The effectiveness of a commercial microbial product in poorly prepared tiger shrimp, Penaeus monodon (Fabricius), ponds

The efficacy of a commercial microbial product was tested in commercial tiger shrimp, Penaeus monodon (Fabricius), ponds for one culture period in Kuala Selangor, Malaysia. Four ponds with replicates for treatment and control were used. The pond bottom was dried but the organic sludge was not removed as normally practised in pond preparation. The ponds were stocked with 15 post‐larvae at the rate of 31.m^?2. Physical, chemical and biological parameters of the pond were analysed every 2 weeks during the culture period. Water quality parameters remained within the optimum range for shrimp culture except for ammonia‐nitrogen being significantly higher in control ponds and silica in treated ponds. Benthic organisms were not found in any of the ponds. The average counts of different bacteria were not significantly higher in treated ponds than control. Because of poor health, the shrimp were harvested earlier (72 days) than the usual 120 days. An average of 875.60 ± 67.00 kg shrimp ha^?1 was obtained in treated ponds with a feed conversion ratio (FCR) of 1.57 ± 0.10 and survival rate of 42.35 ± 5.37% compared with 719.50 ± 130.94 kg shrimp ha^?1, 2.99 ± 0.70 and 21.25 ± 3.26%, respectively, in control ponds. Neither the microbial product nor the frequent water exchange was effective in overcoming the problems caused by the poor pond bottom.     

Beneficial co‐culture of jellyfish Rhopilema esculenta (Kishinouye) and sea cucumber Apostichopus japonicus (Selenka): implications for pelagic‐benthic coupling

This study investigated monthly changes of sedimentation and sediment properties in three different culture systems (ponds) – i.e. jellyfish Rhopilema esculenta monoculture (J), sea cucumber Apostichopus japonicus and jellyfish co‐culture (SJ) and sea cucumber monoculture (S) – to verify the feasibility of co‐culturing jellyfish and sea cucumbers. Results showed that jellyfish culture accelerated the settling velocity of total particulate matter (TPM). Average TPM settling velocities in the SJ (75.6 g m^?2 day^?1) and J (71.1 g m^?2 day^?1) ponds were significantly higher than that in the S pond (21.7 g m^?2 day^?1) from June to September during the jellyfish culture period. Average settling velocities of organic matter (OM), total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in the SJ pond increased significantly by 3.0, 2.9, 3.3 and 3.8 times, respectively, compared with those in the S pond. Sediment contents of OM, TOC, TN and TP in the SJ and J ponds were significantly higher than those in the S pond during the jellyfish culture season. The specific growth rate of sea cucumbers feeding on SJ sediment was significantly higher than that of those feeding on S sediment. Co‐culturing sea cucumbers with jellyfish may help alleviate benthic nutrient loading due to the jellyfish and provide a secondary cash crop.     

室内集约化养虾池以低频率运转水处理系统调控水质效果及氮磷收支

采用低频率运转循环水处理系统(含粗滤器、臭氧仪、气液混合器,蛋白分离器、暗沉淀池等)联用池内设施(微泡曝气增氧机与净水网)开展凡纳滨对虾室内集约化养殖实验。研究了养虾池以水处理系统调控水质效果及氮磷收支。结果表明,养虾水经系统处理后,NO₂-N(53.4%～64.5%)、COD_Mn(53.4%～94.4%)与TAN(31.6%～40.4%)被显著去除,有效改进虾池水质;养殖周期内未换水与用药,虾池主要水化指标均控制在对虾生长安全范围,7号实验池(100 d)与8号对照池(80 d)主要水化指标变化范围:DO分别为 5.07～6.70 mg/L和4.38～6.94 mg/L,TAN 0.248～0.561 mg/L和0.301～0.794 mg/L,NO₂-N 0.019～0.311 mg/L和0.012～0.210 mg/L,COD_Mn 10.88～21.22 mg/L和11.65～23.34 mg/L。7号池对虾生长指数优于8号池(80 d虾病暴发终止),单位水体产量分别为1.398 kg/m²与0.803 kg/m²。氮磷收支估算结果:7号与8号池饲料氮磷分别占总收入:氮93.70%与92.37%,磷98.77%与99.09%;初始水层与虾苗含氮共占总收入6.30%与7.63%,磷共占1.23%与0.91%。总水层(含排污水)氮磷分别占总输出:氮56.45%与59.86%,磷53.26%与55.79%;收获虾体氮磷分别占总输出:氮37.07%与31.94%,磷21.37%与13.11%。7号池饲料转化率较高;池水渗漏与吸附等共损失氮磷分别占总输出:氮7.00%与9.34%,磷25.37%与31.10%。实验结果表明,虾池以低频率运转循环水处理系统联用池内设施可有效控制水质与虾病,具较高饲料转化率。     

Enhancing productivity of Labeo victorianus ponds using maize flour as a carbohydrate source

This study investigated the effects of manipulating carbon–nitrogen (C/N) ratio and fish stocking density on pond productivity: total heterotrophic bacteria counts, plankton biovolume and benthic macro‐invertebrates. Labeo victorianus juveniles were reared for 72 days in 18 hapas suspended in six ponds measuring 150 m² at densities of 10, 15 and 25 fish m^?2. Fish in hapas received a locally formulated and prepared feed containing 295 g kg^?1 crude protein, and ponds were treated with a C/N ratio of either 10 or 20. All treatments were carried out in triplicate. Increasing C/N ratio from 10 to 20 increased phytoplankton by 13% and zooplankton biovolume by 25% in the water column (P < 0.001). Total benthic macro‐invertebrates biovolumes were also 30% higher (P < 0.05) with a C/N ratio of 20 compared to 10. Total heterotrophic bacteria counts increased both in water and sediment by 29% while net yield increased by 15% from 1534 (C/N 10) to 1821 (C/N 20) kg ha^?1 72 day^?1. C/N ratio of 20 and a stocking density of 25 fish m^?2 led to the highest yield, survival, production and net benefits. It is suggested that polyculture may lead to better utilization of pond communities to further improve pond productivity.     

Low-density silver carp Hypophthalmichthys molitrix (Valenciennes) polyculture does not prevent cyanobacterial off-flavours in channel catfish Ictalurus punctatus (Rafinesque)

Silver carp Hypophthalmichthys molitrix (Valenciennes) were co‐cultured with channel catfish Ictalurus punctatus (Rafinesque) in 0.4 ha earthen ponds to determine the impacts of carp grazing on pond phytoplankton communities and cyanobacterial off‐flavours in catfish. Carp were stocked at densities of 0, 75, or 250 fish ha^?1 in seven replicate ponds per treatment. The mean chlorophyll a concentrations (a measure of phytoplankton standing crop) steadily increased in all treatments from about 100 μg L^?1 in April to more than 400 μg L^?1 by mid‐October. Silver carp had no affect (P>0.1) on chlorophyll a concentrations across all sampling dates (April though October) or for sampling dates late in the growing season (August–October) when the prevalence of cyanobacterial off‐flavours among catfish populations is usually greatest. Silver carp did not eliminate odour‐producing cyanobacteria from pond phytoplankton communities: on sampling dates in September and October, three to six ponds in all treatments contained populations of the odour‐producing cyanobacteria Oscillatoria perornata, Anabaena spp., or both. Failure of silver carp to eliminate odour‐producing cyanobacteria resulted in a relatively high incidence in all treatments of ponds with off‐flavoured catfish. On sampling dates in September and October, catfish in three to five ponds in each treatment were tainted with either musty (2‐methylisoborneol) or earthy (geosmin) off‐flavours. The presence of silver carp had no obvious effect on off‐flavour intensity: on each sampling date, at least three ponds in each treatment contained catfish described as distinctly to extremely off‐flavored. Apparently, hypertrophic conditions in catfish ponds overwhelm the effect of silver carp grazing at the low carp densities used in this study.     

Effects of stocking density and feeding duration in cage‐cum‐pond‐integrated system on growth performance,water quality and economic benefits of Labeo victorianus (Boulenger 1901) culture

We evaluated the effect of varying cage stocking density (60, 90 and 120 fish m^?3) and feeding duration (10, 30 and 60 min) in a cage‐cum‐pond‐integrated system on growth performance, water quality and economic benefits in Labeo victorianus culture. Interactions between stocking density and feeding duration significantly (P < 0.05) affected the fish growth performance and yields in the cages‐cum‐pond system. Stocking density of 60 fish m^?3 resulted in the highest growth in cages and in ponds regardless of the feeding duration, but produced lower yields than at stocking density 90 fish m^?3_. The lowest Apparent Food Conversion Ratio (AFCR) in cages occurred at stocking density of 60 fish m^?3 and feeding duration of 30 min. Growth performance in the open ponds declined with increased feeding duration of the caged fish. Survival in cages and in the open ponds decreased with increased cage density, but was not affected by feeding duration. Low dissolved oxygen were recorded, at stocking density of 120 fish m^?3, the lowest DO occurred when feeding of caged fish lasted 60 min. Growth performance, water quality and economic benefits in Labeo victorianus culture positively respond to interaction between stocking density and feeding durations.     

Phytoplankton Community Structure, Biomass, and Off-flavor: Pond Size Relationships in Louisiana Catfish Ponds

Abstract.— Many aquaculture studies are conducted in relatively small research ponds and the results are then extrapolated to larger commercial ponds. Implicit in this research is the assumption that there is no relationship between pond size and phytoplankton composition. Study objectives were to assess phytoplankton composition and biomass by several methods in 17 channel catfish Ictalurus punctatus ponds at the Aqua‐culture Research Station, Louisiana Agricultural Experiment Station in Baton Rouge, Louisiana, USA. Pond size ranged from 0.04–0.60 ha. Sampling occurred weekly from 10 September – 1 October 1997. Water temperatures coincided with a transition from summer to fall‐winter conditions. Biomass was assessed by cell counts and quantification of photopigments. Concentrations of dissolved off‐flavor compounds (2‐methylisoborneol and geosmin) were assessed by gas chromatography/mass spectroscopy of water column samples. Cell count data showed differences in dominant species, biovolume, and diagnostic pigment signatures among ponds. The smaller ponds had more diverse phytoplankton composition compared to the larger ponds, whereas chlorophyll levels were nearly an order of magnitude lower in the smaller ponds. Ultraplanktonic (2–20 μm) unicellular cyanobacteria dominated the numerical counts on most sampling dates; however, biovolume transformations of cell count data reduced the dominance of this component relative to cryptophytes, diatoms, and filamentous cyanobacteria. Pigment and microscopic analyses were well correlated. Unialgal isolates of dominant taxa from these samples indicated the presence of at least five genera of off‐flavor producers in these ponds; these taxa included Anabaena, Aphanizomenon, Pseudanabaena, as well as two species of Oscillatoria. Care in extrapolating results from smaller‐sized research ponds to larger commercial ponds is warranted, as is the potential for taxa other than Oscillatoria and Anabaena in forming off‐flavor compounds.     

Nursery rearing of the Asian catfish, Clarias macrocephalus (Günther), at different stocking densities in cages suspended in tanks and ponds

Growth and survival of hatchery‐bred Asian catfish, Clarias macrocephalus (Günther), fry reared at different stocking densities in net cages suspended in tanks and ponds were measured. The stocking densities used were 285, 571 and 1143 fry m^?3 in tanks and 114, 228 and 457 fry m^?3 in ponds. Fish were fed a formulated diet throughout the 28‐day rearing period. Generally, fish reared in cages in ponds grew faster, with a specific growth rate (SGR) range of 10.3–14.6% day^?1, than those in cages suspended in tanks (SGR range 9–11.3% day^?1). This could be attributed to the presence of natural zooplankton (copepods and cladocerans) in the pond throughout the culture period, which served as additional food sources for catfish juveniles. In both scenarios, the fish reared at lower densities had significantly higher SGR than fish reared at higher densities. In the pond, the SGR of fish held at 228 and 457 m^?3 were similar to each other but were significantly lower than those of fish held at 114 m^?3. The zooplankton in ponds consisted mostly of copepods and cladocerans, in contrast to tanks, in which rotifers were more predominant. Per cent survival ranged from 85% to 89% in tanks and from 78% to 87% in ponds and did not differ significantly among stocking densities and between rearing systems. In conclusion, catfish nursery in cages suspended in tanks and ponds is density dependent. Catfish fry reared at 285 m^?3 in tanks and at 114 m^?3 in ponds had significantly faster growth rates than fish reared at higher densities. However, the desired fingerling size of 3–4 cm total length for stocking in grow‐out culture can still be attained at stocking densities of 457 m^?3 in nursery pond and 571 m^?3 in tanks.     

Ecology of Blue-Green Algae in Aquaculture Ponds

Cyanobacteria (blue-green algae) in the genera Anabaena, Aphanizomenon, Microcystis, and Oscillatoria often form extensive and persistent blooms in freshwater aquaculture ponds. Bloom-forming cyanobacteria are undesirable in aquaculture ponds because: 1) they are a relatively poor base for aquatic food chains; 2) they are poor oxygenators of the water and have undesirable growth habits; 3) some species produce odorous metabolites that impart undesirable flavors to the cultured animal; and 4) some species may produce compounds that are toxic to aquatic animals. Development of cyanobacterial blooms is favored under conditions of high nutrient loading rates (particularly if the availability of nitrogen is limited relative to phosphorus), low rates of vertical mixing, and warm water temperatures. Under those conditions, dominance of phytoplankton communities by cyanobacteria is the result of certain unique physiological attributes (in particular, N₂ fixation and buoyancy regulation) that allow cyanobacteria to compete effectively with other phytoplankton. The ability to fix N₂ provides a competitive advantage under severe nitrogen limitation because it allows certain cyanobacterial species to make use of a source of nitrogen unavailable to other phytoplankton. The ability to regulate cell buoyancy through environmentally-controlled collapse ad reformation of intracellular gas vacuoles is perhaps the primary reason for the frequent dominance of aquaculture pond phytoplankton communities by cyanobacteria. Cyanobacteria that can regulate their position in the water column gain a distinct advantage over other phototrophs in poorly mixed bodies of water. In addition to the physicochemical interactions that influence phytoplankton community dynamics, cyanobacterial-microbial associations may play an important regulatory role in determining community structure. Cyanobacteria are always found in close association with a diverse array of microorganisms, including eubacteria, fungi, and protozoans. These associations, which in the past have often been viewed as antagonistic, are increasingly seen as mutualistic and may function in a positive manner during bloom development.     

鱼蚌混养对池塘水质、藻相结构及三角帆蚌生长的影响

2012年4月26日—2012年12月12日通过在鲢鳙鱼养殖池塘中放养不同密度的三角帆蚌,研究不同三角帆蚌放养比例对鲢鳙鱼养殖池塘中水质、藻相结构及三角帆蚌生长的影响。实验中,鲢鳙放养比例统一为3∶7,总密度为1.5尾/m3。三角帆蚌放养密度则设置4个水平,分别为单养鲢鳙鱼池塘(0只/m3),低密度三角帆蚌混养池塘(0.8只/m3),中密度三角帆蚌混养池塘(1.0只/m3)和高密度三角帆蚌混养池塘(1.2只/m3)。结果显示,混养三角帆蚌池塘的水化指标(TP、PO4-P、NH3-N、NO2-N和NO3-N)均显著低于单养鱼池塘。中密度三角帆蚌混养池塘除NH3-N和化学需氧量(COD)与低密度三角帆蚌混养池塘无显著差异外,其他各项水化指标均显著低于其他3个池塘,并且极显著低于单养鲢鳙鱼池塘。单养鲢鳙鱼池塘藻类平均密度均极显著高于鱼蚌混养池塘,其中在鱼蚌混养池塘中浮游植物密度与三角帆蚌密度成负相关关系。单养鲢鳙鱼池塘的浮游植物生物量均极显著低于中、高密度鱼蚌混养池塘,并且显著低于低密度混养池塘。浮游植物生物量与三角帆蚌密度成正相关关系,鱼蚌池塘中绿藻和裸藻的生物量在养殖过程中上升显著。低、中密度三角帆蚌混养池塘三角帆蚌存活率均显著高于高密度三角帆蚌混养池塘;低密度混养池塘中蚌湿重、壳长及壳宽相对增长率均为最大,显著高于中、高密度三角帆蚌混养池塘。研究表明,养鱼池塘混养三角帆蚌不仅能改善养殖池塘的水质,还能控制藻类数量,促使绿藻和裸藻等大型藻类的生长,提高养殖水体浮游植物的生物量总量,最终还能有效提高三角帆蚌的存活率及生长率。从改善水质,藻相结构,蚌成活率及生长等指标角度考虑,在鲢鳙鱼养殖池塘中,三角帆蚌最佳放养密度为1.0只/m3。     

Polyculture of milkfish Chanos chanos (Forsskal) and the red seaweed Gracilariopsis bailinae (Zhang et Xia) in brackish water earthen ponds

Growth, net production, and survival rates of milkfish cultured with Gracilariopsis bailinae at two stocking density combinations (T₁– 30 fingerlings 100‐m^?2 pond+1‐kg G. bailinae 4‐m^?2 net cage, T₂– 30 fingerlings 100‐m^?2 pond+2‐kg G. bailinae 4‐m^?2 net cage) in brackish water earthen ponds over four culture periods were determined. The control (T₃) was stocked at 30 fingerlings 100‐m^?2 pond. Specific growth and production rates of G. bailinae were also calculated. There were no significant differences in mean growth, survival, and net production rates of milkfish between the three treatments. Irrespective of stocking singly or in combination with G. bailinae, significantly higher mean growth and mean production rates for milkfish were obtained during the third culture period of year 1 than those obtained from the other culture periods. Survival rates were not significantly different among the four culture periods. There were no significant differences in mean specific growth and mean net production rates between the two stocking densities of G. bailinae. Significantly higher mean specific growth and mean net production rates of red seaweed were also obtained during the third culture period of year 1 than those obtained from other culture periods. The production of milkfish and red seaweed was higher during the dry season. Growth rates of milkfish was positively correlated with temperature and salinity, while net production rates were positively correlated with temperature and total rainfall, but was inversely correlated with dissolved oxygen. G. bailinae growth and net production rates were positively correlated with water temperature and salinity. Results show that milkfish can be polycultured with G. bailinae grown in net cages in brackish water ponds at stocking density combination of 30 fingerlings 100‐m^?2 pond+1‐kg G. bailinae 4‐m^?2 net cage.     

The use of high rate algal ponds for the treatment of marine effluent from a recirculating fish rearing system

A high rate algal pond (HRAP) system was used to treat effluent from a recirculating sea water aquaculture system in southern France. Dicentrarchus labrax L. were farmed at a high density, with effluents containing an average of 10 mg L^?1 dissolved inorganic nitrogen (DIN) and 1.3 mg L^?1 reactive phosphorus (RP). On a yearly basis, the algal pond removed 59% of the dissolved nitrogen and 56% of the phosphorus input, which was converted into 3.3 kg DW m^?2 algae. Green macroalgae were dominant throughout the year and the algal biomass mirrored the seasonal changes in daily irradiance and temperature. This first year study supports the possibility of treating marine aquaculture wastes using HPAPs, although conditions will have to be found to mitigate the strong influence of climate on the algal community during winter. During the more temperate season, only 150 m² of treatment ponds would be necessary to remove the nutrients produced by 1 ton of fish. Treated water was characterized by a high pH, elevated levels of dissolved oxygen (midday value) and low concentrations of nutrients and suspended solids. The absence of toxic phytoplankton meant that the water could be recycled through the farm tanks.     

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.     

Short-Term Dinoflagellate Bloom in a Shrimp Pond in Bahía de La Paz,Gulf of California

From mid-August to mid-September 1998, a dinoflagellate bloom in a shrimp pond near La Paz, Baja California Sur, was studied. Daily samples were taken of phytoplankton, dissolved oxygen, nutrient concentrations, photosynthetic pigments and proteins. The bloom occurred at temperatures of 29.7 to 33.2?°C. High densities of a Scrippsiella-like dinoflagellate (15.9?×?10⁶ cells/L) occurred on the first day of sampling, reaching a peak of 249?×?10⁶ cells/L on Day 13, and declining to 4 to 7?×?10⁶ cells/L by Day 26. Chlorophyll a varied from 8.63 mg/m³ on Day 4 to 141.38 mg/m³ on Day 13. Total nitrogen varied widely (0.2–11.50 μM) while phosphates peaked only once on Day 13 (4.14 μM). Proteins ranged from 523 to 6387 μg/L; the latter value occurred two days after the maximal peak of nitrates and coinciding with the highest level of phosphates. Fertilizers added to the ponds increased nutrient concentration and stimulated phytoplankton growth. In turn, the food supply to cultured shrimp noticeably increased throughout the bloom.     

Effects of tilapia (Oreochromis niloticus L.) stocking and artificial feeding on water quality and production in rohu–common carp bi‐culture ponds

Previous research showed that stocking 1.5 rohu (Labeo rohita) and 0.5 common carp (Cyprinus carpio) m⁻² yields the highest production in small holder ponds in Bangladesh. The present study looked into the effects of additional stocking of Nile tilapia (Oreochromis nilotica) in fed or non‐fed ponds on water quality and fish production. A low, additional stocking density of 0.2 Nile tilapia m⁻² was tested. All treatments were executed in triplicate in 100 m² ponds and the duration of the experiment was 4.5 months. The results showed that tilapia addition increased nutrient concentrations and reduced total suspended solid concentration and phytoplankton biomass (P<0.05). Tilapia stocking resulted in additional production without affecting the growth and production of rohu and common carp. Supplemental feeding increased the nitrogen and phosphorus concentrations, phytoplankton availability and the growth and production of rohu and common carp (P<0.01). The combination of supplemental feeding and tilapia stocking resulted in a higher net yield than the other treatments (P<0.05). Stocking 1.5 rohu, 0.5 common carp and 0.2 tilapia m⁻² in fed‐ponds is a good culture combination for polyculture farmers in South Asia.     

Preliminary observations on the tank and pond culture of the glass eels of the Australian shortfin eel, Anguilla australis Richardson

There is expanding interest in the culture of the Australian shortfin eel Anguilla australis Richardson; however, there is a lack of fundamental biology and husbandry information necessary to further develop an industry within Australia. The present study was undertaken to gain a preliminary understanding of basic husbandry requirements for rearing of juvenile A. australis (glass eels and elvers) in tanks and earthen ponds. Newly caught glass eels were successfully acclimated to culture conditions. During tank culture trials, specific growth rates (SGR) and survival rates ranged from ?2.1 to 2.8% day^?1 and 52% to 100% respectively. Glass eels weaned onto a commercial eel diet exhibited a significantly greater SGR and survival rate than those weaned onto a commercial trout diet. Glass eels weaned onto an eel diet over a 15‐day period grew slightly faster than eels weaned over a 5‐day period, but survival rates were not significantly different for each treatment. SGRs (up to 2.8% day^?1) were significantly higher for glass eels fed at 9 and 12% day^?1 than at 6% day^?1. Stocking densities between 2.5 kg m^?3 and 30 kg m^?3 did not influence either SGR or survival rates. SGRs were significantly higher for glass eels cultured at 25 °C than at lower temperatures. During pond culture trials, SGRs and survival rates ranged from 1.36 to 1.65% day^?1 and 39% to 77% respectively. The SGR and survival rates of juvenile eels stocked into ponds receiving supplementary feeding with a commercial eel diet were not significantly different to those of eels stocked into ponds that did not receive supplementary feeding.     

Cage‐pond integration of African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) with carps

Cage‐pond integration system is a new model for enhancing productivity of pond aquaculture system. A field trial was conducted using African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) in cages and carps in earthen ponds. There were four treatments replicated five times: (1) carps in ponds without cage, (2) tilapia at 30 fish m^?3 in cage and carps in open pond, (3) catfish at 100 fish m^?3 in cage and carps in open pond, (4) tilapia and catfish at 30 and 100 fish m^?3, respectively, in separate cages and carps in open pond. The carps were stocked at 1 fish m^?2. The cage occupied about 3% of the pond area. The caged tilapia and catfish were fed and the control ponds were fertilized. Results showed that the combined extrapolated net yield was significantly higher (P < 0.05) in the catfish, tilapia and carps integration system (9.4 ± 1.6 t ha^?1 year^?1) than in the carp polyculture (3.3 ± 0.7 t ha^?1 year^?1). The net return from the tilapia and carps (6860 US$ ha^?1 year^?1) and catfish, tilapia and carps integration systems (6668 US$ ha^?1 year^?1) was significantly higher than in the carp polyculture (1709 US$ ha^?1 year^?1) (P < 0.05). This experiment demonstrated that the cage‐pond integration of African catfish and Nile tilapia with carps is the best technology to increase production; whereas integration of tilapia and carp for profitability.     

Effects of feeding practical diets containing various protein levels on growth, survival, body composition, and processing traits of Australian red claw crayfish (Cherax quadricarinatus) and on pond water quality

A 117‐day feeding trial was conducted in ponds with juvenile Australian red claw crayfish (Cherax quadricarinatus) to evaluate the effects on growth, survival, body composition, and processing traits when fed diets containing three different protein levels (22%, 32%, and 42%), and the effects of feeding these diets on pond water quality. Juvenile crayfish (mean weight of 4.6±2.2 g) were randomly stocked into nine 0.02‐ha ponds at a rate of 500 per pond (25 000 ha^?1), and each diet was fed to three ponds. There were two feedings per day, each consisting of one‐half of the total daily ration. At harvest, there were no significant differences (P>0.05) in the individual weight, percentage weight gain, or specific growth rate among treatments, which averaged 75.3 g, 1535%, and 2.38% day^?1 respectively. Red claw fed the 42% crude protein diet had significantly higher (P<0.05) feed conversion ratio (7.34) compared with crayfish fed diets containing 22% (5.18) or 32% (5.13) crude protein, and had significantly lower percentage survival (46.1%) compared with red claw fed diets with 22% (61.1%) or 32% (58.2%) protein. Total yield was significantly lower (P<0.05) in red claw fed the 42% protein diet (640 kg ha^?1) compared with red claw fed diets containing 22% (920 kg ha^?1) or 32% (904 kg ha^?1) protein. Mean total ammonia nitrogen (TAN) levels were significantly higher (P<0.05) in ponds with red claw fed the 42% protein diet (0.55 mg L^?1) compared with ponds with red claw fed diets containing 22% (0.32 mg L^?1) or 32% (0.38 mg L^?1) protein. Mean total nitrite concentrations in ponds with red claw fed the 42% protein diet was significantly higher (0.05 mg L^?1) compared with red claw fed diets containing 22% (0.01 mg L^?1) or 32% (0.02 mg L^?1) protein. These results indicate that a practical diet containing 22% (as fed basis) protein may be adequate for pond production of red claw when stocked at the density used in this study, and that a diet containing 42% protein adversely affected levels of TAN and nitrite, possibly reducing overall survival of red claw. Use of a diet with 22% protein may allow red claw producers to reduce diet costs and thereby increase profits.     

Isolation Columns as an Alternative to Replicate Ponds in Aquaculture Research

The use of open-ended isolation columns (20 m³) as replicable experimental units was evaluated in two Alabama Piedmont ponds. Isolated columns of water differed limnologically from conditions present in the open ponds. Most of these differences were attributed to open pond sites having significantly higher phytoplankton biomass (chlorophyll-a). However, comparison of pond and column variances indicated that samples collected in columns were generally no more indicated that samples collected in columns were generally no more variable than similar samples collected from the pond that surrounded them. Isolation columns could be used as an alternative to replicate ponds for certain types of short-term, pond culture studies.     

Influence of pond fertilization and feeding rate on growth performance, economic returns and water quality in a small-scale cage-cum-pond integrated system for production of Nile tilapia (Oreochromis niloticus L.)

The effects of pond fertilization and feeding rate on growth, economic returns and water quality were investigated to develop a low‐cost cage‐cum‐pond integrated system for production of Oreochromis niloticus (L.). Hand‐sexed male fingerlings averaging 19±0.39 and 32±0.69 g were stocked in cages and open ponds at 150 fish cage^?1 and 2 fish m^?2 respectively. Fish were cultured for 114 days in five triplicate treatments. Cages were installed into ponds and caged fish were fed a 24% protein diet at 3% (T1) and 6% (T2) body weight day^?1 (BWD) without pond fertilization, and 6% BWD with pond fertilization (T3). The open water in the fourth treatment (T4) was not stocked but contained caged fish, which were fed 6% BWD for the first 57 days followed by 3% BWD for the remaining period. Ponds in the control (T5) had no cages and were neither fertilized nor open‐pond fish fed. Feeding rate and pond fertilization significantly (P<0.05) affected fish growth, profitability and water quality among treatments. Fish growth, feed utilization, fish yield, water quality and profits were significantly (P<0.05) better in T3 than the other treatments. It was concluded that fish production and economic returns were optimized at 6% BWD in fertilized ponds.