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1.
Abstract

The risk efficient live feed system for juvenile haddock production is derived through recursive ex‐ante stochastic cost estimation. Four alternative feeding technologies are simulated to capture the economic costs associated with live feed and juvenile production and scale economies are investigated by simulating three production levels. Using Monte Carlo simulation techniques, multivariate stochastic cost functions are derived in a time‐dependent recursive production model. With the current technologies and price levels, land‐based juvenile haddock production is viable. The marginal impact, in terms of cost‐savings, to additional research on optimal feeding periods will be minimal. On the other hand, the high opportunity cost of capital used in aquaculture production, due to numerous perceived risk premia, may pose a more immediate constraint for capital formation and industry development.  相似文献   

2.
The selection of aerators and correct numbers can play an essential role in reducing the cost of production in aquaculture. The new generation aerators, namely spiral leaf, air‐jet, submersible and impeller, used in aquaculture, were assessed for its aeration efficiency and energy cost compared with the commonly used paddle wheel aerator. Of the aerators tested, the impeller had the highest aeration efficiency of 2.098 kg O2/kW hr, followed by paddle wheel with 1.436 kg O2/kW hr at 20‰ salinity. The spiral and air‐jet aerators had maximum aeration efficiency of 1.326 and 1.419 kg O2/kW hr, respectively, at 35‰ salinity. The submersible aerator was not efficient as its maximum efficiency was 0.380 kg O2/kW hr. The water flow by paddle wheel was 3 ft/sec and also provides better coverage than other types of aerators. The efficiency of aerators was high in optimum salinities (20‰ and 35‰) than the low or high saline condition. The average energy cost of shrimp pond aeration per hectare was lowest for impeller, followed by paddle wheel aerator. The study provided economic comparisons of vannamei culture using different aeration systems by keeping a uniform set of economic assumptions. Shrimp farms with impellors can give 14%–25% high returns across salinities, whereas spiral leaf can provide 5% high returns at 35‰ salinity. The combination of the type of aerators and the calculated use based on the salinity of the culture systems can result in energy‐saving and also a reduction in the production cost.  相似文献   

3.
Exchange and aeration of pond water are common practices in semi‐intensive freshwater prawn culture, but there is lack of scientifically based information on the results. We evaluated the effects of water flow through the ponds and mechanical aeration in semi‐intensive cultures of Macrobrachium amazonicum. A total of 40 juveniles/m2 were stocked for 4 mo in 12 earthen ponds. Four randomly assigned treatments were applied: no aeration + no water exchange (NN), diurnal aeration + no water exchange (DA), nocturnal aeration + no water exchange (NA), and continuous water flow (CF). Temperature, pH, total suspended solids, and soluble orthophosphate in the water column did not differ among treatments. Dissolved oxygen (DO) concentrations in ponds with nocturnal aeration were significantly higher than in other treatments. The concentration of inorganic nitrogen was significantly higher in the CF treatment, whereas organic nitrogen was higher in treatments NN, DA, and NA. This suggests that primary production is higher in static ponds. Thermal stratification started at 0900 h, and the maximum difference between surface and bottom temperature varied from 1.5 (CF) to 2.8 C (NN). The difference between DO levels in the surface and bottom water of the ponds began to appear at 0800 h and varied from 0.50 (CF) to 5.23 mg/L (NN). Diurnal aeration and high continuous water flow were efficient in disrupting the stratification. No significant difference was found for survival, mean weight, apparent feed conversion rate, and productivity among treatments. Thus, disrupting water stratification, aerating ponds at night, or exchanging the pond water are ineffective in Amazon River prawn farming in semi‐intensive systems, at least for stocking densities lower than 40 individuals/m2. About 1000 kg of Amazon River prawn can be produced in static ponds with no aeration in approximately 4 mo. This management strategy saves water and energy and reduces production costs .  相似文献   

4.
ABSTRACT

Production of fingerlings from very small fry depends upon an initial high concentration of rotifers followed by high densities of crustacean zooplankton. High fertilization rates lead to increased zooplankton production but often cause poor water quality conditions that aeration may alleviate. This study was designed to determine the effects of constant, nocturnal, and no aeration on water quality, primary productivity, and standing crops of phytoplankton and zooplankton in heavily fertilized nursery-size ponds that contained no fish.

Four 0.04-ha ponds were aerated continually; four ponds were aerated only at night with a 372-W (1/2 hp) paddlewheel aerator; and four ponds were not aerated. For 21 days after they were filled on July 21, 1999, the ponds received 1,224 kg/ha rice bran and 581kg/ha liquid 9-27-0 fertilizer. Water quality variables, primary production, chlorophyll-a and zooplankton were sampled daily.

Constant aeration resulted in several conditions more conducive to survival of fish fry, such as higher zooplankton densities, more moderate temperatures, and safer dissolved oxygen levels than did nocturnal aeration or no aeration. However, the development of a higher standing crop of phytoplankton and higher total ammonia concentrations in the turbulent, constantly aerated ponds resulted in higher un-ionized ammonia levels that were not favorable to survival and growth of fry. The high concentrations of zooplankton that developed in the aerated ponds have good potential for cropping to inoculate other ponds or to provide live foods for tank culture of zooplanktivorous fish.  相似文献   

5.
Abstract

Reducing water exchange in shrimp aquaculture to minimize discharge of pollutants is a search for sustainability. In desert regions, like most of northwest Mexico, low water exchange must be complemented with artificial aeration to compensate for low levels of oxygen in warm and highly saline water. The economic yield of a low‐water‐exchange production system is compared against yield from a typical water‐exchange‐without‐aeration system for Penaeus vannamei culture. The difference between two systems is centered on pumping and aeration rates for a 100 ha semi‐intensive farm in northwest Mexico.

A bioeconomic model was built to compare the systems. Risk analysis is adopted to account for uncertainty of seed price, shrimp growth rate, survival rate, and shrimp prices.

The typical system was slightly more profitable than the low‐water‐exchange, aerated system. The latter used less electricity than the former in all of the three mortality‐rate scenarios. However, the difference in profitability is so small that for practical purposes both production systems provide similar economic yield. For a typical system, the probability of reaching a positive net present value (NPV) is high, therefore under the assumed risks, a 100 ha semi‐intensive shrimp farm in northwest Mexico is a good investment choice.  相似文献   

6.
Water temperature and water loss by evaporation were monitored in control ponds and in ponds with different rates of aeration (9.2, 18.4, 27.6 and 36.9 kW/ha). The mean decrease in water temperature at 70‐cm depth was greater than that at the surface in aerated ponds than in control ponds. The greater the aeration rate, the cooler was water, both at the surface and at 70 cm. Evaporation rates were found to increase with greater aeration rate. Water loss increased by 32%–92% over 24‐hr periods in ponds with one to four 0.37‐kW Air‐O‐Lator aerators, respectively. The nutrient‐enriched control pond was more turbid, had cooler surface and deep water temperature, and had greater evaporation loss than the control pond without nutrient addition and less turbid water. But, aeration did not increase turbidity. Aeration can increase water loss from ponds and result in lower water temperature. Although aeration should not be used excessively in order to conserve water and reduce production cost, it is essential for many types of feed‐based aquaculture.  相似文献   

7.
The US catfish industry is evolving by adopting production‐intensifying practices that enhance productivity. Catfish producers have increased aeration rates over time, and some now use intensive rates of aeration (>9.33 kW/ha). Costs and production performance were monitored at commercial catfish farms using high levels of aeration (11.2–18.7 kW/ha) in Alabama, Arkansas, and Mississippi. A multivariate‐cluster analysis was used to identify four different management clusters of intensively aerated commercial catfish farms based on stocking density, size of fingerlings at stocking, and feed conversion ratios (FCR). Breakeven prices of hybrid catfish raised in intensively aerated pond systems were estimated to range from $1.86/kg to $2.17/kg, with the lowest costs associated with the second greatest level of production intensity. The two medium‐intensity clusters generated sufficiently high revenues for long‐term profitability. However, the least‐intensive and the most‐intensive clusters were economically feasible only when catfish and feed prices were closer to less probable market prices. Feed price, FCR, and yield contributed the most to downside risk. Intensive aeration in catfish ponds, up to the levels analyzed in this study, appears to be economically feasible under the medium‐intensity management strategies identified in this analysis.  相似文献   

8.
This study evaluated the effect of sublethal doses of antifungal drug miconazole nitrate (MCZ) on immunological responses and its role as a prophylactic drug against S. parasitica in Labeo rohita fingerlings. Fish were fed with sublethal doses of MCZ, that is, T1—6.30 mgMCZ kgBW?1, T2—12.61 mgMCZ kgBW?1 and T3—25.22 mgMCZ kgBW?1, and sampling was done at different time intervals for 240 hr. Immunological parameters viz. lysozyme activity, oxygen radical production and plasma antiprotease activity showed significant enhancement (p < 0.05) in fish fed with T2 and T3 doses. Expression of immune‐relevant genes such as TLR‐22 and β2‐M showed significantly higher expression at 6 hr and 24 hr of sampling in both liver and head kidney. However, these genes showed a downregulation after 120 hr of sampling in both the tissues. Preventive efficacy study showed that single dose of MCZ provides protection against oomycetes up to the fourth day of infection. Significantly higher mortality was observed in control diet‐fed fish as compared to fish fed with MCZ medicated diet. Thus, it can be concluded that the MCZ can act as a potent antifungal agent for preventing oomycetes infection as well as to enhance the immune response.  相似文献   

9.
Abstract

Black bream (Acanthopagrus butcheri) appear an ideal candidate for the developing saline aquaculture industry of inland Western Australia. However, current maximum growth rates of 150g/annum are too slow for profitable production. This study investigated whether enhanced growth rates of black bream would improve profitability and justify a genetic improvement program. A partial budget analysis was conducted for two different fish production systems; a commercial operation that incurred more operating expenses due to costs associated with farm initiation (stand‐alone farm model), and an existing farm that diversified into aquaculture using the saline water resources of established farm dams (integrated farm model). Sensitivity analyses indicated that a 33 per cent increase in growth rate to at least 200g/annum would allow either production system to return a profit at a farm‐gate price of AUS$6/kg whole fish, with fish survival rates of 98 per cent for the stand‐alone farm, and 65 per cent for the integrated farm model. These results are discussed in the context of the genetic and economic consequences of selection for improved growth rates, and for developing breeding objectives and a genetic improvement program for black bream.  相似文献   

10.
The effects of artificial substrate and night‐time aeration on the culture of Macrobrachium amazonicum were evaluated in 12 ponds stocked with 45 prawns m?2. A completely randomized design in 2 × 2 factorial scheme with three replicates was used. The combination of factors resulted in four treatments: with substrate and aeration (SA), with substrate and without aeration (SWA), without substrate and with aeration (WSA) and without substrate and aeration (WSWA). The presence of substrate in SA and SWA treatments reduced suspended particles (seston) by ~17.3% and P‐orthophosphate by ~50%. The use of aerator (WSA and SA treatments) significantly (P < 0.05) increased the concentration of dissolved oxygen, suspended particles and nutrients in the pond water. These results indicate that the effect of substrate on turbidity and total suspended solids (TSS) values is opposite to the effect of the aerator. The aerators in semi‐intensive grow‐out M. amazonicum farming lower water quality because they increased the amount of detritus and nutrients in the pond water. On the other hand, the use of artificial substrate reduces turbidity values, chlorophyll a, TSS and P‐orthophosphate concentrations. Therefore, the combination of substrate addition and night‐time aeration is not interesting because they have opposite effects.  相似文献   

11.
We investigated the variability of shrimp Litopenaeus vannamei production by incorporating stochastic elements into deterministic stock models and determined the contribution that white spot disease, zootechnical parameters, water quality, and alternative management strategies have on variability. The model was calibrated for intensive shrimp cultivation in the State of Nayarit, Mexico. Mean annual production increased as a consequence of improved management from 8000 kg ha−1 to 22,000 kg ha−1 when cultivation was not affected by the disease and from 3200 kg ha−1 to 10,400 kg ha−1 when the disease affected production. When simultaneously considering both cases, mean annual production increased from 6300 kg ha−1 to 16,800 kg ha−1. White spot disease was a major factor determining variability of production. Shrimp production was particularly sensitive to levels of dissolved oxygen when management was inadequate, while final weight and mortality rate of shrimp were more sensitive when management improved. Water temperature and salinity had intermediate importance, and mortality caused by the disease and the time when mortality occurred had intermediate or low relevance. Improving management increased shrimp production and diminished variability. The duration of cultivation and stocking density were the most important management variables controlling variability of production when cultivation was affected by the white spot disease. When the disease was not present, pond size and duration of cultivation were the main factors affecting production. Starting time of aeration had relatively lower importance in determining variability, while the stochastic values of dissolved oxygen, in contrast, became most important. These results call for studies on improving aeration management to reduce variability of dissolved oxygen in ponds.  相似文献   

12.
This paper examines production costs and returns of sutchi catfish (Pangasianodon hypophthalmus) aquaculture under three different farming systems in Bangladesh. Based on the production technology, sutchi catfish farming is classified as extensive, semi‐intensive and intensive. Results showed that sutchi catfish farming is profitable irrespective of the level of intensification and in all three instances the cost of feed dominated the variable costs of production. The average annual production costs were estimated at US$5217 ha?1 in intensive farming, while US$2694 ha?1 in semi‐intensive and US$981 ha?1 in extensive farming. Despite the higher production costs per hectare, the average annual net return was higher in intensive farming (US$3364), compared with semi‐intensive (US$2048) and extensive (US$1099) farming. The average annual production per hectare under intensive farming conditions (13 945 kg) was higher than semi‐intensive (7705 kg) and extensive (3380 kg) farming mainly due to higher levels of inputs, including seed, feed, fertilizer and labour. However, the Cobb–Douglas production function model suggests that inputs are inefficiently used in the intensive farming system. Conversely, there is enough scope to increase the production and income from the semi‐intensive and extensive farming systems by using more inputs.  相似文献   

13.
Abstract

Construction and operating costs for three common snook (Centropomus undecimalis) hatcheries in Florida, USA, are illustrated. Hypothetical capacities and targets of the three hatcheries (Scenarios I, II and III respectively) were 615, 000 juveniles (8 ‐ 10 g in weight) for stock enhancement, and 1, 275, 000 and 3, 000, 000 juveniles (1‐g in weight) for commercial grow‐out. Estimated production costs were lower than for many marine finfish species. The 20‐year mean costs per 1, 000 juveniles were estimated to be $324, $215, and $159, for hatcheries I, II, and III respectively, and the initial capital investments were $731, 660, $1, 162, 460, and $1, 896, 0301, respectively. Major cost items of annual production were labor (22 ‐ 33%), supplies (14 ‐ 20%), fixed costs (15 ‐ 17%), and interest (13 ‐ 15%). The most profitable hatchery was the 3 million 1‐g juvenile hatchery due to the hatchery size effect, with a net present value (NPV) of $1, 760, 000, an internal rate of return (ERR) of 81%, a payback period of 3.6 years, and a profitability index of $2.86 for every dollar invested. Possible cost reductions to increase financial profitability were discussed.  相似文献   

14.
Abstract

The main objective of this study is to examine technical efficiency and its determinants in carp pond culture in Pakistan. A stochastic production frontier involving the model for technical inefficiency effects is applied separately to the samples of semi‐intensive/intensive and extensive carp producers. The mean technical efficiencies for semi‐intensive/intensive and extensive farms were 0.673 and 0.561, respectively. By operating at full technical efficiency the semi‐intensive/intensive farms could, on average, increase their production from 3.0 to 4.5 Mt/ha and the extensive farms from 2.6 to 4.6 Mt/ha. Much of these efficiency gains would come from the improvement in fish, water and feed monitoring and management. Besides improving technical efficiency, potential also exists for raising carp productivity through increased intensification and technological progress. However, the realization of these potentials will depend on continuous government support for adequate provision of inputs, market and infrastructure, technology transfer and development and extension and credit services to carp farmers.  相似文献   

15.
Abstract

This study tested the Kuwaiti new indoor tilapia hatchery using the recirculating system, and compared its production costs with those in the flow‐through system. Breeders were stocked at 4 fish/m2 at 1: 3 male: female sex ratio. Seeds were harvested every two weeks for a period of 1.5 years. Seed production ranged from 45–52 seed/m2/d and 105–130 seed/kg female/d. Water quality parameters in the different components stayed below lethal concentration.

Analysis of the capital and operating expenses revealed that the new recirculating system cost 9.4 cents per fry compared with 11.0 cents in the flow‐through system. Operating expenses accounted for 67.14% of the total annual costs. Salary and wages were the major cost item (74.87%) of the operating expenses.

The cost of producing 0.5‐g fry was 6.2 cents per fry. With the use of more spawning and fry rearing tanks, production can be increased from 630,000 to 735,000 1.0‐g fry or 950,000 0.5‐g with a corresponding decrease in the costs per fry to 7.3 cents and 5.7 cents, respectively.  相似文献   

16.
《Aquacultural Engineering》2011,44(3):114-119
A dynamic stock model was used for quantification of shrimp production and analysis of alternative management schemes of stocking density, pond size, starting time of aeration, and duration of cultivation for intensive commercial production of the shrimp Litopenaeus vannamei. Databases from Mexican farms were used to calibrate the model. Multiple linear regression models were employed to establish relationships between parameters of the stock model and the management variables. Water quality variables (dissolved oxygen, temperature, and salinity) were complementarily analyzed. The final weight of shrimp was directly related to duration of cultivation and dissolved oxygen, and inversely related to stocking density, pond size, and salinity. There were inverse relationships between the growth coefficient and temperature and dissolved oxygen and between mortality rate and temperature. Dissolved oxygen was significantly related to starting time of aeration. Simple linear regression and an equivalence test indicated that biomass at harvest (after 13 weeks in winter, and 20 weeks in summer) was adequately predicted by using the stock model and the multiple regression models. The highest production (winter, 6900 kg ha−1; summer, 12,600 kg ha−1) were predicted using 60 postlarvae m−2, small ponds (2 ha), and starting aeration at the first week of cultivation; while the lowest yields (winter, 2600 kg ha−1; summer, 6000 kg ha−1) were obtained using 40 postlarvae m−2, large ponds (8 ha), and delaying the start of aeration until the fifth week of cultivation. The lowest production was 38% (winter) and 48% (summer) of the highest yield. Using small ponds could be particularly important during winter cycles to increase production, while stocking density and starting time of aeration contributed less. In contrast, pond size played a minor role during summer cycles and stocking density was the most sensitive variable.  相似文献   

17.
Abstract

This paper presents a study of operating costs in shrimp hatcheries. Size effects are presented for fixed, variable, unitary, and marginal costs. Cost structures by functional production department and by cost‐category are discussed for a hypothetical 100‐million postlarvae/month hatchery in an industrialized country, and compared to those of a hatchery in a developing country. Health management issues, mainly measures commonly used to manage bacterial diseases, and their economic impact are discussed, focusing on the trade off between survival rates and sanitation down‐time.

Salaries and benefits represent the largest cost‐component (37%) for hatcheries in industrialized countries, while feeds and operating supplies constitute the most important costs in developing countries (60%). The need to import hatchery feeds and other operating supplies into developing countries works against savings from lower labor costs typical of developing countries.

Total fixed costs depend on the size of a hatchery and are constant for all possible levels of output. Average fixed cost per unit (thousand postlarvae) can be reduced by producing high postlarval outputs. Hatcheries in areas with seasonal shrimp crops face the challenge of covering fixed costs with revenue from a short production season. Hatcheries with large fixed costs can operate in a cost‐efficient manner only by producing high levels of output. Average total cost and average variable cost curves follow a U‐shaped curve, in which costs first decline as output increases, then reach a minimum, and finally increase as output increases above a point of diminishing returns.

In hatcheries total costs are independent of larval survival, but lower output resulting from low survival increases unit costs. This effect is more pronounced at lower levels of output. Bacterial diseases decrease survival rates and increase unit costs.  相似文献   

18.
Abstract

A stochastic Cobb‐Douglas production frontier is used to provide estimates of output‐oriented technical efficiency, input‐oriented technical efficiency, input allocative efficiency and cost efficiency for a sample of seabass and seabream farms in Greece. Mean output‐oriented technical efficiency is estimated at 78.5%, input‐oriented technical efficiency at 73.6%, input allocative efficiency at 79.2%, and cost efficiency at 58.2%. Considering the sources of efficiency differentials among fish farms, it is evidence from the empirical results that large farms tend to achieve higher (technical and allocative) efficiency scores; specialization in either seabass or seabream affects positively technical and cost, but not allocative, efficiency; and utilization of skilled labor seems to have a positive impact only on technical efficiency.  相似文献   

19.
The natural amorphous polymer poly‐β‐hydroxybutyrate (PHB‐A: lyophilized Ralstonia eutropha containing 75% PHB) was used as a biological agent to control bacterial pathogens of blue mussel (Mytilus edulis) larvae. The larvae were supplied with PHB‐A at a concentration of 1 or 10 mg/L for 6 or 24 hr, followed by exposure to either the rifampicin‐resistant pathogen Vibrio splendidus or Vibrio coralliilyticus at a concentration of 105 CFU/ml. Larvae pretreated 6 hr with PHB‐A (1 mg/L) survived a Vibrio challenge better relative to 24 hr pretreatment. After 96 hr of pathogen exposure, the survival of PHB‐A‐treated mussel larvae was 1.41‐ and 1.76‐fold higher than the non‐treated larvae when challenged with V. splendidus and V. coralliilyticus, respectively. Growth inhibition of the two pathogens at four concentrations of the monomer β‐HB (1, 5, 25 and 125 mM) was tested in vitro in LB35 medium, buffered at two different pH values (pH 7 and pH 8). The highest concentration of 125 mM significantly inhibited the pathogen growth in comparison to the lower levels. The effect of β‐HB on the production of virulence factors in the tested pathogenic Vibrios revealed a variable pattern of responses.  相似文献   

20.
We used stochastic models for analysis of the uncertainty involved in semi‐intensive production of shrimp in Nayarit state, Mexico, incorporating partial harvests. Analysis of the database showed that increasing the number of harvests was associated with lower stocking densities, the use of larger ponds, longer cultivation periods, larger final weight of shrimp and total production. Equivalence tests showed that the models adequately fitted the primary data. Monte Carlo simulations indicated that improving management by controlling stocking density and the duration of cultivation increased mean production from 981 to 2573 kg/ha (one partial harvest), from 1808 to 3602 kg/ha (two partial harvests) and from 1364 to 3834 kg/ha (three partial harvests), closely approaching the yields reported in the database. When conducting one and three partial harvests, improved management increased production and the certainty in obtaining the crops, as indicated by diminishing values of the coefficient of variation in output probability distributions. When conducting two partial harvests, however, improved management increased yields, but also increased uncertainty because there was a lower control on production parameters. This does not necessarily imply more uncertainty when conducting two harvests, but that at this stage of knowledge, the primary data only allows detecting limited control on production. Results of a preliminary economic evaluation showed that net revenues ranged from USD$ 2361.1–3488.9, the benefit‐cost ratio from 1.47 to 1.62 and that the best and worse results were obtained by conducting two and one partial harvests. We conclude that the models are useful for analysing uncertainty of semi‐intensive shrimp production incorporating partial harvesting.  相似文献   

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