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1.
The objective of this study was to demonstrate the feasibility of four diets formulated to contain increasing levels (0, 50, 100 and 150 g kg?1 of diet) of grain distillers dried yeast (GDDY) in production diets for Litopenaeus vannamei, reared in outdoor tanks or production ponds. The production pond trial was carried out in 16, 0.1‐ha ponds using four replicates per diet. Juvenile shrimp (38.1 ± 4.26 mg, initial weight) were stocked at 30 shrimp m?2 for a 16‐week period. The same four diets and a commercial reference diet were offered to shrimp maintained in outdoor tanks over a 12‐week period. A total of 20 tanks were stocked with juvenile shrimp (3.05 ± 0.22 g, initial weight) obtained from production ponds at a density of 30 shrimp per tank (40 shrimp m?2). At the conclusion of these trials, mean final weight ranged from 19.77 to 23.05 g, yield ranged between 4760 and 5606 kg ha?1, survival ranged from 69.6% to 89.4%, and feed conversion ratio (FCR) was between 1.02 and 1.23. Shrimp reared in the outdoor tanks confirmed the results of the pond trial. Mean final weight ranged between 18.12 and 18.97 g, survival ranged from 93.3% to 98.3%, and FCR was between 1.25 and 1.29. In both trials, there were no significant differences regarding mean final weight, FCR and survival among dietary treatments. Based on this study, GDDY up to 150 g kg?1 of diet can be used in L. vannamei commercial feed formulation.  相似文献   

2.
Succession of phytoplankton dominance was studied in shrimp culture ponds treated with commercial bacterial products. Diatoms were dominant and the cyanobacteria were absent in both treated and control ponds at the beginning of the culture period. After 34 days, the diatoms significantly decreased whereas cyanobacteria increased in both ponds. Chlorophyll a increased from a mean of 35.56 mg m?3 in the first phase to 186.00 mg m?3 in the final phase, and from 42.12 mg m?3 to 242.81 mg m?3 in the treated and control ponds respectively. Cyanobacteria were significantly higher in the control compared with the treated ponds during the final phase of the culture. Algal bioassay showed that the addition of nitrogen either alone or with silica to pond water significantly increased the specific growth rate of Chaetoceros calcitrans. The specific growth rate of Oscillatoria sp. significantly increased when a combination of nitrogen, phosphorus and carbon was added to the pond water. Addition of silica seemed to depress the growth rate of Oscillatoria sp. Nutrient enrichment should be minimized and the supply of nitrogen and silica should be adequate for promoting the growth of beneficial phytoplankton in aquaculture systems.  相似文献   

3.
The objective of this study was to evaluate the effect of dietary and water supplementation of probiotic Streptococcus phocae PI80 on growth, immune response and feed utilization of tiger shrimp Penaeus monodon in earthen ponds. The probiotic bacterium S. phocae PI80 was cultured in large fermenter (50 L) by adding additional carbon source in the form of molasses and glucose along with yeast extract as nitrogen source to enrich S. phocae PI80 biomass. This enriched S. phocae PI80 was administered to shrimp in feed (6.5 × 1013 bacterial cells mL?1) as well as in pond water (5 L/pond). Shrimp growth performance was significantly improved (P < 0.05) in 120 days culture when the average body weight of treated molasses + yeast extract (MY) (28.41 ± 0.874 g), glucose + yeast extract (GY) (27.013 ± 0.698 g) was significantly higher than control (23.63 ± 0.684 g). Food conversion ratio FCR was also found to be reduced significantly in ponds treated with probiotics when compared with control pond (1.89 ± 0.09). Vibrio and luminescent bacteria were found to be lower in the treatment receiving MY group, and we hypothesize that this may lead to greater shrimp survival. Furthermore, fermentation product of S. phocae PI80 added to pond water and feed additives enhanced the shrimp immune system. The results indicated that total haemocytes count (THC), phenoloxidase (PO) activity, NBT reductase assay and phagocytic activity significantly increased in shrimps treated with S. phocae PI80. Our study demonstrates that administration of S. phocae PI80 in the water and feed at 6.5 × 1013 colony‐forming units (CFU) mL?1 bacterial cells induce immune modulation and enhances the immune ability of P. monodon in pond‐reared shrimp and increased the shrimp production.  相似文献   

4.
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.  相似文献   

5.
Water quality and plankton densities were monitored in shrimp ponds at 12 mixed shrimp‐mangrove forestry farms in Ca Mau province, southern Vietnam, to detail basic water chemistry and assess whether conditions are suitable for shrimp culture. In general, water quality was not optimal for shrimp culture. In particular, ponds were shallow (mean ± 1SE, 50.5 ± 2.8 cm), acidic (pH < 6.5), had high suspended solids (0.3 ± 0.03 g l?1), low chlorophyll a/phytoplankton concentrations (0.2 ± 0.05 µg l?1 and 8600 ± 800 cells l?1 respectively) and low dissolved oxygen (DO) levels (3.7 ± 0.15 mg l?1). Eight out of the 12 farms sampled had potentially acid sulphate soils (pH < 4.2). Salinity, DO and pH were highly variable over short time‐periods (hours); DO in particular was reduced to potentially lethal levels (1–2 mg l?1). Seasonal variations in water chemistry and plankton communities (i.e. salinity, DO, phosphate, temperature, phytoplankton and zooplankton densities) appear to be driven by differences in rainfall patterns. The presence or absence of mangroves on internal pond levees (‘mixed’ versus ‘separate’ farms) and the source of pond water (rivers versus canals) were of lesser importance in determining water quality patterns and plankton biomass. Zooplankton and macrobenthos densities were sufficient to support the current (low) stocking densities of shrimp. However, natural food sources are not adequate to support increases in production by stocking hatchery reared post larvae. Increasing productivity by fertilization and/or supplemental feeding has the potential for adverse water quality and would require improvements to water management practices. Some practical strategies for improving water quality and plankton densities are outlined.  相似文献   

6.
Three intensive growout trials using Penaeus vunnumei were conducted in round ponds in Hawaii in 1987. A 337 m2 experimental pond was stocked at 100 shrimp/m2 for two trials; a 2,000 m2 commercial prototype pond was stocked at 75/m2 for one trial. In the experimental pond trials, shrimp survival averaged 88 ± 10% (SE) and feed conversion averaged 2.2 ± 0.2. Growth averaged 1.5 ± 0.3 g/week, yielding 18.2 ± 1.7 gram shrimp in 80 ± 5.5 days. Combined production in the experimental trials was 32,272 kg/ha in 174 days (from stocking of trial 1 to harvest of trial 2). Comparing these results to 1986 results (Wyban and Sweeney 1988), it was concluded that shrimp growth is not affected and production is doubled by increasing stocking density from 45/m2 to 100/m2. Pooling data from 1986 and 1987, a significant linear regression was obtained when weekly growth of shrimp above four grams individual size was regressed on mean weekly pond temperature: growth = 0.37 * temperature - 8.44, (r2= 0.41; P < 0.01). Multiple regression to examine effects of shrimp size, pond biomass, and shrimp age on the temperature-growth relationship was not significant. In the commercial prototype pond trial, survival was 67% and feed conversion was 2.0. Growth averaged 1.4 g/week, yielding 18.1 gram shrimp in 88 days. Production was 9,120 kg/ha. Individual shrimp size distribution at harvest in the commercial pond was similar to experimental pond results, indicating that shrimp growth in the two systems was comparable. Financial characteristics of a hypothetical 24 pond shrimp farm using these results were determined using an electronic spreadsheet model (hung and Rowland 1987). Feed costs were 40% of total operating costs while postlarvae and labor were 14% and 16% of total operating costs, respectively. Breakeven price (BEP) was far more sensitive to changes in revenuedetermining inputs such as survival and growth than to comparable changes in costdetermining inputs such as feed and postlarvae costs. Together these results suggest that commercial scale round pond production mimics experimental scale production and that round pond technology has commercial potential.  相似文献   

7.
A 60 days feeding experiment was conducted to determine the effects of YK‐6 (a yeast culture feed supplement) on growth and immune responses of white shrimp, Litopenaeus vannamei and aquaculture environment in commercial scale farms composed of nine ponds. Three treatments (control, Diet 1 and Diet 2) were designed to contain YK‐6 levels of 0.0, 1.0 and 1.5 g kg?1 respectively. At the end of the test, the mean production of Diet 1 (0.649 ± 0.030 kg m?2) and Diet 2 (0.648 ± 0.033 kg m?2) were significantly higher than that of the control by 29.5% and 29.3% respectively. The feed conversion ratio decreased significantly by 12.3% (Diet 1) and 8.5% (Diet 2) compared with the control group respectively. The environmental indices indicate that the quality of water and pond sediment was improved. The endotoxin concentrations, the number of Vibrios and heterotrophic bacteria in the shrimp intestine of the treatment groups were significantly lower than that of the control, particularly in the later stage of the farming period. The YK‐6 extended positive effects on growth, improved sediment quality, reduced endotoxin in shrimp intestine, and enhanced activities of lysozyme and phenoloxidase.  相似文献   

8.
The effects of stocking density [range: 2.0-5.5 postlarvae (PL) m?2] and water quality on the production of a traditional tambak tiger shrimp, Penaeus monodon Fabricius, culture system on one farm in Probolinggo, East Java, were studied during one culture period of 126 days using eight ponds. Production characteristics were recorded and water quality parameters monitored. Production was quadratically influenced by stocking density. The optimum density was 4.8 PL m?2, which corresponds with a production per crop of around 300 kg ha?1. Production was also quadratically related to mean shrimp body weight at harvest, while there was an inverse relationship between production and bottom organic matter, indicating that shrimp biomass diminishes the amount of organic matter accumulating at bottom of the tambak.  相似文献   

9.
Soil physicochemical properties of the growout ponds of black tiger shrimp (Penaeus monodon) were examined in relation to shrimp yields for one production cycle. The culture ponds were old (>5 years) and new (newly constructed) types. Soil texture was silty clay with low sand content and high proportion of clay for both the pond types with alkaline soil pH (7.87–9.71). Organic matter (OM) concentration was higher (7.48 ± 0.01%) in old ponds and positively related (r = 0.58, P < 0.05) with total nitrogen (TN). The major cations (Ca, Mg, and Na) were higher in the soil of old ponds and did not fluctuate significantly during culture. The majority of trace elements, i.e., Fe (349.22 ± 35.7 ppm), Mn (56.19 ± 30.2 ppm), Zn (88.56 ± 8.09 ppm), Al (454.3 ± 200.6), Pb (1.3 ± 0.96 ppm), Co (3.4 ± 0.2), V (6.56 ± 1.79 ppm), Cr (19.32 ± 0.63 ppm), Ti (82.78 ± 54.3 ppm), As (5.60 ± 0.28 ppm), Ag (0.38 ± 0.5 ppm), and Sb (3.89 ± 0.48 ppm) were found to be higher in new pond soils than the old ponds. Except for soil manganese, no major fluctuations in trace elements were observed during the culture period. Shrimp growth was not significantly different in the two types of ponds, and no distinct correlation between shrimp growth and element content of soils could be drawn. The results indicate that shrimp pond age may not affect production of shrimp if soils are properly managed pre- and postculture. The differences in production in different ponds might be the result of management practice such as quality of shrimp post larvae, pond preparation, water and feed quality, and available live feed in the pond bottom or other environmental factors like water nutrients and physicochemical parameters.  相似文献   

10.
The performance of the Pacific white shrimp Litopenaeus vannamei (Boone) under various stocking strategies was evaluated in earthen ponds filled with freshwater amended with major ions. Six 0.1‐ha earthen ponds located in Pine Bluff, AR, USA, were filled with freshwater in 2003 and 2004, and potassium magnesium sulphate added to provide 50 mg K+ L?1 and stock salt added to provide 0.5 g L?1 salinity. In 2003, three ponds either were stocked with PL15 shrimp (39 PL m?2) for 125 days of grow out or with PL25 shrimp for 55 days (23 PL m?2) followed by a 65‐day (28 PL m?2) grow‐out period. In 2004, ponds were stocked with 7, 13 or 30 PL15 m?2 for 134 days of grow out. Salinity averaged 0.7 g L?1 during both years, and concentration of SO4?2, K+, Ca2+ and Mg2+ was higher, and Na+ and Cl? was lower in amended pond water than in seawater at 0.7 g L?1 salinity. Potassium concentration in amended water was 52–61% of the target concentration. Shrimp yields ranged from 3449 kg ha?1 in 2003 to 4966 kg ha?1 in 2004 in ponds stocked with 30–39 PL15 m?2 for a 125–134‐day culture period. At harvest, mean individual weight ranged from 17.1 to 19.3 g shrimp?1. In ponds stocked with PL25 shrimp, yields averaged 988 and 2462 kg ha?1 for the 1st and 2nd grow‐out periods respectively. Gross shrimp yield in 2004 increased linearly from 1379–4966 kg ha?1 with increased stocking rate. These experiments demonstrated that L. vannamei can be grown successfully in freshwater supplemented with major ions to a final salinity of 0.7 g L?1.  相似文献   

11.
In the present study, we used TaqMan real‐time polymerase chain reaction to quantify and compare infection of white spot syndrome virus (WSSV) with shrimp production of Fenneropenaeus chinensis cultured in outdoor ponds along the west coast of the South Korea. In 2007, a total of 60 specimens in summer and 116 specimens in autumn were collected from 12 growing‐out ponds and 12 harvest ponds respectively. Pond harvest data were obtained from farmers. Of the summer samples, all specimens were WSSV positive, with a wide range of 12.4–7.0 × 107 (mean 7.5 × 106) copies ng?1 DNA; shrimp production was 1.7 metric tonnes per hectare (mt ha?1). Of the 116 autumn‐sample specimens, 81 (69.8%) were WSSV positive; WSSV infection had been decreased dramatically, to 0–7.2 (mean 3.5) copies ng?1 DNA. Shrimp production of autumn ponds was 2.1 mt ha?1. Statistical analysis indicated that the difference in WSSV infections detected in summer and autumn was highly significant (P<0.01). In summer, seven ponds (58.3%) with low‐WSSV infection loads (0–1000 WSSV copies ng?1 DNA) had shrimp production of 2.7 mt ha?1; the others had shrimp production of only 0.2 mt ha?1. The mean shrimp production between the two infection levels showed a highly statistically significant difference (P<0.01).  相似文献   

12.
The hypothesis that intraspecific competition affects survival and growth during the culture and harvest at extensive/semi-intensive Penaeus vannamei shrimp ponds was evaluated. Thus, the effect of stocking density on the biomass, shrimp average weight, survival, and economic performance during the culture (133 days) and at the harvest of the P. vannamei shrimp was investigated in 400 m2 earthen ponds. In order to reduce the likelihood of infectious diseases, shrimp received preventive health treatments (probiotics and β-1,3/1,6-glucans) during all culture phases. In this way, the effect of density on the intraspecific competition for space/food was isolated. Ponds stocked at 6, 9, and 12 shrimp m?2 showed competition-dependent growth. Ponds stocked at 12 shrimp m?2 presented a mortality (12 %) between days 76 and 99. Competition, and accordingly individual growth reduction, could have begun at day 76 at a density of 5 shrimp m?2. Survival was significantly higher at 6 shrimp m?2 (84.2 ± 6.2 %) compared with the 12 shrimp m?2 (64.8 ± 12.4 %) treatment, while no significant differences in yield were observed between both treatments. Ponds stocked at 3 and 6 shrimp m?2 presented the best benefit–cost rates. The optimal shrimp density during the experimental culture was 5 shrimp m?2. Given the experimental conditions and considering the fraction of density-independent mortality observed, the optimum stocking density was found to be 6 shrimp m?2.  相似文献   

13.
Low and unstable shrimp yields of the improved extensive shrimp system has been a tremendous obstacle for economic development in the coastal areas of Southern Vietnam. To investigate the biological characteristics of this system, ponds in the coastal Cai Nuoc district, Mekong delta of Vietnam, were monitored. Results showed that the system was not optimal for shrimp. While chlorophyll a (chl a) (1.51–37.2 μg L?1), phytoplankton density (6333–974 444 cells L?1) and zooplankton density (7.1–517.2 ind L?1) were abundant and comparable to shrimp farms elsewhere, zoobenthic community was very poor (7–1971 ind m?2). Toxin‐producing cyanobacteria (Oscillatoria limosa, Oscillatoria formosa, Anabaena sp. and Phormidium tenue) were found. Total bacteria and Vibrios were present in large numbers (respectively 1.04 × 105 and 6.64 × 102 CFU mL?1 in pond water, 6.33 × 105 and 9.47 × 103 CFU g?1 in sediment). Presence of toxin‐producing organisms, poor zoobenthic community and abundance of Vibrios all can enhance shrimp susceptibility to diseases. The following measures are recommended to improve the situation: (1) complete testing of seeds for pathogens, (2) not to incorporate fish into shrimp ponds and (3) applying no‐culture breaks and pathogen‐killing chemicals.  相似文献   

14.
Consecutive failure of the improved extensive shrimp farming system has deterred the economy of some coastal areas in Vietnam. To investigate pond physico‐chemical characteristics, a monitoring scheme was performed in the Cai Nuoc district of Southern Vietnam. Results show that the system was not optimal for shrimps. While ponds were not contaminated by organic loadings or major nutrients (N, P) and salinity and pH were most optimal for shrimp, more than 37% of dissolved oxygen (DO) measurements were lower than recommended. In the early morning hours, DO measurements were even much lower (0.84–2.20 mg L?1). Sulphate (SO42?) concentrations were most within the acceptable range. Total suspended solids (TSS) were above the acceptable limit (<50 mg L?1). Iron, alkalinity and hydrogen sulphide were also higher than recommended. Pond sediment was anaerobic (redox potential ?422 to ?105 mV) and contained high amounts of organic matter (9.84–21.96%). Lethal DO levels, high TSS and anoxic sediment are the drawbacks in this system. Suggested measures to improve pond conditions are (1) allowing sedimentation before filling culture ponds, (2) covering dikes, (3) including no‐culture breaks between shrimp crops, (4) drying pond bottom, (5) removing sediment and (6) controlling pond's vegetation.  相似文献   

15.
This paper studied the effects of increased carbon (C) and nitrogen (N) supplementation in pond production of Artemia franciscana cysts in southern Vietnam. Pig manure and tapioca were used to supplement the natural food of Artemia in the ponds at a fixed C/N ratio 10. Addition of pig manure and tapioca at a standard rate (0.210 kg ww and 0.319 kg dw pond?1 day?1, respectively) was used as control. Increasing amounts of supplementation (110, 115, and 120 % of the control) were applied in three treatments. During the 6-week culture period, extra C and N supplementation resulted in a better growth, faster maturation, and higher fecundity of Artemia when compared to the control. Total cyst production was the highest (9.96 kg ww ha?1) at the supplementation level 10 % higher than the control; the lowest cyst production was found in the control (2.84 kg ww ha?1). Increasing the supplementation of C and N at levels 110, 115, and 120 % of the control at C/N ratio 10 may have stimulated the formation of bioflocs in the hypersaline Artemia ponds and helped to improve conditions for increasing cyst yields.  相似文献   

16.
A budget describing the flow of organic carbon (OC), nitrogen (N) and phosphorus (P) through two polyculture ponds (jellyfish–shellfish–fish–prawn) was constructed. The total input of OC was 3107 kg ha?1 in pond 1 and 3358 kg ha?1 in pond 2, while total output was 1759 kg ha?1 in pond 1 and 1325 kg ha?1 in pond 2. In pond 1, the total input of N was 364 kg ha?1 and output was 359 kg ha?1, whereas, in pond 2, the total input of N was 439 kg ha?1 and total output was 331 kg ha?1. The total input of P was 75 kg ha?1 in pond 1 and 66 kg ha?1 in pond 2, while total outputs for pond 1 and pond 2 were 74 and 65 kg ha?1 respectively. Primary production from phytoplankton contributed the largest proportion of total OC (49–56%), while feed contributed the largest proportion of N (78–81%) and P (79–80%). Animals harvested from the aquaculture ponds accounted for the largest proportion of N (50–73%) and P (49–52%), and respiration accounted for the largest proportion of OC (43–61%) output from the system. The OC, N and P use efficiency of harvested animals was 30.30%, 70.19% and 50.14% in pond 1, respectively, and 21.03%, 46.95% and 46.47% in pond 2 respectively. In terms of nutrient use, the filter‐feeding bivalve, Sinonovacula constricta, was the most efficient species within the polyculture system.  相似文献   

17.
A magnesium budget was prepared for a commercial low‐salinity shrimp farm in the Blackland Prairie region of Alabama for one production cycle. Ponds had previously been used for production and fertilized with magnesium; two ponds (S‐5 and S‐6) for four previous years and one pond (N‐9) for one previous season. Fertilization with sulfate of potash magnesia (K2SO4·2MgSO4 or K‐Mag®) was applied to these ponds to obtain the concentrations of 20 mg/L, averaging 1274 kg Mg2+/ha. Additional inputs of magnesium included groundwater, rainfall, and runoff averaged 441.5 kg/ha. A water budget for ponds indicated that 292.6 kg/ha of magnesium in outflows. The difference in inputs and magnesium outputs resulted mainly from adsorption of magnesium by pond bottom soils. However, the increase in exchangeable magnesium in the upper 15‐cm layer of pond bottom soils was not great enough to account for the difference in total magnesium inputs and magnesium outputs in water and shrimp. Possible explanations for this discrepancy are magnesium precipitation, nonexchangeable fixation of magnesium by clay minerals, incomplete extraction of magnesium, and analytical error. The decreased uptake of magnesium by older ponds, S‐5 and S‐6, indicate that the soils had a diminishing affinity for the cation or an equilibrium concentration is being established.  相似文献   

18.
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%)、CODMn(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,CODMn 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。  相似文献   

19.
This article analyses the optimal selection of stocking density and date in semi‐intensive culture of shrimp Litopenaeus vannamei (Boone, 1931). The empirical evaluation of productive and economic scenarios derived from the specific choice of these management variables is often unfeasible for decision makers. To overcome this limitation, the bioeconomic modelling is widely applicable in aquaculture systems. In the present study, profit maximization for a semi‐intensive shrimp farm is obtained through the development of a bioeconomic model to analyse the combination of stocking density (range: 6–30 postlarvae (PL) m?2) and date (from March 1st to June 1st) as decision variables for a shrimp farm located in Sinaloa, Mexico. The results show that pond water temperatures prevailing during culture cycle when the stocking date is June 1st (temperature in 19‐weeks culture period: 30.76 ± 0.87°C) and the stocking density is 20–24 PL m?2 produce a maximized Present Value Profit (PVπ) of  USThis article analyses the optimal selection of stocking density and date in semi‐intensive culture of shrimp Litopenaeus vannamei (Boone, 1931). The empirical evaluation of productive and economic scenarios derived from the specific choice of these management variables is often unfeasible for decision makers. To overcome this limitation, the bioeconomic modelling is widely applicable in aquaculture systems. In the present study, profit maximization for a semi‐intensive shrimp farm is obtained through the development of a bioeconomic model to analyse the combination of stocking density (range: 6–30 postlarvae (PL) m?2) and date (from March 1st to June 1st) as decision variables for a shrimp farm located in Sinaloa, Mexico. The results show that pond water temperatures prevailing during culture cycle when the stocking date is June 1st (temperature in 19‐weeks culture period: 30.76 ± 0.87°C) and the stocking density is 20–24 PL m?2 produce a maximized Present Value Profit (PVπ) of  US$?ha 10 350 and PVπ US$?ha 2526 for weekly mortality rates at low (2.1%) and medium (5.8%) levels respectively. The marginal change in the cost of feed (±1%) has the greatest effect on PVπ (?0.58% and 0.59% respectively). The discussion focuses on the combined effect of mortality rate, stocking density and especially, on the stocking date decision, for a given production planning framework, taking into account that the stocking date is the main management decision variable to cope with viral diseases outbreaks.  相似文献   

20.
Cultivation of Gracilaria (Rhodophyta) in shrimp pond effluents in Brazil   总被引：3，自引：0，他引：3  
Shrimp aquaculture produces a large amount of waste, including nitrogen and phosphorus. To investigate the utilization of those elements as sources of nutrients for the growth of the red seaweed, Gracilaria sp. J. Agardh, an experiment in shrimp pond effluents was carried out over a period of 5 months. The biomass varied significantly (P < 0.01), reaching a maximum of 2540 g m?2 and a minimum of 380 g m?2. The mean was 1418 ± 708 g m?2. The higher biomass values occurred during the first 15 days and sometimes exceeded the initial inoculum by 190%. According to the results, production of 23.93 t ha?1 year?1 (dry weight) can be expected. anova showed significant differences in RGR (relative growth rate) values (P < 0.05). RGR varied from 8.8% per day to 1.8% per day. The fluctuation of nutrients was mainly influenced by pond fertilization frequency, with NH4 being the most abundant nutrient. Correlations between RGR and environmental parameters during the study period were not significant (P > 0.05). We conclude that Gracilaria sp. can be cultivated in shrimp ponds effluents. However, despite this relative success, it is necessary to perform some adjustments regarding the utilized cultivation technique.  相似文献   

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