accumulation were monitored. Data were analyzed using multivariate canonical correlation analysis, cluster analysis and discriminant analysis. The main variability in pond water quality and sediment nutrients was related with food inputs and water exchange rates. Water exchange rate, agro-ecological factors, pond physical properties and human waste input were major variables used to classify ponds. Classification was into: (1) low water exchange rate ponds in the fruit-dominated area, (2) low water exchange rate ponds in the rice-dominated area receiving homemade feed, and (3) high water exchange rate ponds in the rice-dominated areas receiving wastes. Pond water exchange rate was human-controlled and a function of food input patterns, which were determined by livelihood strategies of IAA-households. In the rice-dominated area with deep ponds, higher livestock and human wastes were found together with high water exchange rates. In these ponds, large organic matter loads reduced dissolved oxygen and increased total phosphorus concentrations in the water and increased nutrient (N, OC and P) accumulation in the sediments. In the rice-dominated area with wide ponds, higher homemade feed amounts were added to the ponds with low water exchange rate. This resulted in high phytoplankton biomass and high primary productivity. The contrary occurred in the fruit-dominated area, where fish were grown in shallow and narrow ponds, receiving more plant residue which resulted in lower phytoplankton biomass and lower sediment nutrient accumulation.     

Chemical Budgets for Organically Fertilized Fish Ponds in the Dry Tropics

Chemical budgets were determined for nitrogen, phosphorns, dissolved oxygen and chemical oxygen demand for three 0.1-ha earthen ponds stocked with Onwchrornis nilotieus at the El Carao National Fish Culture Research Center, Comayagna, Honduras, for two 150-d culture periods, corresponding to the rainy and dry seasons. Layer chicken litter was added to ponds weekly at 500 kg dry matter/ha. Concentrations of nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) in pond water increased during each season. No significant seasonal differencea in concentrations of water quality variables were observed. Chicken litter added to ponds represented 92–94% of N input, 93–95% of P input, and 43–52% of COD input. Photosynthesis by phytoplnnkton provided 47–56% of COD and 98% of dissolved oxygen (DO) added to ponds. Net inward diffnsion of oxygen added 1.2–1.5% of total DO. Regulated inflow was a minor source of nutrients, and contributed 3–4% of input N, 3–4% of input P, 1% of COD input, and 1% of DO input. Nutrient inputs from rain were ≤1% of total for each nutrient. Fish harvest accounted for 18–21% of total N, 16–18% of total P and 2% of COD added to ponds. Community respiration accounted for 48–57% of COD and 99.5% of DO added to ponds. Nutrient losses in pond effluent at draining were: 7–9% of total N, 29–37% of total P and 2–3% of COD. While measured gains exceeded measrued losses, significpntly greater N, P and organic matter concentrations in pre-drain samples indicated pond mud was a major sink for added nutrients, accumulation in mud represented 70% of total N, 35–40% of total P, and 38–46% of COD.     

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.     

Effect of Water Exchange Rate on Production, Water Quality, Effluent Characteristics and Nitrogen Budgets of Intensive Shrimp Ponds

Water exchange is routinely used in shrimp culture. However, there are few, if any, systematic investigations upon which to base exchange rates. Furthermore, environmental impacts of pond effluent threaten to hinder further development of shrimp farming in the U.S. The present study was designed to determine effects of normal (25.0%/d), reduced (2.5%/d) and no (0%/d) water exchange on water quality and production in intensive shrimp ponds stocked with Penaeus setiferus at 44 postlarvae/m². Additional no-exchange ponds were stocked with 22 and 66 postlarvae/m² to explore density effects. Water exchange rates and stocking density influenced most water quality parameters measured, including dissolved oxygen, pH, ammonia, nitrite, nitrate, Kjeldahl nitrogen, soluble orthophosphate, biochemical oxygen demand, phytoplankton and salinity. Reduced-exchange and no-exchange treatments resulted in reduced potential for environmental impact. Mass balance of nitrogen for the system indicates that 13–46% of nitrogen input via feed is lost through nitrification and atmospheric diffusion. Growth and survival were excellent in ponds with normal exchange, reduced exchange, and a combination of low density with no water exchange. A combination of higher stocking density and no water exchange resulted in mass mortalities. Mortalities could not be attributed to a toxic effect of any one water quality parameter. Production was 6,400 kg/ha/crop with moderate stocking density (44/m²) and reduced (2.5%/d) water exchange and 3,200 kg/ha/crop with lower stocking density (22/m²) and no water exchange. Results indicate that typical water exchange rates used in intensive shrimp farms may be drastically reduced resulting in a cost savings to farms and reduced potential for environmental impact from effluent.     

家鱼池塘底泥耗氧率与理化因子的相关性分析

采用原位底泥耗氧测定法,研究了10口家鱼鱼池底泥耗氧率与底部水体理化因子(溶氧、温度、pH值、氧化还原电位)和底泥有机质含量及深度的相关关系。结果显示:池塘平均底泥耗氧率(SOD)为0.91 g/(m2.d),变动范围为0.76～1.09 g/(m2.d)。双变量相关性分析表明,底泥耗氧率与池塘底部水体理化指标的相关性均达到极显著水平(P<0.01),与溶氧相关性最高(Pearson相关系数为0.779),其次是温度、pH值和氧化还原电位,相关系数分别为0.587、0.557和-0.421;底泥耗氧率与底泥深度相关性达到显著水平(P<0.05)。偏相关分析结果表明,底泥耗氧率与溶氧和温度呈极显著相关(P<0.01),与其它因素均未达到显著水平。影响底泥耗氧率最重要的环境因子是溶氧,其次是温度。利用BP神经网络分析影响SOD的理化因子,以溶氧、温度和底泥深度为BP神经网络模型的输入变量建立BP神经网络模型对SOD进行预测分析,BP神经网络模型训练和测试相关系数分别为0.911和0.879,平均相对误差分别为11.6%和10.4%,预测值与真实值偏差较小,拟合度较高,可有效预测池塘底泥耗氧率。     

Impact of farming intensity and water management on nitrogen dynamics in intensive pond culture: a mathematical model applied to Thai commercial shrimp farms

A mathematical model is used to investigate the impact of farming intensity and water management on nitrogen dynamics in the water column of intensive aquaculture ponds. The model describes the input of ammonia, its assimilation by phytoplankton or nitrification, and the loss of nitrogen through sedimentation, volatilization, and discharge. The model is calibrated for two commercial shrimp (Penaeus monodon Fabricius) farms in Thailand. Assimilation by phytoplankton with subsequent sedimentation or discharge is the principal process of ammonia removal. When inputs of ammonia exceed the algal assimilation capacity (carrying capacity), nitrification and volatilization of excess ammonia become significant. Carrying capacity is negatively affected by non-chlorophyll turbidity, and was estimated as 6 t ha^?1 cycle^?1 at a non-chlorophyll extinction of 2.6 m^?1. In ponds managed within their carrying capacity, ammonia concentrations are lowest at no water exchange, reach a maximum at exchange rates between 0.2 and 0.4 day^?1, and decline again at higher rates. When the carrying capacity is exceeded, excess ammonia concentrations decline continuously with increasing water exchange. Average exchange rates used in intensive shrimp farms (up to 0.2 day^?1) reduce phytoplankton abundance and sedimentation within ponds, but not ammonia concentrations. Discharges are high in particulate nitrogen at water exchange rates up to 0.3 day^?1, but contain mainly dissolved nitrogen at higher rates.     

The pond's shape matters: differential growth,physiological condition and survival of epibenthic Farfantepenaeus aztecus postlarvae

As a function of the water quality provided by square, circular and oval experimental ponds, the growth, survival and oxygen requirements in epibenthic postlarvae of Farfantepenaeus aztecus were analysed in relation to their routine metabolism and apparent heat increment. Temperature, oxygen concentration, pH and salinity were measured daily in two experimental ponds of each shape. The postlarvae oxygen consumption during two 24‐h cycles, their growth, physiological condition and survival and the productivity in the ponds were estimated. Low values of pH, oxygen concentration and phytobenthos productivity, and reduced postlarvae relative growth and survival were observed in the square ponds. We suggest that the latter results from a deficient water circulation related to the effect of the pond's shape on dissolved oxygen levels and, consequently, on growth and survival. The postlarvae routine metabolism, including feeding, varied between 1.91 and 2.25 mg O₂ h^?1 g^?1 wet weight, whereas the minimum oxygen concentration needed in the ponds is approximately 4.25 mg O₂ L^?1. These conditions were achieved in the oval ponds concurrent with higher survival and growth values, in which individuals distributed randomly, for which we suggest that oval‐shaped ponds could be the most adequate for the culture of this and other penaeid species.     

Effects of Intensification of the Amazon River Prawn,Macrobrachium amazonicum,Grow‐out on Effluent Quality

Studies to determine suitable levels of intensification are essential for developing sustainable aquaculture. The objective of this study was to evaluate the quality of effluents discharged from ponds stocked with 10 (D10), 20 (D20), 40 (D40), and 80 (D80) postlarvae of Macrobrachium amazonicum/m². Intake and effluent water samples were taken throughout a 5.5‐mo grow‐out cycle. In that study, twelve 0.01‐ha earthen ponds were stocked postlarvae with 0.01 g. Average water exchange rate was 15%/d; water was discharged from the bottom of the ponds. Prawns were fed a commercial feed with 38% crude protein according to their biomass (3–10%) and the concentration of dissolved oxygen (DO). In our research, temperature, turbidity, total suspended solids, conductivity, DO, pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), N‐ammonia, N‐nitrite, N‐nitrate, N‐Kjeldahl nitrogen, total phosphorus, and soluble orthophosphate were measured every 15 d throughout the experiment in the early morning (0630 to 0730 h). Turbidity was lower in D10 than in D20 and D40 and total phosphorus was higher in D80 than in D10 and D20. An analysis of principal components comparing treatments and intake water showed three groups: intake, D10 and a cluster of D20, D40, and D80. On the basis of the water characteristics found in our study it appears that the farming of M. amazonicum is likely to have a low environmental impact, at least up to a stocking density of 80 prawns/m².     

对虾工厂化养殖与池塘养殖系统结构与效益比较分析

从浮游植物、浮游动物、底栖生物、水质因子4个方面对工厂化对虾养殖和池塘对虾养殖生态系统的差异进行了观察和分析。结果表明,工厂化对虾养殖系统中浮游植物、浮游动物及底栖生物的丰度均低于池塘对虾养殖系统(分别为22815个/ml<31590个/ml,490.5个/L<650.0个/L,4.5个/10cm2<267.5个/10cm2),而溶解氧(DO)含量、氨态氮(NH4-N)和无机磷(PO4-P)浓度均高于池塘养殖。工厂化养殖对虾的生长量、生长速度及存活率均低于池塘养殖,但其养殖密度高,能很好的弥补生长速度之不足,更好的利用水体获得更高的单位生产量。     

叶轮式增氧机对鱼池溶氧日变化影响的模拟模型初步研究

针对鲜有鱼池溶氧模型考虑增氧机对鱼池溶氧日变化影响的现实,在传统的描述鱼池水温和溶氧日变化多层模型的基础上,通过分析叶轮式增氧机水跃和液面更新对鱼池多层水体中各能量要素和溶氧变化因子的影响,构建了能反映叶轮式增氧机增氧效果的鱼池水温和溶氧日变化模拟模型。通过实验数据对模型的校参和验证,发现溶氧逐小时模拟值与观测数据的均方根误差为0.267(晴天)和0.420(阴天),Nash-Stucliffe效率系数为0.957(晴天)和0.967(阴天),证明该模型能准确反映溶氧质量浓度的变化规律。同时运用模型模拟数据进行分析,结果显示:叶轮式增氧机增氧1 h后,其影响会持续12 h左右,而且效果主要集中在鱼池中下层,表层水层因高溶氧值和复氧原因,其增氧效果不明显;晴天一天之中最佳开机时间为0:00~10:00;阴天增氧效果不是很理想。     

Environmental quality and natural food performance at feeding sites in a carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>) pond

Just like other domesticated animals, common carp (Cyprinus carpio) are able to learn where food can easily be obtained. As a result, carp in semi-intensive polyculture ponds could conceivably restrict their main activity centres to supplemental feeding sites, leading to lowered exploitation of natural food resources (zooplankton and macrozoobenthos) and localised degradation of environmental conditions. At two semi-intensive ponds in southern Moravia (Czech Republic), areas around feeding sites displayed significantly reduced oxygen concentration and saturation (mainly p < 0.001). Likewise, temperature, pH and transparency also decreased significantly at feeding sites (mainly p < 0.05), while turbidity increased. While there was no significant difference in zooplankton biovolume at feeding and non-feeding sites, zoobenthos density and biomass were significantly lower at feeding sites (mainly p < 0.01). The feeding behaviour of carp, therefore, led to significant changes in both abiotic and biotic conditions at supplemental feeding sites.     

Water quality and freshwater fish culture intensification: the Israeli example

Abstract. During the development of freshwater fish culture in Israel there has been a trend toward intensification, which has been accelerated in the last years with the introduction of new culture systems: deep reservoirs, fish cages and mechanically stirred ponds. In the present paper, the main processes affecting water quality variability in outdoor systems with increasing fish culture intensification levels are presented. The analysed systems are semi-intensive shallow ponds with different organic loading, semi-intensive shallow ponds with different fish species combinations, semi-intensive deep reservoirs, and intensive mechanically stirred ponds. The examples are from experiments conducted at the Fish and Aquaculture Research Station Dor and from follow-ups at fish farms.     

Evaluation of rice (Oryza sativa), volunteer vegetation,and alligatorweed (Alternanthera phyloxeroides) in various combinations as crawfish (Procambarus clarkii) forages

Four treatments of naturally occurring plants and planted rice were evaluated as forages in experimental crawfish ponds. Their relationships to biomass production, dawn dissolved oxygen, unstable water levels, and crawfish production were determined.Total standing biomass of forage at fall flooding was significantly lower (P < 0.01) for alligatorweed plus volunteer vegetation ponds compared with all other forage regimes. Average dawn dissolved oxygen during the first 5 weeks after flooding varied between 1.7 mg/l and 4.7 mg/l in ponds containing alligatorweed, compared with 1.0 mg/l and 1.5 mg/l in ponds containing other vegetation. Crawfish yields in kg/ha for ponds with stable water levels were: rice plus alligatorweed, 2852; rice only, 2652; rice plus volunteer vegetation, 2117. These forage treatments appeared to sustain the crawfish population, and stunting of crawfish at unmarketable sizes was not observed.     

Evaluation of nitrogen cycling and fish production in seasonal ponds (‘Fingerponds’) in Lake Victoria wetlands,East Africa using a dynamic simulation model

A dynamic model was developed to simulate nitrogen (N) flows and fish production in seasonal wetland fish ponds (Fingerponds) based on organic manuring and natural food production. The model incorporates pond water depth, food availability, fish stocking densities, fish and fingerling weights at stocking, reproduction rate, manure type and application rates. The ponds were fertilized fortnightly with 1042 kg ha⁻¹ chicken manure. The model captured the dynamics of hydrology, nutrients and fish and demonstrated that similar fundamental processes underlie fish production in these systems. The model predicted annual fish yields of up to 2800 kg ha⁻¹. Simulated fish production, chlorophyll a and dissolved inorganic N concentrations were comparable with field measurements. Using the model, N budgets and estimates of all N flows were made. Most of the N input into the ponds (60–70%) accumulated in the bottom detritus of the pond and only 8–10% was converted into fish biomass, of which about half consisted of small fish. Fish production in Fingerponds was limited by turbidity induced light limitation and by nutrient limitation. Reduction of variability of fish production should come from reduced turbidity and sufficient nutrient input to minimize light limitation and maximize fish growth.     

Fish assemblages of an African river floodplain: a test of alternative models of community structure

In the Oueme River, a lowland river in Benin, Africa, artificial ponds constructed in the floodplain (whedos) are colonised during the high‐water period by a presumably random sample of fishes from the river channel. As water slowly recedes from the floodplain, fishes are isolated in whedos until they are harvested near the end of the dry season. We surveyed fishes in whedos and adjacent main‐channel and floodplain habitats during two low‐water periods (2008 and 2009) and one falling‐water period (2010–2011) to evaluate the relevance of four alternative metacommunity models to these systems. In 2010–2011, we also measured a suite of physicochemical variables including dissolved oxygen, temperature, specific conductivity and per cent cover of aquatic vegetation. Whedos were covered with dense growth of aquatic vegetation, and dissolved oxygen concentrations were lower in whedos and a natural floodplain depression compared with the main channel. Multivariate analyses revealed that habitat types were distinct with regard to assemblage structure and abiotic conditions. Assemblages in whedos and natural floodplain depressions were differentiated from those of the river channel, with the floodplain habitats being dominated by piscivorous fishes that tolerate aquatic hypoxia. Dispersal, aquatic hypoxia and predation act in concert to shape local community structure. Patch dynamics, species sorting and mass effect models all were consistent with patterns in fish assemblage structure in this system. We conclude that the underlying mechanisms of drift, speciation, selection and dispersal ultimately may be more useful for explaining patterns in ecological communities than alternative metacommunity models.     

Turbidity related to shrimp size in tanks with soil substrate

Water turbidity was monitored daily during a 63-day growth trial with juvenile Penaeus vannamei in indoor laboratory tanks. The tanks contained a 2.5 cm layer of soil substrate collected from 14 ponds representing five shrimp farms in Texas. A linear regression model relating turbidity to estimated shrimp length accounted for 49–83% of the total variation in turbidity for the 14 soil groups. For averages of daily turbidity and shrimp length over the 14 soil groups, the linear regression model yielded an r² = 0.92. Turbidity increased with shrimp length (75–135 mm), apparently because the elevated locomotory or feeding activity of the larger shrimp increased the suspension of soil particles. These results suggest the potential of using water turbidity as a tool for estimating shrimp biomass in ponds.     

Chemical Budgets for Polyethylene-lined, Brackishwater Ponds

Budgets for water, nitrogen, phosphorus, chemical oxygen demand (COD), and dissolved oxygen (DO) were estimated from May to October 1986 in three 0.09 ha ponds stocked with striped bass Morone saxatilis (Walbaum). Ponds were lined with highdensity polyethylene sheeting to prevent seepage. Pond bottoms, except for side slopes, were covered with soil. Total rainfall roughly equalled evaporation. Liner runoff augmented rainfall inflow by 43%. The largest source of nitrogen input was feed -88% of the measured input. Overflow was the greatest measured loss of nitrogen. Denitrification and ammonia volatilization apparently removed large amounts of nitrogen. Feed applications and runoff were the major phosphorus inputs. Fish harvest and uptake by mud represented the major losses of phosphorus. The production of each kilogram of fish required 2.09kg of feed and released to the water, as metabolic waste, 118.55g nitrogen, 1.2g phosphorus, and 1.67kg COD. Metabolic wastes from fish resulted in the production of an additional 3.71kg of COD in phytoplankton and benthic algae. Thus, 1kg of live striped bass resulted in a total of 5.38kg of COD. Benthic respiration exceeded respiration of microorganisms in the water column. Total respiration exceeded oxygen produced by photosynthesis, but diffusion of oxygen from the atmosphere into the ponds was sufficient to maintain adequate DO concentrations for fish survival.     

对虾养殖池塘微藻群落结构的调查与分析

分别于2005年秋、2006年春对广东省湛江市东海岛的对虾集约化养殖池(高位池)、半集约化养殖池(土塘)及其引水渠中水体的微藻群落结构进行调查和分析。结果表明,在所调查的对虾池塘中共检出微藻47种,其中春季检出微藻28种,秋季检出微藻21种。主要优势种是颤藻(Oscillatoria sp.)和啮蚀隐藻(Cryptomonas erosa Ehr.)。微藻的多样性指数(H′)平均值为春季东南土塘2.29,东南高位池1.42,东山土塘1.12;秋季东南高位池2.14,东山土塘1.62,而2季节引水渠则处于0.92~3.72之间。对虾池塘微藻平均密度秋季高于春季。     

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。